A novel RNA aptamer identifies plasma membrane ATP synthase beta subunit as an early marker and therapeutic target in aggressive cancer

PURPOSE

Primary breast and prostate cancers can be cured, but metastatic disease cannot. Identifying cell factors that predict metastatic potential could guide both prognosis and treatment.

METHODS

We used Cell-SELEX to screen an RNA aptamer library for differential binding to prostate cancer cell lines with high vs. low metastatic potential. Mass spectroscopy, immunoblot, and immunohistochemistry were used to identify and validate aptamer targets. Aptamer properties were tested in vitro, in xenograft models, and in clinical biopsies. Gene expression datasets were queried for target associations in cancer.

RESULTS

We identified a novel aptamer (Apt63) that binds to the beta subunit of F1Fo ATP synthase (ATP5B), present on the plasma membrane of certain normal and cancer cells. Apt63 bound to plasma membranes of multiple aggressive breast and prostate cell lines, but not to normal breast and prostate epithelial cells, and weakly or not at all to non-metastasizing cancer cells; binding led to rapid cell death. A single intravenous injection of Apt63 induced rapid, tumor cell-selective binding and cytotoxicity in MDA-MB-231 xenograft tumors, associated with endonuclease G nuclear translocation and DNA fragmentation. Apt63 was not toxic to non-transformed epithelial cells in vitro or adjacent normal tissue in vivo. In breast cancer tissue arrays, plasma membrane staining with Apt63 correlated with tumor stage (p < 0.0001, n = 416) and was independent of other cancer markers. Across multiple datasets, ATP5B expression was significantly increased relative to normal tissue, and negatively correlated with metastasis-free (p = 0.0063, 0.00039, respectively) and overall (p = 0.050, 0.0198) survival.

CONCLUSION

Ecto-ATP5B binding by Apt63 may disrupt an essential survival mechanism in a subset of tumors with high metastatic potential, and defines a novel category of cancers with potential vulnerability to ATP5B-targeted therapy. Apt63 is a unique tool for elucidating the function of surface ATP synthase, and potentially for predicting and treating metastatic breast and prostate cancer.

Abstract P4-01-07: A comprehensive liquid biopsy in patients undergoing neoadjuvant therapy

Background: Precision medicine is revolutionizing breast cancer (BC) care. Comprehensive liquid biopsies are a tool for personalized care in patients with locally advanced breast cancer (LABC). Identifying robust biomarkers as part of a comprehensive liquid biopsy to predict response to treatment is of immense clinical interest.

Methods: After obtaining IRB approval, serial blood samples were collected from patients with LABC undergoing neoadjuvant therapy. Paired biopsies were collected prior to treatment and were sent to Foundation Medicine for next-generation sequencing (NGS). We used a sized-base microfilter technology to capture circulating tumor cells (CTCs) and circulating cancer associated fibroblasts (cCAFs). Patients with one or more CTCs or cCAFs were deemed positive for these tests. Additionally, in collaboration with Foundation Medicine, we extracted circulating tumor DNA (ctDNA) and we analyzed it using the FoundationACT platform. Patients with a detectable genomic alteration in their plasma were considered as having a positive ctDNA test. Our primary objective is to determine if a comprehensive liquid biopsy can serve as a prognostic marker of pathologic complete response (pCR).

Results: For this analysis we describe our findings in the initial blood draw of the first 18 patients enrolled. The mean age is 54 years (38-70). All patients who had their tumors sequenced had a detectable mutation. Consistent with the findings of others, we found TP53 mutations to be the most prevalent at 83.3%. We found that 44% of patients had ctDNA, 68.4% had cCAFs and 78.9% had CTCs. Many patients also had clusters of cells, consisting of one cell type, or co-clusters, consisting of both. 38.9% had CTC clusters, 16.7% had cCAF clusters and 16.7% had co-clusters (CTCs and cCAFs together). Some patients with CTCs did not have cCAFs and vice versa. The number of CTCs and cCAFS did not correlate with stage of disease or receptor status.

Conclusions: We describe a comprehensive liquid biopsy combining a sized-based microfilter technology for CTC and cCAFs identification and the FoundationACT platform for ctDNA analysis is feasible and these biomarkers can be detected in patients with LABC prior to the initiation of neoadjuvant therapy. Our study is accruing rapidly, and we will update our results with the longitudinal collection and the prognostic value of a comprehensive liquid biopsy at the time of the meeting.

Citation Format: Sandoval Leon AC, Medina Saenz K, Miller P, Benson A, Calfa C, Mahtani R, Slingerland J, Perez A, Vogel C, Valdes-Albini F, El-Ashry D, Lippman M. A comprehensive liquid biopsy in patients undergoing neoadjuvant therapy [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-01-07.

Abstract P4-15-06: Results of a randomized double blind trial of neoadjuvant anastrozole plus placebo vs anastrozole plus saracatinib for ER+ postmenopausal breast cancer

Antiestrogen mediated cell cycle arrest requires the CDK inhibitor, p27. Src kinase mediates p27 loss and antiestrogen resistance in ER+ breast cancer lines in vitro. In ER+ xenografts, the Src inhibitor, saracatinib, restored antiestrogen responses in resistant tumors. This led to a Phase I/randomized double-blind Phase II trial to test effects of saracatinib with anastrozole for ER+ and/or PR+ postmenopausal breast cancer.

Phase I accrued 12 subjects and showed 175 mg po saracatinib is safely given with 1 mg po daily anastrozole with good PK . In Phase II, postmenopausal women with new ER+ and/or PR+, HER2- breast cancers ≥ 2 cm were randomized 2:1 to either neoadjuvant anastrozole with saracatinib or anastrozole/placebo over 6 months. Response was assayed by clinical 2D measurements each cycle and by MRI pre-study, at 10 weeks and prior to surgery. The Phase II primary endpoint was to test if tumor volume decrease (from 2D clinical measures) with dual therapy (dual) exceeded that of monotherapy (mono) by &gt;20%. Secondary endpoints included tumor response by 3D MRI measures and by RECIST, PK and toxicity, and molecular predictors of drug efficacy in pre-/ post-therapy tumors. Of 58 subjects, 15% were Black, 5% Asian and 79% White. 61% were Hispanic. Dual therapy was well tolerated, with the following grade 1 toxicities: flu-like syndrome 20%, non-pruritic rash 48% (17% for mono), self-limited diarrhea in 55% (33% mono). Transaminasemia with dual therapy was 52.5% and 17% with mono. 6/59 stopped dual due to drug related AEs: 2 had gr 3 hepatitis, one gr 3 anemia, 3 had grade 3 urticarial rash. Dual Rx increased mean anastrozole levels to 50 ng/ml vs 38 ng/ml for mono (T test p= 5.45201 E-05). Mean saracatinib level, 269 ng/ml, was similar to prior studies. All of 50 evaluable subjects showed clinical and MRI tumor responses. 17% in both groups progressed, usually after 16 weeks. Mean tumor vol (calculated from 2D clinic measures) declined more rapidly (by 63% in dual vs 55% in mono at 8 weeks), but both groups showed an 89% mean tumor volume decrease by 20 weeks. Clinical RECIST showed size reductions of 61% in dual and 62% after monotherapy. Tumor volumes based on 3D MRI show a non-significant trend to greater response to dual therapy, with mean volume decreased by 64% vs 45% at the end of dual vs monotherapy. RECIST response by MRI also showed a trend to greater % decrease tumor size post treatment by 34% vs 25% in dual vs mono. Thus, clinical volumetric assessment of response to this neoadjuvant endocrine therapy may overestimate response compared to volumes calculated by MRI, while RECIST may underestimate it. Pathologic responses based on initial and residual tumor burden calculated from initial and final tumor volumes and % cellularity in biopsy and surgical specimens will be presented.

Citation Format: Slingerland JM, Mark P, Hurley J, Net J, Collado-Mesa F, Lippman M, Avisar E, Yepes M, Jorda M, Gomez C. Results of a randomized double blind trial of neoadjuvant anastrozole plus placebo vs anastrozole plus saracatinib for ER+ postmenopausal breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-15-06.

Abstract PD9-10: Circulating CAF/cancer stem cell co-clusters bolster breast cancer metastasis

Background: Metastatic disease is the primary cause of breast cancer (BC) mortality. Cancer associated fibroblasts (CAFs) are the majority of stroma in BC and critical players in BC malignancy. For example, CAFs are the main source of SDF-1, a prominent chemokine in the tumor microenvironment (TME) that also imparts stem cell-like characteristics to BC cells. Metastasis occurs due to the transport of circulating tumor cells (CTC) and clusters of CTCs through the vasculature. Stem-like CTCs and clusters have a greater propensity to establish metastasis. We recently identified circulating CAFs (cCAFs) in blood from patients with BC and in spontaneous, syngeneic, and xenograft mouse models of BC. cCAFs not only circulate individually, but are also found in clusters with CTCs. In this study, we examine the role of CAFs in promoting egress of stem-like CTCs (cCSCs), determine the capacity of stem-like CTCs to cluster with CAFs, and evaluate the involvement of CTC/cCAF clustering in augmenting BC metastasis.

Methods: Our model employs NSG mice with orthotopic xenograft implantation of BC cells, primary CAF cell lines, or co-implantation of BC and CAF cell lines. We used two different BC cell lines: the non-metastatic BC cell line, MCF-7, and the highly metastatic primary BC cell line, DT28. We also employed the MMTV-PyMT spontaneous model of BC metastasis, and we used BALB/c mice injected with syngeneic 4T1 or 67nR cells to evaluate cCAFs, CTCs, and cluster egress in preclinical models. Mice were sacrificed at specific time points, and cardiac blood was collected. Blood was filtered using the faCTChecker microfluidic filtration instrument (Circulogix). Filters were stained for IF and cCAFs, CTCs, cCSCs, and clusters were enumerated. Tumors from CAF co-injected mice were evaluated for their stem cell-like phenotype and re-implanted in mice to evaluate tumorigenicity and metastasis.

Results: In spontaneous, syngeneic, and orthotopic xenograft models of BC, cCAFs, CTCs, and cCAF/CTCs co-clusters appear early in tumor development. cCAF/CTC clusters increase in correlation with tumor burden and metastasis. Co-inoculation of CAFs with BC cells resulted in a significant increase in tumor progression, metastasis, and in a substantially higher number of both individual cells and clusters in circulation. Dissociated tumor cells from CAF co-injected tumors had a higher proportion of CD44+stem cell-like cells (CSCs), enhanced ALDH-1 expression, and enhanced mammosphere formation. CD44+ CSCs, individually and in clusters, are found early on in the circulation of mice injected with dissociated tumor cells from CAF co-injected tumors. Upon re-implantation of CAF co-injected dissociated tumor cells without CAFs, dissociated tumor cells showed enhanced tumorigenicity and malignancy.

Conclusion: CAFs are highly motile and cCAFs precede CTCs into circulation and can do so independently of tumor cells. CAFs sustain egress of tumor cells by augmenting malignancy and stemness of BC cells. cCAF clusters with the highly metastatic stem cell-like subset of CTCs bolster metastatic colonization. Targeting primary CAF function and/or cCAF/cCSC co-clusters may provide novel avenues to abrogate BC metastasis.

Citation Format: Sharma U, Miller P, Medina Saenz K, Picon-Ruiz M, Morata-Tarifa C, Spartz A, Troness B, Park DN, Seagroves TN, Slingerland JM, Lippman ME, El-Ashry D. Circulating CAF/cancer stem cell co-clusters bolster breast cancer metastasis [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD9-10.

Abstract P4-01-05: Cell free DNA analysis identifies actionable ERBB2 amplifications in patients with HER2 equivocal breast cancer

Background:

Determination of ERBB2 (HER2) expression or amplification informs eligibility of HER2-targeted therapies. ASCO and NCCN guidelines recommend evaluation of HER2 status on primary invasive breast cancers and on a metastatic site if stage IV, where possible, as treatment is based on the status of the metastasis. Reassessment of HER2 status should also be considered in patients with disease recurrence as initially HER2-negative tumors may acquire HER2 amplification at progression. HER2 status can be complicated by equivocal results from in situ hybridization (ISH) and/or immunohistochemistry (IHC). Clarification requires reflex testing on the same tissue specimen or repeat testing on a new specimen, however some patients' tissue status remains equivocal. Furthermore, metastases to bone, lung, or brain may be difficult to re-biopsy or of low DNA quality. Rapid and non-invasive blood-based cell-free DNA (cfDNA) NGS may facilitate identification of HER2 targetable disease in advanced breast cancer.

Methods:

We assessed the frequency of ERBB2 amplification detectable by a blood-based cell-free DNA (cfDNA) assay among patients with metastatic breast cancer with equivocal HER2 results in tissue. cfDNA samples were ordered as part of routine clinical care using an assay validated for the detection of copy number amplification in ERBB2 (tests run between 03/2014-04/2017 by Guardant Health, Redwood City, CA). Submitted pathology reports were reviewed for HER2 status which was categorized as positive, negative, or equivocal based on the interpretation issued by the reading pathologist at the time the test was ordered. Patients were included if they had an equivocal result on IHC and/or ISH unless both assays were performed on the same specimen and one provided a definitive negative or positive HER2 result. Additionally, 4 patients with equivocal IHC or ISH results were excluded as biopsy of another tumor site revealed a positive HER2 result around the same time as the equivocal test. For the 349 patients with multiple cfDNA samples, the earliest pathology report was referenced.

Results:

Tissue HER2 status was available for 1,853 unique patients (98.8% female, median age at testing was 58y, range 26-91y). 141 patients (7.6%) had equivocal HER2 results in tissue; 99 by IHC alone, 14 by ISH alone, and 28 were equivocal by both assays. Among these, 126 patients (89.4%) had at least one sample with ctDNA detected. 12/126 (9.5%) had amplification of ERBB2 detected in at least one cfDNA sample. Samples were drawn a median of 267 days after tissue collection (range 4 days – 11.5 years). Frequency of ERBB2 amplification was similar regardless of time between tissue and blood collection but was higher among patients with ISH results alone (4/14, 36.4%) compared to those with IHC alone (6/89, 6.7%) or both assays (6/26, 7.6%; p=0.006).

Conclusion:

cfDNA testing identifies a significant number of patients with HER2-targetable advanced breast cancer whose tissue was HER2 equivocal. cfDNA testing may supplement tissue-based methods to help clarify HER2 status in metastatic disease as well as identify patients who may acquire HER2 amplification subsequent to their initial biopsy.

Citation Format: Rich TA, Raymond VM, Ahn ER, Banks KC, Brufsky A, Lee C, Lippman M, Pluard TJ, Schwab RB, Lanman RB. Cell free DNA analysis identifies actionable ERBB2 amplifications in patients with HER2 equivocal breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-01-05.

Abstract P5-05-13: Quantitative combinatory indexed ChIP-seq reveals distinct transcriptional complexes containing estrogen receptor and GREB1 at chromatin in breast cancer cells

GREB1 is an estrogen-activated gene in estrogen receptor a (ER)-positive breast cancer cells. GREB1 is also required for estrogen-stimulated breast cancer cell growth and its level is highly correlated to ER level in breast cancer cells and tumor samples. In endocrine resistant diseases, GREB1 is often dysregulated. GREB1 has been shown to interact with ER and bind to the same ER binding sites throughout the genome. There is no identified functional domain in GREB1 and it is not completely known how GREB1 exerts its function to regulate the transcription of ER target genes. In order to demonstrate whether GREB1 is present in the ER-containing transcriptional complex at chromatin, we have adapted and developed a quantitative combinatory indexed ChIP-seq assay suitable for dissecting components in a transcriptional cofactor complex in a genome-wide scale. In ER-positive MCF-7 breast cancer cells, we found that almost all GREB1 binding sites are the same sites bound by ER or its bona fide coactivator SRC-3. We further found that GREB1 and SRC-3 are both present in the same ER-containing complex at chromatin. Thus, both GREB1 and SRC-3 are integral members of the ER transcriptional complex at chromatin. Moreover, we discovered that only a portion of GREB1 at chromatin is present in the ER complex while the other portion of GREB1 is present in a different complex lacking ER or SRC-3 at the same genomic loci. Thus, two distinct GREB1-containing complexes are identified in equilibrium at chromatin: one contains ER/SRC-3 and the other one lacks ER/SRC-3. Our results suggest a non-traditional role of GREB1 in transcriptional regulation of ER target genes. The method used in our study can be widely applied for probing components of transcriptional complexes at chromatin.

Citation Format: Sun J, Lippman ME. Quantitative combinatory indexed ChIP-seq reveals distinct transcriptional complexes containing estrogen receptor and GREB1 at chromatin in breast cancer cells [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-05-13.

Abstract P2-01-10: Circulating CAF/CTC complexes and breast cancer metastasis

Background: Metastatic disease in breast cancer (BC) is the leading cause of cancer-related mortality among women worldwide. Synergy between cancer cells and non-cancer cells of the tumor microenvironment (TME) are vital for disease progression. Cancer associated fibroblasts (CAFs) are the major cell type in the stroma of BC and are critical mediators of tumor progression and metastasis. Transport of circulating tumor cells (CTCs) and CTC clusters through the vasculature seeds metastasis and clinical and preclinical studies demonstrate that CTC clusters have a higher metastatic potential than individual CTCs. More recently, circulating cancer stem cells (cCSCs) have been implicated as more metastatic than non-CSC CTCs. In our lab, we have demonstrated that CAFs also circulate (cCAFs). We have observed cCAFs in peripheral blood from breast cancer patients and in murine models of breast cancer. Furthermore, we have observed that cCAFs are present in circulation as both individual cells and as well as in complexes with CTCs. Given the integral role of CAFs in BC metastasis, we hypothesize that cCAFs complex with CTCs/cCSCs to bolster BC metastasis.

Methods: cCAF/CTC clusters were identified and enumerated from peripheral blood of patients with BC, and associations with clinical features and disease outcomes were evaluated. Blood was collected by cardiac puncture from PyMT mice from 4 weeks through to the presence of metastases (10 weeks) and cCAF/CTC clusters enumerated. We co-injected CAFs with MCF-7 cellsl into NSG mice, blood collected by cardiac puncture, and cCAF/CTC clusters were enumerated. At time of final sacrifice, tumors were removed and assessed for presence of CSCs. Using our established model of cCAF/CTC clustering in vitro we interrogated cCAF/CTC complexing with both metastatic and poorly metastatic BC cells.

Results: Circulating cCAFs/CTCs clusters are significantly increased in the blood of patients with advanced stage BC and associate not only with severity of disease but also with poorer clinical outcomes. In the spontaneous PyMT mouse model, the appearance of circulating cCAF/CTC clusters increased significantly as tumors grew but prior to metastasis. We demonstrate that metastatic BC cells form clusters with CAFs in vitro while non-metastatic BC cells do not form complexes with CAFs in vitro. Enriching for stem cells from MCF7 mammospheres, resulted in CAF/CSC clusters in vitro. In mice that were co-injected with non-metastatic MCF7 cells and CAFs from a TNBC/Basal-like BC (CAF23) we observed disease metastasis, an enrichment for cancer stem cell (CSC)-like CTCs, and the presence of circulating cCAF/MCF7-CSC clusters.

Conclusions: Circulating clusters of CTCs and cCAFs are characteristic, and potentially causative, of BC metastasis. Observations of cCAF/CTC clusters from preclinical and clinical samples are corroborated by our determination that the ability of BC cells to form complexes with CAFs in vitro is related to the intrinsic metastatic ability of the breast cancer cells. Both in vitro and in circulation, the BC cells in cCAF/cBC clusters are CSCs, so cCAF/cCSC clusters. Disrupting the formation of cCAF/CTC complexes may be a potential strategy to reduce treat or prevent breast cancer metastasis.

Citation Format: Miller P, Sharma U, Medina-Saenz K, Yeasky T, Picon-Ruiz M, Morata-Tarifa C, Seagroves T, Slingerland J, Lippman M, El-Ashry D. Circulating CAF/CTC complexes and breast cancer metastasis [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-01-10.

Abstract P2-02-12: Cell free DNA analysis identifies actionable ERBB2 amplifications in patients with HER2 negative breast cancer

Identification of ERBB2 (HER2) overexpression in metastatic breast cancer informs utilization of HER2 targeted therapy. The NCCN recommends HER2 expression re-evaluation at the first disease recurrence in patients with negative or equivocal tissue status given results discrepancies due to inadequate tissue biopsy, tumoral heterogeneity, biopsy technique or fixation as well as discordance in ERBB2 (HER2) expression between primary and metastatic lesions. We examined the incidence of ERBB2 (HER2) negative to positive “flips” (e.g. to ERBB2-amplified in plasma) in a cohort of patients who underwent a blood-based cell-free DNA (cfDNA) assay at a CLIA-certified/CAP-accredited/NYSDOH-approved molecular diagnostic laboratory.

Laboratory database was queried for samples from patients with a breast cancer diagnosis. The query was filtered to ensure patients with multiple cfDNA timepoints were counted only once. Patients without a pathology report submitted at any cfDNA collection timepoint or the pathology report did not include ERBB2 (HER2) status, results were inconclusive or quantity not sufficient were excluded. Between March 2014 and April 2017, 1,853 unique patients were identified with reported ERBB2 (HER2) status. For patients with more than one cfDNA timepoint collected (N=349; 18.8%), the earliest pathology report was referenced. 1,386 patient tumor samples were negative for HER2 overexpression (74.8%), 325 (17.5%) were positive, and 142 (7.7%) were equivocal. Twenty-nine of the 1,386 patients with reported tumor negative HER2 status had amplification on subsequent cfDNA analysis (2.1%).

All 29 patients were female. Most patients (N=21) had a single cfDNA timepoint collected. Median age at cfDNA blood draw was 58 years (range 28–68). Median length of time between reported tissue negative status and cfDNA blood draw was 405 days (range 21–4,060). Median plasma ERBB2 copy number was 2.44 (greater than 50th-centile per laboratory data) (range 2.15–16.5).

Clinical follow-up was obtained for 19 patients (65%). Nine patients were lost to follow-up or succumbed to disease prior to initiation of a new therapeutic regimen. One patient was known HER2 positive prior to receipt of the cfDNA results. In the remaining nine patients, six initiated targeted HER2 therapy following receipt of the cfDNA results, with five of six (83%) demonstrating a clinical response. In one patient with known ER/PR positive, HER2 negative disease, progressing through multiple lines of therapy, addition of trastuzumab and pertuzumab to her paclitaxel regimen following identification of the cfDNA ERBB2 amplification resulted in a significant reduction in CEA levels (238 to 37.9 ng/mL) by week five. In a second patient, following identification of the cfDNA ERBB2 amplification, she was treated with trastuzumab and pertuzumab along with docetaxel and had a dramatic response. She continues on trastuzumab and pertuzumab alone.

Although a modest sample size, this is the second cfDNA series demonstrating that ERBB2 (HER2) status may flip from negative to positive upon recurrence or metastasis, and that targeting plasma-detected ERBB2 amplification with anti-HER2 has clinical benefit. cfDNA is a viable alternative to tissue rebiopsy in this patient population.

Citation Format: Raymond VM, Diaz J, Banks KC, Ahn E, Brufsky A, Ellis M, Lippman M, Lee C, Pluard T, Schreeder M, Schwab R, Lanman RB. Cell free DNA analysis identifies actionable ERBB2 amplifications in patients with HER2 negative breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-02-12.

Elevated S100A8 protein expression in breast cancer cells and breast tumor stroma is prognostic of poor disease outcome

PURPOSE

Elevated S100A8 expression has been observed in cancers of the bladder, esophagus, colon, ovary, and breast. S100A8 is expressed by breast cancer cells as well as by infiltrating immune and myeloid cells. Here we investigate the association of elevated S100A8 protein expression in breast cancer cells and in breast tumor stroma with survival outcomes in a cohort of breast cancer patients.

PATIENTS AND METHODS

Tissue microarrays (TMA) were constructed from breast cancer specimens from 417 patients with stage I-III breast cancer treated at the University of Michigan Comprehensive Cancer Center between 2004 and 2006. Representative regions of non-necrotic tumor and distant normal tissue from each patient were used to construct the TMA. Automated quantitative immunofluorescence (AQUA) was used to measure S100A8 protein expression, and samples were scored for breast cancer cell and stromal S100A8 expression. S100A8 staining intensity was assessed as a continuous value and by exploratory dichotomous cutoffs. Associations between breast cancer cell and stromal S100A8 expression with disease-free survival and overall survival were determined using the Kaplan-Meier method and Cox proportional hazard models.

RESULTS

High breast cancer cell S100A8 protein expression (as indicated by AQUA scores), as a continuous measure, was a significant prognostic factor for OS [univariable hazard ratio (HR) 1.24, 95% confidence interval (CI) 1.00-1.55, p = 0.05] in this patient cohort. Exploratory analyses identified optimal S100A8 AQUA score cutoffs within the breast cancer cell and stromal compartments that significantly separated survival curves for the complete cohort. Elevated breast cancer cell and stromal S100A8 expression, indicated by higher S100A8 AQUA scores, significantly associates with poorer breast cancer outcomes, regardless of estrogen receptor status.

CONCLUSIONS

Elevated breast cancer cell and stromal S1008 protein expression are significant indicators of poorer outcomes in early stage breast cancer patients. Evaluation of S100A8 protein expression may provide additional prognostic information beyond traditional breast cancer prognostic biomarkers.

Abstract P4-12-13: High intratumoral and stromal S100A8 expression is prognostic of poor outcome in breast cancer

Background: S100A8 and S100A9 are members of a family of calcium binding proteins that regulate inflammatory response, and are biomarkers of inflammatory diseases, S100A8/A9 preferentially form heterodimers that interact with their receptor, RAGE, to activate signaling pathways (ERK1/2 MAPK, JNK, and NF-κB) and stimulate tumor cells. Elevated expression of S100A8/A9 has been observed in cancers of the bladder, esophagus, colon, ovary, and breast. S100A8/A9 are expressed intratumorally by cancer cells and in the stroma by infiltrating immune and myeloid cells as well. We investigated the associations of elevated expression of intratumoral and stromal S100A8 with survival outcomes in breast cancer.

Methods: Tissue microarrays (TMA) were constructed from breast cancer specimens from patients with stage I-III breast cancer treated at the University of Michigan Comprehensive Cancer Center between 2004-2006, ensuring a minimum of 10-year follow-up. Each patient was represented on the TMA by representative regions of non-necrotic tumor and distant normal tissue. Automative Quantitative Immunofluorescence (AQUA) was performed for S100A8 protein, and samples were scored for intratumoral and stromal S100A8 expression. S100A8 staining was assessed as a continuous value and by exploratory dichotomous cutoffs. Associations with disease-free survival (DFS) or overall survival (OS) and S100A8 expression, either as continuous value or based on the exploratory cutoffs, were determined using the Kaplan-Meier method and Cox proportional hazards models.

Results: In the entire patient cohort, high intratumoral S100A8 expression, as a continuous measure, was a significant prognostic factor for OS (univariable hazard ratio [HR] 1.26, 95% confidence interval [CI] 1.02-1.56, p=0.036), and for DFS (multivariable HR [95%CI] = 1.24 [1.01-1.53], p = 0.043). Exploratory analyses demonstrated optimal cutoffs of intratumoral and intrastromal staining that greatly separated survival curves. We evaluated whether the prognostic significance of S100A8 expression is different in breast cancer patients based on hormone receptor status and determined that neither intratumoral nor stromal S100A8 expression were significantly associated with outcomes.

Conclusions: Elevated intratumoral and stromal expression of S100A8 are significant indicators of poor outcome in breast cancer patients. These data further support a biological role for S100A8 signaling in mammary carcinogenesis and aggressive tumor behavior. Evaluation of S100A8 protein expression might provide additional prognostic information beyond traditional breast cancer prognostic biomarkers. Further validation is necessary to investigate these findings.

Citation Format: Miller P, Kidwell K, Thomas D, Sabel M, Rae J, Hayes DF, Lippman ME, El-Ashry D. High intratumoral and stromal S100A8 expression is prognostic of poor outcome in breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-12-13.

Abstract OT3-04-01: BRE12-158: A phase II randomized controlled trial of genomically directed therapy after preoperative chemotherapy in patients with triple negative breast cancer (TNBC)

Background: About 1/3 of patients with TNBC who receive preoperative therapy will experience a pathological complete response (pCR). Patients with residual disease have a markedly inferior overall survival (OS) compared to those who experience pCR. Recently, the CREATE-X trial demonstrated an improvement in disease free survival (DFS) and OS for post-neoadjuvant capecitebine; although the addition of capecitebine to standard therapy has not previously improved outcome across other non-selected adjuvant or neo-adjuvant trials. Prior data have also demonstrated that the residual tumors are genomically diverse and that these genetic changes are reflected at time of relapse.

Trial Design: This trial is a randomized phase II trial to determine whether a genomically guided therapy in the setting of incomplete response to standard neoadjuvant therapy will improve outcomes compared to standard of care. DNA from archived tumor samples collected at the time of surgery will be extracted and sequenced. The sequencing data will be interrogated for known genomic drivers of sensitivity or resistance to existing FDA approved agents. A cancer genomic tumor board (CGTB) will consider the genomic data along with the patient's prior treatment history, toxicities, and comorbidities and select the optimal therapy. Participants with a CGTB recommendation will be randomized to Experimental Arm A (genomically directed monotherapy) or Control Arm B (standard of care). Participants may have no CGTB recommendation either because sequencing did not identify a matched drug or because the drug was contraindicated and will be assigned to Control Arm B.

Eligibility criteria: Patients must have histologically confirmed TNBC with completion of all definitive local therapy and no evidence of metastatic disease. There must be significant residual disease characterized by &gt;2cm primary tumor, or lymph node positivity or RCB classification II or III. An FFPE tumor block with tumor cellularity &gt;20% is required. All patients must have completed preoperative chemotherapy including a taxane or anthracycline or both.

Specific aims: The Primary Aim is to compare 2-year DFS with a genomically directed therapy vs. standard of care. Secondary Aims include 1-year DFS, 5-year OS, collection of archival specimens for correlative studies, and to describe toxicities. Exploratory Aims are to describe the evolution of genomically directed therapies during the course of the study and to evaluate the drug specific effect on efficacy and toxicity.

Statistical methods: In order to detect an improvement in the fraction of patients free from disease at 2-year from 40% in the control Arm B to 63.2% in the genomically directed Experimental Arm A (corresponding to an HR=0.5), 136 participants will have 80% power to detect a difference in DFS using a two-side log-rank test with 0.05 level of significance.

Present accrual/target accrual: 38 accrued of 136 to be randomized.

Citation Format: Schneider B, Miller KD, Badve S, O'Neil B, Helft P, Chitambar C, Falkson C, Nanda R, McCormick M, Danso M, Blaya M, Langdon R, Lippman M, Paplomata E, Walling R, Thompson M, Robin E, Aggarwal L, Shalaby I, Canfield V, Adesunloye B, Lee T, Daily K, Ma C, Erban J, Radhakrishnan N, Bruetman D, Graham M, Reddy NA, Lynce FC, Radovich M. BRE12-158: A phase II randomized controlled trial of genomically directed therapy after preoperative chemotherapy in patients with triple negative breast cancer (TNBC) [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr OT3-04-01.

Abstract P6-03-02: Chronic CXCL12 exposure induces a metastatic phenotype in ER-positive breast cancer cells through transcriptional reprogramming

The chemokine CXCL12 is transcriptionally activated by estrogen in estrogen receptor (ER)-positive breast cancer cells. We have found that CXCL12 signaling is essential to maintain the long-term growth of ER-positive breast cancer cells and promotes cancer cell growth in the absence of estrogen. Chronic blockade of CXCL12 signaling with AMD3100, an inhibitor of CXCL12 receptor CXCR4, causes cell death in these cells. Chronic exposure to CXCL12 reprograms ER-positive breast cancer cells through genome-wide transcriptional changes and activates numerous signaling pathways including EMT and the inflammatory response. Many ER target genes are activated in CXCL12-reprogrammed cells even in the absence of estrogen which leads to the diminished estrogen modulated transcription in these cells. These cells also show enhanced signaling via TGFb, EGFR and Rac1 pathways, rendering these cells more sensitive to the CDK7 inhibitor, THZ1, and to drug combinations of THZ1 with the EGFR inhibitor Gefitinib or the RAC1 inhibitor EHT 1864. Furthermore, CXCL12-reprogrammed ER-positive breast cancer cells become more motile in vitro and display a metastatic phenotype in a mouse model. The lung-tropic phenotype of CXCL12-reprogramed MCF-7 cells could be explained by increased expression of integrins and pro-inflammatory signaling molecules. Our novel finding of chronic CXCL12 action on ER-positive breast cancer cells suggests a mechanism by which the interaction between stromal and tumor cells leads to increased breast tumor metastatic potential.

Citation Format: Sun J, Slingerland JM, Lippman ME. Chronic CXCL12 exposure induces a metastatic phenotype in ER-positive breast cancer cells through transcriptional reprogramming [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-03-02.

Abstract P3-06-01: Therapeutic targeting of RAGE in the tumor and tumor microenvironment inhibits breast progression and metastasis

Background: The Receptor for Advanced-Glycation End-products (RAGE) is highly expressed in various cancers and its expression is correlated with poorer outcomes in breast cancer. We have previously implicated RAGE in breast cancer, but whether RAGE drives breast cancer progression and metastasis either through tumor cell intrinsic effects, non-tumor cells of the tumor microenvironment, or both, is not fully understood. More importantly, studies are lacking that target RAGE therapeutically in cancer, and may therefore represent a novel treatment for breast cancer metastasis.

Methods: Using multiple human and murine breast cancer models we dissected the tumor intrinsic versus tumor microenvironment role of RAGE in metastasis. RAGE was targeted in tumor cells using multiple shRNAs, in non-tumor cells by global gene knockout in mice, and both by therapeutically targeting with the novel RAGE inhibitor FPS-ZM1. In vivo orthotopic models included the NSG (NOD-SCID-gamma) xenograft mouse model (with MDA-MB-231 cells; herein 231), BALBc (4T-1 and 67NR), and C57BL6 wild-type and RAGE knockout (RAGE -/-) mice (with MMTV-PyMT spontaneous breast cancer derived AT-3 cells).

Results: We first tested how RAGE impacts tumor cell intrinsic mechanisms using either RAGE shRNAs or FPS-ZM1 in 231, 4175 (231 isogenic highly metastatic cells) and 4T-1 cells. RAGE shRNA and FPS-ZM1 both decreased RAGE MAP-kinase signaling, transwell invasion and soft agar colony formation, without affecting proliferation. In vivo, RAGE shRNA knockdown in 231 cells did not affect tumor growth, but inhibited metastasis to lung and liver. RAGE shRNA knockdown in 4175 cells, decreased orthotopic tumor growth, and reduced tumor angiogenesis and tumor recruitment of leukocyte / macrophages. Furthermore, RAGE shRNA knockdown dramatically decreased metastasis of 4175 cells to lung and liver in a time and sized matched manner compared to shRNA controls. Similarly, RAGE knockdown in 4T-1 cells reduced cell invasion and colony formation, and inhibited lung metastasis from the orthotopic site in BALBc immunocompetent mice.

To test the non-tumor cell microenvironment role of RAGE, we performed syngeneic studies with orthotopically injected AT-3 cells in RAGE +/+ and RAGE -/- C57BL6 mice. RAGE -/- mice displayed striking impairment of tumor cell growth compared to RAGE +/+ mice, along with decreased MAP-kinase signaling, tumor angiogenesis and inflammatory cell recruitment.

Finally, to test the combined inhibition of RAGE in both tumor cell intrinsic and non-tumor cells of the microenvironment, we performed in vivo treatment of 4175 tumors with FPS-ZM1 (1mg/kg, twice per week). Compared to vehicle, FPS-ZM1 inhibited primary tumor growth, inhibited tumor angiogenesis and inflammatory cell recruitment, and most importantly prevented metastasis to lung and liver.

Conclusion: These data clearly demonstrate a role for RAGE in breast cancer progression and metastasis through distinct effects in the tumor cell and non-tumor cells of the tumor microenvironment. Furthermore, our data from drug inhibitor studies highlight the combined targeting of RAGE in the tumor and tumor microenvironment, and as a viable therapeutic means for breast and other metastatic cancers.

Citation Format: Kwak T, Drews-Elger K, Ergonul A, Braley A, Hwang GH, El-Ashry D, Slingerland JM, Lippman ME, Hudson BI. Therapeutic targeting of RAGE in the tumor and tumor microenvironment inhibits breast progression and metastasis [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-06-01.

Abstract P6-01-05: Novel cytotoxic RNA aptamers that distinguish between metastasis-prone and indolent breast and prostate cancers

Background: Prostate and breast cancers are, respectively, the most common malignancies diagnosed in men and women worldwide. These cancers develop in different organs but have significant biological similarities: both are typically hormone-dependent, and both require early detection and treatment, as metastatic disease is incurable. At the same time, early stage tumors are often over-treated. Better markers for tumor aggressiveness would help to optimize treatment strategies in both breast and prostate cancer.

Objective: Develop high affinity nucleic acid oligomers (aptamers) that can distinguish between indolent tumors that will remain organ-confined and those with heightened potential to metastasize.

Methods: We performed subtractive RNA Cell-SELEX to select for surface ligands specific to aggressive tumors, using as a positive selector the highly metastasis-competent LN3 subclone of prostate cancer cell line LNCaP, and as negative selectors parental LNCaP and a non-metastasizing subclone, Pro5. . The RNA aptamer pool was PCR amplified from a 40-mer random nucleotide cDNA library with appropriate flanking sequences, and transcribed in vitro. After 11 SELEX cycles, aptamer pools from cycles 0, 4, 9, and 11 were subjected to high-throughput sequencing. Eight aptamers, representing 4 sequence families, were chosen for further study. Representative relevant and irrelevant aptamers were labeled with Cy3 and used to stain LNCaP-LN3 and LNCaP-Pro5 in culture and as xenografts in NOD-SCID-gamma mice. Additional cell and tumor lines from both breast and prostate cancer were used for validation.

Results: Two aptamers bound avidly to the surface of the aggressive LNCaP-LN3 subclone, both in culture and in fixed xenograft tumors, but not to the indolent Pro5 subclone. Aptamer binding led to rapid and specific cytotoxicity in vitro but had no effect on other cell lines to which the aptamer did not bind. The same aptamers showed similar high specificity for multiple other metastasis-competent cancer cells, including the prostate adenocarcinoma PC-3 and PC-3ML subclones, breast cancer cell lines MDA-MB436 and MDA-MB231, and the primary dissociated breast tumor DT28 , while exhibiting no detectable binding to the non-metastasizing MCF-7 breast cancer cell line and DT22 primary dissociated breast tumor cells, and the non-tumorigenic prostate epithelial cell line RPWE-1.

Conclusion: We identified RNA aptamers that specifically bind to metastasis-prone prostate cancer and breast cancer cell surface targets, and exert cell-specific toxicity dependent upon aptamer binding. While the target(s) remain to be identified, we propose that these aptamers may discriminate between progressive and indolent breast and prostate cancers, and may have substantial promise as anticancer agents either alone or suitably liganded to toxic moieties.

Citation Format: Bishopric NH, Speransky S, Serafini P, De la Fuente AC, Bicciato S, El-Ashry D, Lippman ME. Novel cytotoxic RNA aptamers that distinguish between metastasis-prone and indolent breast and prostate cancers [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-01-05.

Abstract P4-03-18: A hierarchy of cancer associated fibroblasts in situ and in circulation promote breast cancer metastasis

Background: Metastasis is the primary cause of breast cancer mortality. Interactions between cancer cells and non-cancer cells of the tumor microenvironment (TME) are pivotal in governing tumor initiation, progression and metastasis, and cancer associated fibroblasts (CAFs) are critical orchestrators of these interactions. We recently identified circulating CAFs (cCAFs) as a novel circulating biomarker associated with metastatic breast cancer. We established CAF cell lines from dissociated luminal A, ER- Her-2 amplified, and triple-negative/basal-like (TN) breast tumors. We demonstrated that “aggressive” CAFs differentially secrete miRNAs that contribute to ER-negativity, activated growth factor signaling, and induction of EMT in breast cancers compared to “indolent” CAFs. We hypothesized that a hierarchy exists within CAFs regarding their ability to facilitate tumor progression and metastasis. Here we demonstrate that CAFs derived from aggressive TN breast tumors differ from those derived from more indolent Luminal A breast tumors in secretion of cytokines and chemokines that can confer differential effects on the behavior of breast cancer cells. We also demonstrate that “aggressive” CAFs more potently facilitate tumor progression and metastasis than “indolent” CAFs. We additionally evaluated if “aggressive” and “indolent” CAFs differ in their ability to mobilize CTCs and circulating CAFs into circulation.

Methods: Conditioned media (CM) from “aggressive” and “indolent” CAFs was analyzed for chemokine/cytokine expression. Luminal A breast cancer cells (MCF-7) or primary tumor cells from an aggressive TN tumor (DT28) were injected into the mammary fat pad of 6-8 week old female NSG mice, either alone or in combination with CAF19-I or CAF23-A. Tumor progression was monitored and mice were examined for metastasis at necropsy. Tissues were harvested for histology and blood was collected by cardiac puncture. Plasma was analyzed for cytokine/chemokine expression and blood was processed for enumeration of circulating tumor cells (CTCs) and cCAFs.

Results: “Aggressive” CAF CM had significantly higher levels of a number of factors, including IL-8, SDF-1, and CXCL1, compared to “indolent” CAF CM. MCF-7 cells co-injected with “aggressive” CAFs formed tumors much faster than those co-injected with the “indolent” CAFs or without CAFs. While DT28 cells readily form tumors and metastasize in the NSG model, fewer DT28 cells do not form metastases in the timeframe that this same lower number of DT28 cells co-injected with “aggressive” CAFs demonstrated robust tumor growth and developed metastases in liver and pancreas. DT28 cells co-injected with “indolent” CAFs did not exhibit metastases.

Conclusion: The data presented here further demonstrate that there is a hierarchy within CAFs regarding their ability to facilitate tumor growth and metastasis, and that this may largely be mediated by secreted soluble factors. “Aggressive” CAFs may retain their programmed role in circulation and accelerate metastasis more than “indolent” CAFs. We suggest that targeting CAFs in situ and in circulation and disrupting their interactions with breast cancer cells could provide novel strategies to combat breast cancer and breast cancer metastasis.

Citation Format: Sharma U, Miller P, Speransky S, Medina-Saenz K, Ferrer P, Lippman M, El-Ashry D. A hierarchy of cancer associated fibroblasts in situ and in circulation promote breast cancer metastasis [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-03-18.

Abstract P2-05-07: RAGE-ligand signaling drives breast cancer metastasis through affecting cells of the tumor and microenvironment

Breast cancer is most common malignant state in women, with 20% of these patients developing metastasis during the course of their disease. Further understanding is needed of the process and mechanisms of metastasis. Our lab and others have been shown that Receptor of Advanced-Glycation End-products (RAGE) plays a role in tumorigenesis and metastasis. RAGE is highly expressed in various cancers including breast cancer and its protein levels correlate with poor patient outcome in breast cancer and other cancers. Activation of RAGE results in increased proliferation, migration and invasion of cancer cells. Further studies in mice have shown it may be a therapeutic target to reduce tumor growth and the resulting metastasis. Further understanding is needed of the role of RAGE in driving metastasis through affecting cells of both the tumor and tumor stroma to design novel therapeutics. Using the breast cancer cell model (MDA-MB-231) and its organotropic sister cells lines selected in vivo for increased metastasis to lung (4175) and bone (1833), we tested the role of RAGE in driving tumor metastasis in vitro and in vivo with xenograft mouse models. To test the role of RAGE in the tumor microenvironment we used the AT-3 syngeneic breast cancer cell model in C57BL6 wild-type and RAGE knockout mice. We demonstrated that the highly metastatic variant of 231 cells (4175 and 1833) have increased expression level of RAGE compared to MDA-MB-231 parental cells. Ectopic over-expression of RAGE in parental 231 cells led to increased migratory and invasive properties compared to vector control cells, without affecting cell proliferation or viability. RAGE knockdown by shRNA in 4175 and 231 parental cells showed decreased cell invasion in transwell assays compared to control scramble shRNA. To validate our data in vivo, we performed mammary fat pad injection of 4175 cells (RAGE and scr shRNA) in NOD SCID gamma mice. Tumor growth and weight was impaired in RAGE gene knockdown 4175 cells compared to scramble (scr) controls. Analysis of lung and liver tissue retrieved from mice revealed RAGE knockdown in 4175 cells prevented metastasis compared to 4175 scr control cells. To test the role of RAGE on non-tumor cells of the breast stroma we next performed syngeneic studies with AT-3 cells (MMTV-PyMT spontaneous BC cell model), by injection into the mammary fat pad of wild-type and RAGE knockout C57BL6 immunocompetent mice. RAGE knockout mice (RAGE -/-) displayed striking impairment of tumor cell growth compared to wild-type (RAGE +/+) mice. We are currently testing whether novel RAGE inhibitors impact breast cancer progression and metastasis.

These data highlight RAGE drives breast cancer progression and metastasis through affecting both tumor cell intrinsic and non-tumor cell microenvironment effects. Future studies will demonstrate the potential of RAGE inhibition as a novel therapeutic approach for preventing and treating metastatic disease in breast and other cancers.

Citation Format: Kwak T, Drews-Elger K, Ergonul A, Zhao D, Besser A, Slingerland JM, Lippman ME, Hudson BI. RAGE-ligand signaling drives breast cancer metastasis through affecting cells of the tumor and microenvironment. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-05-07.

Abstract P2-02-10: Circulating cells from the tumor microenvironment as liquid biopsy biomarkers alongside circulating tumor cells in metastatic breast cancer

Background: Metastasis is a multistep process that involves the shedding of tumor cells in the peripheral circulation. These Circulating Tumor Cells (CTCs) have prognostic implications in patients with metastatic breast cancer (MBC). Cancer Associated Fibroblasts (CAFs) are a major component of the breast tumor microenvironment. The reciprocal signaling between tumor cells and its microenvironment promotes carcinogenesis, invasion, and metastasis. Studies in mouse models have shown that metastatic cells can bring their own stromal components from the primary site to the site of metastasis, and that these cotraveling stromal cells provide an early growth advantage to the accompanying metastatic cancer cells. CAFs have not been identified in the peripheral circulation. Using a microfilter capture technique, we discovered non-tumor, non-immune cells in the blood of metastatic patients and identified these cells as circulating CAFs (cCAFs). The purpose of this study is to demonstrate the presence of cCAFs as a biomarker of metastasis simultaneously with CTCs in patients with MBC.

Materials and Methods: We identified 20 patients with MBC (Metastatic/MET Group) and 10 patients with cured breast cancer (Ductal carcinoma in situ or Stage I post definitive treatment with &gt;5 years of disease free survival i.e. Localized/LOC Group). A total of 7.5 ml of peripheral blood was obtained from each patient. The enumeration of CTCs and cCAFs was carried out by the microfilter capture technique. Identification of these cells was done by a triple immunofluorescence staining for pan-CK (cytokeratin), FAP (Fibroblast Activated Protein) and CD45. cCAFs were identified as CK-, FAP+, CD45- cells and CTCs as CK+, CD45- cells. Identification and confirmation of cCAF was also carried out in parallel samples by a simultaneous FAP/α-Smooth Muscle Actin staining.

Results: cCAFs were detected in 17/20 (85%) MET patients but in only 2/10 (20%) LOC patients. CTCs were detected in 20/20 (100%) MET patients and in 8/10 (80%) LOC patients. The counts of CTCs and cCAFs in MET group ranged between 1-98 (median 13.5) and 0-117 (median 4), respectively. The counts of CTCs and cCAFs in the LOC group ranged between 1-14 (median 6) and 0-2 (median 0), respectively. For patients with exhibited cCAFs, 2/10 LOC and 5/17 MET patients had cCAFs counts of 2 or less. Although the sample size was small, patients exhibiting cCAFs (odds ratio=22.67, 95% CI: 3.14-163.63, p=0.002) were more likely to be in MET group than LOC group.

Conclusion: This is the first demonstration that CAFs, the predominant mesenchymal cell in the breast tumor microenvironment, are shed into the circulation and can be identified and enumerated as cCAFs in MBC patients along with CTCs. There was a clear difference in the numbers of CTCs and cCAFs levels between the MET and the LOC groups suggesting that CTCs and cCAFs are associated with advanced stage disease. While most patients, both in the LOC and MET group, exhibited CTCs, very few LOC patients exhibited cCAFs. We suggest that cCAFs could independently or along with CTCs serve as liquid biopsy biomarkers of metastasis. Validation of these findings in a larger cohort of patients will be presented during the meeting.

Citation Format: Parajuli R, Ao Z, Shah SH, Sengul TK, Lippman ME, Datar R, El-Ashry D. Circulating cells from the tumor microenvironment as liquid biopsy biomarkers alongside circulating tumor cells in metastatic breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-02-10.

Abstract P2-06-03: Leukemia inhibitory factor receptor as a tumor suppressor: A study on migration and invasion of breast cancer cells upon LIFR stimulation

BACKGROUND: Tumorigenesis is the result of a step-wise process during which a mutation activates an oncogene or inactivates a tumor suppressor gene. Identification of these genes is critical in order to develop effective therapies for breast cancer patients. Our group previously discovered the Leukemia Inhibitory Factor Receptor (LIFR) as a novel tumor suppressor gene via an in vivo RNAi screen in HMLE cells. HMLE is a partially transformed non-tumorigenic cell line; these cells can become tumorigenic with a single mutation, such as the Ras mutation that creates the HMLER line. HMLEs were transduced using an shRNA library targeting the entire human genome, and stably transfected cells were xenografted into NOD/SCID mice. Genomic DNA from resultant primary tumors were analyzed for the shRNA sequences that, when integrated, made HMLEs tumorigenic. LIFR emerged from this screen as a novel candidate tumor suppressor gene in breast cancer. Here we report on the decreased migration and invasion of breast cancer cells activated by LIFR stimulation.

METHODS: HMLER cells were plated at 500,000 cells per well of a six-well plate. Twenty-four hours later, HMLERs were treated with 100, 25, 12.5, 5, 2.5, or 0 ng/ml recombinant hLIF. Protein lysates were analyzed for phospho-STAT3 induction upon LIF stimulation. Based on the results, we selected 25 ng/ml as the appropriate hLIF concentration to maximally stimulate LIFR in the migration assay described here. HMLERs were serum starved for 8 hours. DMEM with 10% fetal bovine serum was added to the bottom of the migration assay plate as a chemoattractant. The cells were suspended in DMEM with 0.1% bovine serum albumin and either treated with 25 ng/ml LIF or no LIF. Thereafter, 25,000 cells were added to either a Corning Biocoat Matrigel Invasion Chamber or a control insert lacking a migration matrix. The migration assay plate was incubated at 37°C and the cells were allowed to migrate for 20 hours. Migrated cells were enumerated under the light microscope and a migration percentage was calculated.

RESULTS: In the first portion of the study, we found that low concentrations of LIF (2.5 ng/ml) resulted in p-STAT3 induction in HMLERs, but that p-STAT3 was maximally induced with 25 ng/ml of LIF. In the invasion and migration assay, HMLER cells that had not been treated with LIF displayed an aggressively invasive and migratory phenotype with 61.1% migration in matrigel compared to control inserts without the migration matrix. When HMLERs were treated with 25 ng/ml LIF, the cells displayed decreased invasion and migration with only 50.0% of cells migrating. Based on these results, LIFR stimulation inhibits the invasion and migration of breast cancer cells.

CONCLUSIONS: As a tumor suppressor gene, LIFR is vital to the normal functioning of a non-cancerous cell, and its loss can produce a tumorigenic and metastatic phenotype. Treatment with LIF converts aggressively metastatic breast cancer cells to a less invasive phenotype. Through a deeper understanding of LIFR's tumor suppressor effects, we can harness the anti-tumorigenic and anti-metastatic properties of LIFR stimulation and develop targeted therapies to prevent growth and metastasis of breast cancer.

Citation Format: Dempsey NG, Miller P, Lippman M. Leukemia inhibitory factor receptor as a tumor suppressor: A study on migration and invasion of breast cancer cells upon LIFR stimulation. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-06-03.

Loss of the E3 ubiquitin ligase HACE1 results in enhanced Rac1 signaling contributing to breast cancer progression

The transition from ductal carcinoma in situ (DCIS) to invasive breast cancer (IBC) is a crucial step in breast cancer progression. The specific alterations that govern this transition have not been elucidated. HER2/neu is frequently overexpressed in DCIS but is less common in IBC, thereby suggesting additional requirements for transformation. To identify genes capable of cooperating with HER2/neu to fully transform mammary epithelial cells, we used an insertional mutagenesis screen on cells isolated from wild-type neu expressing mice and identified the E3 ligase HACE1 as HER2 cooperative tumor suppressor gene. Loss of HACE1 expression is commonly seen in clinical breast cancer data sets. HACE1 downregulation in normal human mammary epithelial cells (HMECs) results in the accumulation of the activated GTP-bound Rac1 partially transforming these cells. Overexpression of HER2 activates Rac1, which further accumulates upon HACE1 loss resulting in Rac1 hyperactivation. Although the knockdown of HACE1 or overexpression of HER2 alone in HMECs is not sufficient for tumorigenesis, HER2 overexpression combined with HACE1 downregulation fully transforms HMECs resulting in robust tumor formation. The pharmaceutical interference of Rac function abrogates the effects of HACE1 loss both in vitro and in vivo, resulting in marked reduction in tumor burden. Our work supports a critical role for HACE1 in breast cancer progression and identifies patients that may benefit from Rac-targeted therapies.

Abstract P5-04-06: Loss of the E3 ubiquitin ligase HACE1 plays a critical role in transformation of mammary cells and clinical progression of human breast cancer via accumulation of active Rac1

Invasive ductal breast cancer arises when the immediate precursor, ductal carcinoma in situ (DCIS), breaches the basement membrane of the ductal lumen and invades into the surrounding tissue. Although this transition has been implicated as a crucial step in the progression of breast cancer, the specific alterations responsible for this transition have yet to be identified.

HER2/neu, a member of the epidermal growth family receptor (EGFR) family, is frequently overexpressed in non-invasive lesions (50-60%) but is significantly less common in invasive breast cancer (20-30%). This suggests that while HER2/neu may be partially transformative, additional alterations are required for mammary epithelial cells to achieve full malignant transformation.

To identify novel genes capable of cooperating with HER2, we performed an insertional mutagenesis screen for genes whose alteration induces anchorage-independent growth on primary mouse mammary epithelial cells isolated from MMTV-neu transgenic mice. We identified HECT domain and ankyrin repeat containing E3 ubiquitin-protein ligase 1 (HACE1) as a putative breast tumor suppressor gene whose loss contributes to the transformative process.

Loss of HACE1 expression is commonly seen in publicly available breast cancer patient data sets as well as in established breast cancer cell lines supporting the role of HACE1 as a breast cancer tumor suppressor gene. Knockdown of HACE1 in HER2 overexpressing human mammary epithelial cells (HMECs) enhanced colony formation over HER2 overexpressing HMEC controls cells. Moreover, knockdown of HACE1 alone was sufficient to allow anchorage-independent growth in soft agar in the HMECs while the overexpression of HACE1 in breast cancer cell lines diminishes clonogenic capacity in soft agar.

We confirmed recent studies that have shown that HACE1 is capable of tagging the Rho GTPase Rac1 for ubiquitin-mediated proteasomal degradation. In mammary epithelial cells, the loss of HACE1 leads to enhanced levels of active Rac1 resulting in increased clonogenicity, migration and invasion. Importantly, we show that targeting Rac1 can rescue the effects of HACE1 loss in mammary epithelial cells. Our results establish HACE1 as a breast cancer tumor suppressor gene by attenuating active Rac1 signaling. Our work supports the role of Rac1 as a critical signaling node in breast cancer and that loss of HACE1 leads to enhanced Rac1 signaling resulting in driving cancer progression. Furthermore, our results suggest the role of HACE1 loss as a biomarker for tumor progression and may identify patients vulnerable to Rac1 or Rac effector targeted therapies.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-04-06.

CD44 is prognostic for overall survival in the NCI randomized trial on breast conservation with 25 year follow-up

CD44 is a transmembrane glycoprotein involved in numerous cellular functions, including cell adhesion and extracellular matrix interactions. It is known to be functionally diverse, with alternative splice variants increasingly implicated as a marker for tumor-initiating stem cells associated with poor prognosis. Here, we evaluate CD44 as a potential marker of long-term breast cancer outcomes. Tissue specimens from patients treated on the National Cancer Institute 79-C-0111 randomized trial of breast conservation versus mastectomy between 1979 and 1987 were collected, and immunohistochemistry was performed using the standard isoform of CD44. Specimens were correlated with patient characteristics and outcomes. Survival analysis was performed using the log rank test. Fifty-one patients had evaluable tumor sections and available long-term clinical follow up data at a median follow up of 25.7 years. Significant predictors of OS were tumor size (median OFS 25.4 years for ≤2 cm vs. 7.5 years for >2 cm, p = 0.001), nodal status (median OS 17.2 years for node-negative patients vs. 6.7 years for node positive patients, p = 0.017), and CD44 expression (median OS 18.9 years for CD44 positive patients vs. 8.6 years for CD44 negative patients, p = 0.049). There was a trend toward increased PFS for patients with CD44 positive tumors (median PFS 17.9 vs. 4.3 years, p = 0.17), but this did not reach statistical significance. These findings illustrate the potential utility of CD44 as a prognostic marker for early stage breast cancer. Subgroup analysis in patients with lymph node involvement revealed CD44 positivity to be most strongly associated with increased survival, suggesting a potential role of CD44 in decision making for axillary management. As there is increasing interest in CD44 as a therapeutic target in ongoing clinical trials, the results of this study suggest additional investigation regarding the role CD44 in breast cancer is warranted.

Abstract P1-04-06: Insertional mutagenesis identifies HACE1 as a HER2/Neu Cooperating Breast Cancer Tumor Suppressor Gene

The development of human breast cancer is a multi-step process leading from normal epithelium to fully transformed breast cancer. Early genetic changes result in hyperplasias which evolves into ductal carcinoma in situ (DCIS) and culminates as invasive ductal carcinoma. The transition from DCIS to invasive disease has been implicated as the key transition in breast cancer progression. Specific genomic, transcriptomic, and proteomic alterations responsible for this transition process have yet to been elucidated.

HER2/Neu, a member of the EGFR family of receptor tyrosine kinases, is associated with poor clinical outcome. HER2/Neu overexpression/amplification is commonly seen (50–60%) in non-invasive lesions but is significantly less common (20–30%) in invasive and metastatic breast carcinoma. This indicates that HER2/Neu gives normal epithelium a proliferative advantage but additional genetic alterations are required for full malignant transformation. This idea is supported by the fact that transgenic mice that overexpress HER2/Neu develop spontaneous mammary tumors but only after a prolonged latency period.

Recent forward genetic approaches use insertional mutagenesis to randomly integrate a strong promoter into the genome, activating downstream gene transcription that can lead to either gain or loss-of-function mutations based on the integration site. We used this insertional mutagenesis approach to induce anchorage-independent growth of isolated murine HER2/Neu over-expressing mammary epithelial cells. We identified HECT domain and ankyrin repeat containing E3 ubiquitin protein ligase 1 (HACE1) as a putative breast tumor suppressor protein whose loss leads to the formation of anchorage-independent colonies.

Loss of HACE1 expression is commonly seen in breast cancer patients [as well as other tumor types] supporting the role of HACE1 as a breast tumor suppressor gene. Knockdown of HACE1 in human mammary epithelial cells (HMECs) results in the acquisition of anchorage-independent growth. Moreover, knockdown of HACE1 in established breast cancer cell lines that express moderate levels of HACE1 results in enhanced cloniginicity.

Therefore, we propose that the loss of HACE1 can potentially be used as a predictive marker for breast cancer progression. Additional studies investigating the mechanism of HACE1 action may also identify therapeutic targets that counteract HACE1 loss.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P1-04-06.

Truncated p110 ERBB2 induces mammary epithelial cell migration, invasion and orthotopic xenograft formation, and is associated with loss of phosphorylated STAT5

Truncated-ERBB2 isoforms (t-ERBB2s), resulting from receptor proteolysis or alternative translation of the ERBB2 mRNA, exist in a subset of human breast tumors. t-ERBB2s lack the receptor extracellular domain targeted by therapeutic anti-ERBB2 antibodies and antibody–drug conjugates, including trastuzumab, trastuzumab-DM1 and pertuzumab. In clinical studies, expression of t-ERBB2 in breast tumors correlates with metastasis as well as trastuzumab resistance. By using a novel immuno-microarray method, we detect a significant t-ERBB2 fraction in 18 of 31 (58%) of immunohistochemistry (IHC)3+ ERBB2+ human tumor specimens, and further show that t-ERBB2 isoforms are phosphorylated in a subset of IHC3+ samples (10 of 31, 32%). We investigated t-ERBB2 biological activity via engineered expression of full-length and truncated ERBB2 isoforms in human mammary epithelial cells (HMECs), including HMEC and MCF10A cells. Expression of p110 t-ERBB2, but not p95m (m=membrane, also 648CTF) or intracellular ERBB2s, significantly enhanced cell migration and invasion in multiple cell types. In addition, only expression of the p110 isoform led to human breast epithelial cell (HMLE) xenograft formation in vivo. Expression of t-ERBB2s did not result in hyperactivation of the phosphoinositide kinase-3/AKT or mitogen-activated protein kinase signaling pathways in these cells; rather, phosphoproteomic array profiling revealed attenuation of phosphorylated signal transducer and activator of transcription 5 (STAT5) in p110-t-ERBB2-expressing cells compared to controls. Short hairpin-mediated silencing of STAT5 phenocopied p110-t-ERBB2-driven cell migration and invasion, while expression of constitutively active STAT5 reversed these effects. Thus, we provide novel evidence that (1) expression of p110 t-ERBB2 is sufficient for full transformation of HMEC, yielding in vivo xenograft formation, and (2) truncated p110 t-ERBB2 expression is associated with decreased phosphorylation of STAT5.

P5-01-15: The Functional Role of the Estrogen-Regulated Gene GREB1: Characterization of a Novel GREB1 Knockout Mouse Model

Background: Gene regulated in breast cancer 1 (GREB1) was initially discovered in breast cancers as an estrogen-regulated gene that mediates estrogen-stimulated cell proliferation and is a candidate clinical marker for response to endocrine therapy. However, little is known of the functional role of GREB1 protein in normal breast tissue or breast cancers.

Methods: To address this unknown role, our laboratory designed and created a novel Greb1 Knockout Mouse model (C57/bl MEL Greb1 KO). This constitutive model results in the loss of Greb1 mRNA and protein expression in cells where expression of Cre recombinase promotes the cleavage of exon 1 and intron 1 of the gene encoding Greb1. ROSA26 Cre C57/b1 MEL Greb1 KO mice heterozygous for the floxed Greb1 allele were crossed to generate experimental litters. Initial experiments were designed to evaluate if the complete loss of Greb1 expression in offspring homozygous for the floxed Greb1 allele was lethal during gestation. Experimental litters were tail clipped and genotyped using gDNA and genotype-specific PCR.

Results: Offspring homozygous for the floxed Greb1 allele were identified in expected Mendelian ratios with wild type and heterozygous siblings. Loss of Greb1 expression was confirmed using RT-PCR, in situ hybridization and immunoblotting. Loss of both Greb1 alleles was not observed to be lethal during gestation for either male or female pups. Preliminary gross observation of these homozygous KO mice revealed no overt anatomical differences, however, they were 25–30% smaller than their heterozygous and wild-type siblings. Breeding experiments are underway to determine the fertility of crossbred Greb1 homozygous KO mice. Imaging experiments and necropsy with histochemical analysis of tissues will reveal any alteration in architecture and function. These findings will be summarized in this presentation.

Discussion: As GREB1 has been identified as an estrogen-regulated gene involved in breast cancer cell proliferation and a potential target for new therapeutic strategies, it is important to understand the contribution of GREB1 to the differentiation, development and function of normal tissues as well as in breast cancers. Characterization of this novel Greb1 KO mouse model will provide answers to these functional questions surrounding GREB1.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P5-01-15.

P2-01-25: Truncated p110 ERBB2 (CTF611) Increases Migration and Invasion of Breast Epithelial Cells by Inhibiting STAT5b Activation

Background: Truncated ERBB2 receptors are present in a subset of human ERBB2+ amplified/overexpressing breast tumors, and are associated with trastuzumab resistance, metastasis, and poor clinical prognosis. However, whether truncated ERBB2 receptors are drivers of metastasis has not been well defined. In this study, we examined effects of full-length (p185) and truncated (p110) ERBB2 on the migration and invasion of human mammary epithelial cells, including HMLE and MCF10A cells.

Material and Methods: Recombinant p185 and p110 ERBB2 were stably expressed in human mammary epithelial cells (HMLE) and MCF10A cells via retroviral vector. Expression of comparable levels of p185 and p110 in cells was confirmed by western blot. The phosphorylation states of downstream signaling proteins including STAT5 were assayed via phosphoproteomics and Collaborative Enzyme Enhanced Reactive (CEER™) immunoassay. The effects of the p110 constructs on cell migration and invasion were investigated by transwell assays. shRNA-encoding lentivirus was used for specific silencing of STAT5b in HMLE cells, and STAT5b silencing was confirmed at the protein level using western blot.

Results and Discussion: Expression of p110 ERBB2 increased cell migration (HMLE, p = 0.04; MCF10A, p&lt; 0.01) and invasion (HMLE, p= 0.03) when compared to expression of p185. Furthermore, expression of p110 in HMLE cells was associated with reduced phosphorylation of STAT5b. shRNA mediated silencing of STAT5b was sufficient to increase the migration (p &lt; 0.01) and invasion of HMLE cells, phenocopying the p110 driven effects on HMLE cells. In clinical studies, loss of activated STAT5 protein correlates with breast cancer progression and is a negative predictor of survival. By analyzing publicly available gene expression datasets, we found that STAT5b mRNA expression is also significantly decreased in breast cancer compared to normal breast tissues in several studies, as well as in ERBB2 amplified vs. nonamplified samples. To our knowledge, this is the first reported perturbation of STAT signaling by truncated ERBB2 receptor, and suggests a mechanism by which truncated p110 ERBB2 (CTF611) increases migration and invasion of breast epithelial cells. This study extends the available data regarding STAT5 loss in breast cancer progression.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-01-25.

Abstract P5-06-03: Truncated ERBB2 Receptors: Diagnostic and Therapeutic Targets

Background:

Patients with ERBB2+ breast cancer have aggressive disease and poor prognoses. It is now apparent that many ERBB2+ tumors also express truncated ERBB2 receptors (t-ERBB2s), namely p110 and p95. Increased expression of t-ERBB2s by breast tumors correlates with increased nodal involvement, distant metastasis, and poor clinical outcome in patients. Because t-ERBB2s lack the epitope bound by trastuzumab, expression of high levels of these isoforms may designate patients who would be better treated with alternative anti-ERBB2 therapy such as lapatinib; unfortunately, there is currently no clinical method to distinguish full-length p185- versus t-ERBB2 in patient tumor samples. Materials and Methods:

Recombinant forms of p185-, p110- and p95-ERBB2 were constructed using standard cloning techniques and expressed in human mammary epithelial cells (HMLE) via retroviral vector. The expression and subcellular localization of constructs were confirmed by western blot analysis and confocal microscopy. The ability of p185- and t-ERBB2 constructs to transform HMLE cells was evaluated using soft agar assays, and the effects on migration and invasion of these cells were investigated by transwell assays. Finally, the in vivo tumor formation by p185- vs. t-ERBB2 expressing cells was evaluated in immunodeficient mice. Additionally, a novel proximity-based antibody-capture method method to discern full-length versus t-ERBB2 in patient tumor samples was assessed (COPIA). Block tumors and fine-needle aspirates from patient tumor samples were used for quantifying total and phosphorylated ERBB2 receptors.

Results and Discussion:

Recombinant p185- and t-ERBB2 constructs were stably expressed in HMLE cells, and were correctly targeted to the cell membrane, as shown by confocal immunofluorescence microscopy and immunoblot. Expression of p110 t-ERBB2 increased migration and invasion of HMLE cells compared to p185 ERBB2 (P&lt;0.0001), while p110, p95m and p185 ERBB2s were equally effective at enhancing anchorage-independent growth. In vivo, expression of p110 t-ERBB2 but not other isoforms led to increased tumor formation in mice compared to controls (P&lt;0.005). No apparent phenotypes were elicited by expression of intracellular t-ERBB2 isoforms. Using COPIA testing, t-ERBB2 isoforms were detected in strongly ERBB2- positive tumors (16 of 31 samples, 52%) and were phosphorylated in 10 of 31 (32%). As expected, t-ERBB2s were not detected in ERBB2-negative tumor samples.

Truncated ERBB2s, particularly p110, may be major pathogenic drivers in ERBB2+ cancers. These isoforms may accelerate disease progression by promoting invasion and metastasis, and likely mediate resistance to trastuzumab and other therapies. Thus, t-ERBB2s represent attractive novel targets for diagnosis and treatment of ERBB2+ breast cancers.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P5-06-03.

Abstract P5-05-02: Whole Genome In Vivo RNA Interference Screening Identifies the Leukemia Inhibitory Factor Receptor as a Novel Breast Tumor Suppressor

Background: Cancer is caused by mutations in oncogenes and tumor suppressor genes resulting in the deregulation of processes fundamental to the normal behavior of cells. The identification and characterization of oncogenes and tumor suppressors has led to new treatment strategies that have significantly improved cancer outcome. The advent of next generation sequencing has allowed the elucidation of the fine structure of cancer genomes, however, the identification of pathogenic changes is complicated by the inherent genomic instability of cancer cells. Therefore, functional approaches for the identification of novel genes involved in the initiation and development of tumors are critical. Methods: In order to identify functionally important tumor suppressor genes we have conducted the first human whole genome in vivo RNA interference (RNAi) screen. Partially transformed human mammary epithelial cells (HMLEs), which do not form tumors in immunodeficient mice, were infected with the Expression Arrest™ GIPZ lentiviral shRNA library consisting of 62,000 shRNAs targeting the whole human genome, and injected into the mammary fat pad of immunodeficient mice. shRNAs that silenced tumor suppressor genes fully transformed the mammary epithelial cells resulting in tumor formation. Candidate tumor suppressor genes were identified by PCR amplification and sequencing of tumor integrated shRNAs. For validation, candidate tumor suppressor genes were silenced in HMLEs and ectopically expressed in fully transformed breast cancer cells. The effect of modifying gene expression on the transformed phenotype was assessed using soft agar colony formation assays. Clinical significance was determined by comparing expression in normal and cancerous human breast tissue using Oncomine Research. Results and Discussion: Using our novel approach, we identify previously validated tumor suppressor genes including TP53 and MNT, as well as several novel candidate tumor suppressor genes including leukemia inhibitory factor receptor (LIFR). Silencing LIFR expression with multiple shRNA constructs fully transformed human mammary epithelial cells resulting in enhanced colony formation in soft agar (P&lt;0.05). Furthermore, overexpression of LIFR significantly inhibited colony formation in soft agar of fully transformed MDA231 and MCF7 breast cancer cells (P&lt;0.01). In addition, our analysis of clinical data revealed that LIFR expression is significantly decreased in a large percentage of human cancers including breast (P&lt;0.0001), lung (P&lt;0.0001), hepatocellular (P&lt;0.0001) and gastrointestinal tumors (P&lt;0.0001). These results validate LIFR as a previously unidentified highly significant tumor suppressor, and also demonstrate the power of whole genome in vivo RNAi screens as a method for identifying novel genes regulating tumorigenesis.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P5-05-02.

Development of a Novel GREB1 Monoclonal Antibody and Applications in Breast Cancer Research

It has been well established that GREB1 mRNA expression is induced by estrogen in breast cancers and that GREB1 is critically involved in the estrogen-induced growth of breast cancer. To date, all studies of GREB1 have focused on mRNA levels using PCR and array technologies with very little known about GREB1 protein expression in normal and breast cancer cells. The lack of a specific antibody to GREB1 has inhibited protein-based investigations in target cells. Our collaborative research group has generated a novel monoclonal GREB1 antibody (GREB1ab) for research use in Western blotting as well as immunohistochemical (IHC) applications.Our team created a hybridoma expressing a murine monoclonal antibody against a 119 amino acid peptide specific to human GREB1. By Western Blot Analysis, GREB1ab detects a 216 kD protein corresponding to GREB1a in ER+ breast cancer cells expressing GREB1 as well as cells transfected with a GREB1a expression plasmid. GREB1ab specificity was verified using ICI 182,780, an estrogen receptor antagonist to prevent GREB1 induction, as well as silencing siRNA targeting GREB1 mRNA expression. GREB1 protein expression was reduced in MCF-7 cells treated with estrogen plus ICI 182,780 compared with that of estrogen treatment. There was no detectable GREB1 protein expression when GREB1 mRNA is silenced by siRNA at 48 hours. In a time course study, inhibition of GREB1 protein occurred as early as 24 hours and lasted up to 72 hours. Thus, by Western Blot Analysis, the monoclonal GREB1ab is specific for GREB1 and can be employed to detect changes in GREB1 expression in breast cancer cell lines under various experimental conditions.GREB1ab was validated for detection of GREB1 by IHC in breast cancer cell lines and breast tissue microarrays (TMA). IHC staining with GREB1ab revealed GREB1 was strongly expressed in the ERα-positive breast cancer cell line, MCF-7, with weak GREB1 expression in ERα-negative MDA-231 cells. A panel of breast cancer cell lines was screened for endogenous expression of GREB1 protein in a TMA format using IHC. As expected, ER-positive cell lines (n=5) were observed to express GREB1 while ER-negative cell lines (n=11) did not express detectable levels. Using breast cancer tissue whole sections, IHC with the GREB1ab indicated protein expression in ERα positive breast cancer tissue as well as normal breast tissue, with little GREB1 expression in ERα negative breast cancer tissue.The monoclonal GREB1ab is specific for GREB1 protein. This antibody will serve as a tool for investigations focused on the expression, distribution and function of GREB1 in normal breast and breast cancer tissues.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2126.

Correlations between GREB1 Expression and Estrogen Receptor, HER2 Status in Human Breast Cancer

The two most common endocrine treatment modalities, anti-estrogen therapy and aromatase inhibitor therapy target estrogen receptor (ER) activation and estrogen (E2) biosynthesis, respectively. Although these therapies are effective in many patients with ER-positive tumors, prospective clinical trials have demonstrated that there exists a portion of patients with breast cancers that are initially responsive to endocrine therapy but subsequently relapse. Because of the lack of perfect correlation between ER and/or progesterone receptor (PR) status and patients who benefit from hormone therapy, there is a need to identify additional protein markers that would improve prediction of hormone response.Gene Regulated by Estrogen in Breast cancer 1 (GREB1) is regulated by estrogen (E2) in breast cancer and may serve as a candidate marker to predict response to endocrine therapy. The focus of this study was to define the significance of GREB1 protein expression in breast cancer and its correlation with estrogen receptor α status and epidermal growth factor receptor 2 (HER2) expression. Based on the query of 16 breast cancer expression array studies in the Oncomine Research database, GREB1 mRNA is expressed at greater levels in breast carcinomas than normal breast tissue (p value: 2.1E-5). In addition, GREB1 mRNA is significantly more commonly expressed in ER-positive breast cancer patients (n=1651) than ER-negative patients (n=670) (P value: 4.2E-5 ∼ 1.1E-34). Finally, GREB1 mRNA expression was observed to be lower in HER2+ breast cancer patients than in HER-2 – patients (p-value: 0.034). These mRNA expression data supported the hypothesis that GREB1 may have potential as a new biomarker for predicting E2-dependent and anti-E2 responsive breast cancers.Using a novel GREB1 monoclonal antibody generated by our laboratory, Immunohistochemical staining (IHC) was performed on a tissue microarrays containing invasive breast carcinomas from a cohort of 142 operable breast cancer patients (104 ER+ and 38 ER- cancers) with paired uninvolved tissue from the same patient. GREB1 protein was detected in both uninvolved normal tissue and ER+ breast cancer, but was absent in ER- tumors. Thus, IHC staining revealed GREB1 protein expression, predominantly localized in the cell nucleus, has a significant correlation with ER status (p-value &lt;0.0001). Conversely, as observed in mRNA expression analysis, GREB1 protein levels inversely correlates with HER2 status (p-value &lt;0.0001). Furthermore, decreased HER2 signaling caused by treatment with trastuzumab or lapatinib increased GREB1 (2-10 fold) and other ER target gene expressions, such as insulin receptor substrate 1 (IRS-1), insulin-like growth factor binding protein-4 gene (IGFBP4) and bcl-2 mRNA expression.These findings suggest, in addition to ER and PR, GREB1 may serve as a novel biomarker to distinguish patients who will benefit from tamoxifen therapy as well as identify anti-estrogen resistant breast cancer.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2008.

Truncated p95erbB2 Isoforms Are Capable of Transforming Human Mammary Epithelial Cells

Background:Objective clinical response to trastuzumab monotherapy in erbB2-amplified first line metastatic breast cancer is 34% (Vogel, et al., JCO 20: 719-26, 2002). Amongst patients who respond, most develop resistance (defined by disease progression on trastuzumab). One proposed mechanism of trastuzumab resistance is proteolytic cleavage of erbB2 receptor from its full-length (p185) form into truncated, constitutively active p95. Increased expression of p95erbB2 correlates with increased nodal involvement and poor clinical outcome. Because p95erbB2 lacks the trastuzumab binding epitope, expression may designate patients who would be suitable for treatment with erbB2 kinase inhibitors.Materials and Methods:Recombinant p185erbB2 and p95erbB2 constructs were stably expressed in several cell types via retroviral vector. Additionally, an intracellular form of p95erbB2 that arises via alternative translation and an intracellular p95erbB2 construct containing two copies of a nuclear localization sequence were also expressed. Expression and proper subcellular localization of constructs were confirmed by cell fractionation, western blot analysis and confocal microscopy. Transformation of human mammary epithelial (HMEC) and NIH3T3 cells by p185erbB2 and p95erbB2 isoforms was evaluated by anchorage independent growth using a quantitative fluorescent soft agar assay, and effects on migration and invasion of these cells were investigated by wound-healing and transwell assays. Cells transfected with oncogenic Ras or empty vector were used as positive and negative controls in these experiments.Results and Discussion:Recombinant p185erbB2 and p95erbB2 constructs were stably expressed in HMEC and NIH3T3 cells, and were correctly directed to the cell membrane; nuclear targeted intracellular p95erbB2 was correctly localized to the cell nucleus. Both p185 erbB2 and membrane-bound truncated p95erbB2 were sufficient to transform HMEC cells as compared to empty vector control transfected cells [mean fluorescence intensity empty vector control 2480 ± 464 (1 standard deviation); mean fluorescence intensity p185erbB2 9208 ± 2528, p= 0.0106; mean fluorescence intensity p95erbB2 6615 ± 1588, p= 0.0124)] as was the positive control oncogenic Ras (mean fluorescence intensity 4350 ± 433, p=0.0069). Interestingly, nuclear-targeted p95erbB2 was also sufficient to transform HMEC cells (mean fluorescence intensity 6492 ± 818, p=0.0018). These data support the hypothesis that truncated p95erbB2 species may be major pathogenic drivers in erbB2-amplified cancers. P95erbB2 therefore represents an attractive target for diagnosis and treatment of erbB2+ breast cancer.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3136.

Correlation of GREB1 mRNA with protein expression in breast cancer: validation of a novel GREB1 monoclonal antibody

Studies of gene regulated by estrogen in breast cancer 1 (GREB1) have focused on mRNA levels with limited evidence about GREB1 protein expression in normal and breast cancer cells. A monoclonal antibody that recognizes GREB1 protein in breast tissues could be applied to correlate protein expression with established mRNA expression data. A hybridoma expressing a murine monoclonal antibody targeting a 119 amino acid peptide specific to human GREB1 was generated. The novel monoclonal GREB1 antibody (GREB1ab) was validated for use in Western blotting as well as immunohistochemical (IHC) applications. GREB1ab detects a 216 kDa protein corresponding to GREB1 in estrogen receptor alpha (ERalpha+) breast cancer cells as well as ERalpha- breast cancer cells transduced with a GREB1 expression vector. GREB1ab specificity was verified using an ERalpha antagonist to prevent GREB1 induction as well as a silencing siRNA targeting GREB1 mRNA. GREB1ab was further validated for detection of GREB1 by IHC in breast cancer cell lines and breast tissue microarrays (TMA). ERalpha+ cell lines were observed to express GREB1 while ERalpha- cell lines did not express detectable levels of the protein. Using breast cancer tissue whole sections, IHC with the GREB1ab identified protein expression in ERalpha+ breast cancer tissue as well as normal breast tissue, with little GREB1 expression in ERalpha- breast cancer tissue. Furthermore, these data indicate that GREB1 mRNA expression correlates well with protein expression. The novel monoclonal GREB1ab is specific for GREB1 protein. This antibody will serve as a tool for investigations focused on the expression, distribution, and function of GREB1 in normal breast and breast cancer tissues.

Knowledge mapping as a technique to support knowledge translation

This paper explores the possibility of integrating knowledge mapping into a conceptual framework that could serve as a tool for understanding the many complex processes, resources and people involved in a health system, and for identifying potential gaps within knowledge translation processes in order to address them. After defining knowledge mapping, this paper presents various examples of the application of this process in health, before looking at the steps that need to be taken to identify potential gaps, to determine to what extent these gaps affect the knowledge translation process and to establish their cause. This is followed by proposals for interventions aimed at strengthening the overall process. Finally, potential limitations on the application of this framework at the country level are addressed.

Improved prediction of disease-free survival in tamoxifen-treated patients using an expression signature of estrogen-regulated genes as compared to progesterone receptor

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Background: Progesterone receptor (PR) is a direct downstream target of activated estrogen receptor (ER) and its expression is a marker of estrogen signaling within breast tumors. Studies suggest the absence of PR predicts the likelihood of distant recurrence in patients treated with hormonal therapies such as tamoxifen, but better clinical measures are needed. Methods: Through analysis of public mRNA expression profiling datasets, we identified 36 genes with the following expression patterns similar to PR: (1) induced by 17β-estradiol (E2) in estrogen receptor (ER)-positive breast cancer cell lines in vitro, (2) under-expressed in ER-negative compared to ER-positive breast tumors, and (3) correlated with PR expression in ER-positive tumors. The average expression of these 36 genes was used as a “risk index” for assessing disease-specific survival in two independent tumor profile datasets of 60 and 67 patients treated with tamoxifen (these data not having been used to initially select the 36 genes), with a high risk group in each dataset defined as those with the bottom 25% of risk index values. Results: The Kaplan-Meier estimates of the rates of distant recurrence at 10 years in the low-risk and high-risk groups were 24% and 64% in the one dataset and 32% and 72% in the other dataset. In both validation datasets, the rate in the low-risk group was significantly lower than that in the high-risk group (P=0.008 and P=0.006 by log-rank, respectively), whereas patient groups defined by histologically-assigned PR status did not show significant risk differences (P=0.70 and P=0.94, respectively). In a univariate Cox model, the risk index combined across both validation datasets provided significant predictive power (P=0.03). Conclusions: Through RT-PCR assay of a larger independent cohort of breast tumor samples, we are currently validating the prognostic value of individual genes within the 36-gene signature.

No significant financial relationships to disclose.

A phase I trial of a Bcl-2 antisense (G3139) and weekly docetaxel in patients with advanced breast cancer and other solid tumors

PURPOSE

Expression of the Bcl-2 protein confers resistance to various apoptotic signals. G3139 [oblimersen sodium (Genasense)] is a phosphorothioate antisense oligodeoxynucleotide that targets Bcl-2 mRNA, downregulates Bcl-2 protein translation, and enhances the antitumor effects of subtherapeutic doses of docetaxel (Taxotere).

PATIENTS AND METHODS

We performed a phase I trial to determine the maximum tolerated dose (MTD) and safety profile of combined therapy with G3139 and weekly docetaxel in patients with advanced Bcl-2-positive solid tumors. Cohorts of three to six patients were enrolled to escalating doses of G3139 and a fixed dose of weekly docetaxel using either of two schedules. In part I, G3139 was administered by continuous infusion for 21 days (D1-22), and docetaxel (35 mg/m2) was given weekly on days 8, 15 and 22. In part II, G3139 was given by continuous infusion for 5 days before the first weekly dose of docetaxel, and for 48 h before the second and third weekly docetaxel doses. For both schedules, cycles were repeated every 4 weeks.

RESULTS

Twenty-two patients were enrolled. Thirteen patients were treated on the part I schedule with doses of G3139 escalated from 1 to 4 mg/kg/day. Nine patients were on the part II schedule of shorter G3139 infusion at G3139 doses of 5-9 mg/kg/day. Hematologic toxicities were mild, except for one case of persistent grade 3 thrombocytopenia in part I. The most common adverse events were cumulative fatigue and transaminase elevation, which prevented further dose escalation beyond 4 mg/kg/day for 21 days with the part I schedule. In part II of the study, using the abbreviated G3139 schedule, even the highest daily doses were tolerated without dose-limiting toxicity or the need for dose modification. Objective tumor response was observed in two patients with breast cancer, including one whose cancer previously progressed on trastuzumab plus paclitaxel. Four patients had stable disease. Pharmacokinetic results for G3139 were similar to those of other trials.

CONCLUSIONS

G3139 in combination with standard-dose weekly docetaxel was well tolerated. The shortened and intermittent G3139 infusion had less cumulative toxicities and still allowed similar total G3139 delivery as the longer infusion. Further studies should examine the molecular effect of the regimen, as well as clinical activities in malignancies for which taxanes are indicated.

Rifampin is a selective, pleiotropic inducer of drug metabolism genes in human hepatocytes: studies with cDNA and oligonucleotide expression arrays

We used expression microarrays to test the effects of rifampin on the overall pattern of mRNA expression of multiple metabolic enzymes in primary human hepatocytes. Two microarrays were utilized, a cDNA-based array and one that is oligonucleotide-based. The cDNA-based expression arrays showed that rifampin caused a 7.7 +/- 6.6-fold induction in CYP2A6 and a 4.0 +/- 2.0-fold increase in the CYP2C family of enzymes while having little effect on CYP2E1 or CYP2D6. Many non-P450 enzymes were also induced including FMO-4 and -5, UGT-1A, MAO-B, and GST-P1. The oligonucleotide-based array made it possible to detect different levels of induction within the CYP2C family, with rifampin causing a 6.5-fold increase in expression of CYP2C8 and a 3.7-fold increase in CYP2C9 while having no effect on the level of CYP2C18 mRNA. Rifampin also induced other CYP enzymes including CYP2B6 and all three members of the CYP3A family, with CYP3A4 showing the highest level of induction at 55.1-fold. RNase protection assays were used to validate results from the arrays and a comparison of all three methods of mRNA detection showed qualitatively similar results. These data make it clear that rifampin treatment brings about broad changes in the pattern of gene expression, rather than increased expression of a small number of metabolic enzymes. Clinicians and researchers who use and study rifampin and other drugs that induce drug metabolism should be alert to the possibility of multiple effects.

Overexpression of KAI1 suppresses in vitro invasiveness and in vivo metastasis in breast cancer cells

KAI1 is a metastasis suppressor gene for human prostate cancer and is also involved in the progression of a variety of other human cancers. Previously, we have demonstrated that KAI1 expression was down-regulated in metastatic breast cancer cell lines as well as in highly aggressive breast cancer specimens. To determine whether KAI1 expression is responsible for the metastasis suppression in breast cancer, we transfected the human KAI1 cDNA into two highly malignant breast cancer cell lines, LCC6 and MDA-MB-231, which both have low levels of endogenous KAI1 expression. Parental, vector-only transfectants and KAI1 transfectant clones were injected into the mammary fat pads and tail veins, respectively, of athymic nude mice and assessed for both spontaneous and experimental lung metastasis. High KAI1 expression significantly suppressed the metastatic potential of KAI1-transfected LCC6 cells. Metastasis suppression correlated with the reduced rate of tumor growth and a decreased clonogenicity in soft agar. Furthermore, KAI1 expression significantly suppressed the in vitro cell invasion in KAI1-transfected MDA-MB-231 cells. Our results suggested that KAI1 may function as a negative regulator of breast cancer metastasis.

Indicators of lifetime estrogen exposure: effect on breast cancer incidence and interaction with raloxifene therapy in the multiple outcomes of raloxifene evaluation study participants

PURPOSE

To test the hypothesis that risk factors related to lifetime estrogen exposure predict breast cancer incidence and to test if any subgroups experience enhanced benefit from raloxifene.

PATIENTS AND METHODS

Postmenopausal women with osteoporosis (N = 7,705), enrolled onto the Multiple Outcomes of Raloxifene Evaluation (MORE) trial, were randomly assigned to receive placebo, raloxifene 60 mg/d, or raloxifene 120 mg/d for 4 years. Breast cancer risk was analyzed by the following baseline characteristics indicative of estrogen exposure: previous hormone replacement therapy, prevalent vertebral fractures, family history of breast cancer, estradiol level, bone mineral density (BMD), body mass index, and age at menopause. Therapy-by-subgroup interactions were assessed using a logistic regression model.

RESULTS

Overall, women with the highest one-third estradiol levels (> or = 12 pmol/L) had a 2.07-fold increased invasive breast cancer risk compared with women with lower levels. Raloxifene significantly reduced breast cancer risk in both the low- and high-estrogen subgroups for all risk factors examined (P <.05 for each comparison). The women with the highest BMD and those with a family history of breast cancer experienced a significantly greater therapy benefit with raloxifene, compared with the two thirds of patients with lower BMD or those without a family history, respectively; the subgroup-by-therapy interactions were significant (P =.005 and P =.015, respectively).

CONCLUSION

The MORE trial confirms that increased lifetime estrogen exposure increases breast cancer risk. Raloxifene therapy reduces breast cancer risk in postmenopausal osteoporotic women regardless of lifetime estrogen exposure, but the reduction is greater in those with higher lifetime exposure to estrogen.

Digitized mammography: a clinical trial of postmenopausal women randomly assigned to receive raloxifene, estrogen, or placebo

BACKGROUND

High mammographic density is associated with increased breast cancer risk. Previous studies have shown that estrogens increase breast density on mammograms, but the effect on mammographic density of selective estrogen receptor modulators, such as raloxifene, is unknown. We assessed changes in mammographic density among women receiving placebo, raloxifene, or conjugated equine estrogens in an osteoporosis prevention trial.

METHODS

In a 5-year multicenter, double-blind, randomized, placebo-controlled osteoporosis prevention trial, healthy postmenopausal women who had undergone hysterectomy less than 15 years before the study and had no history of breast cancer received placebo, raloxifene (at one of two doses), or conjugated estrogens (ERT). Women from English-speaking investigative sites who had baseline and 2-year craniocaudal mammograms with comparable positioning (n = 168) were eligible for this analysis. Changes in mammographic density were determined by digital scanning and computer-assisted segmentation of mammograms and were analyzed with the use of analysis of variance. All statistical tests were two-sided.

RESULTS

Among the four treatment groups after 2 years on study, the mean breast density (craniocaudal view) was statistically significantly greater in the ERT group than it was in the other three groups (P<0.01 for all three comparisons). Within treatment groups, the mean breast density from baseline to 2 years decreased statistically significantly in women receiving the placebo or either the higher or lower raloxifene dose (P = 0.003, P = 0.002, and P<0.001, respectively) and showed a nonstatistically significant increase in women receiving ERT.

CONCLUSIONS

In an osteoporosis prevention trial, raloxifene did not increase breast density after 2 years of treatment. Raloxifene administration should not interfere with, and could even enhance, mammographic detection of new breast cancers.

Continued breast cancer risk reduction in postmenopausal women treated with raloxifene: 4-year results from the MORE trial. Multiple outcomes of raloxifene evaluation

Raloxifene, a selective estrogen receptor modulator approved for the prevention and treatment of postmenopausal osteoporosis, has shown a significant reduction in breast cancer incidence after 3 years in this placebo-controlled, randomized clinical trial in postmenopausal women with osteoporosis. This article includes results from an additional annual mammogram at 4 years and represents 3,004 additional patient-years of follow-up in this trial. Breast cancers were ascertained through annual screening mammograms and adjudicated by an independent oncology review board. A total of 7,705 women were enrolled in the 4-year trial; 2,576 received placebo, 2,557 raloxifene 60 mg/day, and 2,572 raloxifene 120 mg/day. Women were a mean of 66.5-years old at trial entry, 19 years postmenopause, and osteoporotic (low bone mineral density and/or prevalent vertebral fractures). As of 1 November 1999, 61 invasive breast cancers had been reported and were confirmed by the adjudication board, resulting in a 72% risk reduction with raloxifene (relative risk (RR) 0.28, 95% confidence interval (CI) 0.17, 0.46). These data indicate that 93 osteoporotic women would need to be treated with raloxifene for 4 years to prevent one case of invasive breast cancer. Raloxifene reduced the risk of estrogen receptor-positive invasive breast cancer by 84% (RR 0.16, 95% CI 0.09, 0.30). Raloxifene was generally safe and well-tolerated, however, thromboembolic disease occurred more frequently with raloxifene compared with placebo (p=0.003). We conclude that raloxifene continues to reduce the risk of breast cancer in women with osteoporosis after 4 years of treatment, through prevention of new cancers or suppression of subclinical tumors, or both. Additional randomized clinical trials continue to evaluate this effect in postmenopausal women with osteoporosis, at risk for cardiovascular disease, and at high risk for breast cancer.

Expression and function of angiopoietin-1 in breast cancer

Angiopoietin-1 (Ang1) has been shown to act as an angiogenic promoter in embryonic angiogenesis by promoting vascular branching, pericyte recruitment and endothelial survival. We have investigated the role of Ang1 in tumour neovascularization under clinical conditions and in animal models. The expression of Ang1 in clinical breast cancer specimens was analysed by using laser-capture microdissection and reverse transcriptase-linked polymerase chain reaction (RT-PCR) on RNA isolated from the samples. Despite the expression of Ang1 in many human breast cancer cell lines, the gene was expressed in only three of 21 breast cancer clinical specimens, even though its receptor, Tie2, is abundant in the vasculature of all of these tumours. Ang1 was then overexpressed in a human breast cancer cell line (MCF-7) on its own and in conjunction with FGF1, an angiogenic factor shown to be able to increase the tumorigenicity of MCF-7 cells. High concentrations of Ang1 were produced in the conditioned media of the transfected cells (range 156-820 ng ml(-1)). However, in contrast to its physiological role as promoter of angiogenesis, overexpression of Ang1 did not enhance tumour growth, but instead caused up to a 3-fold retardation of tumour growth (P = 0.003).

Immunoconjugates of geldanamycin and anti-HER2 monoclonal antibodies: antiproliferative activity on human breast carcinoma cell lines

BACKGROUND

HER2 is a membrane receptor whose overexpression is strongly associated with poor prognosis in breast carcinomas. Inhibition of HER2 activity can reduce tumor growth, which led to the development of Herceptin, an anti-HER2 monoclonal antibody (MAb) that is already in clinical use. However, the objective response rate to Herceptin monotherapy is quite low. HER2 activity can also be inhibited by the highly cytotoxic antibiotic geldanamycin (GA). However, GA is not used clinically because of its adverse toxicity. Our purpose was to enhance the inhibitory activity of anti-HER2 MAb by coupling it to GA.

METHODS

We synthesized 17-(3-aminopropylamino)GA (17-APA-GA) and conjugated it to the anti-HER2 MAb e21, to form e21 : GA. The noninternalizing anti-HER2 MAb AE1 was used as a control. Internalization assays and western blot analyses were used to determine whether the anti-HER2 MAbs and their immunoconjugates were internalized into HER2-expressing cells and reduced HER2 levels. All statistical tests were two-sided.

RESULTS

The immunoconjugate e21 : GA inhibited the proliferation of HER2-overexpressing cell lines better than unconjugated e21 (concentration required for 50% inhibition = 40 versus 1650 microg/mL, respectively). At 15 microg/mL, e21 : GA reduced HER2 levels by 86% within 16 hours, whereas unconjugated e21, 17-APA-GA, or AE1 : GA reduced HER2 levels by only 20%. These effects were not caused by release of 17-APA-GA from the immunoconjugate because immunoconjugates containing [(3)H]GA were stable in serum at 37 degrees C. Furthermore, e21 : GA did not significantly inhibit proliferation of the adult T-cell leukemia cell line HuT102, which is HER2 negative yet highly sensitive to GA.

CONCLUSIONS

Our findings suggest that conjugating GA to internalizing MAbs enhances the inhibitory effect of the MAbs. This approach might also be applied in cellular targeting via growth factors and may be of clinical interest.

Endoscopic mapping and surrogate markers for better surveillance in Barrett esophagus. A study of 700 biopsy specimens

Surveillance methods in Barrett esophagus (BE) using light microscopic examination of random biopsy specimens may miss focal dysplasia. In addition, dysplastic foci identified initially may not be relocated subsequently, making chemoprevention studies difficult. By using a special gastroscope, systematic mapping (4-quadrant biopsy specimens at 1-cm intervals) was performed in 22 patients (33 total mappings yielding 700 biopsy specimens). H&E, immunohistochemistry, and DNA ploidy analysis were performed. c-erbB-2 and positive Ki-67 were detected only in dysplastic sites; thus, their detection did not precede morphologically identifiable dysplasia. On the other hand, aneuploidy and p53 were detected in dysplastic and nondysplastic areas. p53 was correlated with dysplasia, and S-phase narrowly missed correlation, while aneuploidy was not correlated. PCNA and bcl-2 were ubiquitous, limiting their usefulness. On second maps, epithelial type was reidentified with 81% accuracy. A significant correlation was found between p53 and dysplasia. Sites of dysplasia and abnormal biomarkers could be relocated accurately by using endoscopic mapping. Therefore, mapping combined with biomarker studies may provide better surveillance and serve as a useful technique in chemoprevention studies.

KAI1 protein is down-regulated during the progression of human breast cancer

The KAI1 gene was identified as a metastasis suppressor gene for human prostate cancer. Recently, we showed that KAI1 mRNA levels were higher in an immortal, normal-like breast epithelial cell line and nonmetastatic breast cancer cell lines but lower substantially in highly metastatic breast cancer cell lines. In this study, we examined KAI1 protein expression in breast cancer cell lines by Western blot and immunohistochemical study. KAI1 protein levels paralleled KAI1 mRNA levels and were inversely correlated with the metastatic potential of breast cancer cells. Furthermore, we examined KAI1 protein expression immunohistochemically in specimens from 81 patients with breast cancer and then correlated the findings with the clinical and histopathological parameters of the patients. High levels of KAI1 protein expression were found in normal breast tissues and noninvasive breast cancer (ductal carcinoma in situ). In contrast, KAI1 expression was reduced in most of the infiltrating breast tumors. We found that, in general, more malignant tumors demonstrated significantly lower KAI1 expression (P = 0.004). Additionally, among 29 specimens demonstrating multiple stages of malignancy within a single specimen, 23 demonstrated significant differences in KAI1 expression between benign breast tissue, ductal carcinoma in situ, and invasive carcinoma. The higher the incidence for malignancy within a given specimen, the lower the KAI1 expression (P < 0.001). These data suggest that in advanced breast cancer, KAI1 expression is down-regulated. Therefore, KAI1 may be a potentially useful indicator of human breast cancer progression.