Analytical Validation of NavDx, a cfDNA-Based Fragmentomic Profiling Assay for HPV-Driven Cancers

The NavDx^® blood test analyzes tumor tissue modified viral (TTMV)-HPV DNA to provide a reliable means of detecting and monitoring HPV-driven cancers. The test has been clinically validated in a large number of independent studies and has been integrated into clinical practice by over 1000 healthcare providers at over 400 medical sites in the US. This Clinical Laboratory Improvement Amendments (CLIA), high complexity laboratory developed test, has also been accredited by the College of American Pathologists (CAP) and the New York State Department of Health. Here, we report a detailed analytical validation of the NavDx assay, including sample stability, specificity as measured by limits of blank (LOBs), and sensitivity illustrated via limits of detection and quantitation (LODs and LOQs). LOBs were 0-0.32 copies/μL, LODs were 0-1.10 copies/μL, and LOQs were <1.20-4.11 copies/μL, demonstrating the high sensitivity and specificity of data provided by NavDx. In-depth evaluations including accuracy and intra- and inter-assay precision studies were shown to be well within acceptable ranges. Regression analysis revealed a high degree of correlation between expected and effective concentrations, demonstrating excellent linearity (R² = 1) across a broad range of analyte concentrations. These results demonstrate that NavDx accurately and reproducibly detects circulating TTMV-HPV DNA, which has been shown to aid in the diagnosis and surveillance of HPV-driven cancers.

Detection of Occult Recurrence Using Circulating Tumor Tissue Modified Viral HPV DNA among Patients Treated for HPV-Driven Oropharyngeal Carcinoma

PURPOSE

Despite generally favorable outcomes, 15% to 25% of patients with human papillomavirus (HPV)-driven oropharyngeal squamous cell carcinoma (OPSCC) will have recurrence. Current posttreatment surveillance practices rely on physical examinations and imaging and are inconsistently applied. We assessed circulating tumor tissue modified viral (TTMV)-HPV DNA obtained during routine posttreatment surveillance among a large population of real-world patients.

EXPERIMENTAL DESIGN

This retrospective clinical case series included 1,076 consecutive patients across 108 U.S. sites who were ≥ 3 months posttreatment for HPV-driven OPSCC and who had one or more TTMV-HPV DNA tests (NavDx, Naveris Laboratories) obtained during surveillance between February 6, 2020, and June 29, 2021. Test results were compared with subsequent clinical evaluations.

RESULTS

Circulating TTMV-HPV DNA was positive in 80 of 1,076 (7.4%) patients, with follow-up available on all. At first positive surveillance testing, 21 of 80 (26%) patients had known recurrence while 59 of 80 (74%) patients were not known to have recurrent disease. Among these 59 patients, 55 (93%) subsequently had a confirmed recurrence, 2 patients had clinically suspicious lesions, and 2 had clinically "no evidence of disease" (NED) at last follow-up. To date, the overall positive predictive value of TTMV-HPV DNA testing for recurrent disease is 95% (N = 76/80). In addition, the point-in-time negative predictive value is 95% (N = 1,198/1,256).

CONCLUSIONS

These findings highlight the clinical potential for circulating TTMV-HPV DNA testing in routine practice. As a surveillance tool, TTMV-HPV DNA positivity was the first indication of recurrence in the majority of cases, pre-dating identification by routine clinical and imaging exams. These data may inform future clinical and guideline-endorsed strategies for HPV-driven malignancy surveillance. See related commentary by Colevas, p. 4171.

Chemotherapy-Induced Collagen IV Drives Cancer Cell Motility through Activation of Src and Focal Adhesion Kinase

Triple-negative breast cancer (TNBC) is the most aggressive and deadly subtype of breast cancer, accounting for 30,000 cases annually in the United States. While there are several clinical trials ongoing to identify new agents to treat TNBC, the majority of patients with TNBC are treated with anthracycline- or taxane-based chemotherapies in the neoadjuvant setting, followed by surgical resection and adjuvant chemotherapy. While many patients respond well to this approach, as many as 25% will suffer local or metastatic recurrence within 5 years. Understanding the mechanisms that drive recurrence after chemotherapy treatment is critical to improving survival for patients with TNBC. It is well established that the extracellular matrix (ECM), which provides structure and support to tissues, is a major driver of tumor growth, local invasion, and dissemination of cancer cells to distant metastatic sites. In the present study, we show that decellularized ECM (dECM) obtained from chemotherapy-treated mice increases motility of treatment-naïve breast cancer cells compared with vehicle-treated dECM. Tandem-mass-tag proteomics revealed that anthracycline- and taxane-based chemotherapies induce drug-specific changes in tumor ECM composition. The basement membrane protein collagen IV was significantly upregulated in the ECM of chemotherapy-treated mice and patients treated with neoadjuvant chemotherapy. Collagen IV drove invasion via activation of Src and focal adhesion kinase signaling downstream of integrin α1 and α2, and inhibition of collagen IV-driven signaling decreased motility in chemotherapy-treated dECM. These studies provide a novel mechanism by which chemotherapy may induce metastasis via its effects on ECM composition.

SIGNIFICANCE

Cytotoxic chemotherapy induces significant changes in the composition of tumor ECM, inducing a more invasive and aggressive phenotype in residual tumor cells following chemotherapy.

Discordance in Oncotype DX Breast Recurrence Score® Results for Bilateral Breast Cancer

BACKGROUND

The Oncotype DX Breast Recurrence Score^® assay is a clinically useful tool to determine the benefit of chemotherapy in the treatment of early-stage, hormone-receptor-positive breast cancer. Bilateral breast cancer (BBC) is found in ~ 5% of patients with breast cancer, and data regarding discordance of Oncotype DX results between BBC defined by current TAILORx subgroups are limited. Our goals are to study the rate of Oncotype DX discordance between BBC and investigate whether such differences can affect chemotherapy treatment discussions.

METHODS

Patients with BBC were identified in US samples submitted to Genomic Health for 21-gene testing between January 2019 and July 2020. The risk categories were defined as 0-25 and 26-100 as well as 0-17, 18-30, and 31-100 for all patients. Subgroup analysis was also performed for node-negative women age ≤ 50 years with Recurrence Score results of 0-15, 16-20, 21-25, and 26-100.

RESULTS

944 BBC patients with known nodal status (702 node negative, 242 node positive) were identified and included. Among node-negative patients aged > 50 years, the rate of discordance in Recurrence Score by group (0-25 and 26-100) was 4.2% (n = 598). For node-negative patients aged ≤ 50 years, the risk group was discordant in < 3% when considering the risk grouping of 0-25 and 26-100. However, upon subgroup analysis based on TAILORx analysis, the rate of discordance was 48.1% in these younger patients (n = 104).

CONCLUSIONS

This study shows that a clinically relevant rate of discordance in Oncotype DX results in patients with BBC may impact medical decision-making regarding chemotherapy.

Decellularized extracellular matrix scaffolds identify full-length collagen VI as a driver of breast cancer cell invasion in obesity and metastasis

The extracellular matrix (ECM), a major component of the tumor microenvironment, promotes local invasion to drive metastasis. Here, we describe a method to study whole-tissue ECM effects from disease states associated with metastasis on tumor cell phenotypes and identify the individual ECM proteins and signaling pathways that are driving these effects. We show that decellularized ECM from tumor-bearing and obese mammary glands drives TNBC cell invasion. Proteomics of the ECM from the obese mammary gland led us to identify full-length collagen VI as a novel driver of TNBC cell invasion whose abundance in tumor stroma increases with body mass index in human TNBC patients. Last, we describe the mechanism by which collagen VI contributes to TNBC cell invasion via NG2-EGFR cross-talk and MAPK signaling. Overall, these studies demonstrate the value of decellularized ECM scaffolds obtained from tissues to identify novel functions of the ECM.

Abstract 1933: Tissue print Vmem imaging: Visualizing bioelectric signatures in cancer

Work in models of embryonic development shows that membrane voltage, or resting potential (Vmem), regulates cell behaviors that are disrupted in cancer, including proliferation, migration, apoptosis, homeostasis, and cell-cell signaling. Normal cells and tissues maintain stereotypical patterns of Vmem and these patterns are recognizable in Vmem Imaging as bioelectric signatures. In embryonic tissues, cells that are relatively undifferentiated are usually less negative (depolarized) than fully differentiated cells, and different cell lineages have characteristic bioelectric signatures. Recently, the development of innovative imaging technologies using Voltage Sensitive Dyes (VSDs) allows the visualization of Vmem in living cells and tissues. In culture, Vmem Imaging using VSDs can readily differentiate between sister breast cancer cell lines of low and high metastatic potential (EpH4 and EpH4.2, respectively). Although the cultures are identical in bright field images, Vmem Imaging shows a dramatically more heterogeneous bioelectric signature for EpH4.2 than for EpH4 cells, consistent with reduced gap junctional communication. One of the challenges of Vmem Imaging has been the limited thickness of tissue that can be analyzed using the VSDs (about 50 microns). To overcome this limitation, we have combined innovative Tissue Print technologies with Vmem Imaging in order to visualize patterns of electric potential in living cancer cells obtained from human surgical specimens. Tissue Prints are touch preps that transfer a thin layer of viable cells to a nitrocellulose membrane as an oriented imprint; biomarkers identified on these tissues prints can be mapped back to the source tissue to establish pathology and gene expression correlations. Tissue Print Vmem Imaging of radical prostatectomy specimens shows differentiation of bioelectric signatures between cancer and adjacent benign tissue and between cancer of different grades (Gleason pattern 3 and pattern 4). Such differences in bioelectric signatures represent unexplored cancer phenotypes that are made accessible by Tissue Print Vmem Imaging technologies.

Citation Format: Dany S. Adams, Brian H. Tracey, Larry Takiff, James Kearns, Stephen P. Naber, Sandra M. Gaston. Tissue print Vmem imaging: Visualizing bioelectric signatures in cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1933.

American Joint Committee on Cancer's Staging System for Breast Cancer, Eighth Edition: What the Radiologist Needs to Know

The TNM staging system for cancer was developed by Pierre Denoix in France in the 1940s and 1950s. The North American effort to standardize the TNM system for cancer staging was first organized in 1959 as the American Joint Committee for Cancer Staging and End-Results Reporting, which is now the American Joint Committee on Cancer (AJCC). The most recent edition of the AJCC Cancer Staging Manual, the eighth edition, was globally adopted on January 1, 2018. Previous editions of the manual have relied on anatomic methods of staging alone, which used population-based survival data to predict clinical outcomes. In the era of precision medicine, the major change in the eighth edition is the incorporation of prognostic biomarkers to more accurately predict clinical outcomes and treatment response on an individual basis, without relying solely on the anatomic extent of disease. Factors such as tumor grade, hormone receptor and oncogene expression, and multigene panel recurrence scores are now integrated with anatomic information to yield a final prognostic stage group, which will provide better stratification of patient prognosis. The purpose of this article is to review the major changes in the AJCC eighth edition for breast cancer staging, review anatomic TNM staging, familiarize the radiologist with prognostic biomarkers and prognostic staging, and identify key sites of disease that may alter clinical management. ^©RSNA, 2018.

The fibroblast Tiam1-osteopontin pathway modulates breast cancer invasion and metastasis

Background

The tumor microenvironment has complex effects in cancer pathophysiology that are not fully understood. Most cancer therapies are directed against malignant cells specifically, leaving pro-malignant signals from the microenvironment unaddressed. Defining specific mechanisms by which the tumor microenvironment contributes to breast cancer metastasis may lead to new therapeutic approaches against advanced breast cancer.

Methods

We use a novel method for manipulating three-dimensional mixed cell co-cultures, along with studies in mouse xenograft models of human breast cancer and a histologic study of human breast cancer samples, to investigate how breast cancer-associated fibroblasts affect the malignant behaviors of breast cancer cells.

Results

Altering fibroblast Tiam1 expression induces changes in invasion, migration, epithelial-mesenchymal transition, and cancer stem cell characteristics in associated breast cancer cells. These changes are both dependent on fibroblast secretion of osteopontin and also long-lasting even after cancer cell dissociation from the fibroblasts, indicating a novel Tiam1-osteopontin pathway in breast cancer-associated fibroblasts. Notably, inhibition of fibroblast osteopontin with low doses of a novel small molecule prevents lung metastasis in a mouse model of human breast cancer metastasis. Moreover, fibroblast expression patterns of Tiam1 and osteopontin in human breast cancers show converse changes correlating with invasion, supporting the hypothesis that this pathway in tumor-associated fibroblasts regulates breast cancer invasiveness in human disease and is thus clinically relevant.

Conclusions

These findings suggest a new therapeutic paradigm for preventing breast cancer metastasis. Pro-malignant signals from the tumor microenvironment with long-lasting effects on associated cancer cells may perpetuate the metastatic potential of developing cancers. Inhibition of these microenvironment signals represents a new therapeutic strategy against cancer metastasis that enables targeting of stromal cells with less genetic plasticity than associated cancer cells and opens new avenues for investigation of novel therapeutic targets and agents.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-016-0674-8) contains supplementary material, which is available to authorized users.

Granular cell tumor of the stellate ganglion presenting with Horner's syndrome

We report a granular cell tumor (GCT) that occurred within the stellate ganglion of a 26-year-old woman who initially presented with a unilateral Horner's syndrome and progressive right upper extremity pain. We also review the literature related to the differential diagnoses of such a cervicothoracic tumor, with particular emphasis on the embryologic origin of these possibilities. GCT are rare tumors of Schwann cell origin which are more often found in subcutaneous locations than in relation to neural elements. In this woman, a mass identified on preoperative imaging was positioned anterolateral to the T1 vertebral body and displaced the vertebral artery anteriorly. During surgery, the lesion was observed within the sympathetic chain in the area of the stellate ganglion. The sympathetic chain was transected above and below the mass in order to achieve an adequate resection. The pathology demonstrated polygonal cells with diffuse eosinophilic granular cytoplasm positive for CD68 (a marker of lysosomes) and S-100 (a marker of neural crest derivatives) which established the diagnosis of GCT. This is the first patient, to our knowledge, with a granular cell tumor arising from the stellate ganglion.

Human breast progenitor cell numbers are regulated by WNT and TBX3

BACKGROUND

Although human breast development is mediated by hormonal and non-hormonal means, the mechanisms that regulate breast progenitor cell activity remain to be clarified. This limited understanding of breast progenitor cells has been due in part to the lack of appropriate model systems to detect and characterize their properties.

METHODS

To examine the effects of WNT signaling and TBX3 expression on progenitor activity in the breast, primary human mammary epithelial cells (MEC) were isolated from reduction mammoplasty tissues and transduced with lentivirus to overexpress WNT1 or TBX3 or reduce expression of their cognate receptors using shRNA. Changes in progenitor activity were quantified using characterized assays. We identified WNT family members expressed by cell populations within the epithelium and assessed alterations in expression of WNT family ligands by MECs in response to TBX3 overexpression and treatment with estrogen and progesterone.

RESULTS

Growth of MECs on collagen gels resulted in the formation of distinct luminal acinar and basal ductal colonies. Overexpression of TBX3 in MECs resulted in increased ductal colonies, while shTBX3 expression diminished both colony types. Increased WNT1 expression led to enhanced acinar colony formation, shLRP6 decreased both types of colonies. Estrogen stimulated the formation of acinar colonies in control MEC, but not shLRP6 MEC. Formation of ductal colonies was enhanced in response to progesterone. However, while shLRP6 decreased MEC responsiveness to progesterone, shTBX3 expression did not alter this response.

CONCLUSIONS

We identified two phenotypically distinguishable lineage-committed progenitor cells that contribute to different structural elements and are regulated via hormonal and non-hormonal mechanisms. WNT signaling regulates both types of progenitor activity. Progesterone favors the expansion of ductal progenitor cells, while estrogen stimulates the expansion of acinar progenitor cells. Paracrine WNT signaling is stimulated by estrogen and progesterone, while autocrine WNT signaling is induced by the embryonic T-box transcription factor TBX3.

Anatomical localization of progenitor cells in human breast tissue reveals enrichment of uncommitted cells within immature lobules

INTRODUCTION

Lineage tracing studies in mice have revealed the localization and existence of lineage-restricted mammary epithelial progenitor cells that functionally contribute to expansive growth during puberty and differentiation during pregnancy. However, extensive anatomical differences between mouse and human mammary tissues preclude the direct translation of rodent findings to the human breast. Therefore, here we characterize the mammary progenitor cell hierarchy and identify the anatomic location of progenitor cells within human breast tissues.

METHODS

Mammary epithelial cells (MECs) were isolated from disease-free reduction mammoplasty tissues and assayed for stem/progenitor activity in vitro and in vivo. MECs were sorted and evaluated for growth on collagen and expression of lineages markers. Breast lobules were microdissected and individually characterized based on lineage markers and steroid receptor expression to identify the anatomic location of progenitor cells. Spanning-tree progression analysis of density-normalized events (SPADE) was used to identify the cellular hierarchy of MECs within lobules from high-dimensional cytometry data.

RESULTS

Integrating multiple assays for progenitor activity, we identified the presence of luminal alveolar and basal ductal progenitors. Further, we show that Type I lobules of the human breast were the least mature, demonstrating an unrestricted pattern of expression of luminal and basal lineage markers. Consistent with this, SPADE analysis revealed that immature lobules were enriched for basal progenitor cells, while mature lobules consisted of increased hierarchal complexity of cells within the luminal lineages.

CONCLUSIONS

These results reveal underlying differences in the human breast epithelial hierarchy and suggest that with increasing glandular maturity, the epithelial hierarchy also becomes more complex.

NDY1/KDM2B functions as a master regulator of polycomb complexes and controls self-renewal of breast cancer stem cells

The JmjC domain histone H3K36me2/me1 demethylase NDY1/KDM2B is overexpressed in various types of cancer. Here we show that knocking down NDY1 in a set of 10 cell lines derived from a broad range of human tumors inhibited their anchorage-dependent and anchorage-independent growth by inducing senescence and/or apoptosis in some and by inhibiting G1 progression in all. We further show that the knockdown of NDY1 in mammary adenocarcinoma cell lines decreased the number, size, and replating efficiency of mammospheres and downregulated the stem cell markers ALDH and CD44, while upregulating CD24. Together, these findings suggest that NDY1 is required for the self-renewal of cancer stem cells and are in agreement with additional findings showing that tumor cells in which NDY1 was knocked down undergo differentiation and a higher number of them is required to induce mammary adenocarcinomas, upon orthotopic injection in animals. Mechanistically, NDY1 functions as a master regulator of a set of miRNAs that target several members of the polycomb complexes PRC1 and PRC2, and its knockdown results in the de-repression of these miRNAs and the downregulation of their polycomb targets. Consistent with these observations, NDY1/KDM2B is expressed at higher levels in basal-like triple-negative breast cancers, and its overexpression is associated with higher rates of relapse after treatment. In addition, NDY1-regulated miRNAs are downregulated in both normal and cancer mammary stem cells. Finally, in primary human breast cancer, NDY1/KDM2B expression correlates negatively with the expression of the NDY1-regulated miRNAs and positively with the expression of their PRC targets.

Pregnancy-associated breast cancers are driven by differences in adipose stromal cells present during lactation

INTRODUCTION

The prognosis of breast cancer is strongly influenced by the developmental stage of the breast when the tumor is diagnosed. Pregnancy-associated breast cancers (PABCs), cancers diagnosed during pregnancy, lactation, or in the first postpartum year, are typically found at an advanced stage, are more aggressive and have a poorer prognosis. Although the systemic and microenvironmental changes that occur during post-partum involution have been best recognized for their role in the pathogenesis of PABCs, epidemiological data indicate that PABCs diagnosed during lactation have an overall poorer prognosis than those diagnosed during involution. Thus, the physiologic and/or biological events during lactation may have a significant and unrecognized role in the pathobiology of PABCs.

METHODS

Syngeneic in vivo mouse models of PABC were used to examine the effects of system and stromal factors during pregnancy, lactation and involution on mammary tumorigenesis. Mammary adipose stromal cell (ASC) populations were isolated from mammary glands and examined by using a combination of in vitro and in vivo functional assays, gene expression analysis, and molecular and cellular assays. Specific findings were further investigated by immunohistochemistry in mammary glands of mice as well as in functional studies using ASCs from lactating mammary glands. Additional findings were further investigated using human clinical samples, human stromal cells and using in vivo xenograft assays.

RESULTS

ASCs present during lactation (ASC-Ls), but not during other mammary developmental stages, promote the growth of carcinoma cells and angiogenesis. ASCs-Ls are distinguished by their elevated expression of cellular retinoic acid binding protein-1 (crabp1), which regulates their ability to retain lipid. Human breast carcinoma-associated fibroblasts (CAFs) exhibit traits of ASC-Ls and express crabp1. Inhibition of crabp1in CAFs or in ASC-Ls abolished their tumor-promoting activity and also restored their ability to accumulate lipid.

CONCLUSIONS

These findings imply that (1) PABC is a complex disease, which likely has different etiologies when diagnosed during different stages of pregnancy; (2) both systemic and local factors are important for the pathobiology of PABCs; and (3) the stromal changes during lactation play a distinct and important role in the etiology and pathogenesis of PABCs that differ from those during post-lactational involution.

Obesity promotes breast cancer by CCL2-mediated macrophage recruitment and angiogenesis

Obesity is one of the most important preventable causes of cancer and the most significant risk factor for breast cancer in postmenopausal women. Compared with lean women, obese women are more likely to be diagnosed with a larger, higher grade tumor, an increased incidence of lymph node metastases, and elevated risk of distant recurrence. However, the mechanisms connecting obesity to the pathogenesis of breast cancer are poorly defined. Here, we show that during obesity, adipocytes within human and mouse breast tissues recruit and activate macrophages through a previously uncharacterized CCL2/IL-1β/CXCL12 signaling pathway. Activated macrophages in turn promote stromal vascularization and angiogenesis even before the formation of cancer. Recapitulating these changes using a novel humanized breast cancer model was sufficient to promote angiogenesis and prime the microenvironment prior to neoplastic transformation for accelerated breast oncogenesis. These findings provide a mechanistic role for adipocytes and macrophages before carcinogenesis that may be critical for prevention and treatment of obesity-related cancer.

Epigallocatechin-3-gallate inhibits stem-like inflammatory breast cancer cells

Inflammatory Breast Cancer (IBC) is a highly aggressive form of cancer characterized by high rates of proliferation, lymphangiogenesis and metastasis, and an overall poor survival. As regular green tea consumption has been associated with improved prognosis of breast cancer patients, including decreased risk of recurrence, here the effects of the green tea polyphenol epigallocatechin-3-gallate (EGCG) were tested on two IBC lines: SUM-149 and SUM-190. EGCG decreased expression of genes that promote proliferation, migration, invasion, and survival. Consistently, growth, invasive properties, and survival of IBC cells were reduced by EGCG treatment. EGCG also reduced lymphangiogenesis-promoting genes, in particular VEGF-D. Conditioned media from EGCG-treated IBC cells displayed decreased VEGF-D secretion and reduced ability to promote lymphangiogenesis in vitro as measured by hTERT-HDLEC lymphatic endothelial cell migration and tube formation. Tumorsphere formation by SUM-149 cells was robustly inhibited by EGCG, suggesting effects on self-renewal ability. Stem-like SUM-149 cells with high aldehyde dehydrogenase (ALDH) activity, previously implicated in poor patient prognosis, were isolated. EGCG treatment reduced growth and induced apoptosis of the stem-like SUM-149 cells in culture. In an orthotopic mouse model, EGCG decreased growth of pre-existing tumors derived from ALDH-positive stem-like SUM-149 cells and their expression of VEGF-D, which correlated with a significant decrease in peritumoral lymphatic vessel density. Thus, EGCG inhibits the overall aggressive IBC phenotype. Reduction of the stem-like cell compartment by EGCG may explain the decreased risk of breast cancer recurrence among green tea drinkers. Recent clinical trials demonstrate the efficacy of green tea polyphenol extracts in treatment of prostate cancer and lymphocytic leukemia with low toxicity. Given the poor prognosis of IBC patients, our findings suggest further exploration of EGCG or green tea in combinatorial treatments against active IBC disease or in maintenance regimens to avoid recurrence is warranted.

Abstract A94: Epigallocatechin-3-gallate inhibits stem-like inflammatory breast cancer cells

Inflammatory Breast Cancer (IBC) is a highly aggressive form of cancer characterized by an unusual growth pattern with nests of tumor emboli rather than a solid mass, rapid spread via lymphatic dissemination and high proliferative rates. Multi-modality therapies have improved survival but the outcome still remains poorer for these patients. Given the potent anti-cancer properties of green tea polyphenols, including epigallocatechin-3-gallate (EGCG), here we tested the hypothesis that EGCG inhibits IBC cells. Two IBC cell lines were studied. SUM-149 cells have a triple negative receptor status (ER-, PR-, Her-2-), while SUM-190 cells are ER-, PR- and Her-2 amplified. Doses of EGCG used ranged from 5 μg/ml (10.9 μM) to 160 μg/ml (349.1 μM), depending upon the presence of serum which inactivates the polyphenol. Treatment with 40 μg/ml (87.3 μM) EGCG decreased mRNA expression of genes that promote migration and invasion (RHOC, FN1, CDH1 and VIM), lymphangiogenesis (VEGF-D), proliferation (CCND1), and survival (BCL-XL) in both lines. Consistently, EGCG treatment resulted in decreased invasive phenotype, ability for anchorage independent growth and viability, as judged by Matrigel outgrowth, soft agar colony assays and ATP assays. Substantial apoptosis was detected starting at 80 μg/ml (174.5 μM) and 160 μg/ml (349.1 μM) of EGCG for SUM-149 and SUM-190 cells, respectively. Conditioned media isolated from EGCG-treated IBC cells displayed decreased secretion of the pro-lymphangiogenic factor VEGF-D and reduced ability to promote cultured hTERT-HDLEC lymphatic endothelial cell migration in wound healing assays and tube formation in Matrigel, processes critical for lymphangiogenesis. The poor clinical outcome of IBC patients has been attributed to a stem-like cell compartment, which is characterized by increased aldehyde dehydrogenase (ALDH) activity. The SUM-149, but not the SUM-190, line has been reported to contain such a stem-like compartment. EGCG treatment inhibited SUM-149 cell spheroid formation and decreased the size of pre-formed spheroids, suggesting efficacy on the cancer stem-like cells. ALDH-positive SUM-149 cells were isolated using an ALDEFUOR Fluorescence Activated Cell Sorting-based assay. EGCG treatment of these cells led to a significant dose-dependent decrease in ATP levels. Furthermore, doses of 80 and 160 μg/ml EGCG induced apoptosis, as judged by increased Caspase-3 and -7 activities. ALDH-positive SUM-149 cancer stem-like cells were used in an orthotopic mammary fat pad mouse model (n = 6/ group). After 25 days, palpable tumors were detected in all of the mice. The experimental group was given a 0.1 ml intraperitoneal injection of 16.5 mg/kg EGCG while the control group was injected with vehicle 1X PBS. Treatment was administered five times a week for five weeks and then daily for one last week for a total of 43 days. EGCG significantly reduced the growth of pre-existing tumors derived from ALDH-positive stem-like SUM-149 cells such that at the end of the experiment a 37.7 ± 4.4% decrease in tumor volume was seen in the EGCG-treated vs control groups. RT-PCR and immunoblot analyses revealed substantially reduced expression of VEGF-D RNA and VEGF-D protein within tumor tissues of EGCG-treated vs control animals, which correlated with a trend toward decreased peritumoral lymphatic vessel density. Thus, EGCG has pleiotropic inhibitory effects on IBC cells, including the cancer stem-like cell compartment believed to be responsible for recurrence. Recent clinical trials using various green tea polyphenol preparations have shown efficacy in treatment of prostate cancer and lymphocytic leukemia, and low toxicity. Our studies suggest the use of EGCG or green tea in combination with standard therapeutic modalities for IBC patients warrants further exploration.

Citation Format: Nora D. Mineva, K. Eric Paulson, Stephen P. Naber, Amy S. Yee, Gail E. Sonenshein. Epigallocatechin-3-gallate inhibits stem-like inflammatory breast cancer cells. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr A94.

Functional heterogeneity of breast fibroblasts is defined by a prostaglandin secretory phenotype that promotes expansion of cancer-stem like cells

Fibroblasts are important in orchestrating various functions necessary for maintaining normal tissue homeostasis as well as promoting malignant tumor growth. Significant evidence indicates that fibroblasts are functionally heterogeneous with respect to their ability to promote tumor growth, but markers that can be used to distinguish growth promoting from growth suppressing fibroblasts remain ill-defined. Here we show that human breast fibroblasts are functionally heterogeneous with respect to tumor-promoting activity regardless of whether they were isolated from normal or cancerous breast tissues. Rather than significant differences in fibroblast marker expression, we show that fibroblasts secreting abundant levels of prostaglandin (PGE2), when isolated from either reduction mammoplasty or carcinoma tissues, were both capable of enhancing tumor growth in vivo and could increase the number of cancer stem-like cells. PGE2 further enhanced the tumor promoting properties of fibroblasts by increasing secretion of IL-6, which was necessary, but not sufficient, for expansion of breast cancer stem-like cells. These findings identify a population of fibroblasts which both produce and respond to PGE2, and that are functionally distinct from other fibroblasts. Identifying markers of these cells could allow for the targeted ablation of tumor-promoting and inflammatory fibroblasts in human breast cancers.

Genetic predisposition directs breast cancer phenotype by dictating progenitor cell fate

Women with inherited mutations in the BRCA1 gene have increased risk of developing breast cancer but also exhibit a predisposition for the development of aggressive basal-like breast tumors. We report here that breast epithelial cells derived from patients harboring deleterious mutations in BRCA1 (BRCA1(mut /+) give rise to tumors with increased basal differentiation relative to cells from BRCA1+/+ patients. Molecular analysis of disease-free breast tissues from BRCA1(mut /+) patients revealed defects in progenitor cell lineage commitment even before cancer incidence. Moreover, we discovered that the transcriptional repressor Slug is an important functional suppressor of human breast progenitor cell lineage commitment and differentiation and that it is aberrantly expressed in BRCA1(mut /+) tissues. Slug expression is necessary for increased basal-like phenotypes prior to and after neoplastic transformation. These findings demonstrate that the genetic background of patient populations, in addition to affecting incidence rates, significantly impacts progenitor cell fate commitment and, therefore, tumor phenotype.

Mapping the cellular and molecular heterogeneity of normal and malignant breast tissues and cultured cell lines

Introduction

Normal and neoplastic breast tissues are comprised of heterogeneous populations of epithelial cells exhibiting various degrees of maturation and differentiation. While cultured cell lines have been derived from both normal and malignant tissues, it remains unclear to what extent they retain similar levels of differentiation and heterogeneity as that found within breast tissues.

Methods

We used 12 reduction mammoplasty tissues, 15 primary breast cancer tissues, and 20 human breast epithelial cell lines (16 cancer lines, 4 normal lines) to perform flow cytometry for CD44, CD24, epithelial cell adhesion molecule (EpCAM), and CD49f expression, as well as immunohistochemistry, and in vivo tumor xenograft formation studies to extensively analyze the molecular and cellular characteristics of breast epithelial cell lineages.

Results

Human breast tissues contain four distinguishable epithelial differentiation states (two luminal phenotypes and two basal phenotypes) that differ on the basis of CD24, EpCAM and CD49f expression. Primary human breast cancer tissues also contain these four cellular states, but in altered proportions compared to normal tissues. In contrast, cultured cancer cell lines are enriched for rare basal and mesenchymal epithelial phenotypes, which are normally present in small numbers within human tissues. Similarly, cultured normal human mammary epithelial cell lines are enriched for rare basal and mesenchymal phenotypes that represent a minor fraction of cells within reduction mammoplasty tissues. Furthermore, although normal human mammary epithelial cell lines exhibit features of bi-potent progenitor cells they are unable to differentiate into mature luminal breast epithelial cells under standard culture conditions.

Conclusions

As a group breast cancer cell lines represent the heterogeneity of human breast tumors, but individually they exhibit increased lineage-restricted profiles that fall short of truly representing the intratumoral heterogeneity of individual breast tumors. Additionally, normal human mammary epithelial cell lines fail to retain much of the cellular diversity found in human breast tissues and are enriched for differentiation states that are a minority in breast tissues, although they do exhibit features of bi-potent basal progenitor cells. These findings suggest that collections of cell lines representing multiple cell types can be used to model the cellular heterogeneity of tissues.

The role of fibroblast Tiam1 in tumor cell invasion and metastasis

The co-evolution of tumors and their microenvironment involves bidirectional communication between tumor cells and tumor-associated stroma. Various cell types are present in tumor-associated stroma, of which fibroblasts are the most abundant. The Rac exchange factor Tiam1 is implicated in multiple signaling pathways in epithelial tumor cells and lack of Tiam1 in tumor cells retards tumor growth in Tiam1 knock-out mouse models. Conversely, tumors arising in Tiam1 knock-out mice have increased invasiveness. We have investigated the role of Tiam1 in tumor-associated fibroblasts as a modulator of tumor cell invasion and metastasis, using retroviral delivery of short hairpin RNA to suppress Tiam1 levels in three different experimental models. In spheroid co-culture of mammary epithelial cells and fibroblasts, Tiam1 silencing in fibroblasts led to increased epithelial cell outgrowth into matrix. In tissue-engineered human skin, Tiam1 silencing in dermal fibroblasts led to increased invasiveness of epidermal keratinocytes with premalignant features. In a model of human breast cancer in mice, co-implantation of mammary fibroblasts inhibited tumor invasion and metastasis, which was reversed by Tiam1 silencing in co-injected fibroblasts. These results suggest that stromal Tiam1 may play a role in modulating the effects of the tumor microenvironment on malignant cell invasion and metastasis. This suggests a set of pathways for further investigation, with implications for future therapeutic targets.

Abstract LB-265: Mutations in BRCA1 impair breast epithelial differentiation through the transcriptional repressor Slug

Human breast cancers can be broadly classified based on their molecular and gene expression profiles into luminal and basal-like tumors. These tumor subtypes express markers corresponding to the two major differentiation states of epithelial cells in the breast: luminal cells that line the breast ducts and the outer myoepithelial/basal cells that provide contractile functions. Women with inherited mutations in the BRCA1 gene have increased breast cancer risk and also exhibit a specific predisposition to the development of aggressive basal-like breast cancers. Accumulating evidence suggests that BRCA1 has a role in breast epithelial differentiation and we wanted to further understand how this could contribute to the formation of basal-like tumors. Microarray, flow cytometry and immunohistochemical analysis of breast epithelial cells from disease-free women harboring deleterious mutations in BRCA1 (BRCA1 mut/+) compared to those from BRCA1 +/+ reduction mammoplasties showed an increase in markers of basal differentiation and a decrease in markers of luminal differentiation. We also created breast cancers from single cell suspensions of BRCA1 mut/+ and BRCA1 +/+ epithelial cells that had been transformed with identical oncogenes and injected into humanized mammary fat pads. Tumors derived from BRCA1 mut/+ cells had increased basal differentiation relative to cells obtained from BRCA1 +/+ patients, indicating that the perturbed differentiation evident prior to neoplastic transformation was mirrored in the tumors. Pathway analysis of the microarray data comparing BRCA1 mut/+ and BRCA1 +/+ cells from disease-free tissue indicated that signaling components relating to the transcriptional repressor Slug were overexpressed in BRCA1 mut/+ tissues. We confirmed that Slug protein levels were elevated in BRCA1 mut/+ tissues and in human tumors from BRCA1 mutation carriers. RNAi-mediated downregulation of slug in primary breast epithelial cells and cell lines derived from BRCA1 mut/+ tissue as well as breast cancer cell lines known to harbor BRCA1 mutations, led to a decrease in markers of basal differentiation, indicating that elevated Slug protein levels seen in BRCA1-associated tissues and tumors are contributing to the basal phenotype. Furthermore, RNAi-mediated knockdown of BRCA1 led to an increase in Slug protein expression and breast cancer cell lines harboring BRCA1 mutations showed an increase in Slug protein stability, indicating that loss of BRCA1 protein by mutation contributes to elevated Slug protein levels. These results reveal an important mechanism by which BRCA1 can regulate breast epithelial differentiation and may explain how, in addition to affecting incidence rates, the genetic background of patients could impact tumor phenotype.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-265.

Distinct roles of the three Akt isoforms in lactogenic differentiation and involution

The three Akt isoforms differ in their ability to transduce oncogenic signals initiated by the Neu and PyMT oncogenes in mammary epithelia. As a result, ablation of Akt1 inhibits and ablation of Akt2 accelerates mammary tumor development by both oncogenes, while ablation of Akt3 is phenotypically almost neutral. Since the risk of breast cancer development in humans correlates with multiple late pregnancies, we embarked on a study to determine whether individual Akt isoforms also differ in their ability to transduce hormonal and growth factor signals during pregnancy, lactation and post-lactation involution. The results showed that the ablation of Akt1 delays the differentiation of the mammary epithelia during pregnancy and lactation, and that the ablation of Akt2 has the opposite effect. Finally, ablation of Akt3 results in minor defects, but its phenotype is closer to that of the wild type mice. Whereas the phenotype of the Akt1 ablation is cell autonomous, that of Akt2 is not. The ablation of Akt1 promotes apoptosis and accelerates involution, whereas the ablation of Akt2 inhibits apoptosis and delays involution. Mammary gland differentiation during pregnancy depends on the phosphorylation of Stat5a, which is induced by prolactin, a hormone that generates signals transduced via Akt. Here we show that the ablation of Akt1, but not the ablation of Akt2 or Akt3 interferes with the phosphorylation of Stat5a during late pregnancy and lactation. We conclude that the three Akt isoforms have different roles in mammary gland differentiation during pregnancy and this may reflect differences in hormonal signaling.

Genetic mapping in mice identifies DMBT1 as a candidate modifier of mammary tumors and breast cancer risk

Low-penetrance breast cancer susceptibility alleles seem to play a significant role in breast cancer risk but are difficult to identify in human cohorts. A genetic screen of 176 N2 backcross progeny of two Trp53(+/-) strains, BALB/c and C57BL/6, which differ in their susceptibility to mammary tumors, identified a modifier of mammary tumor susceptibility in an approximately 25-Mb interval on mouse chromosome 7 (designated SuprMam1). Relative to heterozygotes, homozygosity for BALB/c alleles of SuprMam1 significantly decreased mammary tumor latency from 70.7 to 61.1 weeks and increased risk twofold (P = 0.002). Dmbt1 (deleted in malignant brain tumors 1) was identified as a candidate modifier gene within the SuprMam1 interval because it was differentially expressed in mammary tissues from BALB/c-Trp53(+/-) and C57BL/6-Trp53(+/-) mice. Dmbt1 mRNA and protein was reduced in mammary glands of the susceptible BALB/c mice. Immunohistochemical staining demonstrated that DMBT1 protein expression was also significantly reduced in normal breast tissue from women with breast cancer (staining score, 1.8; n = 46) compared with cancer-free controls (staining score, 3.9; n = 53; P < 0.0001). These experiments demonstrate the use of Trp53(+/-) mice as a sensitized background to screen for low-penetrance modifiers of cancer. The results identify a novel mammary tumor susceptibility locus in mice and support a role for DMBT1 in suppression of mammary tumors in both mice and women.

Systemic stromal effects of estrogen promote the growth of estrogen receptor-negative cancers

Numerous hormonal factors contribute to the lifetime risk of breast cancer development. These include inherited genetic mutations, age of menarche, age of menopause, and parity. Inexplicably, there is evidence indicating that ovariectomy prevents the formation of both estrogen receptor (ER)-positive and ER-negative breast cancers, suggesting that ER-negative breast cancers are dependent on ovarian hormones for their formation. To examine the mechanism(s) by which this may be occurring, we investigated the hypothesis that steroid hormones promote the outgrowth of ER-negative cancers by influencing host cell types distinct from the mammary epithelial cells. We used a novel xenograft mouse model of parturition-induced breast carcinoma formation, in which the tumors that arise following pregnancy lack the expression of nuclear hormone receptors, thereby recapitulating many clinical cases of this disease. Despite lacking ER expression, the tumors arising following pregnancy in this model require circulating estrogens for their formation. Moreover, increasing the levels of circulating estrogens sufficed to promote the formation and progression of ER-negative cancers, which was accompanied by a systemic increase in host angiogenesis and was attendant with the recruitment of bone marrow-derived stromal cells. Furthermore, bone marrow cells from estrogen-treated mice were sufficient to promote tumor growth. These results reveal a novel mechanism by which estrogens promote the growth of ER-negative cancers.

Akt1 ablation inhibits, whereas Akt2 ablation accelerates, the development of mammary adenocarcinomas in mouse mammary tumor virus (MMTV)-ErbB2/neu and MMTV-polyoma middle T transgenic mice

Ample evidence to date links the phosphatidylinositol 3-kinase-regulated protein kinase Akt with the induction and progression of human cancer, including breast cancer. However, there are three Akt isoforms with limited information about their specificity during oncogenesis. This study addresses the role of the three isoforms in polyoma middle T (PyMT) and ErbB2/Neu-driven mammary adenocarcinomas in mice. The effects of ablation of Akt1, Akt2, and Akt3 on the induction and the biology of these tumors were dramatically different, with ablation of Akt1 inhibiting, ablation of Akt2 accelerating, and ablation of Akt3 having a small, not statistically significant, inhibitory effect on tumor induction by both transgenes. Whereas PyMT-induced tumors are all invasive, Akt1(-/-)Neu-induced tumors are more invasive than Akt2(-/-)Neu-induced tumors. Invasiveness, however, does not always correlate with metastasis. Ablation of individual Akt isoforms does not affect the development of the mammary gland during puberty or the expression of the transgenes. Akt ablation, therefore, influences tumor induction by modulating transgene-induced oncogenic signaling. Immunostaining for Ki-67 and cyclin D1 and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assays on tissue sections revealed that the delay of tumor induction in Akt1 knockout mice is due to the inhibitory effects of Akt1 ablation on cell proliferation and survival. Given that these animal models exhibit significant similarities to human breast cancer, the results of the present study may have significant translational implications because they may influence how Akt inhibitors will be used in the treatment of human cancer.

A mouse model of human breast cancer metastasis to human bone

Currently, an in vivo model of human breast cancer metastasizing from the orthotopic site to bone does not exist, making it difficult to study the many steps of skeletal metastasis. Moreover, models used to identify the mechanisms by which breast cancer metastasizes to bone are limited to intracardiac injection, which seeds the cancer cells directly into the circulation, thus bypassing the early steps in the metastatic process. Such models do not reflect the full process of metastasis occurring in patients. We have developed an animal model of breast cancer metastasis in which the breast cancer cells and the bone target of osteotropic metastasis are both of human origin. The engrafted human bone is functional, based on finding human IgG in the mouse bloodstream, human B cells in the mouse spleen, and normal bone histology. Furthermore, orthotopic injection of a specific human breast cancer cell line, SUM1315 (derived from a metastatic nodule in a patient), later resulted in both bone and lung metastases. In the case of bone, metastasis was to the human implant and not the mouse skeleton, indicating a species-specific osteotropism. This model replicates the events observed in patients with breast cancer skeletal metastases and serves as a useful and relevant model for studying the disease.

The melanocyte differentiation program predisposes to metastasis after neoplastic transformation

The aggressive clinical behavior of melanoma suggests that the developmental origins of melanocytes in the neural crest might be relevant to their metastatic propensity. Here we show that primary human melanocytes, transformed using a specific set of introduced genes, form melanomas that frequently metastasize to multiple secondary sites, whereas human fibroblasts and epithelial cells transformed using an identical set of genes generate primary tumors that rarely do so. Notably, these melanomas have a metastasis spectrum similar to that observed in humans with melanoma. These observations indicate that part of the metastatic proclivity of melanoma is attributable to lineage-specific factors expressed in melanocytes and not in other cell types analyzed. Analysis of microarray data from human nevi shows that the expression pattern of Slug, a master regulator of neural crest cell specification and migration, correlates with those of other genes that are important for neural crest cell migrations during development. Moreover, Slug is required for the metastasis of the transformed melanoma cells. These findings indicate that melanocyte-specific factors present before neoplastic transformation can have a pivotal role in governing melanoma progression.

Loss of Heterozygosity Occurs via Mitotic Recombination in Trp53+/− Mice and Associates with Mammary Tumor Susceptibility of the BALB/c Strain

Loss of heterozygosity (LOH) occurs commonly in cancers causing disruption of tumor suppressor genes and promoting tumor progression. BALB/c-Trp53(+/-) mice are a model of Li-Fraumeni syndrome, exhibiting a high frequency of mammary tumors and other tumor types seen in patients. However, the frequency of mammary tumors and LOH differs among strains of Trp53(+/-) mice, with mammary tumors occurring only on a BALB/c genetic background and showing a high frequency of LOH, whereas Trp53(+/-) mice on a 129/Sv or (C57BL/6 x 129/Sv) mixed background have a very low frequency of mammary tumors and show LOH for Trp53 in only approximately 50% of tumors. We have performed studies on tumors from Trp53(+/-) mice of several genetic backgrounds to examine the mechanism of LOH in BALB/c-Trp53(+/-) mammary tumors. By Southern blotting, 96% (24 of 25) of BALB/c-Trp53(+/-) mammary tumors displayed LOH for Trp53. Karyotype analysis indicated that cells lacking one copy of chromosome 11 were present in all five mammary tumors analyzed but were not always the dominant population. Comparative genomic hybridization analysis of these five tumors indicated either loss or retention of the entire chromosome 11. Thus chromosome loss or deletions within chromosome 11 do not account for the LOH observed by Southern blotting. Simple sequence length polymorphism analysis of (C57BL/6 x BALB/c) F1-Trp53(+/-) mammary tumors showed that LOH occurred over multiple loci and that a combination of maternal and paternal alleles were retained, indicating that mitotic recombination is the most likely mechanism of LOH. Nonmammary tumors of BALB/c mice also showed a high frequency of LOH (22 of 26, 85%) indicating it was not a mammary tumor specific phenomenon but rather a feature of the BALB/c strain. In (C57BL/6 x BALB/c) F1-Trp53(+/-) mice LOH was observed in 93% (13 of 14) of tumors, indicating that the high frequency of LOH was a dominant genetic trait. Thus the high frequency of LOH for Trp53 in BALB/c-Trp53(+/-) mammary tumors occurs via mitotic recombination and is a dominant genetic trait that associates with the occurrence of mammary tumors in (C57BL/6 x BALB/c) F1-Trp53(+/-) mice. These results further implicate double-strand DNA break repair machinery as important contributors to mammary tumorigenesis.

Loss of expression of the putative tumor suppressor NES1 gene in biopsy-proven ductal carcinoma in situ predicts for invasive carcinoma at definitive surgery

PURPOSE

The loss of expression of NES1, a novel putative tumor suppressor gene, is an early marker of breast tumorigenesis. NES1 is expressed in normal breast tissue and ductal hyperplasia but is absent or markedly diminished in invasive cancer. In cases of ductal carcinoma in situ (DCIS), NES1 expression has been shown previously to be present in approximately 50% of specimens. This study examined the expression level of NES1 in diagnostic biopsy samples found to contain pure DCIS. These data were then correlated with the pathologic findings found at definitive local surgery.

METHODS AND MATERIALS

Twenty-nine cases with initial biopsy showing DCIS without invasive carcinoma followed by subsequent reexcision were discovered and archived. Formalin-fixed tissue specimens were obtained for analysis. Each biopsy specimen was subjected to hematoxylin-eosin staining and reviewed by two pathologists to confirm the diagnosis of pure DCIS. NES1 cDNA (1069 bp), including 238 bp of 5' and 3' untranslated region and the entire protein-coding region, was cloned into a vector. To generate the antisense and sense RNA probes, the plasmid was linearized and the transcription reaction was carried out with polymerases T7 and T3, respectively. The detection of in situ hybridization probes was performed using an mRNAlocator-Biotin Kit. Staining was characterized as negative (0/1+) or positive (2+/3+). Subsequent to an initial biopsy diagnosis of DCIS, all cases had a definitive surgical procedure. Detailed sectioning of the resultant tissue was performed and subjected to hematoxylin-eosin staining to determine the presence or absence of invasive carcinoma.

RESULTS

The initial diagnostic biopsy specimens showed that 17 of 17 high-grade, 3 of 7 intermediate-grade, and 3 of 5 low-grade DCIS specimens were negative for NES1 expression. Of the 6 cases of DCIS found to be positive for NES1 expression, none (0%) were subsequently found to have invasive carcinoma at definitive surgery. In contrast, the loss of NES1 expression in the initial diagnostic biopsy was associated with a 40% incidence of invasive carcinoma at definitive surgery. Additional stratification by nuclear grade showed invasive carcinoma in 5 (83%) of 6 NES1-negative, low- to intermediate-grade DCIS (p </=0.01) and 4 (24%) of 17 NES1-negative, high-grade DCIS (p </=0.05).

CONCLUSION

These results show that a lack of NES1 expression in DCIS identified at the diagnostic biopsy predicts for a high risk of invasive cancer in the definitive surgical specimen. The predictive value of NES1 expression appears to be particularly relevant for low- and intermediate-grade DCIS.

BALB/c alleles for Prkdc and Cdkn2a interact to modify tumor susceptibility in Trp53+/- mice

In mice heterozygous for p53 (Trp53(+/-)), the incidence of mammary tumors varies among strains, with C57BL/6 being resistant and BALB/c being susceptible. Mammary tumor phenotypes were examined in female Trp53(+/-) F1 mice (C57BL/6 x BALB/c;n = 19) and N2 backcross mice [(C57BL/6 x BALB/c) x BALB/c] (n = 224). Susceptibility to mammary tumors segregated as a dominant phenotype in F1 females, but a higher frequency and shorter latency in N2 mice indicated a contribution from recessive-acting modifiers. Segregation of the hypomorphic BALB/c alleles for DNA-dependent protein kinase catalytic subunit (Prkdc) and p16(INK4A) (Cdkn2a) was analyzed in the N2 mice. The time to first tumor (considering all tumor types) was significantly different among the four genotype combinations (P = 0.01). Cdkn2a had a strong effect (P = 0.008) but was restricted to Prkdc(B/B) mice (P = 0.001), indicating a strong interaction between the loci. Differences in mammary tumor occurrence among genotypes for Prkdc and Cdkn2a in N2 mice were not statistically significant. This study indicates that BALB/c Prkdc and Cdkn2a alleles do modify tumor incidence in Trp53(+/-) mice and highlights the complexity of gene interaction effects in determining cancer phenotypes but discounts these alleles as major recessive loci contributing to spontaneous mammary tumor susceptibility.

Epithelial cell cycling predicts p53 responsiveness to γ-irradiation during post-natal mammary gland development

The tumor suppressor gene, TP53, plays a major role in surveillance and repair of radiation-induced DNA damage. In multiple cell types, including mammary epithelial cells, abrogation of p53 (encoded by Trp53) function is associated with increased tumorigenesis. We examined γ-irradiated BALB/c-Trp53+/+ and -Trp53–/– female mice at five stages of post-natal mammary gland development to determine whether radiation-induced p53 activity is developmentally regulated. Our results show that p53-mediated responses are attenuated in glands from irradiated virgin and lactating mice, as measured by induction of p21/WAF1 (encoded by Cdkn1a) and apoptosis, while irradiated early- and mid-pregnancy glands exhibit robust p53 activity. There is a strong correlation between p53-mediated apoptosis and the degree of cellular proliferation, independent of the level of differentiation. In vivo, proliferation is intimately influenced by steroid hormones. To determine whether steroid hormones directly modulate p53 activity, whole organ cultures of mammary glands were induced to proliferate using estrogen plus progesterone or epidermal growth factor plus transforming growth factor-α and p53 responses to γ-irradiation were measured. Regardless of mitogens used, proliferating mammary epithelial cells show comparable p53 responses to γ-irradiation, including expression of nuclear p53 and p21/WAF1 and increased levels of apoptosis, compared to non-proliferating irradiated control cultures. Our study suggests that differences in radiation-induced p53 activity during post-natal mammary gland development are influenced by the proliferative state of the gland, and may be mediated indirectly by the mitogenic actions of steroid hormones in vivo.

Analysis of normal epithelial cell specific-1 (NES1)/kallikrein 10 mRNA expression by in situ hybridization, a novel marker for breast cancer

PURPOSE

Normal epithelial cell specific-1 (NES1)/kallikrein 10 gene is expressed in normal mammary and prostate epithelial cells, but the expression of NES1 mRNA and protein is markedly reduced in established breast and prostate cancer cell lines although the NES1 gene is intact. Here, we wished to assess whether NES1 expression is down-regulated in primary breast cancers.

EXPERIMENTAL DESIGN

We developed and used an in situ hybridization technique with an antisense NES1 probe to detect NES1 mRNA in sections of normal breast specimens, typical and atypical ductal hyperplasia, ductal carcinoma in situ, and infiltrating ductal carcinoma.

RESULTS

All of the 30 normal breast specimens showed high NES1 expression. Notably, 18 (75%) of 24 typical and atypical breast hyperplasia specimens showed high NES1 expression, with weak-to-moderate expression in 6 (25%). Significantly, 13 (46%) of 28 ductal carcinoma in situ specimens lacked NES1 expression, and the remaining 15 (54%) showed weak-to-moderate expression. Finally, 29 of 30 (97%) infiltrating ductal carcinoma grades I-III samples lacked NES1 mRNA, with weak expression in the remaining one sample.

CONCLUSIONS

Our results demonstrate that NES1 mRNA is expressed in normal breast tissue and benign lesions, with loss of NES1 expression during tumor progression. We suggest that NES1 expression may serve as a molecular tool in the study of breast cancer progression. Studies with larger series of specimens should help assess whether NES1 expression can be a diagnostic and/or prognostic marker in breast and other cancers.

Development of spontaneous mammary tumors in BALB/c p53 heterozygous mice. A model for Li-Fraumeni syndrome

Breast cancer is the most frequent tumor type among women in the United States and in individuals with Li-Fraumeni syndrome. The p53 tumor suppressor gene is altered in a large proportion of both spontaneous breast malignancies and Li-Fraumeni breast cancers. This suggests that loss of p53 can accelerate breast tumorigenesis, yet p53-deficient mice rarely develop mammary tumors. To evaluate the effect of p53 loss on mammary tumor formation, the p53(null) allele was back-crossed onto the BALB/c genetic background. Median survival was 15.4 weeks for BALB/c-p53(-/-) mice compared to 54 weeks for BALB/c-p53(+/-) mice. Sarcomas and lymphomas were the most frequent tumor types in BALB/c-p53(-/-) mice, whereas 55% of the female BALB/c-p53(+/-) mice developed mammary carcinomas. The mammary tumors were highly aneuploid, frequently lost the remaining wild-type p53 allele, but rarely lost BRCA1. Although mammary tumors were rarely detected in BALB/c-p53(-/-) female mice, when glands from BALB/c-p53(-/-) mice were transplanted into wild-type BALB/c hosts, 75% developed mammary tumors. The high rate of mammary tumor development in the BALB/c background, but not C57Bl/6 or 129/Sv, suggests a genetic predisposition toward mammary tumorigenesis. Therefore, the BALB/c-p53(+/-) mice provide a unique model for the study of breast cancer in Li-Fraumeni syndrome. These results demonstrate the critical role that the p53 tumor suppressor gene plays in preventing tumorigenesis in the mammary gland.

Cytoplasmic sequestration and functional repression of p53 in the mammary epithelium is reversed by hormonal treatment

Proper function of the p53 tumor suppressor gene is critical for inhibiting tumor development in a broad spectrum of tissues. Although the mammary gland is highly susceptible to tumor formation, the functional status of p53 in the normal tissue had not been investigated. Therefore, expression, localization, and activity of p53 were examined in normal mammary tissues. High levels of p53 protein were found expressed in the cytoplasm of the ductal epithelium of the quiescent mammary gland. Ionizing radiation failed to recruit p53 to the nucleus, and p53-dependent responses were minimal. However, transient hormonal stimulation resulted in nuclear accumulation of p53, an induction of p21/WAF1, and a 5-fold increase in apoptosis after ionizing radiation. Therefore, the functional state of wild-type p53 in the mammary epithelium can be regulated by hormonal stimuli.

Expression of MDM2 during mammary tumorigenesis

The MDM2 oncoprotein encodes a 90 kDa nuclear phosphoprotein capable of abrogating the growth suppressive functions of p53 and pRb tumor suppressor proteins by direct interaction. Alternative splicing of MDM2 protein coding sequences has been documented during tumor progression in human ovarian and bladder carcinomas. The aim of this study was to determine whether alternative splicing of MDM2 occurs during breast tumorigenesis in mice and humans and whether protein coding sequences were affected. Specimens representing normal and malignant breast tissues from the murine D2 mammary tumor model system and human breast carcinomas were examined. Three distinct mdm2 mRNA transcripts of 3.3, 1.6 and 1.5 kb were detected in normal and malignant murine mammary tissues by Northern blot analysis using a full-length mdm2 cDNA probe. Additional Northern blot analysis using a probe derived from exon 12 of murine mdm2 demonstrated that the 1.5 and 1.6 kb transcripts lack sequences encoding the C-terminus of the protein. No evidence of internal deletions of protein coding sequences of mdm2 was detected in any of the normal mammary tissues or D2 murine mammary tumors examined by reverse transcription PCR (RT-PCR). Three distinct MDM2 transcripts of 6.7, 4.7 and 1.9 kb were detected in malignant human breast tissue by Northern blot analysis using a cDNA probe specific for the complete open reading frame of human MDM2. However, a cDNA probe specific for the last exon of human MDM2 hybridized only to the 6.7 and 4.7 kb transcripts, demonstrating that the 1.9 kb transcript lacked protein coding sequences contained in exon 12. Similarly, no internal deletions were detected in a panel of malignant human breast tissues using RT-PCR and analogous primers within human MDM2. Therefore, breast tumors differ from other solid tumors reported previously in that no internal deletions of MDM2 protein coding sequences were observed. However, the data document the presence of multiple MDM2 mRNA transcripts in both normal and malignant breast tissues. A subset of MDM2 transcripts were shown to lack the last exon which contains sequences coding for the RING and zinc fingers and domains which are targets for caspase-3 mediated proteolytic degradation and are required to target p53 for proteosomal degradation.

Regulation of p53 and its targets during involution of the mammary gland

Post-lactational involution of the mammary gland provides a system in which to study the expression and function of genes that regulate apoptosis in the context of a normal tissue. The functions of the p53 tumor suppressor gene have been extensively studied as a mediator of apoptosis in response to DNA damage, but its regulation in normal physiologic processes has been poorly characterized. Expression of p53 mRNA was shown to be among the first genes to be induced in mammary tissue following weaning of neonates. Although involution proceeds in the absence of a functional p53 gene, it is delayed compared to normal individuals. Therefore, involution can be viewed as biphasic with initial responses being sensitive to p53, whereas secondary responses being p53-independent. These observations can be exploited to determine the subset of genes that are p53-responsive and that mediate the effects of p53 in normal mammary tissue.

Delayed involution of the mammary epithelium in BALB/c-p53null mice

In mammals, weaning of neonates and subsequent milk stasis initiates removal of the secretory epithelium of the mammary gland by apoptosis. The p53 tumor suppressor gene is induced rapidly following weaning of neonates, but its role in the process of involution has not been defined. Therefore, experiments were performed to identify the cell types in which the p53 gene is expressed during involution and determine the consequences of its absence in BALB/c-p53null mice. Both p53 mRNA and protein were detected in the mammary epithelium within 48 h following weaning and resulted in an eightfold increase in levels of p21WAF1 mRNA. Induction of p21WAF1 mRNA was absent in BALB/c-p53null mice, and therefore, was shown to be p53-dependent. The BALB/c-p53null mice exhibited delayed involution of the mammary epithelium, as measured by 60% greater epithelial area compared to BALB/c-p53(wt) mice through 5 days post-weaning. The delay was transient with no differences being apparent at 7 days post-weaning. Expression of the stromal protease stromelysin-1 was unaffected by the absence of p53 suggesting that stromal responses were intact. These data demonstrate that p53 participates in the first stage of involution initiated by the epithelium itself, but does not affect the second phase during which stromal proteases are induced.

Continuing role of a frozen-tissue bank in molecular pathology

The growth of molecular diagnostics and its application in various clinical laboratories have made it necessary to standardize the methods used to freeze and store tissues used in molecular testing. It may now be advantageous to preserve fresh tissues and other specimen types in a central frozen-tissue bank so that sample preparation and storage conditions are appropriate for molecular applications and so that the specimen inventory can be efficiently managed. The pathology laboratory is a logical site for the facility because the professional and technical expertise available is focused on the complex scientific and regulatory aspects of laboratory medicine. Organizationally, the tissue-bank program should be overseen by a surgical pathologist to integrate it into routine surgical pathology activities. A member of the laboratory technical staff can serve as the tissue-bank coordinator with responsibility for systematic storage and retrieval of specimens and routine maintenance of equipment and supplies. To facilitate the tissue-freezing procedure and efficient storage of multiple types of specimens, 2.0 ml cryogenic vials are used as the uniform storage container. All specimens are stored at -140 to -150 degrees C in the vapor phase of liquid nitrogen. The specimen inventory data are maintained with a computerized program specifically designed to manage complex specimen storage. A frozen-tissue bank is easily implemented in a pathology laboratory and is a valuable institutional asset for diagnostic and research purposes.

The role of androgen receptor gene mutations in male breast carcinoma

Certain germline mutations (607Arg-Gln, 608Arg-Lys) in the androgen receptor gene have been associated with the occurrence of breast cancer in males suffering from partial androgen insensitivity. To assess whether somatic mutations in this gene could be detected in breast carcinoma, archival tumor tissue of males without clinical evidence of androgen insensitivity was screened for point mutations in the androgen receptor gene. DNA was retrieved by chloroform-phenol extraction from formalin-fixed, paraffin-embedded tissues. Exons 2-8 of the androgen receptor gene, encoding the DNA- and hormone-binding regions of the receptor, were amplified by polymerase chain reaction and subjected to nonisotopic single strand conformation assay (SSCA) to screen for point mutations. In the tumor DNA, no variations suggestive of mutations were encountered on SSCA. However, in a control patient with partial androgen insensitivity and predominantly female phenotype, the germline mutation 607Arg-Gln was identified in blood leukocyte DNA. Our results indicate that somatic mutations of the androgen receptor are not required for the development of male breast cancer. This, however, does not exclude an increased risk of breast carcinoma in patients with androgen insensitivity.

Ring chromosomes in dermatofibrosarcoma protuberans are composed of interspersed sequences from chromosomes 17 and 22

Ring chromosomes are found in most dermatofibrosarcoma protuberans (DFSPs), and recent reports demonstrate that portions of the DFSP ring chromosomes derive from chromosome 17. In this study we characterized ring chromosomes in three DFSPs using a combined approach of karyotyping, chromosome painting, and comparative genomic hybridization. Chromosome painting demonstrated that the ring chromosomes in each DFSP were composed of discontinuous, interwoven sequences from chromosomes 17 and 22. Amplification of chromosomes 17 and 22 sequences was confirmed in each of these cases by comparative genomic hybridization, and over-representation of chromosomes 17 and 22 sequences was also demonstrated by comparative genomic hybridization in 1 of 2 cytogenetically unremarkable DFSPs. We conclude that amplification of chromosomes 17 and 22 sequences, in ring form, is a characteristic aberration in DFSP.

Specimen storage and the use of a relational database

Advances in genetic research make laboratory specimens a valuable source of DNA. Regulations call for quick turnaround time in locating stored specimens. Personal computers and database software make it possible to store, locate, and inventory samples efficiently and assist in research work and cooperation between laboratory sites.

Platelet-derived growth factor in fibrous musculoskeletal disorders: a study of pathologic tissue sections and in vitro primary cell cultures

Despite the great variability in the clinical behavior of fibrous lesions of the musculoskeletal system, they are composed of cytologically similar fibrocytes. Receptors for estrogen or progesterone, or both, are present in some of these lesions and some increase their rate of growth during periods of high levels of sex steroid hormones. The platelet-derived growth factor-B (PDGF-B) proto-oncogene encodes the B chain of PDGF, a mitogen for fibrocytes. Tissue from aggressive fibromatosis, fibrous dysplasia, plantar fibromatosis, and recurrent plantar fibromatosis was analyzed with use of the polymerase chain reaction and in situ hybridization for the expression of PDGF-B and PDGF beta receptor. Cell culture was used to determine if estrogen and progesterone stimulation modulated the expression of PDGF-B. Aggressive fibromatosis, fibrous dysplasia, and recurrent plantar fibromatosis expressed PDGF-B; plantar fibromatosis, normal plantar fascia, normal fascia lata, and mature scar did not. All of the tissues expressed PDGF beta receptor. The level of expression in aggressive fibromatosis and fibrous dysplasia was four times that in the recurrent plantar fibromatosis. Estrogen and progesterone stimulation in aggressive fibromatosis resulted in an increase in the level of expression. Therefore, the detection of PDGF-B may be an adjunct in the pathologic identification of locally invasive lesions. Its production may be a common mechanism leading to a fibroproliferative response through deregulation of the control of growth by both paracrine and autocrine mechanisms.

Equipment and organization of a frozen tissue bank--an update

The growth of molecular diagnostics and its application in various clinical laboratories has made it necessary to standardize the methods used to freeze and store tissues used in molecular testing. It may now be advantageous to preserve fresh tissues and other specimen types in a central frozen tissue bank so that sample preparation and storage conditions are appropriate for molecular applications and so that the specimen inventory can be efficiently managed. The pathology laboratory is a logical site for this facility since the professional and technical expertise available is focused on the complex scientific and managerial aspects of laboratory medicine. Organizationally, the tissue bank program should be overseen by a surgical pathologist in order to integrate it into routine surgical pathology activities. A member of the laboratory technical staff can serve as the tissue bank coordinator with responsibility for systematic storage and retrieval of specimens and routine maintenance of equipment and supplies. In order to facilitate the tissue freezing procedure as well as efficient storage of multiple types of specimens, 2.0 ml cryogenic vials are used as the uniform storage container. All specimens are stored at -140 to -150 degrees C in the vapor phase of liquid nitrogen. The specimen inventory data are maintained with a computerized program specifically designed to manage complex specimen storage. A frozen tissue bank is easily implemented in a pathology laboratory and is a valuable institutional asset for diagnostic and research purposes.

Molecular biology of brain tumors

Molecular technology has opened new vistas in the analysis of brain tumors. It appears that, for most tumors, there is a complex interaction between two sets of genes--the oncogenes and tumor suppressor genes. The successive mutation and loss of these genes lead to the multistep process of tumor formation. In this article, current understanding of the genetic aberrations in a number of primary human brain tumors is discussed.

Neu oncogene expression in ovarian tumors: a quantitative study

We studied neu mRNA expression by slot blot analysis and protein product expression by capture ELISA and immunohistochemistry in 57 primary and metastatic ovarian neoplasms, two paraovarian leiomyosarcomas, and eight normal ovaries. Some 61% of ovarian tumors but none of the paraovarian neoplasms or normal ovaries overexpressed neu mRNA. A total of 96% of the ovarian tumors that overexpressed neu were of epithelial type. Epithelial ovarian tumors had significantly higher amounts of the neu oncogene product as determined by capture ELISA than either germ cell and stromal tumors or normal ovaries (p less than 0.025). Different subtypes of ovarian carcinomas had significantly different amounts of neu oncogene product as measured by capture ELISA; endometrioid tumors had the highest, and poorly differentiated carcinomas not otherwise specified had the lowest (p less than 0.025). ELISA values, mRNA overexpression, and immunohistochemical staining intensity did not correlate with stage at diagnosis or architectural or nuclear grade in ovarian tumors. We conclude that capture ELISA is a simple, effective way to measure the neu oncogene protein product and that there is a good correlation between ELISA levels and immunohistochemical staining intensity. However, ELISA values did not correlate with stage or histologic prognostic factors in ovarian neoplasms.