Butaphosphan and Cyanocobalamin Supplementation in Semen Extender on Chilled Boar Sperm Quality and Life Span

The objective of the present study was to determine the effect of butaphosphan and cyanocobalamin supplementation in semen extender on chilled boar sperm quality and life span. A total of 35 ejaculates of boar semen were included. The semen was diluted with Beltsville thawing solution extender supplemented with different concentrations of butaphosphan and cyanocobalamin [0 (control), 0.1, 0.2, 0.3, 0.4, and 0.5%] in the diluted semen. The semen samples were evaluated using a computer-assisted sperm analysis system to determine sperm motility and sperm kinetic parameters (i.e., the curvilinear velocity, VCL; straight line velocity, VSL; average path velocity, VAP; linearity, LIN; straightness, STR; amplitude of lateral head, ALH; wobble, WOB; and beat cross frequency, BCF). Additionally, sperm viability, acrosome integrity, mitochondrial activity, and plasma membrane integrity were evaluated after 4 (day 0), 72 (day 3), 120 (day 5), and 168 (day 7) h of storage using SYBR-14-ethidium homodimer-1 (EthD-1), EthD-1, JC-1, and the short hypo-osmotic swelling test, respectively. The analyses were carried out by using the general linear mixed model (MIXED) procedure of SAS. The statistical models for each data set included group, day after storage, and interaction between group and day after storage. The boar was included as a random effect. On day 0 after storage, progressive motility, VCL, VSL, VAP, and plasma membrane integrity of boar sperm in 0.3% of butaphosphan and cyanocobalamin supplementation were greater than those in the 0.4 and 0.5% groups (P < 0.05). On day 3 after storage, total motility and progressive motility, VCL, VSL, VAP, LIN, WOB, BCF, and plasma membrane integrity in 0.3% of butaphosphan and cyanocobalamin supplementation were significantly greater than those in the control group (P < 0.05). The total motility and progressive motility, VAP, and WOB in 0.3% of butaphosphan and cyanocobalamin supplementation were greater than those in the control group on day 5 after storage (P < 0.05). No effects of butaphosphan and cyanocobalamin supplementation on acrosome integrity and mitochondria activity were found on days 3, 5, and 7 after storage. However, the motility and progressive motility and the values for all sperm kinetic parameters except ALH in 0.3% of butaphosphan and cyanocobalamin supplementation were greater than those in the control group on day 7 after storage (P < 0.05). In conclusion, 0.3% of butaphosphan and cyanocobalamin supplementation in semen extender improved sperm motility, sperm activity, morphology, and life span in chilled boar sperm.

Abstract P3-11-05: Predictive gene signatures of adjuvant capecitabine benefit in triple negative breast cancer in the FinXX trial

Background: Recent studies have demonstrated a benefit of adjuvant capecitabine in early stage breast cancer, particularly in patients with residual disease after neoadjuvant chemotherapy. Subset analyses suggest that patients with triple negative breast cancer (TNBC) may be more likely to benefit with capecitabine in this setting. However, more precise biomarkers to predict which patients are most likely to benefit from capecitabine are needed.

Methods: The NanoString Breast Cancer 360TM (BC360) panel was used to quantify mRNA expression in FFPE tissue samples from patients with TNBC in the FinXX trial. Gene signature scores were analyzed using prespecified algorithms developed by NanoString. 30 additional custom genes related to capecitabine metabolism and function were added. Patients in FinXX trial were randomized to receive either 3 cycles of docetaxel followed by 3 cycles of cyclophosphamide, epirubicin, and fluorouracil (T+CEF) or 3 cycles of docetaxel plus capecitabine followed by 3 cycles of cyclophosphamide, epirubicin, and capecitabine (TX+CEX). Cox proportional hazard ratio (HR) was used to determine the association of each gene signature with recurrence free survival (RFS).

Results: A total of 111 samples from patients with TNBC in the FinXX trial were available for gene expression analysis. 57 patients were treated with T+CEF and 54 patients were treated with TX+CEX. The median age was 52 years and median follow up was 10.2 years. Consistent with the previous analysis of the FinXX trial, patients with TNBC had nonsignificant but favorable RFS with capecitabine (HR 0.60, 95% CI 0.27-1.3, p 0.2). Among 39 individual genes and metagene signatures generated with the BC360 panel, there were 4 gene signatures significantly associated with improved RFS favoring an addition of capecitabine with TX+CEX compared to T+CEF. These were the cytotoxic cell signature (HR 0.37, 95%CI 0.15-0.92, p 0.03), endothelial signature (HR 0.18, 95%CI 0.04-0.83, p 0.03), mast cell signature (HR 0.43, 95%CI 0.21-0.88, p 0.02), and PDL2 gene (HR 0.29, 95%CI 0.09-0.99, p 0.05). PAM50 intrinsic subtype was not predictive of capecitabine benefit within this TNBC subset. Moreover, we identified additional individual 12 genes that were significantly associated with capecitabine benefit (p-FDR&lt;0.05). Among these genes, high expression of CES1, which encodes an enzyme that activates capecitabine, was significantly associated with improved RFS when treated with capecitabine (HR 0.71, 95%CI 0.32-1.61 with p-interaction=0.04).

Conclusion: Our analyses demonstrated potential predictive individual genes and metagene signatures that may be used to identify TNBC patients who are more likely to benefit from adjuvant capecitabine. Interestingly, several gene signatures related to immune response and genes related to capecitabine activation were associated with improved outcome in TNBC patients treated with capecitabine in the FinXX trial. While these findings are compatible with basic science reports, future studies are needed to validate the significance of these gene signatures as predictive biomarkers for capecitabine benefit.

Citation Format: Chumsri S, Asleh K, Brauer HA, Mashadi-Hossein A, Lauttia LS, Lindman H, Nielsen TO, Joensuu H, Thompson EA. Predictive gene signatures of adjuvant capecitabine benefit in triple negative breast cancer in the FinXX trial [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 P3-11-05.

Abstract PD5-06: Prognostic value of molecular tumor infiltrating lymphocyte (mTIL) signatures in HER2-positive breast cancer patients in N9831 and FinHer/FinXX trials

Background: While previous study showed that the enrichment of immune-related gene expression was associated with outcome in HER2+ patients receiving sequential or concurrent trastuzumab (H), stromal tumor infiltrating lymphocytes (sTIL) have not been consistently shown to associate with outcome in this group of patients. Given that TIL scoring may be subjective, we analyzed molecular signatures of different subsets of tumor infiltrating immune cell populations, using NanoStringTM gene expression data to assess molecular TIL (mTIL) signature enrichment and intrinsic subtype as a function of relapse-free survival (RFS).

Methods: NanoStringTM technology was used to quantify mRNA in samples from 1,280 patients in N9831, 168 patients in FinHer, and 170 patients in FinXX. In N9831, patients in arm A were treated with chemotherapy alone (AC-T), arm B received chemotherapy followed by sequential H (AC-T-H), and arm C received H concurrently with chemotherapy (AC-TH). In the FinHer trial, H was given concurrently for 9 weeks and either 1 year or 9 weeks in FinXX trial. Cox proportional hazard ratio (HR) was used to determine the association of each gene signature with RFS. Different immune subset signatures, including CD45, B-cells, CD8 T-cells, cytotoxic-cells, and T-cells were analyzed using algorithms developed by NanoString.

Results: In N9831, CD45, cytotoxic-cell, and T-cell signatures were significantly associated with improved RFS in patients receiving chemotherapy alone and AC-T-H. However, none of the mTIL signatures were significantly associated with outcome in patients receiving AC-TH. Patients lacking CD45 enrichment had better outcome when H was given concurrently with chemotherapy. The 10-year Kaplan-Meier estimates for RFS in arm B patients with CD45 enrichment or no enrichment were 81.3% and 72.6%, respectively (HR 0.63 [95% CI, 0.42-0.93]; p = 0.02), and in arm C were 83.6% and 79.8%, respectively (HR 0.79, 95%CI 0.49-1.28; p = 0.34). Among patients with HER2-enriched subtype, all of the mTIL signatures were associated with improved RFS in arm A (AC-T) and B (AC-T-H) but remained non-significant in arm C (AC-TH). In patients with luminal subtypes, mTIL signatures were not significantly associated with outcome in patients treated with chemotherapy alone. Similar findings were observed in the FinHer and FinXX trials, in which, none of mTIL signatures were significantly associated with outcome among patients who received H.

Conclusion: This analysis sheds light on previous discrepancy between immune-related gene signature and sTIL findings. Our data also suggests that the poor prognosis associated with lack of infiltrating immune cells can be partly overcome by the concomitant administration of H with chemotherapy. mTIL signatures, specifically CD45, cytoxic, and T cells, were prognostically associated with improved outcome in patients receiving chemotherapy without concurrent trastuzumab. Understanding the role of the immune system in response to H will require a higher degree of granularity than can be achieved by histological quantification of TILs. Further studies are needed to validate the significance of mTIL signatures as predictive or prognostic biomarker in HER+ patients.

Citation Format: Chumsri S, Serie DJ, Mashadi-Hossein A, Tenner KS, Lauttia SL, Moreno-Aspitia A, McLaughlin SA, Nassar A, Warren S, Danaher P, Colon-Otero G, Lindman H, Joensuu H, Perez EA, Thompson EA. Prognostic value of molecular tumor infiltrating lymphocyte (mTIL) signatures in HER2-positive breast cancer patients in N9831 and FinHer/FinXX trials [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 PD5-06.

Abstract P2-11-10: Epigenetic immune modulation by entinostat in breast cancer: Correlative analysis of ENCORE 301 trial

Background: Entinostat, a class I HDAC inhibitor (HDACi), has shown promising activity in ENCORE 301, a randomized, placebo-controlled, phase II trial of entinostat + exemestane (EE) vs. exemestane + placebo (EP) in advanced hormone receptor-positive breast cancer progressed on nonsteroidal aromatase inhibitors. ENCORE 301 met the primary progression free survival endpoint and showed a median 8.3-month improvement in the overall survival (OS) exploratory endpoint for the EE arm. Emerging preclinical work suggests that entinostat has immunomodulatory effects and can eradicate modestly immunogenic mouse tumors in combination with immune checkpoint blockade agents via reduction of circulating myeloid-derived suppressor cells (MDSC). Based on these data, we conducted an analysis of immune subsets in blood samples from ENCORE 301 breast cancer patients.

Method: Blood was collected from a subset of 49 patients (27 EE and 22 EP) representative of the 130 patients enrolled in ENCORE 301 on cycle 1 day 1 (C1D1; pre-treatment), C1D2, C1D8, and C1D15 for biomarker analysis. Of these, 34 patient samples (20 EE and 14 EP) were analyzed for circulating immune subsets. The percent change in subsets at C1D15 vs. baseline was assessed based on the following surface markers: Lin-MDSC (lin; CD3, CD19, CD56)-HLA-DR-CD11b+CD33+), granulocytic MDSC (CD14-CD11b+CD33+), monocytic MDSC (Lin-HLA-DR-CD11b+CD33+CD14+), immature MDSC (Lin-HLA-DR-CD11b+CD33+CD14-), CD8+ T-cells (CD4-CD8+), Foxp3-CD4+ T-cells (CD8-CD4+Foxp3-), and Tregs (CD4+CD8-CD25hiFoxp3+). Monocytes were analyzed for three populations: CD14+, CD14+HLA-DRhi, and CD14+HLA-DRlow/negative. In addition, PD-1, CTLA-4, and TIM-3 were measured on T-cell subsets, and CD40 was measured on MDSCs.

Results: In line with preclinical data, we observed a significant reduction in granulocytic MDSC (-14.67% vs. +20.56%, p 0.029) and monocytic MDSC (-62.3% vs. +1.97%, p 0.002) in EE. Entinostat did not alter immature MDSC levels (-20.9% vs. -15.0%, p 0.93) suggesting a downstream effect of entinostat on MDSC subsets. Interestingly, CD40, a costimulatory receptor required for MDSC-mediated immune suppression was significantly down-regulated in all MDSC subsets except granulocytic MDSC where a downward trend was observed. Entinostat did not significantly impact the ratio of CD8+ T-cells per CD4+ T-cells or per Tregs or alter expression of CTLA4, PD-1, or TIM3 on T-cell subsets. Reduced expression of HLA-DR on monocytes has been associated with poor prognosis in cancer. Consistent with entinostat-mediated immunomodulatory effects, a significant increase in the number of HLA-DR+ monocytes (34.1% vs. -11.38%, p 0.0004) and level of HLA-DR expression on monocytes (16.3% vs. -4.7%; p 0.015) was observed.

Conclusion: Data with entinostat combined with exemestane in ENCORE 301 provide the first evidence of HDACi-mediated reduction of immunosuppressive MDSCs and increased immunocompetent CD14+HLA-DRhi monocytes in patients. These findings may explain the improved OS seen with EE in ENCORE 301 and provide strong rationale for planned combination studies of entinostat with immune checkpoint blockade agents.

Citation Format: Chumsri S, Lee M-J, Tomita Y, Lee S, Tomita S, Cruickshank S, Ordentlich P, Trepel JB. Epigenetic immune modulation by entinostat in breast cancer: Correlative analysis of ENCORE 301 trial. [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 P2-11-10.

Abstract P3-07-05: Non-amplification ERBB2 genomic alterations in 5,605 cases of refractory and metastatic breast cancer: An emerging opportunity for anti-HER2 targeted therapies

Background: Non-amplification ERBB2 alterations (ERBB2 mut) in advanced/metastatic breast cancer (mBC) are not detected by IHC or FISH, but when detected by DNA sequencing assays can lead to clinical responses to anti-HER2 targeted therapy. We queried a database of more than 43,000 clinical cases to uncover the frequency, type and associated genomic alterations (GA) in mBC driven by ERBB2 mut and highlight clinical responses to small molecule drug and antibody-based anti-HER2 therapeutics.

Methods: DNA was extracted from 40 microns of FFPE sections from 5,605 mBC. Comprehensive genomic profiling (CGP) was performed using a hybrid-capture, adaptor ligation based next generation sequencing assay of up to 315 genes to a mean coverage depth of &gt;600X. The results were analyzed for base substitutions, short insertions and deletions, selected rearrangements, and copy number changes.

Results: 698 (12.5%) of 5,605 mBC featured ERBB2 alterations. 596 (10.6%) featured ERBB2 amplifications and 137 (2.4%) featured ERBB2mut. 35 (0.6%) of total mBC had both ERBB2amp and ERBB2mut, which accounted for 5.0% of all ERBB2 altered mBC. The 137 ERBB2mut mBC cases had a median age of 61 years (range 29 to 93 years) and were sequenced to a mean depth of 600X. Samples utilized for CGP included 52 (38%) from the patient's primary BC and 85 (62%) from metastatic sites including bone/soft tissue/skin (12%), liver (20%), LN (14%), serous cavities (6%), lung (4%) and miscellaneous sites (6%). 71 (52%) mBC were submitted as carcinoma NOS, 44 (32%) as IDC, 22 (16%) as ILC and 1 (1%) as mucinous mBC. Of the 137 ERBB2mut cases, 8 featured more than 1 ERBB2 mut. There were 124 (85%) ERBB2 kinase domain mutations and 15 (10%) extra-cellular domain ERBB2mut. The most common genes co-altered in ERBB2mut mBC were TP53 (49%), PIK3CA (42%), CDH1 (37%), MYC (17%), and CCND1 (16%). The enrichment of ERBB2mut in CDH1 mut mBR was significant (p=0.0006) and associated with relapsed lobular mBC. Multiple case examples of kinase domain and extra-cellular domain ERBB2mut mBC responding to a variety of anti-HER2 targeted therapies will be presented.

Conclusions: In this large series of 5,605 mBC, 20% of the total ERBB2 alterations were non-amplification ERBB2mut not detectable by standard of care IHC and FISH slide-based HER2 tests. Given the demonstration of ERBB2mut driven mBC responsive to anti-HER2 targeted therapies in this study, expansion of clinical trials designed to detect these ERBB2mut cases with CGP and optimize the targeted therapies for these patients is strongly recommended.

Citation Format: Ross JS, Wang K, Ali SM, Chumsri S, Elvin JA, Vergilio J-A, Suh J, Yelensky R, Lipson D, Chmielecki J, Miller VA, Stephens PJ. Non-amplification ERBB2 genomic alterations in 5,605 cases of refractory and metastatic breast cancer: An emerging opportunity for anti-HER2 targeted therapies. [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 P3-07-05.

Abstract P2-04-02: Immunomodulatory effects of entinostat on PD-L1 and MHC class I and II in different subtypes of breast cancer

Background: Targeting immune checkpoint programmed death receptor 1 (PD-1)/PD-L1 pathway has shown promising clinical activity with some preliminary association of clinical benefit with PD-L1 expression on tumors. Recent preclinical and clinical studies highlight the beneficial immunomodulatory potential of epigenetic therapy. Entinostat is a class I specific histone deacetylase inhibitor (HDACi). A promising preclinical study showed that entinostat in combination with immune checkpoint blockade agent can eradicate modestly immunogenic breast tumors in mice via reduction in immunosuppressive myeloid-derived suppressor cells. In this study, we investigated the effects of entinostat on expression of immune-related genes in breast cancer cells to further explore the potential mechanism of its combined activity.

Method: Gene expression was assessed on Nanostring platform using the nCounter GX Human ImmunologyV2 panel comprised of 594 immune-related and 15 reference genes. Gene expression was normalized to the internal positive controls and reference genes using nSolver2.0 software. Hormone receptor-positive (HR+) breast cancer (MCF-7 and T47D) and triple negative breast cancer (TNBC) cell lines (MDA-MB-231 and Hs578T) were used for the analysis. Gene expression analysis was performed on control and after 24-hour treatment of entinostat at clinically relevant 125 and 500 nM concentrations.

Results: Overall, a greater number of immune-related genes were induced &gt; 2 fold with entinostat at 125 and 500 nM in TNBC compared to HR+: 77 and 118 genes in MDA-MB-231, 80 and 147 genes in Hs578T, 20 and 64 genes in MCF-7, and 73 and 72 genes in T47D, respectively. In particular, MHC class I (HLA-A, HLA-B, HLA-C) and II (HLA-DMA, HLA-DMB, HLA-DOA, HLA-DOB, HLA-DPA1, HLA-DPB1, HLA-DQA1, HLA-DQA2, HLA-DQB1, HLA-DQB2, HLA-DRA, and HLA-DRB1) genes were induced by entinostat in a dose dependent manner (range 1.5-22.44 fold). These inductions were observed in both HR+ and TNBC cell lines. Interestingly, we found higher baseline expression and a several fold increase in PD-L1 expression in TNBC. PD-L1 mRNA expression increased by 1.74 and 2.14 fold in MDA-MB-231 and 3 and 9.6 fold in Hs578T with 125 and 500 nM treatment, respectively. Corresponding increase in PD-L1 protein expression after entinostat treatment was also observed. In contrast, there appeared to be no significant changes in PD-L1 expression after entinostat treatment in MCF-7 and T47D. Furthermore, we also identified 21 genes that were differentially induced by entinostat in TNBC but not in HR+. These genes include PTPN22, ARG2, CISH, IL17A, ICAM2, KIR3DL1, CXCR3, TLR2, CFD, CCR5, IL13, LILRA3, IL8, TNFRSF9, DPP4, MR1, SELPLG, PTGS2, IL1B, CD3D, and MBL2. No significant change in PDL2 expression was observed in any of the cell lines.

Conclusion: Our data suggest that entinostat induces immune-related genes involved in antigen presentation in both ER+ and TNBC cells, potentially increasing the immunogenicity of these tumors. Given the significant induction of PD-L1 expression with entinostat in TNBC, our preclinical data provides support for further investigation of entinostat in combination with anti-PD1 or anti-PD-L1 in this subtype of breast cancer.

Citation Format: Chumsri S, Necela BM, Ordentlich P, Advani P, Moreno-Aspitia A, McLaughlin SA, Geiger X, McDonough M, Vallow LA, Perez EA, Thompson EA. Immunomodulatory effects of entinostat on PD-L1 and MHC class I and II in different subtypes of 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 P2-04-02.

Abstract P5-09-05: Progranulin (GP88) expression and letrozole resistance in breast cancer

The 88 kDa glycoprotein GP88 (Progranulin, PCDGF, acrogranin) is the largest member of the granulin/epithelin family of growth modulators. GP88 was originally characterized in our laboratory through a biological screen to identify drivers of tumorigenesis. Published studies have established that GP88 represents an ideal therapeutic and diagnostic target in breast cancer (BC) leading to the development of validated tools to measure GP88 in tumor biopsies and biological fluids as well as blocking its action. It was shown that: 1) GP88 expression increases with tumorigenesis; 2) in ER+ breast cancer cells, GP88 stimulates proliferation and its overexpression confers estrogen independence and resistance to several anti-estrogens and aromatase inhibitor; 3) inhibition of GP88 expression by antisense transfection inhibited proliferation in vitro and in vivo; 4) In Her-2 overexpressing breast tumors, GP88 stimulated Her-2 phosphorylation and conferred trastuzumab resistance; 5) GP88 is expressed in 80% invasive ductal carcinoma (IDC) and 60% of ductal carcinoma whereas it is negative in lobular carcinoma, benign lesions and normal mammary tissues; 6) GP88 is secreted and can be detected in the serum of BC patients at an increased level when compared to healthy subjects; 7) Pathological studies with 530 cases of ER+ IDC with clinical outcomes showed that GP88 tumor expression was an independent prognostic indicator of recurrence in early stage BC patients. Training study followed by an independent validation study demonstrated that high GP88 tissue expression (GP88 3+) was associated with a 4-fold increase in risk of recurrence at 5 years.

Since GP88 displays not only diagnostic but also therapeutic potentials, we developed a neutralizing anti-GP88 antibody AG1 that inhibited GP88 biological effect (proliferation and migration) in a dose-dependent fashion in vitro. AG1 was expressed in a high yield CHO cell line and formulated. We have shown that in tamoxifen resistant cells, treatment with AG1 would inhibit tumor growth and restore tamoxifen sensitivity. The present study examined the effect of AG1 in letrozole resistant cells. We have developed from a letrozole sensitive cell ER+ BC cell line, a letrozole-resistant cell line by long term selection in letrozole-supplemented medium. This cell line (LetR) shows also decreased letrozole responsiveness in vivo and therefore constitutes an excellent model for investigating letrozole resistance in vivo as well as in vivo. Here we investigated the effect of various doses of AG1 on LetR tumor development alone or in combination with letrozole. Treatment with AG1 (10 mg/kg i.p.) in combination with letrozole was efficient to maintain long term responsiveness to letrozole and inhibited tumor growth. In addition to the mouse xenografts study, an IRB approved clinical study examines changes in GP88 circulating levels in patients with resistance to aromatase inhibitors. Preliminary data will be presented.

In conclusion, inhibiting GP88 could provide a novel and alternative therapeutic strategy for patients with resistance to anti-estrogen therapy, being tamoxifen or letrozole.

This work is supported by 2R44CA124179 and HHSN 261201200060C from NCI and 02- 2013-018 from the Avon Foundation for Women.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-09-05.

Abstract OT3-2-11: A phase II study of letrozole and lapatinib followed by an addition of everolimus in postmenopausal women with advanced endocrine resistant breast cancer (BC)

Background: Several preclinical studies demonstrated that crosstalk between growth factor receptor pathways, particularly HER2, and ER signaling confers resistance to endocrine therapy (ET). There are emerging data showing the involvement of immune system and miRNA with endocrine resistance. EGF30008 trial showed a benefit of lapatinib in combination with letrozole, mainly in HER2-positive (HER+) metastatic BC (MBC) while a subset analysis of this trial showed that HER2-negative (HER2-) patients (pts) with acquired endocrine resistance may also benefit from this combination. Our preclinical study suggests that everolimus is synergistic with letrozole and lapatinib.

Trial Design: This is a single arm phase II study for postmenopausal women with hormone receptor-positive MBC progressing after aromatase inhibitor, tamoxifen, or fulvestrant. The total target accrual is 76 pts (38 HER2+ pts and 38 HER- pts). In the first phase of the study, pts will be treated with letrozole and lapatinib (1,500 mg daily). Upon disease progression, pts will enter the second phase where everolimus (5 mg daily) will be added to letrozole and the dose of lapatinib will be reduced to 1,250 mg daily. For correlative studies, peripheral blood samples will be serially collected to evaluate for serum HER2 extracellular domain (ECD), circulating miRNAs, PC cell-derived growth factor (GP88), immune regulatory cells including myeloid-derived suppressor cells, NK cells, and Treg cells. These parameters will be correlated with tumor response. In pts with accessible tumors, optional serial biopsies will be performed at baseline and upon progression in each phase of the study. The tumor tissue will be tested for total HER1, HER2, and HER2 expressions as well as HER2:HER2 homodimers, HER2:HER3 heterodimers, HER1:HER2 heterodimers, p95, and HER3/PI3K (p85 subunit) using VeraTag assay.

Statistical Method: The primary objective is to evaluate the clinical benefit rate (CBR: CR, PR, SD &gt; 24 weeks) of the combination of letrozole and lapatinib as well as the combination of everolimus, letrozole, and lapatinib. This is a three-stage design which is an extension of the Simon's two-stage design. The sample size is based on the assumption that a CBR below 10% (null hypothesis) would indicate ineffective therapy and the statistical power is set at a higher CBR of 30% which we consider is plausible. Therefore, if 0 of the first 10 pts in each cohort have clinical benefit, the study will be closed; otherwise additional 8 pts will be enrolled. If ≤ 1 of the total 18 pts has clinical benefit, the study will be closed; otherwise an additional 9 pts will be enrolled. If ≤ 5 pts have clinical benefit the therapy is considered not promising; and if ≥ 6 pts of the total of 27 have clinical benefit, the therapy is considered worth pursuing. This design has ∼90% probability to accept the therapy for further trials if the true CBR is indeed at least 30% and 10% probability to accept it if the true clinical benefit is indeed below 10%.

To date, there are a total of 6 pts enrolled. Accrual is currently ongoing. Please contact ntait@umm.edu for further information.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr OT3-2-11.

Abstract PD5-2: Preclinical assessment of HDAC inhibitor entinostat combined with all trans retinoic acid (ATRA) in aromatase inhibitor resistant breast cancer

Treatment with aromatase inhibitors (AI’s) is highly effective against breast cancer in ER positive postmenopausal women. However, some patients eventually become resistant to AIs. Tumor initiating cells (TIC’s) represent a subpopulation of tumor cells, which show self-renewal capacity. We are focused towards discovering strategies to reduce the growth of breast cancer TICs, which may result in resistance. We have developed a xenograft model that mimics post-menopausal hormone responsive breast cancer. In this model, aromatase transfected human hormone sensitive MCF-7 cells (MCF-7Ca) are inoculated in ovariectomized athymic nude mice and allowed to grow in presence of D4A (aromatizable substrate of estrogen). Results obtained using this model have been confirmed by numerous clinical trials. Using this model, we have established that single agent AI is better than tamoxifen in controlling tumor growth. We also observed that although, AI letrozole provides a longer control over tumor growth, tumors eventually began to grow. In the current study, we investigated the effect of ATRA (All-trans Retinoic acid) (125μg/day, ip) and a histone deacetylase (HDAC) inhibitor entinostat (SNDX- 275) (50μg/day, po) with or without letrozole on letrozole resistant tumors in a xenograft model system. Ovariectomized athymic nude mice bearing xenografts of MCF-7Ca cells, were treated with letrozole till they became resistant (15 weeks). At this time, the mice were grouped to receive ATRA, entinostat plus ATRA or the combination of ATRA plus entinostat plus letrozole till week 23. The mice treated with entinostat plus ATRA letrozole showed a significant decrease in tumor growth rate compared to mice treated with single agents or entinostat plus ATRA (p&lt;0.0001, p = 0.02). On week 20 weeks, 2 mice from each treatment group were euthanized and tumors were harvested. The tumors were digested enzymatically with collagenase and hyaluronidase and freed of debris using centrifugation and filtration. Mammosphere forming ability of TICs in the tumor tissue was measured by seeding 10,000 viable cells from each treated tumors under non-adherent conditions to access the self-renewal capacity. Quantitative PCR analysis of tumors cells showed a significant downregulation of the known TIC molecular markers, BCRP, ALDH, BMI-1 and Nanog compared to letrozole treated tumors. Similar results were also obtained when LTLT-Ca (long term letrozole treated MCF-7Ca) cells treated with ATRA and entinostat in combination with letrozole and then seeded in non-adherent conditions. The combination of ATRA plus ENT plus letrozole significantly (p&lt;0.01) reduced number of mammospheres formed compared to single agents alone. We have shown previously, that LTLT-Ca cells have higher percentage of side population (cells expressing higher level of efflux pumps such as BCRP) compared to MCF-7Ca cells. The treatment of LTLT-Ca cells with the combination of ENT and ATRA with letrozole drastically reduced the percentage of side population. Overall, these studies indicate that the combination of ATRA, entinostat and letrozole is effective in reducing tumor recurrence in letrozole resistant tumors.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr PD5-2.

Abstract P1-07-01: Histone deacetylase inhibitor entinostat reverses epithelial to mesenchymal transition of breast cancer cells by reversing the repression of E-cadherin

Loss of ERa in breast cancer correlates with poor prognosis, increased recurrence rates and higher incidence of metastasis. In our previous studies, we have shown that histone deacetylase (HDAC) inhibitor entinostat (ENT) can upregulate ERα and aromatase in ER-negative cells and tumors, making them sensitive to aromatase inhibitors (AIs). In the current study, we are showing that ENT can also reverse epithelial to mesenchymal transition (EMT), which is considered to be a first step in the process of metastases formation. EMT is characterized by loss of intracellular adhesion (loss of E-cadherin); loss of epithelial markers such as cytokeratins and upregulation of mesenchymal markers such as vimentin; acquisition of fibroblast-like spindle morphology and increased motility. Various carcinomas undergo varying degrees of EMT and capacity to undergo EMT correlates inversely with levels of E-Cadherin. It is widely accepted that loss of E-cadherin is associated with more invasive phenotype. Epigenetic silencing of E-cadherin has been implicated in metastatic cell lines and invasive breast cancers.

Triple negative breast cancer cells such as MDA-MB-231 and Hs578T show a basal phenotype characterized by loss of E-cadherin expression and higher expression of mesenchymal markers such as N-cadherin, vimentin along with transcriptional repressors such as twist and snail.

In this study, we measured the effect of entinostat on the EMT. When MDA-MB-231 and Hs578T cells were treated with ENT, E-cadherin transcription was increased along with reduction in N-cadherin mRNA expression. Similar results were also seen in tumors of MDA-MB-231 and Hs578T xenografts treated with ENT (for 5 weeks and 2 weeks respectively). A dose dependent increase in E-cadherin was seen along with a dose dependent decrease in N-cadherin mRNA. Although, we did not observe any reduction in vimentin protein, phosphorylation of vimentin was increased and vimentin remodeling was changed as seen by immunofluorescence. We performed chromatin immunoprecipitation (ChIP) assay to measure the activation of E-cadherin promoter. Treatment of MDA-MB-231 and Hs578T cells increased the activation of E-cadherin promoter as seen by increased acetyl histones at the promoter region of E-cadherin. Twist and snail are known repressors of E-cadherin gene and we saw that ENT treatment reduced the association of twist and snail with the E-cadherin promoter. ENT was also able to downregulate twist, which may be responsible for reduced twist association with the E-cadherin promoter.

In summary, these findings suggest that HDAC inhibitor ENT can reverse EMT and may help reduce the formation of metastasis.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-07-01.

P4-12-13: A Multi-Center Randomized Controlled Double Blind Trial Assessing the Effect of Acupuncture in Reducing Musculoskeletal Symptoms in Breast Cancer Patients Taking Aromatase Inhibitors: First Interim Analysis

Background: Aromatase inhibitors (AIs) are recommended as first-line adjuvant hormonal therapy in postmenopausal women with hormone-receptor-positive breast cancer, as monotherapy or sequential therapy after tamoxifen. AI-associated musculoskeletal symptoms (AIMSS) occur in approximately 50% of women receiving AIs and in some may result in discontinuation of treatment. Symptom management is essential to ensure that breast cancer patients receive the full recommended duration of AI therapy. We conducted a randomized, placebo-controlled trial to evaluate the effect of acupuncture on AIMSS and report the first interim analysis.

Method: Postmenopausal women with early stage breast cancer, experiencing AIMSS, who had not had acupuncture in the year prior to the study, were eligible. Patients were randomized to 8 weekly acupuncture or sham acupuncture. Health assessment questionnaire disability index (HAQ-DI ranging 0–3.0) and pain visual analog scale (VAS ranging 0–100) were used to assess clinical musculoskeletal disorder severity at weeks 0, 4, 8, and 12 or 24. Change in HAQ-DI (ΔHAQ-DI) and VAS scores (ΔVAS) from baseline were compared between patients receiving acupuncture versus sham acupuncture using exact Wilcoxon rank sum test. Serum samples were collected for measurements of estrogens and beta endorphin concentrations and cytokine profile before and after the intervention to evaluate the etiology of AIMSS and the mechanism of acupuncture in treating AIMSS.

Results: Between May 2008 and June 2011, 48 patients were enrolled, 2 patients were not evaluable due to noncompliance to treatment and lost to follow up, 10 were still receiving treatment and therefore not evaluable. Thirty-six were evaluable, and were equally distributed between the real and sham acupuncture groups. Baseline characteristics were balanced between the two groups with regard to age, race, and body mass index (BMI) with the exception that baseline mean HAQ-DI was higher in the acupuncture group (0.9 vs 0.55, p=0.04). White/Black/Asian: 26/7/3, Median (range): age: 61 (45-82); BMI (kg/m2): 31.1 (22.9−59.6). At week 8, both groups showed a wide range of ΔHAQ-DI (ΔHAQ-DI =HAQ-DIweek8-HAQ-DIbaseline): from −1.38 to 0.5 in the acupuncture group versus from −1 to 0.12 in sham acupuncture group. There was no statistically significant difference in mean ΔHAQ-DI between the real and sham acupuncture groups (−0.33 vs −0.33, p=0.87). Eleven patients in each group (61%) reported decreased HAQ-DI scores, which correlated with improved function. There was no difference in mean ΔVAS between the real and sham acupuncture groups (−9.27 vs −13.82, p=0.67). No significant side effects were reported. Changes in other time points and in serum biomarkers will be presented at the meeting.

Conclusions: The majority of breast cancer patients experiencing AIMSS who participated in our study reported a reduced HAQ-DI score both from acupuncture and sham acupuncture. We did not observe significant differences between responses to real versus sham acupuncture after 8 weekly treatments. The study remains open to accrual to reach 50 evaluable patients.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-12-13.

P1-12-20: The Safety and Tolerability of Vorinostat in Combination with Lapatinib in Advanced Solid Tumors

Background: Lapatinib has been previously shown to markedly decrease cancer stem cells (CSC) in HER2−positive breast cancer. In preclinical models, we have demonstrated that histone deacetylase inhibitors (HDACi) such as vorinostat can induce differentiation and decrease CSC. The combination of vorinostat and lapatinib is synergistic with a combination index of 0.32 (synergism if CI &lt;1). We therefore undertook a pilot study to evaluate the combination of these two drugs in advanced solid tumors.

Method: Patients were eligible if they were: age ≥ 18 years with incurable solid tumors, ECOG PS 0–2, adequate organ function, and no prior exposure to HDACi. The first 3 patients received lapatinib at the dose of 1,250 mg continuous daily and vorinostat 300 mg 4 days on 3 days off. The second dose level with lapatinib 1,250 mg continuous daily and vorinostat 400 mg 4 days on 3 days off were administered in 6 patients. Cycles were repeated every 21 days until disease progression. Echocardiogram and radiologic evaluation were performed every 12 weeks. During the first cycle, pharmacokinetic (PK) evaluation was performed on days 18 and 21.

Results: Nine consented patients (7 with metastatic breast cancer, 1 with non-small cell lung cancer, and 1 with thyroid cancer) have been enrolled with the median age of 52 (range 25–66). Patients received an average of 6 prior treatments (range 2–10). No dose limiting toxicity or drug related death have been observed. Grade 1–2 toxicities including diarrhea, fatigue, muscle cramps and stomatitis were observed. No grade 3 or 4 hepatic, renal or cardiac toxicity were observed (including no QTc prolongation and no significant reduction in the left ventricular ejection fraction). Patients have received the maximum of 7 cycles (median 3 cycles, range 2–7). Response: as of June 2011, 2 patients are still on treatment. Two patients achieved stable disease (triple negative metastatic breast cancer and HER2−positive breast cancer), 6 patients with progressive disease, and 1 patient is too early to evaluate for response. PK analysis will be presented at the time of the meeting.

Conclusions: The combination of vorinostat and lapatinib is tolerable and has some antitumor activity in heavily pretreated advanced solid tumors. A phase II study in HER2−positive metastatic breast cancer is underway with lapatinib 1,250 mg continuous daily and vorinostat 400 mg 4 days on 3 days off.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-12-20.

Early evidence of increasing national mastectomy rates for the treatment of breast cancer

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Background: The use of mastectomy for the treatment of breast cancer has declined since initial randomized trials demonstrated equivalent survival with breast conservation therapy. Recent single institution series, however, have reported increasing mastectomy rates within the past decade.

Methods: In order to verify these findings at the national level, we analyzed data from the Surveillance, Epidemiology, and End Results database, including women diagnosed with T1-2 N0-3 M0 breast cancer from 2000 to 2007. We evaluated therapeutic mastectomy rates by the year of diagnosis and performed a multivariable logistic regression analysis to determine predictors of mastectomy as the treatment choice.

Results: A total of 228,240 patients met the entry criteria. The proportion of women treated with mastectomy decreased from 40.3% to 35.6% between 2000 and 2005. Subsequently, the mastectomy rate increased to 37.9% in 2007 (p < 0.0001). The mastectomy rate in 2007 was the highest since 2002 (38.6%). A reversal in previously declining mastectomy rates was noted in nearly all cohorts, but was most pronounced among younger women. Multivariable analysis found that age, race, marital status, geographic location, involvement of multiple regions of the breast, lobular histology, increasing tumor size, lymph node positivity, increasing grade, negative hormone receptor status, and synchronous diagnosis of an ipsilateral or contralateral breast cancer were independent predictors of mastectomy. Additionally, multivariable analysis confirmed that women diagnosed in 2007 were more likely to undergo mastectomy than women diagnosed in 2005 (HR = 1.14, CI: 1.09 to 1.18, p < 0.0001).

Conclusions: There is evidence of a reversal in the previously declining national mastectomy rates, with the mastectomy rate reaching a nadir in 2005 and subsequently rising. Further follow-up to confirm this trend and investigation to determine the underlying cause of this trend and its impact on outcomes are warranted.

Comparing survival with breast-conservation therapy or mastectomy in the management of young women with early-stage breast cancer

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Background: Previous studies have shown that young women with breast cancer treated with breast-conservation therapy (BCT) experience higher local recurrence rates. Whether such patients are better treated with mastectomy is unclear. The purpose of this study was to evaluate survival outcomes of young women with early-stage breast cancer treated with BCT or mastectomy using a large, population-based database.

Methods: Using the Surveillance, Epidemiology, and End Results (SEER) database, information was obtained for all female patients age 20 to 39 diagnosed with T1-2 N0-1 M0 breast cancer between 1990 and 2007 who underwent either BCT (lumpectomy and radiation treatment) or mastectomy. Multivariable analysis as well as a matched pair analysis were performed to compare overall survival (OS) and cause-specific survival (CSS) of patients undergoing BCT and mastectomy.

Results: 14,760 women were identified, of whom 45% received BCT and 55% received mastectomy. Median follow-up was 5.7 years (range: 0.5 to 17.9 years). Multivariable analysis revealed year of diagnosis, age, race/ethnicity, grade, PR status, tumor size, number of lymph nodes positive, and number of lymph nodes examined were independent predictors of OS and CSS while ER status was of borderline significance. After accounting for all patient and tumor characteristics, multivariable analysis found that BCT resulted in similar OS (HR: 0.93; CI: 0.83-1.04; p = 0.16) and CSS (HR: 0.93, CI: 0.83-1.05; p = 0.26) as mastectomy. Matched pair analysis, including 4,644 BCT and mastectomy patients, confirmed no difference in OS or CSS: the 5/10/15-year OS for BCT and mastectomy were 92.5%/83.5%/77.0% and 91.9%/83.6%/79.1%, respectively (p = 0.99) and the 5/10/15-year CSS for BCT and mastectomy were 93.3%/85.5%/79.9% and 92.5%/85.5%/81.9%, respectively (p = 0.88).

Conclusions: Young women with early-stage breast cancer have equivalent survival whether treated with BCT or mastectomy. These patients should be counseled appropriately regarding their treatment options, and should not choose a mastectomy based on the assumption of improved survival.

Abstract P6-06-01: Relationship between Vitamin D Deficiency and Breast Cancer Histology: A Retrospective Database Review

Background: Vitamin D deficiency has recently been shown to be correlated with high rates of developing breast cancer (Chen P et al, Breast Cancer Res Treat; Oct 2009). However, the association between the degree of vitamin D deficiency and specific histological subtypes of breast cancer remains unclear. Preclinical data has suggested that vitamin D plays an essential role in the terminal differentiation of breast cancer cells, and thus vitamin D deficiency would be associated with the pathogenesis of estrogen receptor negative tumors (Welsh J et al, Journal of Steroid Biochem Mol Biol; Feb 2003), in particular triple-negative tumors, which are associated with a particularly aggressive clinical course. Methods: Beginning in July 2008, the majority of newly diagnosed breast cancer patients at University of Maryland Greenebaum Cancer Center had Vitamin D 25-OH levels testedon initial presentation to the clinic. We conducted a retrospective chart review to obtain information about tumor histology and vitamin D levels in these patients. Results: We include data on 71 patients who presented with newly-diagnosed breast carcinoma or DCIS between June 2008 and December 2009. Average age at diagnosis was 57 (range 36-87), and 58% of patients were African American. Stage distribution of the cohort included; DCIS-3%, stage I-15%, stage II-41%, stage III-28%, and stage IV-10%. Overall, 80% of the patients were vitamin D deficient at diagnosis, with vitamin D levels under 30 ng/ml, and 57% had levels under 20 ng/ml. Patients with triple-negative tumors were the most likely to be vitamin D deficient at diagnosis (90%) compared to hormone receptor-positive patients (75%), and they had the lowest mean and median vitamin D levels compared to all other patients.

Percentage of patients with Vitamin D deficiency

Vitamin D level by histological subtype

Hormone receptor-positive patients were significantly more likely to have normal vitamin D levels at diagnosis and significantly less likely to have severe deficiency (level &lt;10 ng/ml) than those with hormone receptor-negative tumors (p=0.037). African-American women in this cohort were also more likely to be severely vitamin D deficient, with levels &lt;10 ng/ml, than were Caucasian women (34% vs. 7%, p=0.048). Conclusion: Vitamin D deficiency is common among patients with newly-diagnosed breast cancer. Patients with triple-negative tumors may have a higher likelihood of being vitamin D deficient than patients with other histological subtypes.

Abstract P4-03-05: The Warburg Effect and RUNX2-Regulated Metabolic Switching in Breast Cancer: A New Therapeutic Target?

Breast cancer (BC) is the leading cause of cancer deaths among women in North America and Western Europe. Numerous studies have shown that breast tumor progression is associated with a switch from mitochondrial oxidative phosphorylation (OxPhos) to increased utilization of glucose and aerobic glycolysis (Warburg effect). Uncovering underlying mechanisms regulating this progression may lead to innovative approaches for treatment. The RUNX2 DNA-binding transcription factor is expressed in highly aggressive BC and regulates bone metastasis in animal models. We observed increased expression of RUNX2 in primary human ductal carcinoma in situ (DCIS), which correlated with grade and proliferative index (Ki67 staining), decreased estrogen receptor/progesterone receptor expression (ER/PR status), increased glucose uptake values by PET scanning, and increased expression of the glucose transporter, GLUT1. Further, more than 80% (9 out of 11) of triple-negative BC cell lines examined expressed RUNX2. Therefore, to test the hypothesis that RUNX2 may alter the metabolic status of breast cancers and increase their dependence on glycolysis during tumor progression, we have generated a Tet-OFF model system using MCF7 cells with inducible RUNX2 expression. RUNX2-positive MCF7 cells exhibited increased cell death under conditions of glucose depletion or when treated with 2-deoxy-glucose, a competitive inhibitor of hexokinase II. Conversely, RUNX2-positive cells were more resistant to OxPhos inhibitors (rotenone, oligomycin) than RUNX2-negative cells. We also observed higher expression levels of GLUT1 and pAKT in RUNX2-positive MCF7 cells. Hypoxia-inducible factor-α (HIF1α) is a transcription factor that regulates cancer metabolism through its activation of glycolytic genes, while SIRT6, an NAD-dependent deacetylase, is a negative regulator of HIF1α activity. This occurs, in part, via inhibition of HIF1α transcriptional activity. RUNX2-positive or negative cells expressed HIF1α in response to glucose but RUNX2-positive cells exhibited lower SIRT6 expression than RUNX2-negative cells, suggesting that with the loss of SIRT6, HIF1α might be more active in promoting glycolysis in the presence of RUNX2. These results suggest that RUNX2 may have clinical diagnostic value as an indicator of BC metabolic stress and predictor of poor prognosis. Current strategies are utilizing computer-assisted drug design to develop RUNX-specific inhibitors to target BC glycolysis and tumor growth.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P4-03-05.

Side-population cells in luminal-type breast cancer have tumour-initiating cell properties, and are regulated by HER2 expression and signalling

BACKGROUND

The expression of side-population (SP) cells and their relation to tumour-initiating cells (T-ICs) have been insufficiently studied in breast cancer (BC). We therefore evaluated primary cell cultures derived from patients and a panel of human BC cell lines with luminal- or basal-molecular signatures for the presence of SP and BC stem cell markers.

METHODS

The SPs from luminal-type BC were analysed for BC T-IC characteristics, including human epidermal growth factor receptor 2 (HER2), ERalpha, IGFBP7 expression and their ability to initiate tumours in non-obese diabetic severe combined immunodeficiency (NOD/SCID) mice. Pharmacological modulators were used to assess the effects of HER2 signalling and breast cancer-resistance protein (BCRP) expression on SPs.

RESULTS

The SP was more prevalent in the luminal subtype of BC compared with the basal subtype. HER2 expression was significantly correlated with the occurrence of an SP (r(2)=0.75, P=0.0003). Disappearance of SP in the presence of Ko143, a specific inhibitor of the ATP-binding cassette transporter BCRP, suggests that BCRP is the predominant transporter expressed in this population. The SP also decreased in the presence of HER2 signalling inhibitors AG825 or trastuzumab, strengthening the notion that HER2 contributed to the SP phenotype, likely through downstream AKT signalling. The SP cells from luminal-type MCF-7 cells with enforced expression of HER2, and primary cells with luminal-like properties from a BC patient, displayed enrichment in cells capable of repopulating tumours in NOD/SCID mice. Engraftment of SP cells was inhibited by pretreatment with AG825 or by in vivo treatment with trastuzumab.

INTERPRETATION

Our findings indicate an important role of HER2 in regulating SP and hence T-ICs in BC, which may account for the poor responsiveness of HER2-positive BCs to chemotherapy, as well as their aggressiveness.

Expression of ERα and Aromatase in MDA-MB-231 Tumors by HDAC Inhibitor Entinostat Leads to Growth Inhibition by Aromatase Inhibitor Letrozole

The treatment for hormone receptor-positive breast cancer has improved significantly since the development of aromatase inhibitors (AIs). Nevertheless, AIs are ineffective in estrogen receptor-negative (ER-) tumors, which comprise of approximately 25% of breast cancers and tend to be more aggressive. Studies have shown that repression of ER in these hormone receptor-negative tumors may be due to epigenetic modifications. The discovery of recruitment of histone deacetylase enzymes in gene silencing provides a rationale for inhibition of HDAC activity to release transcriptional repression as a potential therapeutic strategy. The objective of the present study was to express ERα and aromatase with HDACI treatment and thereby sensitize tumors to growth inhibition with aromatase inhibitors. In this study we used ER negative, hormone refractory MDA-MB-231 human breast cancer cells. Treatment with HDAC inhibitor entinostat led to upregulation of ERα, aromatase and its activity in a dose dependent manner in cells and xenografts. MDA-MB-231 xenografts were grown in ovariectomized female nude mice. Mice were inoculated with 2.5 X 106 cells per site subcutaneously. When the tumors reached 150 mm3, the mice were grouped into 4 groups (n=10), so that the mean tumor volume was not statistically different across groups (p=0.88). Tumor volumes were measured twice weekly. The mice in the letrozole group had a mean tumor growth rate (β = 0.023 ± 0.014) that was not statistically different (p=0.76) from that of the control group (β = 0.038 ± 0.007). Also, the growth rate of entinostat group (β = 0.034 ± 0.011) was not significantly lower than that of the control (p=0.33). However, the growth rate of entinostat plus letrozole group ((β = -0.003 ± 0.013) was significantly lower than that of the control (p=0.01), entinostat (p=0.03) and letrozole (p=0.049) groups. The combined treatment of entinostat plus letrozole was significantly more effective than either agent alone. In addition, the ability of this combination to inhibit migration in vitro was examined by wound healing assay. The combination of entinostat plus letrozole provides superior inhibition of migration (p&lt;0.001) compared to control, entinostat and letrozole alone. To test the efficacy of this combination in preventing the outgrowth of tumor foci in the lung, mice received an inoculation of 3 X 106 cells intravenously via the tail vein. They were treated three weeks later with entinostat alone, letrozole alone, or the combination. Mice were treated for six weeks, and then euthanized. Treatment with entinostat alone or letrozole was not significantly effective, but the combination resulted in a significantly reduced number of both visible and micrometastases (p=0.03) compared to no treatment (control) and the entinostat alone group. Thus, up-regulation of ERα and aromatase resulted in sensitization of tumors to significant inhibition of growth, cell migration and formation of micro-metastases by the aromatase inhibitor letrozole.Our results provide the basis for possible use of AIs in combination with HDAC inhibitors for the treatment of hormone refractory ERα negative breast cancer. This could open a new avenue for the management of ER- breast cancer.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 401.

Drug Response Indicator Test (DRIT) as a predictive test for treatment outcomes in advanced breast cancer patients (ABC)

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Background: There are limited options for selecting an optimal treatment regimen for ABC patients (pts). DRIT is a platform technology that provides a profile of a patient's tumor's sensitivity or resistance to commonly used chemotherapeutic, hormonal, or biological agents as a basis for individualized anticancer treatment approach. DRIT may allow physicians to choose more effective drug treatments before initiation of therapy and improve the efficacy and toxicity profile of cancer therapies. Methods: DRIT analysis is based on fluorescent dye-labeled monoclonal antibody staining followed by computer-assisted microscopy to quantitatively measure expression levels in tumor sections. The interpretation of DRI expression levels results in classification of tumors as sensitive or resistant to treatment with a mechanistically related drug. This study utilized the following drug/DRI combinations: hormonal therapy/estrogen receptor; capecitabine/thymidylate synthase; docetaxel, paclitaxel, abraxane/β-tubulin isoform III; trastuzumab/HER-2; gemcitabine/ribonucleotide reductase. DRIT was performed on the tumor tissue of consented study participants with ABC who were then deemed to be sensitive or resistant to a given agent/agents. We then analyzed retrospectively clinical treatment outcomes (clinically sensitive to therapy defined as-stable disease+partial response+complete response or resistant to therapy-no response to therapy) for 91 treatment interventions in 71 pts with the DRIT tissue data. Results: We found that the DRIT sensitivity was 0.99, with specificity of 0.59, positive predictive value of 0.88, negative predictive value of 0.93 and overall predictive value of 88% for treatment outcomes for this cohort of ABC pts. Conclusions: This study suggests that DRIT can provide more accurate prediction of treatment outcomes for ABC pts than the standard of care approach and therefore has a potential to avoid unnecessary ineffective drug treatment exposure. Prospective study in ABC pts is currently conducted at the UMGCC.

[Table: see text]