Citations

Abstract Background: Biomarkers to predict response to platinum-based therapy in early breast cancer are needed. HRD is a promising predictor of response to DNA damaging agents, such as platinums. We hypothesized that HRD (high HRD score ≥ 42 and/or tumor BRCA [tBRCA] mutation) would predict pathological complete response (pCR) in patients with HER2-negative early breast cancer treated with PST comprising a platinum, regardless of estrogen receptor (ER) status. Methods: TBCRC008 was a multicenter placebo-controlled trial that investigated pCR (no invasive cancer in breast/axilla) following 12 weeks of preoperative carboplatin and albumin-bound paclitaxel with or without vorinostat in patients with ER-positive or triple-negative breast cancer (TNBC) (Connolly RM. JNM 2015). The pCR rate was similar in both arms (vorinostat 25.8%, placebo 29%). We performed an exploratory biomarker study correlating baseline tumor biopsy HRD status with pCR. The analysis population included all patients with available HRD and pCR data. We compared the proportion of patients with pCR by HRD status using Fisher's exact test. A subset analysis compared pCR proportions by high (≥42) vs. low (<42) HRD score in those patients who did not have tBRCA mutation. A logistic regression model included HRD status, ER status, treatment arm, tumor grade and use of additional anthracycline-based non-study chemotherapy prior to definitive surgery. Results: HRD status and pCR data were available for 48/62 patients (30 ER-positive, 18 TNBC). Of these, 46% of tumors were HR deficient (n=22/48, 33% ER-positive [10/30], 67% TNBC [12/18]). We observed a significantly higher pCR rate in patients with HR deficiency vs not (50% vs 7.7%, p=0.002) in the overall population. A similar trend was observed in ER-positive (30% vs 5%, p=0.095) and TNBC (66.7% vs 16.7%, p=0.13) patients. There was no significant difference when analyzed by treatment arm (vorinostat vs placebo). In a subgroup analysis (n=40) of patients without tBRCA (25 ER-positive, 15 TNBC), a significantly higher pCR rate was observed in those with high vs low HRD score (64.3% vs 7.7%, p <0.001). After adjusting for ER status, randomized treatment, use of AC treatment, and tumor grade, patients whose tumors exhibited HR deficiency had a greater than 6 fold increase in pCR compared to those without HR deficiency (adjusted odds ratio = 6.76, 95% CI = 0.85-53.99, p=.072). Conclusion: This is the first study to evaluate the predictive role of HRD status in patients with ER-positive, HER2-negative breast cancer treated with platinum-based therapy. Our results also support prior observations that HRD status is a promising predictive biomarker of response to platinum agents in TNBC. Further evaluation of this question is warranted in both TNBC and ER-positive breast cancer. Citation Format: Connolly R, Elkin E, Timms K, Goetz M, Boughey J, Zhang Z, Walsh B, Carpenter J, Storniolo A, Watkins S, Gabrielson E, Hartman A-R, Stearns V. Homologous recombination deficiency (HRD) as a predictive biomarker of response to preoperative systemic therapy (PST) in TBCRC008 comprising a platinum in HER2-negative primary operable 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 P3-07-13.

Abstract 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 >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 Importance: 20-25% of patients with early stage HER2-positive breast cancer develop tumor relapse after adjuvant trastuzumab. Identification of such patients is a key goal for clinical management decisions. Objective: To assess molecular heterogeneity among early stage HER2-positive patients using the Prosigna™ algorithm, to define intrinsic subtypes, and to determine the clinical significance of such heterogeneity. Design: The NanoString® platform was used to measure the abundance of the PAM50 subtype signature transcripts. Samples from the NCCTG (Alliance) N9831 trial were analyzed using the Prosigna™ algorithm to define intrinsic subtype and risk scores. Subtypes were evaluated for recurrence-free survival following chemotherapy with or without trastuzumab. Setting: Samples were obtained from a multi-center randomized phase III trial of chemotherapy versus chemotherapy plus trastuzumab. Participants: All tumors were centrally evaluated for HER2 positivity, defined as IHC 3+ and/or FISH >2.0; 1392 patients were evaluated for molecular subtype. Intervention(s): Patients received adjuvant chemotherapy (doxorubicin plus cyclophosphamide followed by paclitaxel) (n=484) or chemotherapy plus trastuzumab (n=908). Main Outcome Measure(s): The primary outcome was recurrence-free survival as a function of subtype and treatment. Results: Patients with HER2-positive tumors with HER2-enriched features comprised about 70% of the sample cohort, and these individuals received significant benefit from adjuvant trastuzumab (HR=0.68, 95%CI: 0.52, 0.89, p=0.005), as did the relatively fewer patients (291/1392) with Luminal-type tumors (HR=0.52, 95%CI: 0.32, 0.85, p=0.01). The sample cohort contained a small number of patients with tumors having Basal-like features (97/1392), and the data suggest that these individuals may have received less benefit from trastuzumab, beyond that received from chemotherapy alone (HR=1.06, 95%CI:0.53,2.13, p=0.87). Conclusions: The majority of HER2-positive tumors are classified as HER2-enriched or Luminal using the Prosigna algorithm, and patients with such tumors benefit from adjuvant trastuzumab. About 10% of HER2-positive tumors exhibit Basal-like genomic features, and such tumors appear to recur at fairly similar frequency irrespective of treatment with chemotherapy or chemotherapy plus trastuzumab. Patients with HER2-positive/Basal-like tumors may represent a cohort that should be considered for enrollment in trials to evaluate emerging novel HER2-targeted agents, other targeted therapies, or combinations of both approaches. Support provided in part by CA129949 and CA15083. Citation Format: Perez EA, Ballman KV, Mashadi-Hossein A, Tenner KS, Kachergus JM, Norton N, Necela BM, Carr JM, Ferree S, Perou CM, Cheang MCU, Thompson EA. Intrinsic subtype and therapeutic response among early stage HER2-positive breast tumors from the North Central cancer treatment group (Alliance) N9831 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 P3-07-04.

Abstract 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 Background: Recent studies have indicated that vaccination can protect against cancer development. One key aspect of developing vaccines is circumventing peripheral tolerance by identifying subdominant epitopes that are unique to the deregulated tumor microenvironment. While existing subdominant epitope vaccines are showing efficacy in preventing cancer, these vaccines are applicable only for subsets of patients with specific HLA subtypes. Therefore, we recently developed a degenerate HER2 subdominant epitope-based vaccine that should be useful in approximately 85% of all patients. The vaccine consists of a pool of four HLA-DR-restricted 15-amino acid epitopes (p59, p88, p422, and p885) that are naturally processed and are designed to elicit helper T cell immunity, the cornerstone of immune surveillance. Here we present Phase I trial results of this multi-peptide HER2 vaccine. Methods: Eligible women had HER2+ breast cancer (Stages II-III) and had completed standard treatment (i.e. surgery, chemotherapy, and trastuzumab) at least 90 days prior to enrollment and were rendered disease free. Vaccine included the above epitope pool along with adjuvant GM-CSF. Patients were vaccinated six times over six months and were monitored for toxicity at each visit. Peripheral blood samples were collected for immune responses evaluating for T cell and antibody immunity. Endpoints were safety and immunogenicity leading to the development CD4 helper T cells that recognized naturally-processed HER2. Results: Twenty-two subjects (age 33 to 69 years) were enrolled. At the present analysis, 21 have completed all 6 vaccination cycles; one patient withdrew after developing a grade 1 injection site reaction during the first vaccination cycle. Twenty patients have had LVEF measured after vaccination; only 2 patients had an LVEF drop of 10% or more but remained in the normal LEVF range. One severe toxicity was reported: a grade 3 INR increase considered unrelated to treatment. Mild to moderate (grade 1-2) toxicities included injection site reactions, fatigue, and white blood cell count decreases. All patients were alive at analysis and only one experienced a recurrence (median follow-up 507 days, range 22 – 844). Twenty patients have had immune response assessments. Vaccine induced T cell immunity was observed in 94% of patients to p59, in 94% of patients to p88, in 82% of patients to p422, and in 74% of patients to p885. Importantly, T cell immunity to naturally processed HER2 proteins occurred in 94% of patients. The mean number of T cells specific for each peptide, post vaccination, ranged from 349–528 T cells per million peripheral blood mononuclear cells (PBMCs). The mean number of T cells specific for whole HER2 protein was 783 T cells per million PBMCs compared to a mean of 898 T cells/million PBMCs specific for the foreign tetanus toxin. In contrast to T cell responses, modestly increased antibody immunity to HER2 occurred in 35% of patients, consistent with the T cell-inducing design of the vaccine. Conclusion: Our results show that it is possible to develop vaccines with broad HLA coverage that circumvent natural tolerance and induce tumor antigen-specific immunity in the vast majority of patients. Citation Format: Knutson KL, Kalli KR, Block MS, Hobday TJ, Padley DJ, Erskine CL, Dockter T, Suman VJ, Wilson G, Degnim AC. Robust generation of T cell immunity to HER2 in HER2+ breast cancer patients with a degenerate subdominant HLA-DR epitope vaccine. [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 P2-11-02.

Abstract Background: The Trial Assigning Individualized Options for Treatment (TAILORx) is a prospective trial evaluating the role of endocrine therapy or chemoendocrine therapy in patients 18-75 years of age with estrogen receptor (ER)-positive, HER2-negative breast cancer, a primary tumor between 0.6-5.0 cm, and negative axillary nodes, a population for whom chemotherapy is typically recommended or least considered based on National Comprehensive Cancer Center Network (NCCN) guidelines. Methods: The trial was designed to demonstrate non-inferiority of endocrine therapy compared with chemoendocrine therapy in the randomized group with an Oncotype DX Recurrence Score (RS) of 11-25. Patients with a low RS < 11 were assigned to endocrine therapy alone and with a high RS > 25 assigned to chemoendocrine therapy, and both groups were followed in a prospective registry. The definition of an intermediate RS differed in this trial (RS 11-25) from the original reports (RS 18-30) in order to reduce the risk of chemotherapy undertreatment in patients with a mid-range or low RS (Sparano & Paik. J Clin Oncol 2008; 26:721-728). Results: The trial enrolled 10,273 patients between April 2006 and October 2010, of whom 6907 patients (67.2%) had a mid-range RS of 11-25, 1737 (16.9%) had a high RS > 25, and 1639 (15.9%) had a low RS of < 11. At the fourth planned interim analysis, the ECOG-ACRIN data monitoring committee recommended that the study continue as planned for the randomized group with a RS 11-25, and that the results be released to the investigators for the low risk group with a RS <11. The characteristics of the low risk registry population are as follows: age 50 or less (27%), 51-60 (35%), > 60 (39%); tumor size < 1 cm (8%), 1-2 cm (61%), > 2 cm (31%); histologic grade low (34%), intermediate (59%), high (7%); breast conservation (68%) or mastectomy (32%). Initial endocrine therapy included tamoxifen in 35%, aromatase inhibitors in 59%, ovarian function suppression in 3%, and unspecified therapy in 3%; 5 patients received adjuvant chemotherapy (1 of whom relapsed). Five-year rates (and 95% confidence intervals [CI]) for low RS group were 99.2% (98.5, 99.6%) for distant relapse free interval, 98.5% (97.7, 99.1%) for relapse-free interval, 93.7% (92.2, 94.9%) for invasive disease free survival, and 98.2% (97.3, 98.7%) for overall survival. Information regarding ER, PR, and HER2 RNA expression will be presented. Conclusions: Despite meeting guidelines for recommending or at least considering adjuvant chemotherapy based on classical clinicopathologic features, the risk of recurrence was very low at 5 years in patients with ER-positive, HER2-negative, axillary node-negative breast cancer and a low RS of < 11 treated with endocrine therapy alone without chemotherapy. Citation Format: Sparano JA, Gray RJ, Makower DF, Pritchard KI, Albain KS, Hayes DF, Geyer Jr CE, Dees EC, Perez EA, Olson Jr JA, Zujweski J, Keane MM, Gomez Moreno HL, Reddi RP, Goggins TF, Mayer IA, Brufsky AM, Toppmeyer DL, Kaklamani VG, Atkins JN, Berenberg JL, Sledge Jr GW. Prospective trial of endocrine therapy alone in patients with estrogen receptor positive, HER2-negative, node-negative breast cancer: Results of the TAILORx low risk registry. [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 P2-08-01.

Abstract Background: The identification of organ-specific targetable signatures may help design more effective treatment for patients with metastatic breast cancer (MBC). We took a multi-OMIC approach to assess whether the AKT-mTOR pathway is globally activated during metastatic progression or whether it represents an organ-specific target. Methods: Snap frozen biopsies from 25 MBC patients enrolled in a prospective phase II trial were used. Sites of metastasis were classified as liver (n=8) and others (n=17), the latter including cutaneous, lung, lymph nodes, and intra-abdominal lesions. Signaling analysis of the 25 cases was performed using Reverse Phase Protein Microarray (RPPA) coupled with Laser Capture Microdissection. Activation of the AKT-mTOR pathway was quantified as phosphorylation of AKT (S473) and the mTOR target p70S6 (T389). Matched exome (WES) and RNASeq data were available for 17 of 25 patients, five with liver metastases. Sequencing data was processed using an in-house developed pipeline to identify somatic events including coding mutations, copy number alterations, gene fusions, and differential expression. Activation of the AKT-mTOR pathway and sequencing data were compared between hepatic and non-hepatic lesions using an integrated RPPA and genomic approach. Results: Among liver metastases, AKT was activated in 4 of the 8 (50.0%) patients, while 6 of the 8 cases (75.0%) showed activation of p70S6. Sequencing data revealed mutation of PIK3CA in 4 of the 5 liver metastases (80.0%). Three of the PIK3CA mutated specimens with catalytic domain mutations (codons 1023 and 147) demonstrated co-activation of AKT and p70S6, while the fourth case, containing a helical domain mutation (E542K), had activation of p70S6 only. The PIK3CA wild-type liver metastasis demonstrated low activation of AKT and p70S6. For non-hepatic metastases AKT was activated in 2 of the 17 cases (11.8%) and p70S6 in 5 of the 17 patients (29.4%). Discussion: Although these results need further validation, activation of the AKT-mTOR pathway appears to be a hepatic specific signature in MBC and could be used for the selection of targeted agents for hepatic lesions. Citation Format: Pierobon M, Wong S, Reeder A, Anthony SP, Robert NJ, Northfelt DW, Jahanzeb M, Vocila L, Wulfkuhle J, Dunetz B, Aldrich J, Byron S, Craig D, Liotta L, Petricoin EF, Carpten J. The AKT-mTOR pathway as a potential organ-specific drug target signature of hepatic metastases from 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 P2-05-21.

Abstract 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 > 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 Background ACOSOG Z1041 (Alliance) found pathological complete response rates in women with operable HER2-positive breast cancer were similar with FEC → P+T (Arm 1) and P+T → FEC+T (Arm 2) where treatment was administered as 5-FU 500 mg/m2, epirubicin 75 mg/m2 and cyclophosphamide 500 mg/m2 day 1 of a 21-day cycle x 4; paclitaxel 80 mg/m2 weekly x 12 and trastuzumab 4 mg/kg once then 2 mg/kg weekly x 11. We now report DFS and OS results with a median follow up of 4.4 years (range: 26 days to 6.2 years). Methods All patients who began study treatment were included in the analyses. Stratified log rank tests and stratified proportional hazard models were used to assess differences in DFS and OS from randomization between treatment arms. Results From September 15, 2007 to December 15, 2011, 282 women with HER2-positive breast cancer were enrolled. Two patients randomized to arm 1 withdrew consent prior to treatment and are excluded from these analyses. Patient and disease characteristics of the remaining 280 women (arm 1, n=138; arm 2, n=142) were similar between treatment arms. Recurrences and deaths are shown in the table. DFS were not found to differ with respect to treatment arm (stratified logrank p=0.6870; HR stratified (Arm2/Arm1)=0.88; 95%CI: 0.48-1.61). Also, OS was not found to differ with respect to treatment arm (stratified logrank p=0.8790; HR stratified (Arm2/Arm1)=1.07; 95%CI: 0.43-2.69). Conclusions Concurrent administration of trastuzumab with anthracyclines offers no additional benefit in terms of achieving pathologic complete response or improving survival and is not needed. FEC → P+TP+T → FEC+T Arm 1Arm 2n138142Recurrences2022Deaths811 Grant Support: U10 CA76001 The study is registered with ClinicalTrials.gov, number NCT00513292. Citation Format: Buzdar AU, Suman VJ, Meric-Bernstam F, Leitch AM, Ellis MJ, Boughey JC, Unzeitig GW, Royce ME, Ewer MS, Hunt KK. Disease-free (DFS) and overall survival (OS) data from ACOSOG Z1041 (Alliance) a randomized neoadjuvant trial comparing FEC followed by paclitaxel plus trastuzumab (FEC → P+T) with paclitaxel plus trastuzumab followed by FEC plus trastuzumab (P+T → FEC+T) in HER2-positive operable 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 P1-14-02.

Abstract Background: Etirinotecan pegol (EP) is a long-acting Top1 inhibitor providing sustained levels of active metabolite throughout the entire chemotherapy cycle. The phase 3 BEACON trial compared EP to treatment of physician's choice (TPC) in patients with advanced breast cancer, demonstrating a non-statistically significant 2.1 month difference in survival favoring EP in the intent to treat population. A novel aspect of the BEACON trial is to explore the utility of biomarkers measured in CTCs for predicting efficacy with EP. Pre- and post-treatment CTCs were isolated from blood of 77% of the 852 BEACON patients. Target-specific pharmacodynamic biomarkers for EP measured in CTCs were analyzed to identify patients most responsive to treatment with EP. Methods: Donation of blood samples for CTC analysis was voluntary. Participating BEACON patients had serial (baseline, Cycle 2 Day 1 [C2D1], Cycle 4 Day 1 [C4D1], End of Treatment) 7.5-mL whole blood samples drawn in EDTA tubes and shipped within 96 hours ambient to ApoCell (Houston, TX) for processing. PBMCs were separated by Ficoll® gradient, and CTCs were isolated using ApoStream® technology. Isolated cells were deposited on three slides and stained for DAPI, CD45, cytokeratin markers, as well as Top1, Top2, Ki67, γH2AX, Rad51, ABCG2, and TUNEL. Biomarkers were quantified by iCys® laser scanning cytometer equipped with image analysis software, and correlated with OS using Cox multiple regression and Kaplan-Meier analyses. Results: The CTC substudy yielded 611 pre-treatment, 519 C2D1, 268 C4D1, and 431 End of Treatment samples. Among the successfully processed blood samples, 98% had detectable CTCs, with a median of 63, 46, 51, and 57 CTCs/mL at baseline, C2D1, C4D1, and End of Treatment, respectively. Cox regression analyses of CTC number and percentage of Top1, Top2, Ki67, or TUNEL positive CTCs identified a correlation for post-treatment number of Top1-positive CTCs with OS in patients receiving EP. To assess the impact of Top1-positive CTCs, patients were classified as Top1-High (> median) or Top1-Low (≤ median) based on the percent of Top1-positive CTCs at baseline. Among the Top1-High patients at baseline, significantly improved OS (HR 0.54, p=0.007) was observed for those who converted to Top1-Low after their first treatment with EP (C2D1), but not TPC (HR 1.12, p=0.613). These results suggest that decreased number of Top1-positive CTCs may reflect EP target engagement with Top1, as these patients derived the most benefit from treatment. Conclusions: CTC collection and analysis was successfully incorporated into the phase 3 BEACON study, with 77% patient participation. CTC detection rate using ApoStream® was high, permitting evaluation of biomarkers at baseline and post-treatment. Significantly improved OS was observed in patients who had a decreased number of Top1-positive CTCs following cycle 1 of EP. Citation Format: Rugo HS, Cortes J, Awada A, O'Shaughnessy J, Twelves C, Im S-A, Hannah AL, Lu L, Sy S, Caygill K, Zajchowski D, Davis DW, Hoch U, Perez EA. Early change in topoisomerase 1 (Top1) positive circulating tumor cells (CTCs) is associated with overall survival (OS) in patients with advanced breast cancer after treatment with etirinotecan pegol. [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 P1-13-02.