Triple-negative Breast Cancer Cohort Research Articles

Abstract P1-07-03: Mesenchymal subtype negatively associates with the presence of immune infiltrates within a triple negative breast cancer classifier

Abstract Introduction: Lehmann and colleagues (Lehmann et al., 2011) devised a gene expression classification system for triple negative breast cancer (TNBC) consisting of seven subtypes—IM, BL1, BL2, LAR, M, MSL, and UNS (unselected). We (Ring et al., 2016) recently modified this original algorithm of 2188 gene subtyping into a 101-gene algorithm. In addition to a reduction of genes, the 101-gene algorithm has two methodological differences: first, the immunomodulatory (IM) signature was treated not as a subtype but rather as a binary feature of one of the other subtypes (e.g. BL1/IM+, LAR/IM-); second, when tumors—by a predefined correlation coefficient—showed traits of more than one subtype, both subtypes were reported as “dual subtypes.” Aim: Our aim was to apply the 101-gene algorithm for TNBC subtyping and to establish the relation of TNBC subtypes with their IM-status across several independent data sets. Methods: 951 patients from four independent TNBC cohorts with available gene expression data were analyzed by the 101-gene algorithm. Of these 848 were classified with at least one subtype. Results: The distribution of the 5 TNBC subtypes in both single and dual subtypes was 47%,10%,15%,18%,11%, for BL1, BL2, LAR, M, and MSL respectively. The majority of cases gave only one subtype (572, 67%) with M (Mesenchymal) being 9% (n=54) of these. Given this frequency of 9% of M as a baseline, in the remaining 276 (33%) cases with dual subtypes, the expectation that M would be one of the two is 11% (64 subtype calls). However, M is one of the two of the dual subtypes at a much higher frequency of 40% (222 subtype calls, Chi-Squared, P<0.0001). IM+ is a common feature across these cohorts (n=310 or 37%). When examining the IM feature within the patients exhibiting the M subtype as either a single subtype or one of the two dual subtypes (n=276, 33%), IM positive tumors are never of the M phenotype (Chi-Squared, p<0.0001). Conclusions: We further have confirmed with the 101-gene algorithm that the IM signature inversely associates with the M subtype as it has been observed with the 2188 gene algorithm (Lehmann et al., 2016). Moreover, the M signature is occasionally a confounder of other subtypes however still identifies those tumors negative for immune infiltrates. This raises important opportunities to understand the relationships between intrinsic tumor biology reflected in TNBC subtypes and their interaction with variable immune cell stroma which are the subject of ongoing analyses. Citation Format: Grigoriadis A, Quist J, Mirza H, Cheang MC, Ring BZ, Hout DR, Bailey DB, Seitz RS, Tutt AN. Mesenchymal subtype negatively associates with the presence of immune infiltrates within a triple negative breast cancer classifier [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 P1-07-03.

Abstract B12: Racial differences in Androgen Receptor status among triple-negative breast cancers

Abstract Background: Triple Negative Breast Cancer (TNBC) is an aggressive subtype of breast cancer with high recurrence and mortality rates. Currently, there are no effective targeted therapies available for TNBC. Emerging data suggest that androgen receptor (AR), a nuclear steroid hormone receptor expressed in 10-43% of TNBCs, has emerged as a promising new biomarker with potential predictive value for certain TNBC subtypes. African American (AA) women suffer from earlier onset of the breast cancer along with significant aggressive disease course when compared to European American (EA) women. This study aimed to determine the prognostic value of AR in a large TNBC cohort and evaluate racewise trends in AR expression status among TNBCs. Methods: We evaluated AR expression immunohistochemically in formalin-fixed paraffin-embedded samples from 822 TNBC patients (142, 95 and 264 patients from Emory, Northside and Grady Memorial Hospitals, respectively, in Atlanta, and 321 from Nottingham Hospital, UK) for whom complete clinicopathologic and overall survival (OS) data were available. Ethnicity data were available for 138 AA and 675 EA TNBC cases. Samples with <1% nuclear-stained cells were considered quadruple-negative (QN). Associations between nuclear AR status, race, other clinicopathologic variables and OS were evaluated through survival analyses and multivariate Cox regression. Results: In this study, 45.6% of the TNBC cases were QN and AAs had a much higher proportion (80.8%) of QN cases than EAs (40.1%, p<0.0001). QN receptor status was significantly associated with younger age (age< 25) at diagnosis, AA ethnicity and higher (KI>14%) proliferative index (p<0.001 for all) in univariate analyses. In multivariate analyses, loss of AR expression was associated with poorer OS (p<0.05, HR=2.8) after adjusting for grade, stage and adjuvant therapy. Conclusion: This study suggest that a higher prevalence of QN breast cancer among AAs may be a plausible reason for the ethnic disparity in outcomes among TNBC patients and strongly support the prognostic role of AR in this breast cancer subtype. Citation Format: Bhattarai Shristi, Jun Xia, Ceyda Sonmez Wetherilt, Sergey Klimov, Ansa Riaz, Sonal Pattni, Mohammad A. Aleskandarany, Andrew R. Green, Emad A. Rakha, Ian O. Ellis, Guilherme Cantuaria, Xiaoxian (Bill) Li, Uma Krishnamurthi, Remus Mihai Osan, Padmashree CG Rida, Ritu Aneja. Racial differences in Androgen Receptor status among triple-negative breast cancers. [abstract]. In: Proceedings of the Ninth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2016 Sep 25-28; Fort Lauderdale, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2017;26(2 Suppl):Abstract nr B12.

Predictors of Chemosensitivity in Triple Negative Breast Cancer: An Integrated Genomic Analysis.

BackgroundTriple negative breast cancer (TNBC) is a highly heterogeneous and aggressive disease, and although no effective targeted therapies are available to date, about one-third of patients with TNBC achieve pathologic complete response (pCR) from standard-of-care anthracycline/taxane (ACT) chemotherapy. The heterogeneity of these tumors, however, has hindered the discovery of effective biomarkers to identify such patients.Methods and FindingsWe performed whole exome sequencing on 29 TNBC cases from the MD Anderson Cancer Center (MDACC) selected because they had either pCR (n = 18) or extensive residual disease (n = 11) after neoadjuvant chemotherapy, with cases from The Cancer Genome Atlas (TCGA; n = 144) and METABRIC (n = 278) cohorts serving as validation cohorts. Our analysis revealed that mutations in the AR- and FOXA1-regulated networks, in which BRCA1 plays a key role, are associated with significantly higher sensitivity to ACT chemotherapy in the MDACC cohort (pCR rate of 94.1% compared to 16.6% in tumors without mutations in AR/FOXA1 pathway, adjusted p = 0.02) and significantly better survival outcome in the TCGA TNBC cohort (log-rank test, p = 0.05). Combined analysis of DNA sequencing, DNA methylation, and RNA sequencing identified tumors of a distinct BRCA-deficient (BRCA-D) TNBC subtype characterized by low levels of wild-type BRCA1/2 expression. Patients with functionally BRCA-D tumors had significantly better survival with standard-of-care chemotherapy than patients whose tumors were not BRCA-D (log-rank test, p = 0.021), and they had significantly higher mutation burden (p < 0.001) and presented clonal neoantigens that were associated with increased immune cell activity. A transcriptional signature of BRCA-D TNBC tumors was independently validated to be significantly associated with improved survival in the METABRIC dataset (log-rank test, p = 0.009). As a retrospective study, limitations include the small size and potential selection bias in the discovery cohort.ConclusionsThe comprehensive molecular analysis presented in this study directly links BRCA deficiency with increased clonal mutation burden and significantly enhanced chemosensitivity in TNBC and suggests that functional RNA-based BRCA deficiency needs to be further examined in TNBC.

Differences in the mutational landscape of triple-negative breast cancer in African Americans and Caucasians.

Triple-negative breast cancer (TNBC) occurs at higher frequency in African Americans compared with Caucasians. It is unclear if the biology of TNBC is different in African American versus Caucasians. In this study, we sought to evaluate racial differences in the molecular pathology of TNBC. Using data from The Cancer Genome Atlas, we identified TNBC patients with information on race. We analyzed differences in clinical characteristics, tumor somatic mutations, and gene expression patterns by race from whole exome and microarray data. 1104 patients were identified, of which 178 had TNBC. TNBC was more frequent in African Americans than Caucasians (33.3 vs 14.9%). Although more African Americans than Caucasians overall were classified as basal-like from PAM50 gene expression (34.8 vs 16.1%), no differences in the TNBC cohort were observed. Median tumor somatic mutation counts were higher in African Americans versus Caucasians (39.5 vs 34), but no racial differences in the mutation counts in TNBC were observed. Somatic mutation analysis revealed racial differences in specific high prevalence genes in all patients (TP53 46% in African Americans vs 27% in Caucasians; PIK3CA 23% in African Americans vs 34% in Caucasians; and MLL3 12% in African Americans vs 6% in Caucasians). TNBC patients did not have any specific high prevalence genes associated with racial differences. There were no racial differences in gene expression patterns in selected genes involved in breast cancer biology. Overall, African Americans had shorter TTP and worse DFS. Racial differences in clinical outcomes were not observed in TNBC. The mutational landscape of TNBC is similar between African Americans and Caucasians. The higher frequency of TNBC in African Americans is therefore not associated with a different genomic profile of commonly established tumor regulatory pathway genes. Other modifiable factors may exist that contribute to the racial disparity in TNBC.

Identification of BRCA1-like triple-negative breast cancers by quantitative multiplex-ligation-dependent probe amplification (MLPA) analysis of BRCA1-associated chromosomal regions: a validation study.

BackgroundTriple-negative breast cancer (TNBC) with a BRCA1-like molecular signature has been demonstrated to remarkably respond to platinum-based chemotherapy and might be suited for a future treatment with poly(ADP-ribose)polymerase (PARP) inhibitors. In order to rapidly assess this signature we have previously developed a multiplex-ligation-dependent probe amplification (MLPA)-based assay. Here we present an independent validation of this assay to confirm its important clinical impact.MethodsOne-hundred-forty-four TNBC tumor specimens were analysed by the MLPA-based “BRCA1-like” test. Classification into BRCA1-like vs. non-BRCA1-like samples was performed by our formerly established nearest shrunken centroids classifier. Data were subsequently compared with the BRCA1-mutation/methylation status of the samples. T-lymphocyte infiltration and expression of the main target of PARP inhibitors, PARP1, were assessed on a subset of samples by immunohistochemistry. Data acquisition and interpretation was performed in a blinded manner.ResultsIn the studied TNBC cohort, 63 out of 144 (44 %) tumors were classified into the BRCA1-like category. Among these, the MLPA test correctly predicted 15 out of 18 (83 %) samples with a pathogenic BRCA1-mutation and 20 of 22 (91 %) samples exhibiting BRCA1-promoter methylation. Five false-negative samples were observed. We identified high lymphocyte infiltration as one possible basis for misclassification. However, two falsely classified BRCA1-mutated tumors were also characterized by rather non-BRCA1-associated histopathological features such as borderline ER expression. The BRCA1-like vs. non-BRCA1-like signature was specifically enriched in high-grade (G3) cancers (90 % vs. 58 %, p = 0.0004) and was also frequent in tumors with strong (3+) nuclear PARP1 expression (37 % vs. 16 %; p = 0.087).ConclusionsThis validation study confirmed the good performance of the initial MLPA assay which might thus serve as a valuable tool to select patients for platinum-based chemotherapy regimens. Moreover, frequent PARP1 upregulation in BRCA1-like tumors may also point to susceptibility to treatment with PARP inhibitors. Limitations are the requirement of high tumor content and high-quality DNA.

UPAR enhances malignant potential of triple-negative breast cancer by directly interacting with uPA and IGF1R.

BackgroundDue to lack of a targeted therapy for the triple-negative breast cancer (TNBC) patients, it is important to explore this aggressive breast cancer type in more detail and to establish novel therapeutic approaches. TNBC is defined negative for the protein expression of oestrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2). One prominent feature of this cancer type is the frequent overexpression of major components of the urokinase-type plasminogen activator system (uPAS) including uPA, its receptor uPAR and the inhibitor PAI-1, which may be valuable as therapeutic targets.MethodsDirect interactions of uPAR with interactors were demonstrated by immunoprecipitations and proximity ligation assays. For stable knockdowns of target proteins, lentiviral vectors were used and the effects were analysed by immunoblottings and using in vitro cell viability, migration and invasion assays. Immunohistochemical and statistical analyses of biomarkers and clinical parameters were conducted in a TNBC cohort (n = 174).ResultsDirect tumour-promoting interactions of uPAR with uPA and the insulin-like growth factor receptor 1 (IGF1R) were shown in TNBC cells and these interactions were significantly reduced (p = 0.001) when uPAR was downregulated. The combined knockdown of uPAR and uPA or IGF1R additively and significantly reduced cell viability, migration and invasion of the model cell lines. In TNBC tissue, the complexes formed by uPAR with uPA or with IGF1R significantly correlated with the histological grade (p = 0.0019) as well as with cathepsin B and D (p ≤ 0.0001) that are implicated in cell invasion and metastasis.ConclusionsOur outcomes show that not only overexpressed biomarkers promote tumourigenesis, but rather their interactions further potentiate tumour progression. This study emphasises the potential of combined approaches targeting uPAR and its interactors with regard to an improved therapy of TNBC.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-016-2663-9) contains supplementary material, which is available to authorized users.

Cyr61 and YB-1 are novel interacting partners of uPAR and elevate the malignancy of triple-negative breast cancer.

The triple-negative breast cancer (TNBC) is a very aggressive tumor type often occurring in young women and is associated with a bad prognosis for the patients. TNBC lacks established targets for breast cancer therapy, such as the estrogen receptor (ER), progesterone receptor (PR) and the human epidermal growth factor receptor 2 (HER2). Therefore, novel therapeutic targets and strategies are needed for an improved treatment of this breast cancer subtype. TNBC and respective cell lines often overexpress proteins of the urokinase plasminogen activator system (uPAS) including uPA, its receptor uPAR and inhibitor PAI-1, which together with co-factors contribute to the malignancy of TNBC. Here, two novel interacting partners of uPAR, the cysteine-rich angiogenic inducer 61 (Cyr61) and the Y-box-binding protein 1 (YB-1) were identified and their differential expression demonstrated in TNBC cells as well as in tumors. In the TNBC cohort, both interactors significantly correlated with expression levels of cathepsin B, c-Met and the tumor grade. In addition, expression levels of Cyr61 significantly correlated with cathepsin D (p=0.03), insulin receptor (p≤0.001), insulin-like growth factor receptor 1 (IGF1R, p=0.015) and also with YB-1 (p=0.0004) levels. The interactions of uPAR with Cyr61 significantly correlated with expression levels of tumor-promoting biomarkers including plasminogen (p=0.0014), cathepsin B (p=0.032), c-Met (p=0.0192) as well as with the tumor grade (p=0.02). In multivariate survival analysis, YB-1 showed independent prognostic value (p=0.01). As the novel interacting partners, also together with uPAR, contribute to tumor progression and metastasis, both may be potential therapeutic targets in breast cancer.

Neoadjuvant Chemotherapy in Triple Negative Breast Cancer: An Observational Study.

Triple negative breast cancer (TNBC) is a phenotype of breast cancer with aggressive clinical behavior. Because of the absence of optimal treatment, the prognosis of this disease is poor. The main purpose of this study was to detect the response to neoadjuvant chemotherapy (NACT) in a TNBC cohort and compare the long-term survival between patients with and without pathological complete response (pCR). A total of 53 patients diagnosed with TNBC from 2005 to 2013 who received NACT at the University Hospital Birmingham were enrolled in this study. Overall survival (OS) and progression-free survival (PFS) were compared between the pCR group and non-pCR group. Demographic information and clinical or pathologic parameters were also analyzed to explore potential predictive and prognostic factors. Fourteen patients (26.4%) achieved pCR to NACT. In univariate analysis, patients with pCR had longer PFS time (p = 0.013) and OS time (p = 0.054) compared with their counterparts without pCR. In multivariate analysis, the existence of lymphovascular invasion (LVI) significantly reduced OS (HR = 17.404, 95% CI = 2.923–103.644) and PFS (HR = 7.776, 95% CI = 1.645–36.753). The achievement of pCR to NACT can significantly postpone the incidence of disease progression in patients with TNBC. There is not enough evidence showing its influence on ultimate survival. LVI may be a more potent prognostic factor than pCR in the TNBC cohort.

Eligibility Criteria and Genetic Testing Results from a High-Risk Cohort for Hereditary Breast and Ovarian Cancer Syndrome in Southeastern Ontario

Germline mutations in breast and ovarian cancer are rare, with approximately 5% to 10% and 13% being hereditary in origin, respectively. In 2001, the Ontario Ministry of Health and Long Term Care, in an effort to contain costs, defined criteria to determine an individual's eligibility for BRCA genetic screening. We studied a cohort of individuals that have undergone genetic testing at Kingston General Hospital between 2001 and late 2013. We focused on determining whether the 13 risk criteria, defined by an expert working group for the Ontario Ministry of Health and Long Term Care, have performed according to expectations in this cohort. Our findings show that all of the criteria perform well by identifying carriers at the expected 10% rate defined by the guidelines. We demonstrate that loose application of the risk criteria does not further enrich for BRCA variant carriers. Our assessment of the established risk criteria that have been in use in Ontario for more than a decade, provide evidence for their effectiveness, and offer insights into how they may be expanded or improved.

MxA expression is associated with tumor-infiltrating lymphocytes and is a prognostic factor in triple-negative breast cancer.

Interferons (IFNs) play an important role in tumor-immune system interactions. As one of the main mediators of IFNs, myxovirus resistance A (MxA) is upregulated in various cancers. However, the exact role of MxA in breast cancer is not fully understood. As part of the immune response to tumors, tumor-infiltrating lymphocytes (TILs) have prognostic significance in breast cancer. The aim of our present study was to examine the relationship between MxA and immune system components, including the amount of TILs and human leukocyte antigen (HLA) expression, in breast cancer. TILs, MxA expression, HLA intensity, and clinicopathological factors were retrospectively analyzed in 688 patients with primary breast cancer between 1993 and 1998 and in 705 patients with triple-negative breast cancer (TNBC) between 2004 and 2011. MxA expression was higher in TNBC tumors than in other subtypes. High MxA levels were associated with a higher histologic grade, abundant TILs, and stronger HLA-ABC expression in both the TNBC subtype within the consecutive breast cancer cohort and the validation TNBC cohort. MxA expression showed a significant positive correlation with TILs, the number of CD8(+) cells, and the number of CD69(+) cells in the validation TNBC cohort. High MxA levels and abundant TILs were found to be independent prognostic factors for disease-free survival in patients with TNBC. These results indicate that MxA expression is closely related to TILs in TNBC and, along with TILs, provides prognostic information after chemotherapy in patients with TNBC.

Abstract A18: miR-9 and miR-200 regulate PDGFRβ-mediated endothelial differentiation of neoplastic cells in triple-negative breast cancer

Abstract Tumor vascularization is a fundamental step in solid tumor progression and is orchestrated by different pathways of vasculogenesis. In malignant tumors, neoplastic cells can differentiate into endothelial-like cells acquiring the expression of endothelial markers (i.e. CD31 and CD34) and participating in the formation of vascular-like structures that functionally deliver oxygen and nutrients to the tumor site. We recently identified PDGFRβ as an important player of this process in triple negative breast cancer (TNBC). Interestingly, increasing evidence supported a connection between PDGFRβ and epithelial to mesenchymal transition (EMT), important step for the endothelial trans-differentiation process. PDGFR signaling arose as a promising target for TNBC; thus a better understanding of this new role of PDGFRβ could be relevant in the biology and treatment of TNBC. We then aimed at investigating microRNAs able to regulate tumor vascularization via PDGFRβ-mediated endothelial differentiation in TNBC, focusing on miR-9 and miR-200 family in light of their known relation with PDGFRβ and EMT. Tube formation assay showed that in MDA-MB-231 and MDA-MB-157 TNBC cell lines transfection of miR-9 and miR-200 family members (miR-200b and miR-200c) promoted or inhibited, respectively, the ability of cells to form vascular-like structures when seeded on matrigel. Stimulation of PDGFRβ with PDGF-BB ligand induced miR-9 expression and enhanced the loop formation ability of treated cells. This advantage was, however, almost completely abrogated by the concomitant inhibition of miR-9, thus demonstrating that miR-9 contributed to PDGFRβ-mediated vasculogenic properties of TNBC. Moreover, we found that silencing of STARD13, direct target of miR-9 validated by luciferase reporter assay, improved the vasculogenic potential. Ectopic expression of miR-200 members, instead, suppressed PDGFRβ at protein level in both TNBC cell lines. Furthermore, the silencing of ZEB1, known target of miR-200 family, induced downregulation of PDGFRβ at protein and mRNA level; interestingly, the mRNA levels of ZEB1 and PDGFRβ strongly correlated in the TNBC subset of the TGCA dataset. The in vivo effect of miR-9 and miR-200 family on vasculogenic properties of TNBC was then validated first through the generation of MDA-MB-231 clones for stable inhibition of miR-9 and restoration of miR-200c; the resulting miR-9 sponge and miR-200c xenografted tumors showed lower number of vascular lacunae than controls, identified through immunohistochemical (IHC) staining for CD31. These results were validated in orthotopic MDA-MB-231 breast tumors treated with miR-9 inhibitors or miR-200c mimics by peritumoral injection. We finally evaluated PDGFRβ, by IHC, and miR-9 and miR-200c, by Real-time PCR, in a cohort of TNBC. IHC analysis demonstrated that PDGFRβ staining identified tumor cells participating in vascular lacunae, data further confirmed by immunofluorescence co-localization of PDGFRβ and CD31. Interestingly, unlike miR-9, the expression of miR-200c negatively associated with both the presence of vascular lacunae and tumor nests positive for PDGFRβ. Finally, in situ hybridization analysis revealed that miR-200c was mainly expressed by tumor cells. In conclusion, our results suggest that miR-9 and miR-200 family play an opposite role in the regulation of the vasculogenic aptitude of TNBC. MiR-9 is induced by PDGFRβ and enhances the vasculogenic properties of tumor cells in part through the negative regulation of STARD13. MiR-200, instead, inhibits this aggressive phenotype indirectly suppressing PDGFRβ through targeting of ZEB1. Citation Format: Elvira D'Ippolito, Ilaria Plantamura, Lucia Bongiovanni, Patrizia Casalini, Sara Baroni, Claudia Piovan, Rosaria Orlandi, Ambra V. Gualeni, Annunziata Gloghini, Anna Rossini, Filippo De Braud, Elda Tagliabue, Claudio Tripodo, Marilena V. Iorio. miR-9 and miR-200 regulate PDGFRβ-mediated endothelial differentiation of neoplastic cells in triple-negative breast cancer. [abstract]. In: Proceedings of the AACR Special Conference on Noncoding RNAs and Cancer: Mechanisms to Medicines ; 2015 Dec 4-7; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2016;76(6 Suppl):Abstract nr A18.

Abstract C54: High caveolin-1 expression in a cohort of African American women with triple-negative breast cancer

Abstract In the U.S., the incidence rates of breast cancer (BC) among Caucasian (CA) women are lower than those of African American (AA), however, AA women have a significantly higher mortality rate. AA women often present at a younger age, with later stage and higher grade tumors. In fact, AA women are 3x more likely to be diagnosed with the more aggressive molecular subtype, triple-negative breast cancer (TNBC), than CA women. Socioeconomic and lifestyle factors may be contributory; however, it is imperative that we investigate the underlying molecular biology that may be the cause of health disparities between AA and CA with TNBC. In this study, gene expression profiling, using the Almac BC DSA Research Tool, was performed on archived FFPE samples, obtained from CA and AA women diagnosed with early stage (Node 0) TNBC. Unsupervised hierarchical clustering revealed a pattern of differential gene expression in the AA cohort compared to CA. Using the TNBC type: A Subtyping Tool for TNBC, we found a distinct distribution pattern of TNBC molecular subtypes in the AA cohort, which was very different than the CA cohort; Basal-like (14%), Immunomodulatory (43%) and Mesenchymal (43%). Gene expression analyses, comparing the AA and CA cohort (fold change &amp;gt; 2.0, p-value &amp;lt;.05), resulted in 190 differentially expressed genes (DEG). Pathway enrichment analysis conducted in MetaCore GeneGo, revealed that the DEGs were over-represented in cytoskeletal remodeling, cell adhesion, tight junctions, and immune response in the AA TNBC cohort. Furthermore, several genes in the Wnt/β-catenin pathways were over-expressed in the top 10-enrichment pathways. We validated our results using RT-qPCR and identified Caveolin-1 (CAV1) as being significantly expressed in the AA-TNBC cohort (p-value 1.22 x 10-05). An independent cohort of FFPE samples, from AA and CA women with early stage TNBC, was used to create a tissue microarray (TMA). Immunohistochemistry results showed no difference in localization of Cav1 between the AA and CA cohorts, however, the AA cohort had significantly higher levels of Cav1 staining (p-value 0.04). Additionally, using RT-qPCR, we demonstrated that CAV1 mRNA was significantly higher in the AA TNBC Cohort (p-value 0.48). Furthermore, endogenous Cav1 was shown to be highly expressed in a cell line panel of TNBC, in particular, those of the mesenchymal and basal-like molecular subtype. Finally, using siRNA, we demonstrated that CAV1 silencing resulted in a significant decrease in cell proliferation, for each of the TNBC cell lines while it showed no effect on the luminal ER+ cell lines. Our combined study results suggest that CAV1 over-expression may be a biological contributor to the observed health disparity between AA women and CA diagnosed with early stage TNBC. Citation Format: Julie E. Getz, Davyd B. Teoh, Sara Nasser, Christophe R. Legendre, Waibhav Tembe, Venkata Yellapantula, Mary Ellen Ahearn, Carmen R. Gomez, Merce Jorda, Shuk Mei Wong, Mark D. Pegram, John D. Carpten, Lisa L. Baumbach-Reardon. High caveolin-1 expression in a cohort of African American women with triple-negative breast cancer. [abstract]. In: Proceedings of the Eighth AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 13-16, 2015; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2016;25(3 Suppl):Abstract nr C54.

Cytoplasmic expression of high mobility group B1 (HMGB1) is associated with tumor-infiltrating lymphocytes (TILs) in breast cancer.

High mobility group box 1 (HMGB1) is a prototypic alarmin or damage-associated molecule inducing inflammatory mediator release and immune response. Several studies have revealed the prognostic and predictive importance of tumor-infiltrating lymphocytes (TILs) in breast cancer. The present study analyzed the expression of HMGB1 in each breast cancer subtype and the relationship between the expression level of HMGB1 and pathologic parameters including TILs. Two cohorts were studied: 575 consecutive breast cancer patients who underwent surgery between 1995 and 1998; and 767 triple negative breast cancer (TNBC) patients who underwent surgery between 2004 and 2010. The immunohistochemical expression level of HMGB1 in cytoplasm and nucleus was evaluated using tissue microarrays. High HMGB1 expression in cytoplasm was associated with high histologic grade, pT stage, and abundant TILs in the consecutive breast cancer cohort. Cytoplasmic HMGB1 expression was higher in TNBCs and HER2-positive tumors than in hormone receptor-positive tumors. In the TNBC cohort, high cytoplasmic HMGB1 expression was significantly associated with high histologic grade, abundant TILs, and high numbers of CD8+ cells. However, nuclear HMGB1 expression was not associated with histologic grade or TIL levels. Neither cytoplasmic nor nuclear expression of HMGB1 showed prognostic significance in TNBC. Cytoplasmic HMGB1 expression is associated with TIL levels in breast cancer.

Abstract P3-07-55: Predictive value of O6-methylguanine-DNA methyltransferase (MGMT) promoter gene methylation in triple-negative breast cancer patients receiving carboplatin

Abstract Background: The epigenetic profile of triple-negative breast cancer (TNBC) showed a wide prevalence of MGMT promoter methylation.Aberrant methylation of MGMT seems to be an independent predictor of poor survival in patients with basal-like breast cancer. Moreover, patients with MGMT-negative basal-like tumors who received cyclophosphamide had asignificantly improved DFS and OS compared with MGMT-positive tumors.However, the impact of MGMT methylation in the context of modern therapy concepts is not clear. Methods: We retrospectively evaluated 174 TNBC tumors of patients enrolled into the neoadjuvantGeparSixtotrial from 08/2011 to 12/2012. Patients were randomized to receive 18 weeks of neoadjuvant treatment with paclitaxel (80mg/m2/week) and non-pegylated liposomal doxorubicin (20mg/m2/week) with or without addition of carboplatin (AUC 2.0-1.5/week).Hormone-receptor status, HER2status, and Ki67 were centrally confirmed prior to randomization. We defined pathological complete response (pCR)as ypT0/is ypN0. MGMT promoter methylation status was determined by PCR using EZ DNA Methylation Kit™ (Zymo Research); TNBCtumors were considered to be methylated if they had an average methylation ≥10%, some tumors were considered borderline due to high heterogeneity among GpC islands.We investigated the effect of MGMT methylation on pCR and its correlation with baseline characteristics. Results: A total of210 tumors from the TNBC cohort of the GeparSixtotrial(n=315) were available with a tumor content &amp;gt;20%. In 174 tumors the methylation assay was performed successfully. The number of tumorswith methylated MGMT was similar in carboplatin vs. non-carboplatin treated cohorts. In the carboplatin group 19.3% (17/88) of TNBC were methylated, 65.5% (58/88)unmethylated, and 14.8% (13/88) borderline.In the non-carboplatin group 20.9% (18/86) of TNBC were methylated, 62.8% (54/86)unmethylated, and 16.3% (14/86) borderline.In the entire cohort,there was no association between MGMT methylation status and pCR (p=0.522).Non-carboplatin cohort: 33.3% (6/18) of patients with methylated MGMT achieved pCR vs. 51.9% (28/54) of unmethylatedand 21.4% (3/14) of borderline (p=0.079).Carboplatin cohort: 52.9% (9/17) of patients with methylated MGMT achieved pCR vs. 55.2% (32/58) of unmethylatedand 76.9% (10/13) of borderline (p=0.320). In TNBC patients with methylated MGMT, the addition of carboplatin resulted in a 20% increased pCR rate (p=0.241). Conclusion: In this study no statistically significant association between MGMT methylation andpCR was found.Patients with MGMT methylation seemed to have a lower possibility to achieve a pCR and the addition of carboplatin seemed to reverse this effect. However, a clear classification of the borderline MGMT samples and further studies in larger series of TNBC are warranted. Citation Format: Fontanella C, Gehlhaar C, Denkert C, Schneeweiss A, Heppner B-I, Koch I, Blohmer J-U, Jackisch C, Lederer B, Fasching PA, Müller V, Untch M, Aprile G, Puglisi F, Nekljudova V, Heppner F, von Minckwitz G, Loibl S. Predictive value of O6-methylguanine-DNA methyltransferase (MGMT) promoter gene methylation in triple-negative breast cancer patients receiving carboplatin. [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 P3-07-55.

A47 - Inherited mutations in breast cancer susceptibility genes among a triple negative breast cancer cohort unselected for family history of breast cancer

A47 - Inherited mutations in breast cancer susceptibility genes among a triple negative breast cancer cohort unselected for family history of breast cancer

Survival outcomes in Egyptian patients with triple-negative breast cancer: Single institute experience.

158 Background: Triple-negative breast cancer (TNBC) is a unique subtype and consider as an aggressive disease without established targeted treatment options. This study conducted to determine the incidence, characteristics, and survival outcomes of TNBC patients in an Egyptian cancer institute. Methods: Medical records of 520 patients treated between 2010-2011 in Clinical Oncology Department-Ain Shams University-Egypt were analyzed. Cox proportional hazards models were used to evaluate the association between TNBC and DFS and OS after adjusting for other covariates. Results: Among the 520 patients, 139 were TNBC .The median age was 50 years (SD±11.767, Range 20-80 ) versus 52 years (SD±12.134, Range 20-80), median tumor diameter was 5 cm (SD± 1.408, Range 1-7) versus was 5 cm (SD± 1.401, Range 1-7) , and median number of positive axillary LN was 3 (SD± 4.779, Range 0-37) versus 3 (SD± 4.832, Range 0-25) in non TNBC and TNBC respectively . Median disease-free survival was 24 months (SD± 14.128, Range 1-69 ) versus 15 months (SD± 8.811, Range 1-43 ) and median overall survival was 41 months (SD± 16.249, Range 3-60) versus 31 months (SD± 12.184, Range 7-60 ) in non TNBC and TNBC respectively. About 85.6 % of the TNBC tumors were IDC, 4.4 % were ILC and 5% were mixed. About 1.4 % of the TNBC tumors were grade I, 70.5 % were grade II and 28.1% were grade III. Median disease-free survival was 24 months (95%CI 21.679- 26.321) versus 15 months (95%CI 12.587-17.413) (p&lt; 0.001) and median overall survival was 44 months (95%CI 41.396-46.604) versus 31 months (95%CI 29.460-32.540) (p&lt; 0.001) in non TNBC and TNBC respectively. In TNBC cohort , DFS was 12 months (95%CI 11.464-12.536) in patients with grade III tumors versus 25 months (95%CI 22.359-27.641 )in patients with other grades (p&lt; 0.001), this was also reflected in OS as 29 months (95%CI 25.129-32.871 ) versus 44 months (95%CI 41.238-46.762 ) (p&lt; 0.001). Conclusions: Multivariate analyses supported a conclusion that TNBC subtype was an independent adverse prognostic factor for survival along with other known risk factors such as tumor grade.

1977 Synergy of LCL161, an antagonist of inhibitor of apoptosis proteins (IAPs), with paclitaxel in a gene expression signature-enriched cohort of triple-negative breast cancer (TNBC)

1977 Synergy of LCL161, an antagonist of inhibitor of apoptosis proteins (IAPs), with paclitaxel in a gene expression signature-enriched cohort of triple-negative breast cancer (TNBC)

Abstract 2859: Inhibition of PD-L1 by MPDL3280A leads to clinical activity in patients with metastatic triple-negative breast cancer (TNBC)

Abstract Introduction: TNBC is a mutationally complex breast cancer subtype with poor prognosis and no current targeted therapy options. Compared with other intrinsic breast cancer subtypes, TNBC has higher programmed death-ligand 1 (PD-L1) expression levels, which may hinder antitumor T-cell responses. MPDL3280A is a monoclonal anti-PDL1 antibody, engineered for optimized efficacy and safety, that blocks signaling through the PD-L1/PD-1 and PD-L1/B7.1 pathways. Methods: MPDL3280A was tested in a metastatic TNBC expansion cohort as part of a multicenter Phase Ia study. Pts received MPDL3280A at 15 mg/kg, 20 mg/kg or 1200 mg flat dose IV q3w. AEs were summarized for the safety follow-up duration from the first dose to 30 days after the last dose before the clinical cutoff on Sept 2, 2014. Responses were assessed by RECIST v1.1 criteria in pts who received MPDL3280A by Jul 21, 2014, evaluable for efficacy (≥ 6-wk follow-up). PD-L1 expression on tumor-infiltrating immune cells (ICs) at baseline was centrally evaluated by IHC in archival or fresh biopsies, and pts were scored as PD-L1 IHC (IC) 0, 1, 2 or 3. Peripheral biomarkers were assayed using FACS and multiplex immunoassays. Results: In the TNBC cohort, 27 pts were selectively enrolled. These pts had a median age of 48 y (29-82 y) and were evaluable for safety; 52% had ECOG PS 0 and 44% had ECOG PS 1. Visceral and bone metastases were present at baseline in 59% and 11% of pts, respectively. In addition, 85% received ≥ 4 prior systemic regimens (neoadjuvant, adjuvant or metastatic), including anthracyclines (78%), taxanes (82%) and platinum agents (15% cisplatin, 41% carboplatin). All-grade treatment-related AEs occurred in 67% of pts, most frequently fatigue (22%), pyrexia (15%), neutropenia (15%) and nausea (15%). 11% of pts experienced a Grade 3-5 related AE (5 Grade 3 events: adrenal insufficiency, neutropenia, nausea, vomiting, decreased WBC count; 1 Grade 5 pulmonary hypertension event in a pt with an atrial septal defect). Among 21 efficacy-evaluable PD-L1 IHC 2 or 3 pts (13 IHC 2 and 8 IHC 3), the unconfirmed RECIST ORR was 24% (95% CI, 8% to 47%); 3 PRs and 2 CRs were observed. Response duration ranged from 0.1+ to 41.6+ wks, with the median not yet reached. Pts with evidence of durable nonclassical responses suggestive of pseudoprogression were also observed. Overall, the 24-wk PFS rate was 33% (95% CI, 12% to 53%). Biomarker analysis revealed transient elevation of plasma cytokines and proliferating CD8 cells following MPDL3280A treatment. Updated clinical data, including PD-L1-negative pts, will be presented. Conclusions: MPDL3280A was generally well tolerated and demonstrated promising efficacy in pretreated metastatic PD-L1 IHC 2 or 3 TNBC pts. Furthermore, circulating biomarker analyses revealed pharmacodynamic responses to MPDL3280A. Clinical evaluation of MPDL3280A in metastatic PD-L1 IHC 0 or 1 TNBC is ongoing (NCT01375842). Citation Format: Leisha A. Emens, Fadi S. Braiteh, Philippe Cassier, Jean-Pierre Delord, Joseph Paul Eder, Marcella Fasso, Yuanyuan Xiao, Yan Wang, Luciana Molinero, Daniel S. Chen, Ian Krop. Inhibition of PD-L1 by MPDL3280A leads to clinical activity in patients with metastatic triple-negative breast cancer (TNBC). [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2859. doi:10.1158/1538-7445.AM2015-2859

S100P and HYAL2 as prognostic markers for patients with triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a group of very aggressive breast tumours, characterised by lack of expression of oestrogen receptor (ER), progesterone receptor (PR) and erb-b2 receptor tyrosine kinase 2 (ERBB2/HER2). Nevertheless, TNBCs show different clinical characteristics and are very diverse regarding prognostic outcome. So far, only a few prognostic markers for TNBC have been reported that could be helpful for therapeutic stratification. Here we have analysed the expression of S100P and HYAL2 using immunohistochemistry (IHC) in a TNBC cohort of 98 patients with a follow-up for recurrence and death. TNBC patients with high expression of both proteins showed significantly shorter progression-free survival (PFS) (mean PFS=35.9months, P=0.001) compared to TNBC patients with high expression levels of only one of the proteins (mean PFS=69.4months) and to TNBC patients with low expression of both proteins (mean PFS=83.3months). Moreover, multivariate Cox-regression model showed the combined expression of S100P and HYAL2 as independent prognostic factor for PFS (P=0.001). The expression of S100P and HYAL2 indicated similar prognostic effect to the overall survival (OS) of TNBC patients. In addition, high expression levels of both S100P and HYAL2 showed significant association with different clinicopathological characteristics, such as more recurrence events (P=0.004), and higher occurrence of metastasis (P=0.002). Our study proposes S100P and HYAL2 as potential prognostic markers for TNBC.

Frequent incidence of BARD1-truncating mutations in germline DNA from triple-negative breast cancer patients.

Triple-negative breast cancer (TNBC) accounts for 10-20% of all breast cancers (BCs), and conventional chemotherapy is the only effective systemic treatment. Germline BRCA1/2 mutations are found in approximately 15% of TNBC patients. In the past, we have documented pathogenic mutations in BARD1, a BRCA1 interacting protein, in families at high risk for BC. In this study, we have analyzed germline DNA from 61 estrogen receptor negative patients (of which 42 were TNBC) for the presence of mutations in the BRCA1, BRCA2 and BARD1 gene. BRCA1/2 mutations were found in 8 out of 42 (19%) TNBC patients, but not in the ER-/HER2+ cohort. We also found four good candidate pathogenic BARD1 mutations in the TNBC cohort, including two protein-truncating mutations (p.Gln564Ter and p.Arg641Ter). Our data suggest that TNBC patients are enriched for pathogenic BARD1 germline mutations as compared to control samples and high BC risk families. Ten of the 42 investigated TNBC patients carry a BRCA pathway mutation (in BRCA1, BRCA2 or BARD1) rendering them susceptible to homologous recombination deficiency. These patients should become eligible for exploring the efficacy of poly (ADP-ribose) polymerase (PARP) inhibitors.