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Evasion of apoptosis contributes to both tumourigenesis and drug resistance in non-small cell lung carcinoma (NSCLC). The pro-apoptotic BCL-2 family proteins BAX and BAK are critical regulators of mitochondrial apoptosis. New strategies for targeting NSCLC in a mitochondria-independent manner should bypass this common mechanism of apoptosis block. BRCA1 mutation frequency in lung cancer is low; however, decreased BRCA1 mRNA and protein expression levels have been reported in a significant proportion of lung adenocarcinomas. BRCA1 mutation/deficiency confers a defect in homologous recombination DNA repair that has been exploited by synthetic lethality through inhibition of PARP (PARPi) in breast and ovarian cells; however, it is not known whether this same synthetic lethal mechanism exists in NSCLC cells. Additionally, it is unknown whether the mitochondrial apoptotic pathway is required for BRCA1/PARPi-mediated synthetic lethality. Here we demonstrate that silencing of BRCA1 expression by RNA interference sensitizes NSCLC cells to PARP inhibition. Importantly, this sensitivity was not attenuated in cells harbouring mitochondrial apoptosis block induced by co-depletion of BAX and BAK. Furthermore, we demonstrate that BRCA1 inhibition cannot override platinum resistance, which is often mediated by loss of mitochondrial apoptosis signalling, but can still sensitize to PARP inhibition. Finally we demonstrate the existence of a BRCA1-deficient subgroup (11-19%) of NSCLC patients by analysing BRCA1 protein levels using immunohistochemistry in two independent primary NSCLC cohorts. Taken together, the existence of BRCA1-immunodeficient NSCLC suggests that this molecular subgroup could be effectively targeted by PARP inhibitors in the clinic and that PARP inhibitors could be used for the treatment of BRCA1-immunodeficient, platinum-resistant tumours.

not available at time of publication. Abstract not available at time of publication. Retrospective studies on male breast cancer (MBC) have suff ered from small numbers of cases available from any one centre; thus a signifi cant problem in eff ectively studying this disease is accruing suffi ciently large numbers to allow comparative analysis of biomarkers associated with response. Using a coordinated multicentre approach, we present the fi rst large-scale study to address the relevance of the expression of hormone receptors in MBC and female breast cancer (FBC) using immunohistochemistry combined with a novel bioinformatics approach. Following ethical approval, 523 archival blocks (260 MBCs and 263 matched FBCs) were obtained retrospectively. Tissue microarrays were constructed and sections stained for ERα, ERβ1, ERβ2, ERβ5, total PR, PRA, PRB and AR and typed using CK5/6, CK14, CK18 and CK19 by immunohistochemistry. Following scoring, a range of ordination techniques were conducted on the datasets including hierarchical clustering and principal component analysis (PCA) + ) were infrequent in both. Hierarchical clustering revealed common clusters between MBC and FBC including total PR-PRA-PRB and ERβ1/2 clusters. ERα occurred on distinct clusters between males and females. AR, ERβ1, ERβ2 and ERβ5 all existed on the same cluster but with a diff erent substructure, particularly around the positioning of AR. ERα associated with this cluster in the male but not the female group. PCA confi rmed that in both groups strong infl uences came from PR-PRA-PRB. In MBC strong infl uences additionally came from AR and ERβ1, ERβ2 and ERβ5, whereas in FBC strong infl uences came from ERα alone. Our data support the hypothesis that breast cancer is biologically diff erent in male and females, which could have implications for therapy. Introduction The response rarely sustains long among the responders for Herceptin (trastuzumab) monotherapy treatment. It is still poorly understood how Herceptin exerts its mechanism of action and how the acquired resistance to this drug occurs. Materials and methods We used a multidisciplinary approach including fl uorescence resonance energy transfer and biochemical methods to assess the eff ects of Herceptin on various signalling pathways and to determine the acquired resistance mechanisms of Herceptin in various HER2-positive breast cell lines and a BT474 xenograft model. Results We have shown that Herceptin does not decrease HER2 phosphorylation despite the eff ect on HER2 receptor downregulation. HER2 phosphorylation is maintained by the activation of EGFR, HER3 and HER4 via their dimerisation with HER2 in breast cancer cells. The activation of EGFR, HER3 and HER4 is induced by HER ligand release, including heregulin and betacellulin. The release of HER ligands is mediated by ADAM proteases including ADAM17/TACE. Furthermore, we demonstrated that the feedback loop involving HER ligands and ADAM proteases is activated due to a decrease in PKB phosphorylation induced by Herceptin t...

Background: The BRCA1 tumour suppressor gene is mutated in the germline of women who are predisposed to developing breast cancer. Gene expression profiling has identified at least five different breast cancer subtypes with BRCA- mutated breast tumours clustering with triple negative breast cancers. The majority of BRCA1-mutated breast tumours are characterised as being negative for the estrogen receptor-α (ER-α), however, the underlying molecular biology of these tumours has not yet been fully determined. The aim of this study is to identify and characterise novel proliferation-associated BRCA1 target genes that are activated in BRCA1 mutated estrogen receptor negative (ER-ve) breast tumours. Methods: Gene expression profiling and data analysis was performed on a cohort of 46 FFPE (Formalin Fixed Paraffin Embedded) derived BRCA1 mutated (ER-ve) breast tumours and matched sporadic controls using the Almac Diagnostics Breast DSA research tool. Profiling was also performed on a panel of 15 breast cancer cell lines. Bioinformatics analysis was performed using Oncomine, DAVID and Metacore. High throughput siRNA screens using HiPerFect were performed on the Qiagen Flexiplate siRNA. Validation of gene targets was performed by qRT-PCR and ChIP assay. Clonogenic assays were performed to independently validate the effect of selected target genes on cell survival. Results: A list of differentially expressed transcripts was derived from the comparison of 23 (ER-ve) BRCA1 mutated breast tumours and 23 matched sporadic controls. A genome-wide ChIP-Chip promoter analysis was also performed in MCF7 breast cancer cells. By overlapping these two datasets, a list of tumour derived BRCA1 promoter bound target genes was identified. Functional analysis of this gene list has identified the main pathways and processes that are deregulated in BRCA1 mutated (ER-ve) breast cancer including: (1) immune response (2) induction of the epithelial to mesenchymal transition (EMT) (3) cell cycle regulation and (4) apoptosis and survival. Hierarchical clustering of these 46 breast tumours and 15 breast cancer cell lines was performed and the BRCA1 mutated (ER-ve) breast cancer cell lines (MDA436 and SUM149) were identified as those that best reflect the biology BRCA1 mutated (ER-ve) tumours. High throughput siRNA screening in these cell lines has identified a set of transcripts that when inhibited have a negative impact on cellular proliferation. Independent validation by qRT-PCR, ChIP assay, western blotting and clonogenic assays have confirmed HE4 (WFDC2) as a novel BRCA1 target gene that provides a growth advantage in BRCA1 mutated (ER-ve) breast cancer cells. Conclusions: Gene expression profiling of an extensive cohort of BRCA1 mutated (ER-ve) breast tumours and matched sporadic controls has identified a profile of BRCA1 mutated (ER-ve) breast cancer. This list has been further refined to generate a list of BRCA1 promoter bound transcriptional target genes. High throughout siRNA screening has revealed a panel of genes that are implicated in the proliferation of BRCA1 mutated (ER-ve) breast cancer. HE4 has been identified as a novel BRCA1 transcriptional target gene that promotes the survival of BRCA1 mutated (ER-ve) breast tumours. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr PD10-05.

Background: Approximately 5-10% of all breast cancers are hereditary and the majority of these arise due to germline mutations in the BRCA1 and BRCA2 tumour suppressor genes. BRCA1 is involved in multiple cellular pathways including DNA damage signalling, DNA repair, cell cycle regulation, protein ubiquitination, chromatin remodelling, transcriptional regulation and apoptosis. Several distinct pathological features can be used to estimate the likelihood of the presence of a BRCA1 mutation, however, it is not yet possible to fully categorise a BRCA1 mutated tumour. BRCA1-associated breast cancers are generally defined as being ER (Estrogen Receptor) negative and indeed triple negative for ER, PR and HER2. However, approximately 10-36% of BRCA1 mutated breast cancers are, in fact, ER positive. These tumours less frequently demonstrate the characteristics more commonly associated with BRCA 1 -associated breast cancers. Initial molecular evidence also suggests that there is heterogeneity within BRCA1-associated breast tumours and this is dependent on the presence or absence of the estrogen receptor. The aims of this study are to investigate the underlying biology of BRCA1-mutated (ER positive) and BRCA1-mutated (ER negative) breast tumours. Methods: Extensive gene expression profiling and data analysis was performed on a cohort of 70 FFPE (Formalin Fixed Paraffin Embedded) derived BRCA1 mutated breast tumours and matched sporadic controls using the ALMAC Breast Cancer DSA™ research tool. Within this dataset we have generated molecular profiles of: (1) BRCA 1 -mutated ER positive and (2) BRCA1-mutated ER negative breast cancer. Functional analysis was performed using DAVID and METACORE. Validation of gene targets was performed by qRT-PCR and Western blotting. Results: A list of differentially expressed transcripts was derived from the comparison of 35 BRCA1 mutant breast tumours and 35 matched sporadic controls. Further analysis based on the presence and absence of ER identified a set of transcripts defining BRCA1-mutated (ER positive) and BRCA1-mutated (ER negative) breast cancer. Functional analysis of these two datasets has identified the main pathways and processes that are deregulated. Specifically, BRCA1-deficiency in the absence of ER was associated with deregulation of pathways implicated in immune response whereas BRCA 1 deficiency in the presence of ER was associated with pathways implicated in cell adhesion and cytoskeletal remodelling. Validation of the key genes underlying these two BRCA1-deficient breast cancer subtypes has been performed. Discussion: This approach has revealed significant heterogeneity within BRCA1 mutated breast cancer based on the presence or absence of ER. Significant differences in the transcripts and molecular processes underlying BRCA1-mutated (ER positive) and BRCA1-mutated (ER negative) breast tumours have been identified. The ability to identify BRCA 1 -deficiency by gene expression profiling from FFPE derived breast tissue may also have significant clinical application. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-04-14.