Highlights d IL6/STAT3 signaling drives metastasis in ER + breast cancer mouse models d IL6/STAT3 establishes shared ER-FOXA1-STAT3 enhancers independent of FOXA1 d STAT3 co-opts shared enhancers to drive a distinct gene program independent of ER d JAK inhibitor ruxolitinib represses IL6/STAT3 activity and in vivo invasion Authors

Male breast cancer (MBC) is rare and poorly characterized. Like the female counterpart, most MBCs are hormonally driven, but relapse after hormonal treatment is also noted. The pan-hormonal action of steroid hormonal receptors, including estrogen receptor alpha (ERα), androgen receptor (AR), progesterone receptor (PR), and glucocorticoid receptor (GR) in this understudied tumor type remains wholly unexamined. This study reveals genomic cross-talk of steroid hormone receptor action and interplay in human tumors, here in the context of MBC, in relation to the female disease and patient outcome. Here we report the characterization of human breast tumors of both genders for cistromic make-up of hormonal regulation in human tumors, revealing genome-wide chromatin binding landscapes of ERα, AR, PR, GR, FOXA1, and GATA3 and enhancer-enriched histone mark H3K4me1. We integrate these data with transcriptomics to reveal gender-selective and genomic location-specific hormone receptor actions, which associate with survival in MBC patients.

The limited efficacy of immune checkpoint inhibitor treatment in triple-negative breast cancer (TNBC) patients is attributed to sparse or unresponsive tumor-infiltrating lymphocytes, but the mechanisms that lead to a therapy resistant tumor immune microenvironment are incompletely known. Here we show a strong correlation between MYC expression and loss of immune signatures in human TNBC. In mouse models of TNBC proficient or deficient of breast cancer type 1 susceptibility gene (BRCA1), MYC overexpression dramatically decreases lymphocyte infiltration in tumors, along with immune signature remodelling. MYC-mediated suppression of inflammatory signalling induced by BRCA1/2 inactivation is confirmed in human TNBC cell lines. Moreover, MYC overexpression prevents the recruitment and activation of lymphocytes in both human and mouse TNBC co-culture models. Chromatin-immunoprecipitation-sequencing reveals that MYC, together with its co-repressor MIZ1, directly binds promoters of multiple interferon-signalling genes, resulting in their downregulation. MYC overexpression thus counters tumor growth inhibition by a Stimulator of Interferon Genes (STING) agonist via suppressing induction of interferon signalling. Together, our data reveal that MYC suppresses innate immunity and facilitates tumor immune escape, explaining the poor immunogenicity of MYC-overexpressing TNBCs.

The purpose of this study was to identify critical pathways promoting survival of tamoxifen-tolerant, estrogen receptor  positive (ER+) breast cancer cells, which contribute to therapy resistance and disease recurrence. Gene expression profiling and pathway analysis was performed in ER+ breast tumors of patients before and after neo-adjuvant tamoxifen treatment and demonstrated activation of the NFκB pathway and an enrichment of EMT/stemness features.Exposure of ER+ breast cancer cell lines to tamoxifen, in vitro and in vivo, gives rise to a tamoxifen-tolerant population with similar NFκB activity and EMT/stemness characteristics.Small molecule inhibitors and CRISPR/Cas9 knock out were used to assess the role of the nuclear factor κB (NFκB) pathway and demonstrated that survival of tamoxifen-tolerant cells requires NFκB activity. Moreover, this pathway was essential for tumor recurrence following tamoxifen withdrawal. These findings establish that elevated NFκB activity is observed in breast cancer cell lines under selective pressure with tamoxifen in vitro and in vivo, as well as in patient tumors treated with neo-adjuvant tamoxifen therapy. This pathway is essential for survival and regrowth of tamoxifen-tolerant cells, and, as such, NFκB inhibition offers a promising approach to prevent recurrence of ER+ tumors following tamoxifen exposure.Implications: Understanding initial changes that enable survival of tamoxifen-tolerant cells, as mediated by NFκB pathway, may translate into therapeutic interventions to prevent resistance and relapse, which remain major causes of breast cancer lethality.

Of all damage occurring to DNA, the double strand break (DSB) is the most toxic lesion. Luckily, cells have developed multiple repair pathways to cope with these lesions. These different pathways compete for the same break, and the location of the break can influence this competition. However, the exact contribution of break location in repair pathway preference is not fully understood. We observe that most breaks prefer classical non-homologous end-joining, whereas some depend on DNA end-resection for their repair.Surprisingly, we find that for a subset of these sites, the activation of resection-dependent repair induces a detrimental DNA damage response. These sites exhibit extensive DNA end-resection due to improper recruitment of 53BP1 and the Shieldin complex due to low levels of H4K20me2. Most of these sites reside in close proximity to DNAseI hypersensitive sites. Compacting or removing these regions reduces extensive DNA end-resection and restores normal repair. Taken together, we found that DSB in open chromatin is highly toxic, due to the improper activity of 53BP1 and Shieldin, resulting in extensive DNA end-resection.

Background: Invasive lobular carcinoma (ILC) accounts for 10-15% of primary breast cancers and is typically estrogen receptor alpha positive (ER+) and ERBB2 non-amplified. Somatic mutations in ERBB2/3 are emerging as a tractable mechanism underlying enhanced human epidermal growth factor 2 (HER2) activity. We tested the hypothesis that therapeutically targetable ERBB2/3 mutations in primary ILC of the breast associate with poor survival outcome in large public datasets. Methods: We performed in silico comparison of ERBB2 non-amplified cases of ER+ stage I-III primary ILC (N = 279) and invasive ductal carcinoma (IDC, N = 1301) using METABRIC, TCGA, and MSK-IMPACT information. Activating mutations amenable to HER2-directed therapy with neratinib were identified using existing functional data from in vitro cell line and xenograft experiments. Multivariate analysis of 10-year overall survival (OS) with tumor size, grade, and lymph node status was performed using a Cox regression model. Differential gene expression analyses by ERBB2 mutation and amplification status was performed using weighted average differences and an in silico model of response to neratinib derived from breast cancer cell lines.

BackgroundNext Generation Sequencing (NGS) is expected to lift molecular diagnostics in clinical oncology to the next level. It enables simultaneous identification of mutations in a patient tumor, after which targeted therapy may be assigned. This approach could improve patient survival and/or assist in controlling healthcare costs by offering expensive treatment to only those likely to benefit. However, NGS has yet to make its way into the clinic. Health Technology Assessment can support the adoption and implementation of a novel technology, but at this early stage many of the required variables are still unknown.MethodsScenario drafting and expert elicitation via a questionnaire were used to identify factors that may act as a barrier or facilitate adoption of NGS-based molecular diagnostics. Attention was paid to predominantly elicit quantitative answers, allowing their use in future modelling of cost-effectiveness.ResultsAdequately informing patients and physicians, the latters’ opinion on clinical utility and underlying evidence as well as presenting sequencing results within a relevant timeframe may act as pivotal facilitators. Reimbursement for NGS-based testing and accompanying therapies (both general and in case of off-label prescription) was found to be a potential barrier. Competition on the market and demonstrating clinical utility may also be challenging. Importantly, numerous quantitative values for variables related to each of these potential barriers/facilitators, such as such as desired panel characteristics, willingness to pay or the expected number of targets identified per person, were also elicited.ConclusionsWe have identified several factors that may either pose a barrier or facilitate the adoption of NGS in the clinic. We believe acting upon these findings, for instance by organizing educational events, advocating new ways of evidence generation and steering towards the most cost-effective solution, will accelerate the route from bench-to-bedside. Moreover, due to the methodology of expert elicitation, this study provides parameters that can be incorporated in future cost-effectiveness modeling to steer the development of NGS gene panels towards the most optimal direction.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-016-2100-0) contains supplementary material, which is available to authorized users.

Acquired drug resistance is a major problem in the treatment of cancer. hTERT-immortalized, untransformed RPE-1 (RPE) cells can acquire resistance to taxol by derepressing the ABCB1 gene, encoding for the multidrug transporter P-gP. Here we have investigated how the ABCB1 gene is derepressed. We show that activation of the ABCB1 gene is associated with reduced DNA methylation, reduced H3K9 trimethylation and increased H3K27 acetylation at the ABCB1 promoter. In addition, we find that the ABCB1 locus has moved away from the nuclear lamina in the taxol-resistant cells. This raises the question which of these alterations were causal to derepression. Directly modifying DNA methylation or H3K27 methylation had neither significant effect on ABCB1 expression, nor did it promote drug resistance. In contrast, the disruption of Lamin B Receptor (LBR), a component of the nuclear lamina involved in genome organization, did promote the acquisition of a taxol-resistant phenotype in a subset of cells. Using CRISPRa-mediated gene activation, we could further substantiate a model in which disruption of lamina association renders the ABCB1 gene permissive to derepression. Based on these data we propose a model in which nuclear lamina dissociation of a repressed gene allows for its activation, implying that deregulation of the 3D genome topology could play an important role in tumor evolution and the acquisition of drug resistance.