The evolving role of oestrogen receptor beta in clinical breast cancer

Controversy surrounds the potential clinical importance of oestrogen receptor (ER)β in breast cancer, and three recent papers have sought to resolve this. In the present issue of Breast Cancer Research Novelli and colleagues explored the significance of ERβ1 expression in 936 breast cancer patients, and they showed diverse relationships according to lymph node status. A second paper examined 442 breast cancers in which ERβ1 was an independent predictor of recurrence, disease-free survival and overall survival. Finally a third paper showed that ERβ2 was a powerful prognostic indicator in 757 breast cancers but this was dependent on cellular location, with nuclear ERβ2 expression predicting good survival whilst cytoplasmic expression predicted worse outcome. These papers point to a clinical role for ERβ in breast cancer and shall be discussed

Downregulation of 15-hydroxyprostaglandin dehydrogenase during acquired tamoxifen resistance and association with poor prognosis in ERα-positive breast cancer

Aim: Tamoxifen (TAM) resistance remains a clinical issue in breast cancer. The authors previously reported that 15-hydroxyprostaglandin dehydrogenase (HPGD) was significantly downregulated in tamoxifen-resistant (TAMr) breast cancer cell lines. Here, the authors investigated the relationship between HPGD expression, TAM resistance and prediction of outcome in breast cancer. Methods: HPGD overexpression and silencing studies were performed in isogenic TAMr and parental human breast cancer cell lines to establish the impact of HPGD expression on TAM resistance. HPGD expression and clinical outcome relationships were explored using immunohistochemistry and in silico analysis. Results: Restoration of HPGD expression and activity sensitised TAMr MCF-7 cells to TAM and 17β-oestradiol, whilst HPGD silencing in parental MCF-7 cells reduced TAM sensitivity. TAMr cells released more prostaglandin E2 (PGE2) than controls, which was reduced in TAMr cells stably transfected with HPGD. Exogenous PGE2 signalled through the EP4 receptor to reduce breast cancer cell sensitivity to TAM. Decreased HPGD expression was associated with decreased overall survival in ERα-positive breast cancer patients. Conclusions: HPGD downregulation in breast cancer is associated with reduced response to TAM therapy via PGE2-EP4 signalling and decreases patient survival. The data offer a potential target to develop combination therapies that may overcome acquired tamoxifen resistance

Genomic and expression analyses define MUC17 and PCNX1 as predictors of chemotherapy response in breast cancer

Poor prognosis breast cancers are treated with cytotoxic chemotherapy, but often without any guidance from therapy predictive markers since universally-accepted markers are not currently available. Treatment failure, in the form of recurrences, is relatively common. We aimed to identify chemotherapy predictive markers and resistance pathways in breast cancer. Our hypothesis was that tumour cells remaining after neoadjuvant chemotherapy (NAC) contain somatic variants causing therapy resistance, while variants present pre-NAC but lost post-NAC cause sensitivity. Whole exome sequencing was performed on matched pre- and post-NAC cancer cells, which were isolated by laser microdissection, from 6 cancer cases, and somatic variants selected for or against by NAC were identified. Somatic variant diversity was significantly reduced after therapy (p<0.05). MUC17 variants were identified in 3 tumours and were selected against by NAC in each case, while PCNX1 variants were identified in 2 tumours and were selected for in both cases, implicating the function of these genes in defining chemoresponse. In vitro knock-down of MUC17 or PCNX1 was associated with significantly increased or decreased chemotherapy sensitivity respectively (p<0.05), further supporting their roles in chemotherapy response. Expression was tested for predictive value in two independent cohorts of chemotherapy-treated breast cancers (n=53, n=303). Kaplan-Meier analyses revealed that low MUC17 expression was significantly associated with longer survival after chemotherapy, while low PCNX1 was significantly associated with reduced survival. We concluded that therapy-driven selection of somatic variants allows identification of chemotherapy response genes. With respect to MUC17 and PCNX1, therapy-driven selection acting on somatic variants, in vitro knock-down data concerning drug sensitivity, and survival analysis of expression levels in patient cohorts all define the genes as mediators of and predictive markers for chemotherapy response in breast cancer

Analysis of the ATR-Chk1 and ATM-Chk2 pathways in male breast cancer revealed the prognostic significance of ATR expression

The ATR-Chk1 and ATM-Chk2 pathways are central in DNA damage repair (DDR) and their over-activation may confer aggressive molecular features, being an adaptive response to endogenous DNA damage and oncogene-induced replication stress. Herein we investigated the ATR-Chk1 and ATM-Chk2 signalings in male breast cancer (MBC). The expression of DDR kinases (pATR, pATM, pChk1, pChk2, and pWee1) and DNA damage markers (pRPA32 and γ-H2AX) was evaluated by immunohistochemistry in 289 MBC samples to assess their association. Survival analyses were carried out in 112 patients. Survival curves were estimated with the Kaplan-Meier method and compared by log-rank test. Cox proportional regression models were generated to identify variables impacting survival outcomes. The expression of pATR conferred poorer survival outcomes (log rank p = 0.013, p = 0.007 and p = 0.010 for overall, 15- and 10-year survival, respectively). Multivariate Cox models of 10-year survival and overall indicated that pATR expression, alone or combined with pChk2, was an independent predictor of adverse outcomes (10-year survival: pATR: HR 2.74, 95% CI: 1.23–6.10; pATR/pChk2: HR 2.92, 95% CI: 1.35–6.33; overall survival: pATR: HR 2.58, 95% CI: 1.20–5.53; pATR/pChk2: HR 2.89, 95% CI: 1.37–6.12). Overall, the ATR/ATM-initiated molecular cascade seems to be active in a fraction of MBC patients and may represent a negative prognostic factor

Additional consensus recommendations for conducting complex innovative trials of oncology agents: a post-pandemic perspective

In our 2020 consensus paper, we devised ten recommendations for conducting Complex Innovative Design (CID) trials to evaluate cancer drugs. Within weeks of its publication, the UK was hit by the first wave of the SARS-CoV-2 pandemic. Large CID trials were prioritised to compare the efficacy of new and repurposed COVID-19 treatments and inform regulatory decisions. The unusual circumstances of the pandemic meant studies such as RECOVERY were opened almost immediately and recruited record numbers of participants. However, trial teams were required to make concessions and adaptations to these studies to ensure recruitment was rapid and broad. As these are relevant to cancer trials that enrol patients with similar risk factors, we have added three new recommendations to our original ten: employing pragmatism such as using focused information sheets and collection of only the most relevant data; minimising negative environmental impacts with paperless systems; and using direct-to-patient communication methods to improve uptake. These recommendations can be applied to all oncology CID trials to improve their inclusivity, uptake and efficiency. Above all, the success of CID studies during the COVID-19 pandemic underscores their efficacy as tools for rapid treatment evaluation