Analysis of genomic and non-genomic signalling of oestrogen receptor in PDX models of breast cancer treated with a combination of the PI3K inhibitor Alpelisib (BYL719) and fulvestrant

Background Endocrine therapies targeting oestrogen signalling have significantly improved breast cancer (BC) patient survival, although 40% of ERα-positive BCs do not respond to those therapies. Aside from genomic signalling, oestrogen triggers non-genomic pathways by forming a complex containing methylERα/Src/PI3K, a hallmark of aggressiveness and resistance to tamoxifen. We aimed to confirm the prognostic value of this complex and investigated whether its targeting could improve tumour response in vivo.Methods The interaction of ERα/Src and ERα/PI3K was studied by proximity ligation assay (PLA) in a cohort of 440 BC patients. We then treated patient-derived BC xenografts (PDXs) with fulvestrant or the PI3K inhibitor alpelisib (BYL719) alone or in combination. We analysed their anti-proliferative effects on 6 ERα + and 3 ERα- PDX models. Genomic and non-genomic oestrogen signalling were assessed by measuring ERα/PI3K interaction by PLA or the expression of key oestrogen target genes by RT-QPCR, respectively.Results We confirmed that ERα/Src and especially ERα/PI3K interaction were associated with a trend to poorer survival. In ERα + tumours, the combination of BYL719 and fulvestrant was more effective than fulvestrant alone in 3 models, irrespective of PI3K, PTEN status or ERα/PI3K targeting. Interestingly, in some ERα- models, fulvestrant alone impacted tumour growth and this was associated with a decrease in ERα/PI3K interaction.Conclusions Our results demonstrate that ERα/PI3K may constitute a new prognostic marker, as well as a new target in BC. Indeed, resistance to fulvestrant was clearly associated with a lack of ERα/PI3K targeting in the cytoplasm.

Molecular basis of distinct oestrogen responses in endometrial and breast cancer

Up to 80% of endometrial and breast cancers express oestrogen receptor alpha (ERα). Unlike breast cancer, anti-oestrogen therapy has had limited success in endometrial cancer, raising the possibility that oestrogen has different effects in both cancers. We investigated the role of oestrogen in endometrial and breast cancers using data from The Cancer Genome Atlas (TCGA) in conjunction with cell line studies. Using phosphorylation of ERα (ERα-pSer118) as a marker of transcriptional activation of ERα in TCGA datasets, we found that genes associated with ERα-pSer118 were predominantly unique between tumour types and have distinct regulators. We present data on the alternative and novel roles played by SMAD3, CREB-pSer133 and particularly XBP1 in oestrogen signalling in endometrial and breast cancer.

The complex nature of oestrogen signalling in breast cancer: enemy or ally?

The pleiotropic nature of oestradiol, the main oestrogen found in women, has been well described in the literature. Oestradiol is positioned to play a unique role since it can respond to environmental, genetic and non-genetic cues to affect genetic expression and cellular signalling. In breast cancer, oestradiol signalling has a dual effect, promoting or inhibiting cancer growth. The potential impact of oestradiol on tumorigenesis depends on the molecular and cellular characteristics of the breast cancer cell. In this review, we provide a broad survey discussing the cellular and molecular consequences of oestrogen signalling in breast cancer. First, we review the structure of the classical oestrogen receptors and resultant transcriptional (genomic) and non-transcriptional (non-genomic) signalling. We then discuss the nature of oestradiol signalling in breast cancer including the specific receptors that initiate these signalling cascades as well as potential outcomes, such as cancer growth, proliferation and angiogenesis. Finally, we examine cellular and molecular mechanisms underlying the dimorphic effect of oestrogen signalling in breast cancer.

Production, crystallization and X-ray diffraction analysis of the protease CT441 fromChlamydia trachomatis

The prokaryotic obligate intracellular pathogenChlamydia trachomatisis the most prevalent cause of preventable blindness, affecting approximately six million people worldwide. In addition,C. trachomatisis the most commonly reported sexually transmitted pathogen in Europe and the US, causing pelvic inflammation, ectopic pregnancy and infertility. As in other intracellular pathogens, proteases play crucial roles during most stages of the complex life cycle ofChlamydia. CT441 is a chlamydial protease that has been reported to interfere with oestrogen signalling of the host cell. Here, the recombinant production, purification and crystallization of an inactive variant of CT441, designated CT441° (active-site Ser455 replaced by Ala), are described. CT441° was crystallized in space groupP22121, with unit-cell parametersa= 86.7,b= 184.0,c= 209.6 Å. A complete diffraction data set was collected to a resolution of 2.95 Å.