151PD - ARID1A role in cell cycle regulation and proliferation in mouse and human gynaecological tissues reveals potential therapeutic targets

Date 29 September 2014
Event ESMO 2014
Session Trials and tribulations in oncology: Future approaches
Topics Basic Science
Gynaecologic Malignancies
Translational Research
Presenter Ioannis Gounaris
Citation Annals of Oncology (2014) 25 (suppl_4): iv53-iv57. 10.1093/annonc/mdu325
Authors I. Gounaris, J. Brenton
  • Cruk Cambridge Institute, University of Cambridge, CB2 0RE - Cambridge/GB

 

Abstract

Aim

Ovarian clear cell carcinoma (OCCC) arises from endometriosis and can be considered an ectopic uterine cancer. ARID1A mutations occur as an early event in 50% of OCCC and 30% of high-grade endometrial cancers. We aimed to characterise the function of ARID1A in the normal uterus and ovary using an Arid1a mouse model and immortalised human ovarian surface epithelium cells.

Methods

Arid1a expression during the mouse estrus cycle and its relationship to estrogen (ER), progesterone receptor and proliferation were assayed in a cohort of 28 mice. Illumina Beadchip arrays and MetaCore pathway analysis were used to assay ARID1A-driven transcriptional programmes in mouse uterus and, after siRNA-mediated knockdown, in mouse embryonic fibroblasts (MEF), immortalised human ovarian surface epithelium (IOSE) and JHOC-5 OCCC cells. SRB proliferation assays were performed in MEFs, IOSE and OCCC cell lines. Proliferation in the uterus was assessed 28 days after tamoxifen-induced knockout in Arid1afl/fl ROSA26Cre-ERT2 or wild type (WT) mice.

Results

Arid1a expression was not hormonally regulated in the mouse uterus at either the mRNA or protein level, but Arid1a expression was correlated with stromal ER expression (r = 0.6, p = 0.0003). ARID1A-regulated genes in mouse uterus, MEFs and IOSE cells overlapped significantly (p = 1.7x10-13). Pathways involved in the G2/M checkpoint were significantly enriched in all 3 systems. The conserved core transcriptional program included AURKA, PLK1, PLK4, CCNB1 and CCND1. Conversely, genes involved in inflammation and cell adhesion pathways were ARID1A-regulated in JHOC-5 cells. ARID1A knockdown increased proliferation in MEFs, IOSE cells in an HNF1B-dependent manner and in 4 of 6 ARID1A-expressing OCCC cell lines. In vivo knockout in the uterine epithelium resulted in a dramatic increase in Ki67 staining in Arid1afl/fl compared to WT mice.

Conclusions

A core ARID1A-driven transcriptional programme, conserved accross normal tissues and species appears to exist, centred around regulation of genes involved in the G2/M checkpoint. ARID1A loss promotes proliferation in normal tissues, providing important clues as to the mechanisms of ARID1A-driven carcinogenesis. Mitotic kinases emerge as potential therapeutic targets in ARID1A mutant tumours, an observation that is not evident from studies in cancer cell lines.

Disclosure

All authors have declared no conflicts of interest.