Abstract 1570: ARID1A regulation of ATAD2 in gynecologic cancer

Abstract

Abstract ARID1A the DNA binding component of the SWI/SNF nucleosome and chromatin remodeling complex has recently been identified as a tumor suppressor and inactivating mutations have been reported in several tumor types including uterine and ovarian cancer. Approximately 30% of ovarian endometrioid cancers (OEC), 50% of clear cell ovarian cancers (OCCC) and 40% of uterine endometrial cancers harbor ARID1A inactivating mutations. Little is known regarding the subunit composition of SWI/SNF complexes that contain ARID1A in ovarian and uterine cells and less is known regarding the transcriptional and functional consequences of ARID1A loss. In order to further explore the function of ARID1A in gynecologic cancers we restored ARID1A in ACI-98 (undifferentiated uterine cancer) an ARID1A negative and TP53 positive cell line using an inducible Tet-on system. Restoration of ARID1A induced apoptosis in ACI-98 cells after 48h doxycycline (Dox) treatment. We examined the proteome of these cells and catalogued the protein changes following ARID1A complementation using LC MS/MS. Specifically we identified 523 highly significantly differentially expressed proteins (z-score <0.01) from this analysis. Among these was the AAA domain containing 2 (ATAD2) that was dramatically down-regulated in ARID1A restored cells. ATAD2 is a highly conserved protein normally expressed in germ cells but is also over-expressed in some cancers. Affymetrix gene expression results also showed that ATAD2 is over-expressed in some ovarian and uterine cancers compared to normal controls. We further examined the clinical consequence of ATAD2 expression in ovarian cancers using the Kaplan-Meier plots website (http://kmplot.com) and found that the high-expression group has a worse overall survival than those in the low-expression group. ATAD2 associates via its bromodomain with histone H3 and it is known to act as a co-factor for E2Fs, MYC, androgen and estrogen receptors and whose over-expression drives the expression of target genes that induce cell proliferation and resistance to apoptosis. qRT-PCR results indicated that transcription of ATAD2 was not changed by restoration of ARID1A, moreover, anti-ARID1A ChIP-sequence revealed that SWI/SNF-ARID1A is not binding to the promoter of ATAD2. From these results, we suspect that the down regulation of ATAD2 is through a non-transcriptional mechanism. In addition, ARID1A-IP-MS result suggested that ARID1A is itself making complexes with ATAD2. We performed ATAD2 and ARID1A immunohistochemistry on a set of OCCC and OEC primary cancers and found that all cases with ARID1A negative staining preferentially over-express ATAD2. In summary our data indicate that ARID1A decreases levels of ATAD2, that ARID1A-negative OCCC and OEC are a subset of ovary cancer that preferentially overexpress ATAD2, and that ATAD2 over-expressing cancers have worse survival than weak expressers. Citation Format: Yutaka Shoji, Kelly A. Conrads, Rusheeswar Challa, Brian L. Hood, Guisong Wang, Kathleen M. Darcy, Chad A. Hamilton, George Larry Maxwell, Thomas P. Conrads, John I. Risinger. ARID1A regulation of ATAD2 in gynecologic cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1570. doi:10.1158/1538-7445.AM2014-1570