Loss of Nuclear ARID-1A Expressions Is Associated with Hormone Receptor Status in Breast Cancers

Half of most frequently mutated genes in breast cancer are expressed differentially between premenopausal and postmenopausal breast cancer patients

Breast cancer has distinct causes and molecular characteristics at premenopausal and postmenopausal ages. The age-standardized incidence rate for postmenopausal breast cancer is more than 10 times higher than in premenopausal breast cancer. Here, we showed that the expression of 10 out of 20 most frequently mutated genes in breast cancer (namely, PIK3CA, CDH1, MUC16, PTEN, FAT3, FAT1, SPEN, ARID1A, LRP1B and RUNX1) is higher in premenopausal women with breast cancer than in postmenopausal women with breast cancer. The most significant differences in the expression in terms of menopause status were observed for RUNX1 and FAT1. Furthermore, we found that the majority of these 10 genes also show ER (estrogen receptor) or PR (progesterone receptor) status-dependent expression in both premenopausal and postmenopausal breast cancer patients. Unlike what we observed in the case of ER or PR status, the expression of most of these genes does not change depending on HER2 (human epidermal growth factor receptor 2) status in both premenopausal and postmenopausal breast cancer patients. Combined, our analysis suggests that menopause status might influence the expression of most frequently mutated genes in breast cancer, and that the most of these genes whose expression differ between pre- and post-menopausal women with breast cancer also show ER or PR status-dependent expression in women with breast cancer.

ARID1A Regulates Progesterone Receptor Expression in Early Endometrial Endometrioid Carcinoma Pathogenesis

Loss of progesterone receptor (PR) expression is an established risk factor for unresponsiveness to progesterone therapy in patients with endometrial atypical hyperplasia and endometrioid carcinoma. ARID1A is one of the most commonly mutated genes in endometrioid carcinomas, and the loss of its expression is associated with tumor progression. In this study, we investigated the roles of ARID1A deficiency in PR expression in human and murine endometrial epithelial neoplasia. An analysis of genome-wide chromatin immunoprecipitation sequencing in isogenic ARID1A-/- and ARID1A+/+ human endometrial epithelial cells revealed that ARID1A-/- cells showed significantly reduced chromatin immunoprecipitation sequencing signals for ARID1A, BRG1, and H3K27AC in the PgR enhancer region. We then performed immunohistochemistry to correlate the protein expression levels of ARID1A, estrogen receptor, and PR in 50 human samples of endometrial atypical hyperplasia and 75 human samples of endometrial carcinomas. The expression levels of PR but not were significantly lower in ARID1A-deficient low-grade endometrial carcinomas and atypical hyperplasia (P = .0002). When Pten and Pten/Arid1a conditional knockout murine models were used, Pten-/-;Arid1a-/- mice exhibited significantly decreased epithelial PR expression in endometrial carcinomas (P = .003) and atypical hyperplasia (P < .0001) compared with that in the same tissues from Pten-/-;Arid1a+/+ mice. Our data suggest that the loss of ARID1A expression, as occurs in ARID1A-mutated endometrioid carcinomas, decreases PgR transcription by modulating the PgR enhancer region during early tumor development.

Enhancement of E-cadherin expression and processing and driving of cancer cell metastasis by ARID1A deficiency

The ARID1A gene, which encodes a subunit of the SWI/SNF chromatin remodeling complex, has been found to be frequently mutated in many human cancer types. However, the function and mechanism of ARID1A in cancer metastasis are still unclear. Here, we show that knockdown of ARID1A increases the ability of breast cancer cells to proliferate, migrate, invade, and metastasize in vivo. The ARID1A-related SWI/SNF complex binds to the second exon of CDH1 and negatively modulates the expression of E-cadherin/CDH1 by recruiting the transcriptional repressor ZEB2 to the CDH1 promoter and excluding the presence of RNA polymerase II. The silencing of CDH1 attenuated the migration, invasion, and metastasis of breast cancer cells in which ARID1A was silenced. ARID1A depletion increased the intracellular enzymatic processing of E-cadherin and the production of C-terminal fragment 2 (CTF2) of E-cadherin, which stabilized β-catenin by competing for binding to the phosphorylation and degradation complex of β-catenin. The matrix metalloproteinase inhibitor GM6001 inhibited the production of CTF2. In zebrafish and nude mice, ARID1A silencing or CTF2 overexpression activated β-catenin signaling and promoted migration/invasion and metastasis of cancer cells in vivo. The inhibitors GM6001, BB94, and ICG-001 suppressed the migration and invasion of cancer cells with ARID1A-deficiency. Our findings provide novel insights into the mechanism of ARID1A metastasis and offer a scientific basis for targeted therapy of ARID1A-deficient cancer cells.