ALDH1A2 Is a Candidate Tumor Suppressor Gene in Ovarian Cancer

Aldehyde dehydrogenase 1 family member A2 (ALDH1A2) is a rate-limiting enzyme involved in cellular retinoic acid synthesis. However, its functional role in ovarian cancer remains elusive. Here, we found that ALDH1A2 was the most prominently downregulated gene among ALDH family members in ovarian cancer cells, according to complementary DNA microarray data. Low ALDH1A2 expression was associated with unfavorable prognosis and shorter disease-free and overall survival for ovarian cancer patients. Notably, hypermethylation of ALDH1A2 was significantly higher in ovarian cancer cell lines when compared to that in immortalized human ovarian surface epithelial cell lines. ALDH1A2 expression was restored in various ovarian cancer cell lines after treatment with the DNA methylation inhibitor 5-aza-2'-deoxycytidine. Furthermore, silencing DNA methyltransferase 1 (DNMT1) or 3B (DNMT3B) restored ALDH1A2 expression in ovarian cancer cell lines. Functional studies revealed that forced ALDH1A2 expression significantly impaired the proliferation of ovarian cancer cells and their invasive activity. To the best of our knowledge, this is the first study to show that ALDH1A2 expression is regulated by the epigenetic regulation of DNMTs, and subsequently that it might act as a tumor suppressor in ovarian cancer, further suggesting that enhancing ALDH1A2-linked signaling might provide new opportunities for therapeutic intervention in ovarian cancer.