Inhibition of DNA methyltransferases, histone deacetylases and lysine-specific demethylase-1 suppresses the tumorigenicity of the ovarian cancer ascites cell line SKOV3

Ovarian cancer is one of the most lethal female malignancies and epigenetic abnormalities are thought to play a vital role in the pathogenesis, development and progression of ovarian cancer. Our goal was to investigate whether the combination of trichostatin A (TSA) and 5-aza-2'-deoxycytidine (decitabine) was superior to single agent on tumorigenicity of ovarian cancer cells. We found that tumorigenicity and metastasis of SKOV3 cells were significantly suppressed by the combination of TSA and decitabine in xenograft mouse models. Migration capacity was markedly suppressed through the induction of E-cadherin and suppression of N-cadherin when treated with TSA and decitabine. Invasion was also suppressed at least partially through inhibition of MMP-2 and MMP-9 with the combined treatment. The combination drugs markedly inhibited spheroid formation and significantly impaired migration and invasion capacity of spheroid derived cells through inhibition of Twist, N-cadherin, MMP-2, MMP-9 and induction of E-cadherin. Epigenetically, the activity of DNA methyltransferases (DNMTs) and histone deacetylases (HDACs) were markedly inhibited when TSA was used in combination with decitabine, especially the expression of DNMT3A/3B and HDAC1/2. Acetylation of histone H3 and H4 were more markedly stimulated with the combination than with either agent alone. The expression level of lysine-specific demethylase-1 (LSD1) was also suppressed. The transcription activity marker dimethylated-H3K4 was induced, but the dimethylated-H3K9 was suppressed by exposure to the combined drugs. These results suggest that the combination of TSA and decitabine significantly suppresses tumorigenicity by inhibiting migration and invasion of ovarian cancer cells via regulating the expression of the cadherins and MMPs, which may be epigenetically regulated by DNA methylation and histone modification.