Purpose: Methylation is an epigenetic mechanism acting as a barrier for successful chemotherapy. Decitabine is a demethylating agent recently used in treating cancer. However, its effect on hepatocellular carcinoma (HCC) has not been well understood. This work aims at evaluating the action of decitabine alone or in combination with doxorubicin on methylation and gene expression of a group of genes involved in adhesion, EMT and apoptosis in the HepG2 cell line in an attempt to evaluate the therapeutic potential of decitabine in HCC.

Methods: Methylation of SNAI1 and ECDH1 and expression of ECDH1, NCDH1, SNAI1, BCL2, BAX and TWIST were studied on HepG2 cells treated with decitabine, doxorubicin and dec./dox. combination. Treated cells were tested for apoptosis and cell cycle analysis by flow cytometry.

Results: Decitabine induced ECDH1 methylation and SNAI1 demethylation. Higher ECDH1 methylation was significantly correlated to lower SNAI1 methylation (P = 0.0001). The result was confirmed by high SNAI and low ECDH1 expressions. Decitabine and combination treated cells showed high BCL2 and BAX2 expressions. TWIST and NCDH1 were downregulated in all treated cells. ECDH1 expression was significantly correlated to NCDH1 expression (P= 0.0001). SNAI1 expression was significantly correlated with BCL2 expression (P< 0.00001). Inhibition of apoptosis was noticed in decitabine treated cells. doxorubicin and combination treated cells showed necrotic cell death. Doxorubicin was significantly better than decitabine (P= 0.0061) and sequential combination (P=0.00043) in inducing G2 arrest.

Conclusion: Decitabine induces the EMT-related transcription factor SNAI1 and the antiapoptotic factor BCL2 in HepG2 cells. Decitabine attenuates the action of doxorubicin by activating EMT and inhibiting apoptosis. Decitabine may attenuate the action of doxorubicin if the combination of both drugs is applied for HCC treatment. the activation of SNAI1 and Bcl2 in our study may be due to the random demethylation caused by decitabine