SAHA ANTICANCER ACTIVITY THROUGH DEREPRESSION EFFECT ON CRITICAL GENES IN HPV CELL LINES

The interaction between DNA and histones is crucial for modulating the accessibility of transcription factors to DNA regulatory sequence. The chromatin structure is important for transcription regulation, the balance between active or silenced status being coordinated by the activity of enzyme effectors involved in chromatin remodeling, which modify DNA (DNA methyltransferase - DNMT) and histones (histone acetyltransferase - HAT and histone deacetylase - HDAC). New anticancer drugs are therefore currently targeting these epigenetic factors by their inhibitors, aiming at reactivation of the aberrantly silenced tumor suppressor genes. Current experimental and epidemiologic data confirmed that the human papillomavirus (HPV) is the causal agent in the development of cervical carcinoma. Taking into account HPV role in carcinogenesis, the aim of our study was to investigate the antitumor effect of SAHA (suberoylanilide hydroxamic acid, a histone deacetylase inhibitor) in cell culture models. HPV immortalized cell lines CaSki and Hela and a low risk HPV cell line obtained from a cervical xenograft, were treated with increasing doses of SAHA (0.5-2.5 kM) for 24 through 48 h. We noticed that SAHA has an antitumor activity by blocking cell proliferation and inducing tumor cell apoptosis in HeLa and CasKi cell lines. p21(WAF1) and p53 expression levels were higher at 2.5 kM/24h SAHA as appreciated in real-time PCR. mRNA levels of Dnmt1 were slightly increased at the same concentration of SAHA and were appreciated in the same conditions. By contrast, in lrHPV line, DNMT1 activity seems to increase at 2.5 kM SAHA after 48 of SAHA treatment. An interestingly effect upon DNA methyltransferases has been also observed. While DNMT1 mRNA levels slightly increased, DNMT3b immunoreactivity presented a rather constant feature. The only affected enzyme was DNMT3a whose immunoreactivity decreased significantly at high SAHA concentrations.