Combinatorial epigenetic treatment approach for hepatocellular carcinoma

10066 Hepatocellular carcinoma (HCC) displays a striking resistance to chemotherapeutic drugs. Alternative approaches comprise employment of epigenetic compounds such as histone deacetylase inhibitors (HDAC-I) or demethylating agents (DA). Since we could recently demonstrate that HDAC-I exhibit inherent in vitro therapeutic activities against HCC cells, we now explored the potential of a HDAC-I / DA combined epigenetic treatment approach for the highly chemotherapy resistant tumor entity HCC. Methods: HCC cell lines (HepG2, Hep3B, HuH7) and primary human hepatocytes (PHH) were treated with a HDAC-I compound (Suberoylanilide hydroxamic acid - SAHA) together with or without a DA (5-aza-2dC) and examined for cellular damage (enzyme release), proliferation inhibition (SRB), apoptotic cells (FACS), histone acetylation pattern (Western blot) and methylation status (methylation specific PCR). The in vivo activity of our approach was investigated in a HuH7 xenograft mouse hepatoma model. Results: Both SAHA and 5-aza-2dC were found to induce substantial antiproliferative effects and apoptotic cell death in HCC cells; interestingly, combinatorial treatment (SAHA plus 5-aza-2dC) resulted in strongly enhanced anti-HCC effects. Interferences between DA and HDAC-I activities could be excluded by determining both (i) the methylation status of two model genes (p16, SOCS-1; known to be abberantly methylated in HCC) as well as (ii) patterns of histone acetylation. Most importantly, non-malignant primary human hepatocytes (5 different donors) did not exhibit any relevant cellular damage even when high doses of SAHA plus 5-aza-2dC were applied. Finally, in vivo testing of our combinatorial regimen (SAHA plus 5-aza-2dC) was found to be superior in suppression of tumor cell growth when compared to the application of single substances (SAHA or 5-aza-2dC) or placebo. Conclusion: Our combined epigenetic approach in chemotherapy resistant HCC not only has been found to be a highly active treatment option with profound anti-tumor effects both in vitro and in a small animal model in vivo, but did not impair primary human hepatocytes. Thus, this combination therapy now is considered for further investigation in clinical trials. No significant financial relationships to disclose.