APE1/Ref-1 is up-regulated in HCC and protects hepatocytes against oxidative stress induced apoptosis

DI MASO, V., MEDIAVILLA, M. G., RANIERI, C., VASCOTTO, C., CROCÈ, L., TELL, G. Y TIRIBELLI, C.

Milán, Italia

Congreso; Third Annual Conference of the International Liver Cancer Association; 2009

International Liver Cancer Association (ILCA)

Background: APE1/Ref-1 is a master regulator of cellular response to oxidative stress and its cytoplasmic localization in HCC tissue correlates with poor prognosis. Oxidative stress damage, proliferation and escape from apoptosis are common features of hepatocarcinogenesis. Objectives: This study was conducted to investigate APE1/Ref-1 expression pattern in vivo and in vitro and to assess its possible anti-apoptotic role. Methods: mRNA level of APE1/Ref-1 was assessed in normal liver (NL) and in surrounding liver cirrhosis (SLC) and HCC tissues of HCC affected patients. In parallel, APE1/Ref-1 mRNA and proteins levels were analyzed in two hepatoma cell lines: Huh7 (well-differentiated HCC) and JHH6 (poor-differentiated HCC); Immortalized Human Hepatocytes (IHH) were used as normal control. IHH were stably transfected with WT APE1/Ref-1 (IHH/pRef-1) and exposed to H2O2 and UV radiation. Viability was assessed by MTT assay and apoptosis by Annexin V adhesion. Results: APE1/Ref-1 mRNA levels resulted 2-fold higher in HCC than in SLC. JHH6 showed APE1/Ref-1 mRNA level significantly higher than Huh7 and IHH and this was confirmed at protein level since APE1/Ref-1 resulted 3-fold higher in JHH6 than in Huh7. IHH/Ref-1 were more resistant to H2O2 exposure and APE1/Ref-1 over-expression inhibits apoptosis since the percentage of IHH/Ref-1 apoptotic cells, with respect to the control, was about 50% lower. Conclusion: APE1/Ref-1 was up-regulated in HCC and the expression increased accordingly to disease progression. Poorly-differentiated HCC cells showed the highest levels of APE1/Ref-1 indicating a relationship between APE1/Ref-1 level and HCC differentiation. APE1/Ref-1 over-expression protects hepatocytes from oxidative stress insult by inhibiting apoptosis. These data indicate that APE1/Ref-1 over-expression is associated with HCC progression both in vivo and in vitro and suggest the anti-apoptotic role of this protein as a possible mechanism involved in HCC development.