GADD45-alpha expression in cirrhosis and hepatocellular carcinoma: relationship with DNA repair and proliferation.

Growth arrest and DNA damage 45-alpha (GADD45-alpha) is a nuclear protein involved in maintenance of genomic stability, DNA repair, and suppression of cell growth through interaction with nuclear elements, including cyclin-dependent kinase inhibitor 1A (CDKN1A) and PCNA. In this study, GADD45-alpha expression was assessed in 28 cases of hepatocellular carcinoma (HCC) and matched cirrhosis tissues, and correlated with the presence of DNA-bound PCNA and CDKN1A as markers of DNA repair, as well as with clinicopathologic variables including histopathologic grade, tumor size, nodularity, viral status, alpha-fetoprotein serum levels, and p53 and Ki67 immunostaining. GADD45-alpha and CDKN1A messenger RNA (mRNA) were analyzed by reverse transcriptase-polymerase chain reaction. GADD45-alpha protein expression was evaluated by Western blot (WB) and enzyme-linked immunosorbent assays (ELISAs). PCNA and CDKN1A DNA-bound fractions were determined by WB. GADD45-alpha mRNA was down-regulated in 20 of 26 HCCs with respect to matched cirrhosis, but no correlation was found with the corresponding protein levels assessed by both WB and ELISA. GADD45-alpha and CDKN1A protein levels were related to each other both in cirrhotic and in neoplastic tissues, and a concordant up- or down-regulation was observed in HCCs with respect to cirrhosis. DNA-bound PCNA and CDKN1A were present in 5 HCCs and were associated with higher GADD45-alpha protein levels assessed by ELISA. No significant association was found in HCCs between GADD45-alpha protein expression and histopathologic grading, nodule size, focality, and proliferation, whereas a positive correlation was found with alpha-fetoprotein serum levels. In conclusion, GADD45-alpha mRNA was down-regulated with respect to matched cirrhosis in most HCCs; however, no correlation was found between mRNA and protein levels. GADD45-alpha protein levels were higher in HCCs with DNA-bound CDKN1A and PCNA, suggesting a possible role in DNA repair.