[Significance of p33(ING1b) and p53 gene expression in hepatocellular carcinoma]

To explore the significance of p33(ING1b) protein expression and p53 protein expression and investigate the mutation rate of ING1b gene in hepatocellular carcinoma (HCC).

Immunohistochemical method was employed to detect the expressions of p33(ING1b) and p53 proteins and the X antigen of hepatitis B virus (HBV) in 57 cases of HCC, 51 cases of surrounding non-tumor tissues surrounding HCC, and 12 cases of normal liver tissues; PCR-single strand conformation polymorphism (SSCP) was applied to reveal the mutation rates of two exons of ING1b gene in HCC. DNA fragments exhibiting abnormal shifting were cloned into PMD18-T vector and sequenced.

The positive rates of p33(ING1b) protein and of p53 protein were 42.1% and 57.9% respectively among the 57 cases of HCC. Both p33(ING1b) protein and p53 protein were positive in 19 cases (33.3%) of HCC tissues, and they were distributed in the same areas, mostly in the nucleus. The expression of p33(ING1b) was significantly correlated with that of p53 protein (r = 0.783, P < 0.01). The matched surrounding non-tumor tissues and normal liver tissues all showed negative p53 staining, while weak positive expression of p33(ING1b) was observed in 13 cases out of the 51 non-tumor tissues and 2 cases out of 12 normal liver tissues. Thirty-five cases, all with hepatocellular carcinoma, out of the 57 HCC cases showed positive HBV X protein (76.4%). The correlation of HBV infection with the expression of p33(ING1b) and p53 proteins was significant (P < 0.01). PCR-SSCP showed that the mutation rate of ING1b gene in HCC was 7.1% (2/28).

The expression of p33(ING1b) protein is significantly related to the expression of p53 protein in hepatocellular carcinoma; The existence of p33(ING1b) may have some other p53-independent pathway; Gene mutation was not the main reason that ING1b loses its tumor suppressing function in HCC. HBV infection has a close relationship with p33(ING1b) and p53 proteins expression.