Acquired expression of p27 is a favorable prognostic indicator in patients with hepatocellular carcinoma

The p27 cyclin-dependent kinase inhibitor is a negative regulator of cell-cycle progression. In many human epithelial malignancies, decreased expression of p27 correlates with high grade, early recurrence, and poor prognosis. To evaluate the prognostic significance of p27 in hepatocellular carcinoma (HCC), we studied 54 HCCs along with corresponding nontumoral tissue. Immunohistochemistry (IHC) and Western blot (WB) analysis before and after immunoprecipitation with Cdk2 were performed on paraffin-embedded tissues and protein homogenates, respectively, to compare localization and expression of the p27 protein and to determine the total and active (Cdk2-bound) fractions of p27. Correlations were analyzed between IHC-assessed levels of p27, survival, and major clinical and pathological variables. IHC revealed no p27 expression in the majority of hepatocytes from normal and cirrhotic liver, whereas 14 HCCs (26%) were high p27 expressers (>50% positive cells), 26 (48%) low expressers (<50% positive cells), and 14 (26%) negative. High IHC signals of p27 correlated with Cdk2-bound p27 as assessed by immunoprecipitation-WB; by contrast, WB alone displayed similar levels of p27 protein in all normal and tumoral samples. High IHC p27 expression correlated with prolonged survival (P = 0.027), whereas the presence of cirrhosis was associated with poor outcome (P = 0.029). We conclude that with respect to their nonneoplastic counterparts, a subset of HCCs acquire significant p27 expression and that high expression of p27 is a favorable independent prognostic parameter for HCC.