Expression of p57/Kip2 protein in extrahepatic bile duct carcinoma and intrahepatic cholangiocellular carcinoma

BACKGROUND: Evaluation of the biological character of carcinomas requires understanding of cell cycle regulators. P57 (Kip2) belongs to the Cip/Kip family and is known to be one of the universal negative regulators of cell cycle. METHODS: In the present study, therefore, we investigated p57 expression in 37 extrahepatic bile duct carcinomas (BDC) and 28 intrahepatic cholangiocellular carcinomas (CCC). RESULTS: The average p57 labeling index (LI) in BDC and CCC were 60.8 +/- 7.9 and 58.6 +/- 18.6, respectively, which were significantly lower (p = 0.0008 and p = 0.0408, respectively) than those in normal duct epithelia (73.1 +/- 7.9, 70.4 +/- 8.2). p57 LI was significantly lower in BDC and CCC cases with biological aggressive phenotypes such as poor differentiation (p = 0.0260 and p = 0.0069), lymph node metastasis (p = 0.0274 and p = 0.0214), high Ki-67 LI (p = 0.0164 and p = 0.0343) and cyclin D1 overexpression (p = 0.0359 and p = 0.0255). CONCLUSION: These findings suggest that decreased p57 expression is related to the increased activity of cell proliferation and also the progression of these carcinomas.