Frequency of p16(INK4A) alterations and k-ras mutations in intrahepatic cholangiocarcinoma of the liver

Background-Inactivation of the tumour suppressor gene p16 (CDKN2/MTS-1/INK4 A) and K-ras mutations are among the most frequent genetic alterations in h uman malignancies. Aims-To investigate the tumour suppressor gene p16 and its possible associa tion with K-ras mutations in intrahepatic cholangiocarcinomas of the liver. Methods-The status of p16 was evaluated in 41 cholangiocarcinomas by methyl ation specific polymerase chain reaction, microsatellite analysis, DNA sequ encing, and immunohistochemical staining. K-ras mutations were determined b y direct DNA sequencing analyses after microdissection. The results obtaine d were correlated with histopathological variables and patient survival. Results-Hypermethylation of the 5' CpG island of the p16 gene was found in 34 of 41 (83%) carcinomas. Homozygous deletion at the p16 region was presen t in two (5%), and loss of heterozygosity (LOH) in eight cases (20%). We fa iled to detect p16 gene missense mutations. K-ras mutations were found in 2 2 of 41 (54%) cholangiocarcinomas and in two cases of tumour surrounding no n-neoplastic liver tissue. All 22 cancers with K-ras mutations also exhibit ed methylated p16. We failed to observe a correlation between K-ras or p16 status and histopathological factors or prognosis of patients. Conclusion-These data suggest that inactivation of the p16 gene is a freque nt event in cholangiocarcinoma. The most common somatic alteration is promo tor methylation of the p16 gene which is closely associated with K-ras muta tions. We failed to establish p16 or K-ras status as independent prognostic factors in these tumours.