Mutations of CDKN2 (MTS1/p16I(NK4A)) and MTS2/p15(INK4B) genes in human stomach, hepatocellular, and cholangio-carcinomas

Kim, Jae Ryong; Kim, Seong Yong; Lee, Bong Hwan; Kim, Sang Woon; Kim, Hong Jin; Kim, Jung Hye

Abstract

The CDKN2 (MTS1/p16(INK4A)) and MTS2/p15(INK4B) genes, encoding cyclin dependent kinase inhibitors, were found to be homozygously deleted at high frequency in cell lines from many different types of cancer and some primary cancers. To determine the frequency of CDKN2 and MTS2 mutations in human stomach, liver, and cholangio-cancers, molecular analyses of CDKN2 and MTS2 were performed on 4 stomach cancer cell lines, 14 primary stomach adenocarcinomas, 11 hepatocellular carcinomas, and 5 cholangiocarcinomas. Two (50%) of the four stomach cancer cell lines (SNU1, SNU5, SNU16 and Kato III) had mutations of the CDKN2 and MTS2 gene: SNU16, a homozygous deletion; SNU5, a nonsense mutation, CGA to TGA (Arg to stop) at codon 72 of the CDKN2 gene. No mutations were observed in the 14 primary stomach cancer tissues. In contrast to the mutations of CDKN2 and MTS2, Northern blot analysis showed that expression of CDKN2 was absent or decreased in all the remaining four stomach cancer cell lines and 11: of the 14 (79%) primary stomach adenocarcinomas. Five of the 11 (45%) hepatocellular carcinomas and one of the 5 (20%) cholangiocarcinomas have possible mutations in CDKN2 exon 2 and MTS2. One of hepatocellular carcinoma was expressed mobility shift on PCR-SSCP analysis and a missense mutation, GAC to GAA (Asp to Glu) at codon 105 of CDKN2 gene. These results suggest that mutations or inactivation of the CDKN2 gene may be a critical genetic change in the formation of stomach, hepatocellular, and cholangiocarcinomas.