Frequency of mutation and deletion of the tumor suppressor gene CDKN2A (MTS1/p16) in hepatocellular carcinoma from an Australian population

Abstract

comprises multiple cumulative genetic alterations, consistent The tumor suppressor gene CDKN2A (MTS1/p16), lowith the multistage nature of all late onset cancers, 5 which cated on chromosome 9p21, is inactivated in a variety of has been well investigated in colorectal cancer. tumors including melanomas and tumors of the biliaryThe multiple genetic alterations that occur in human cantract, pancreas, and stomach. The aim of the present cer target both oncogenes and tumor suppressor genes. 7 Tustudy was to determine whether this gene is inactivated mor suppressor genes function as negative regulators of cell in hepatocellular carcinoma (HCC). Twenty-three priproliferation, the loss of function being associated with the mary HCCs and four HCC cell lines were examined. Loss emergence of a cancerous phenotype. 8 Frequent loss of hetof heterozygosity (LOH) analysis was performed using erozygosity (LOH) at specific chromosomal loci in tumor eight polymorphic markers immediately surrounding DNA, detected by polymorphic DNA markers, can identify CDKN2A, and showed a contiguous region of loss, with specific chromosomal regions associated with malignancy the two most commonly deleted markers being D9S1604, and suggest the presence of a tumor suppressor gene in that located between the p16 and p15 genes, at which 7 of 13 region that may have been inactivated by such loss. For exinformative tumors (54%) showed loss, and D9S171, with ample, the p53 gene has been shown to be inactivated by 4 of 14 LOH (29%). Exons 1, 2, and 3 of CDKN2A were LOH in 30% to 70% of HCCs from patients living in countries amplified by polymerase chain reaction to detect homoin which HCC is prevalent.9 zygous deletions, and single-strand conformation polyThe tumor suppressor gene CDKN2A (MTS1/p16) located morphism (SSCP) analysis was performed to screen for on chromosome 9p21-22 appears to be frequently involved in mutations. No homozygous deletions were detected in many types of cancer, including melanoma, 10 biliary tract any sample. SSCP and sequence analysis showed the cancers, 11 pancreatic cancers, 12 and gastric carcinomas. 13 The same nucleotide change at codon 148 in four tumors.changes involve translocation, inversion, LOH, and homozyThis has been reported elsewhere as a polymorphism.gous deletion. The gene CDKN2A comprises three exons that One of these four tumors also contained a mutation at encode the protein p16, an inhibitor of a cyclin-dependent codon 119, resulting in the substitution of an acidic kinase (cdk-4) which negatively regulates the cell cycle. 14 Alamino acid for a basic one. It is concluded that CDKN2A though alteration of CDKN2A exon 2 has been investigated is infrequently deleted or mutated in HCC. The region previously in HCC, 15 chromosome 9p LOH including of allelic loss upstream from CDKN2A might result in CDKN2A has not been studied extensively in HCC. To examinactivation of regulatory sequences important in the ine whether suppressor loci on chromosome 9p are involved expression of this gene; alternatively, a seco...

Genetic aberration in primary hepatocellular carcinoma: correlation between p53 gene mutation and loss-of-hetero- zygosity on chromosome 16q21-q23 and 9p21-p23

“…Inactivation of this gene has been found in a variety of human cancers caused by different mechanisms, including mutation, homozygous deletion of MTS1/p16 loci or hypermethylation of 5 CpG island [25][26][27]. In our specimens, the 9p21-p23 showed high frequency of genetic alteration, but somatic mutation of MTS1/ p16 was infrequent in primary hepatic carcinoma, a finding similar to that found among Australian population [28]. The most common mechanism of silencing the p16 gene in HCC may be due to de novo hypermethylation of 5 CpG island [26], [27].…”

High frequency of p16INK4A gene alterations in hepatocellular carcinoma

“…Although LOH on the p16 region is common in various types of tumors, yet the reported LOH in HCC showed varying frequencies (Kita et al, 1996;Biden et al, 1997;Chaubert et al, 1997). In addition, LOH on chromosome region 9p21 in HCC has not been thoroughly investigated.…”

“…By using two polymorphic markers¯anking the 9p21 region (IFNA and D9S126), Kita et al (1996) reported 17.9% of the HCC from Japan had LOH on 9p21. On the other hand, Biden et al (1997), used eight polymorphic markers¯anking the same region, detected LOH in 44% of the HCC samples from Australia. Using a larger number of HCC cases and more microsatellite markers, our study showed the highest frequency of LOH (60.4%) on 9p21 region in HCC which is in accordance with results from other types of cancers.…”

“…Multiple mechanisms of p16 inactivation, such as point mutations, homozygous deletion, loss of heterozygosity (LOH) and hypermethylation, have been reported in dierent kinds of human tumors, including hepatocellular carcinoma (HCC) and HCC is a common and fatal cancer frequently seen on the Southern coast of China, Taiwan, Japan and Hong Kong. However, previous reports by Kita et al (1996) and Biden et al (1997) showed that homozygous deletions or mutations of the p16 gene were infrequent in a total of 85 cases of HCC samples from Japan and Australia. Furthermore, Kita et al (1996) showed 17.9% of the HCC from Japan had LOH, while Biden and coworkers showed 44% of the HCC from Australia had LOH on the p16 loci.…”

Genetics of hepatocellular tumors

“…Methylation of the p16 INK4 promoter leading to the absence of protein expression was found in 30-70% of the tumors (Liew et al, 1999;Matsuda et al, 1999;Jin et al, 2000;Weihrauch et al, 2001). Somatic inactivating mutations and homozygous deletions of the gene are rarely observed in HCC (Biden et al, 1997;Jin et al, 2000). Finally, Gankyrin was found to be overexpressed in all cases of 34 analysed HCC (Higashitsuji et al, 2000).…”