P16 hypermethylation contributes to the characterization of gene inactivation profiles in primary gastric cancer.
The objective of this study was to investigate the contribution of p16 inactivation in gastric cancer and to compare it with p53. A cohort of 34 primary GCs were analyzed for p16 mutations and transcriptional silencing of the gene due to hypermethylation of the promoter. SSCP analysis and direct sequencing of exons 1 and 2 of the p16 gene were performed to detect any structural alterations. The methylation specific PCR (MSP) assay was applied to reveal hypermethylation of the 'CpG' island in the regulatory region using specific primer pairs for methylated and unmethylated nucleotides after a chemical reaction converting cytosines into uracile when unmethylated. SSCP and direct sequencing analysis did not detect any p16 mutations. The MSP assay showed 4 MSP(+) variants (11.8%). Three MSP(+) were stage III-IV disease and 1 MSP(+) was detected in an early stage disease (IB). All MSP(+) were diffuse type adenocarcinomas. The MSP(+) samples were different from previously reported samples harboring p53 mutations in the same cohort. These data increase the number of gastric cancers showing alterations of either p53 or p16 to 29.4% (10/34). Functional inactivation by hypermethylation of the p16 locus and p53 mutations could play a significant, complementary role in the pathogenesis of sporadic gastric cancer.
Ficorella
Corrado
C
Department of Experimental Medicine, University of L'Aquila, Italy. ricevuto@fismedw2.univaq.it
Cannita
Katia
K
Ricevuto
Enrico
E
Toniato
Elena
E
Fusco
Carlo
C
Sinopoli
Nuntia Teresa
NT
De Galitiis
Federica
F
Di Rocco
Zorika Christiana
ZC
Porzio
G
G
Frati
Luigi
L
Gulino
Alberto
A
Martinotti
Stefano
S
Marchetti
Paolo
P
D000230:Adenocarcinoma / Q000235:genetics*; D015331:Cohort Studies; D018899:CpG Islands; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics*; D019175:DNA Methylation; D017931:DNA Primers; D004273:DNA, Neoplasm / Q000235:genetics*; D017353:Gene Deletion; D020868:Gene Silencing; D016158:Genes, p53 / Q000502:physiology; D006801:Humans; D009154:Mutation / Q000235:genetics; D009367:Neoplasm Staging; D016133:Polymerase Chain Reaction; D018807:Polymorphism, Single-Stranded Conformational; D011401:Promoter Regions, Genetic; D013274:Stomach Neoplasms / Q000235:genetics*
D019941:Cyclin-Dependent Kinase Inhibitor p16; D017931:DNA Primers; D004273:DNA, Neoplasm