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Prognostic significance of CDKN2A (p16) promoter methylation and loss of expression in 902 colorectal cancers: Cohort study and literature review
Author(s) -
Shima Kaori,
Nosho Katsuhiko,
Baba Yoshifumi,
Cantor Mami,
Meyerhardt Jeffrey A.,
Giovannucci Edward L.,
Fuchs Charles S.,
Ogino Shuji
Publication year - 2010
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.25432
Subject(s) - cdkn2a , cancer research , dna methylation , methylation , colorectal cancer , cdkn2b , biology , cpg site , microsatellite instability , cyclin d1 , mlh1 , oncology , cancer , medicine , cell cycle , gene expression , genetics , dna mismatch repair , gene , allele , microsatellite
Abstract A cyclin‐dependent kinase inhibitor CDKN2A (p16/Ink4a) is a tumor suppressor and upregulated in cellular senescence. CDKN2A promoter methylation and gene silencing are associated with the CpG island methylator phenotype (CIMP) in colon cancer. However, prognostic significance of CDKN2A methylation or loss of CDKN2A (p16) expression independent of CIMP status remains uncertain. Using a database of 902 colorectal cancers in 2 independent cohort studies (the Nurses' Health Study and the Health Professionals Follow‐up Study), we quantified CDKN2A promoter methylation and detected hypermethylation in 269 tumors (30%). By immunohistochemistry, we detected loss of CDKN2A (p16) expression in 25% (200/804) of tumors. We analyzed for LINE‐1 hypomethylation and hypermethylation at 7 CIMP‐specific CpG islands (CACNA1G, CRABP1, IGF2, MLH1, NEUROG1, RUNX3 and SOCS1); microsatellite instability (MSI); KRAS, BRAF and PIK3CA mutations; and expression of TP53 (p53), CTNNB1 (β‐catenin), CDKN1A (p21), CDKN1B (p27), CCND1 (cyclin D1), FASN (fatty acid synthase) and PTGS2 (cyclooxygenase‐2). CDKN2A promoter methylation and loss of CDKN2A (p16) were associated with shorter overall survival in univariate Cox regression analysis [hazard ratio (HR): 1.36, 95% CI: 1.10–1.66, p = 0.0036 for CDKN2A methylation; HR: 1.30, 95% CI: 1.03–1.63, p = 0.026 for CDKN2A (p16) loss] but not in multivariate analysis that adjusted for clinical and tumor variables, including CIMP, MSI and LINE‐1 methylation. Neither CDKN2A promoter methylation nor loss of CDKN2A (p16) was associated with colorectal cancer‐specific mortality in uni‐ or multivariate analysis. Despite its well‐established role in carcinogenesis, CDKN2A (p16) promoter methylation or loss of expression in colorectal cancer is not independently associated with patient prognosis.