BACKGROUND AND AIMS: Colorectal cancers with high levels of microsatellite instability (MSI-H) have an unexplained low rate of p53 gene mutations. Most such cancers have the CpG island methylator phenotype (CIMP+) with methylation and transcriptional silencing of the mismatch repair gene MLH1. The p14 (ARF) gene on chromosome 9p is deleted and/or silenced by hypermethylation in a subset of human malignancies. There is evidence suggesting that p14 suppresses tumorigenicity by stabilizing the p53 protein. METHODS: We investigated the role of p14 in colorectal cancer by determining its methylation status in cancers that were studied previously for microsatellite instability, CIMP, and mutations of p53 and K-RAS. RESULTS: p14 methylation was present in 21 of 94 cases overall (22%) and was frequent particularly in the subgroups with MSI-H (52% [11 of 21] vs. 14% [10 of 72], P = 0.004), in CIMP+ cases (40% [19 of 48] vs. 4% [2 of 46], P < 0.001), and in cases without p53 alterations (36% [17 of 47] vs. 7% [3 of 44], P = 0.004). Of 91 fully characterized cases, 41 (45%) had p53 mutations alone, 17 (19%) had p14 methylation alone, 30 (33%) had neither, but only 3 (3%) had both p53 mutations and p14 methylation. p14 methylation is an early event in colorectal carcinogenesis, being detectable in normal aging epithelium by using sensitive assays. CONCLUSIONS: In colorectal cancer, p14 methylation is associated with the presence of microsatellite instability and with absence of p53 mutations. The results provide a possible explanation for the paucity of p53 mutations in colon cancers with microsatellite instability.
BACKGROUND AND AIMS: Colorectal cancers with high levels of microsatellite instability (MSI-H) have an unexplained low rate of p53 gene mutations. Most such cancers have the CpG island methylator phenotype (CIMP+) with methylation and transcriptional silencing of the mismatch repair gene MLH1. The p14 (ARF) gene on chromosome 9p is deleted and/or silenced by hypermethylation in a subset of humanmalignancies. There is evidence suggesting that p14 suppresses tumorigenicity by stabilizing the p53 protein. METHODS: We investigated the role of p14 in colorectal cancer by determining its methylation status in cancers that were studied previously for microsatellite instability, CIMP, and mutations of p53 and K-RAS. RESULTS:p14 methylation was present in 21 of 94 cases overall (22%) and was frequent particularly in the subgroups with MSI-H (52% [11 of 21] vs. 14% [10 of 72], P = 0.004), in CIMP+ cases (40% [19 of 48] vs. 4% [2 of 46], P < 0.001), and in cases without p53 alterations (36% [17 of 47] vs. 7% [3 of 44], P = 0.004). Of 91 fully characterized cases, 41 (45%) had p53 mutations alone, 17 (19%) had p14 methylation alone, 30 (33%) had neither, but only 3 (3%) had both p53 mutations and p14 methylation. p14 methylation is an early event in colorectal carcinogenesis, being detectable in normal aging epithelium by using sensitive assays. CONCLUSIONS: In colorectal cancer, p14 methylation is associated with the presence of microsatellite instability and with absence of p53 mutations. The results provide a possible explanation for the paucity of p53 mutations in colon cancers with microsatellite instability.
Authors: Jaime Madrigano; Andrea Baccarelli; Murray A Mittleman; David Sparrow; Pantel S Vokonas; Letizia Tarantini; Joel Schwartz Journal: Epigenetics Date: 2012-01-01 Impact factor: 4.528
Authors: T Ishii; J Murakami; K Notohara; H M Cullings; H Sasamoto; T Kambara; Y Shirakawa; Y Naomoto; M Ouchida; K Shimizu; N Tanaka; J R Jass; N Matsubara Journal: Gut Date: 2006-06-19 Impact factor: 23.059
Authors: Eddy H J van Roon; Marjo van Puijenbroek; Anneke Middeldorp; Ronald van Eijk; Emile J de Meijer; Dianhdra Erasmus; Kim A D Wouters; Manon van Engeland; Jan Oosting; Frederik J Hes; Carli M J Tops; Tom van Wezel; Judith M Boer; Hans Morreau Journal: BMC Cancer Date: 2010-05-05 Impact factor: 4.430