Journal Article

Genetic and epigenetic profiling in early colorectal tumors and prediction of invasive potential in pT1 (early invasive) colorectal cancers

Katsuhiko Nosho, Hiroyuki Yamamoto, Taiga Takahashi, Masashi Mikami, Hiroaki Taniguchi, Nobuki Miyamoto, Yasushi Adachi, Yoshiaki Arimura, Fumio Itoh, Kohzoh Imai and Yasuhisa Shinomura

in Carcinogenesis

Volume 28, issue 6, pages 1364-1370
Published in print June 2007 | ISSN: 0143-3334
Published online December 2006 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/bgl246
Genetic and epigenetic profiling in early colorectal tumors and prediction of invasive potential in pT1 (early invasive) colorectal cancers

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Morphologically, early colorectal tumors are divided into two groups, protruded-type tumors and flat-type tumors. Although some studies have shown genetic alterations in protruded-type tumors, little is known about genetic and epigenetic alterations in flat-type tumors, as well as pT1 (early invasive) colorectal cancers (CRCs). In the current study, we compared the frequencies of genetic and epigenetic alterations of the RAS–RAF and Wnt signaling pathways in flat-type and protruded-type tumors. In addition, we investigated the relationship between those alterations and invasive potential of pT1 CRCs. Methylations of RASSF2, O-6-methylguanine-DNA methyltransferase (MGMT), Wnt inhibitory factor-1 (WIF-1), EPHB2, CDKN2A and MLH1 were detected in 44.3, 30.3, 81.4, 7.5, 43.6 and 13.4% of the 307 early colorectal tumors, respectively. Mutations of KRAS, BRAF, catalytic subunit alpha of phosphatidylinositol 3′-kinase (PIK3CA) and β-catenin were detected in 25.4, 4.6, 1.6 and 9.4% of those tumors, respectively. Methylations of MGMT, WIF-1 and CDKN2A were detected in significantly higher percentages of protruded-type tumors than in flat-type tumors. Mutation of at least one gene was detected in a significantly higher percentage of flat-type tumors than in protruded-type tumors. RASSF2 methylation was correlated significantly with KRAS, BRAF or PIK3CA mutation. Multiple logistic analysis showed that lymphatic invasion and RASSF2 methylation with KRAS, BRAF or PIK3CA mutation were independent risk factors for venous invasion in pT1 CRCs. In conclusion, since genetic alterations of these pathways have frequently occurred in flat-type tumors, flat-type tumors seem to have a distinct genetic profile different from that of protruded-type tumors. RASSF2 methylation with oncogenic activation is a promising biomarker for predicting invasive potential of pT1 CRCs.

Journal Article.  4303 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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