Macroscopic morphologic subtypes of laterally spreading colorectal tumors showing distinct molecular alterations.
Recent advances in colonoscopic techniques have resulted in more frequent detection of superficial-type colorectal tumors, that is, laterally spreading tumors (LSTs), although little is known about the characteristic clinical features and genetic alterations of LSTs. To elucidate the molecular characteristics of LSTs, genetic alterations in the KRAS, BRAF and PIK3CA genes and abnormal expression of the p53, beta-catenin and MYC proteins were analyzed using direct DNA sequencing and immunohistochemistry for 50 protruded-type tumors (Protruded), 35 granular-type LSTs (LST-G) and 19 nongranular-type LSTs (LST-NG). In addition, loss of heterozygosity (LOH) close to the adenomatous polyposis coli (APC) gene (5q21) was examined in these tumors. In univariate analyses, significant differences were noted in the percentages with KRAS mutations (Protruded, LST-G, LST-NG = 30.0%, 54.3%, 21.1%, respectively, p = 0.0156), nuclear accumulation of beta-catenin (Protruded, LST-G, LST-NG = 50.0%, 37.1%, 68.4%, respectively, p = 0.0267), expression of MYC (Protruded, LST-G, LST-NG = 26.0%, 17.1%, 42.1%, respectively, p = 0.0456) and LOH at the APC gene locus (Protruded, LST-G, LST-NG = 22.0%, 20.0%, 47.4%, respectively, p = 0.0302). Multivariate analysis demonstrated that the macroscopic subtype of LST was significantly associated with KRAS mutation (for LST-NG: odds ratio [OR] 0.23, 95% CI 0.06-0.90) and nuclear accumulation of beta-catenin (for LST-NG: OR 4.05, 95% CI 1.11-14.8). Our data revealed that the 2 subtypes of LST have different molecular characteristics, suggesting that 2 or more different molecular mechanisms result in colorectal tumors with a similar growth pattern.
Sugimoto
Takafumi
T
Department of Gastroenterology, Graduate School of Medicine, University of Tokyo, Tokyo, Japan.
Ohta
Miki
M
Ikenoue
Tsuneo
T
Yamada
Atsuo
A
Tada
Motohisa
M
Fujishiro
Mitsuhiro
M
Ogura
Keiji
K
Yamaji
Yutaka
Y
Okamoto
Makoto
M
Kanai
Fumihiko
F
Kawabe
Takao
T
Omata
Masao
M
D000236:Adenoma / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D000368:Aged; D002895:Chromosomes, Human, Pair 5; D015179:Colorectal Neoplasms / Q000201:enzymology / Q000235:genetics* / Q000473:pathology*; D004252:DNA Mutational Analysis; D017931:DNA Primers; D004273:DNA, Neoplasm / Q000235:genetics; D005260:Female; D016158:Genes, p53; D011905:Genes, ras; D006801:Humans; D019656:Loss of Heterozygosity; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics; D051176:beta Catenin / Q000235:genetics
D017931:DNA Primers; D004273:DNA, Neoplasm; D016271:Proto-Oncogene Proteins c-myc; D051176:beta Catenin; D019869:Phosphatidylinositol 3-Kinases; D048493:Proto-Oncogene Proteins B-raf