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Gastroenterol Clin Biol. 1998 Aug-Sep;22(8-9):679-87.

[Analysis of genetic disorders of cancer of the rectum: differences in relation to cancer of the colon].

[Article in French]

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  • 1INSERM U434-CEPH, Paris.



We studied the mechanisms of colon and rectal carcinogenesis by analysing in a series of 83 rectal tumors the prevalence of the two tumor types characteristic of colon cancer, i.e., the LOH+ type, defined by p53 and APC mutations (studied by DGGE and protein truncation assay), and the RER+ type, which is characterized by the instability of some mononucleotide repeat microsatellites (Bat 25 and Bat 26). Additionally, we analyzed the occurrence of Ki-Ras mutations (direct sequencing).


Only one tumor turned out to be RER+. Moreover, in 59% of the tumor cases mutations were found in p53, essentially affecting codon 175. The APC and Ki-Ras genes were found to be mutated in 40 and 26% of the rectal tumors, respectively. In 18 tumors (21%) none of the genes studied were mutated.


The RER+ phenotype is rare among rectal tumors, which are essentially LOH+. In these LOH+ tumors the p53 gene is more frequently mutated than in colorectal tumors with the same phenotype. Mutations in the APC and Ki-Ras genes, on the other hand, are less frequent in rectal tumors. Tumors with the RER- and LOH- phenotype may develop as a result of a third carcinogenesis model which must be defined.

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