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Colorectal cancer (CRC) is one of the most common cancers worldwide. Understanding of the tumor behavior, in a much closer look, at the molecular level, results in a more effective treatment and accurate prognosis of the disease. From among various genes altered in colorectal cancer K-ras is assumed to be of diagnostic and prognostic significance. K-ras mutations are believed to be a critical event in colorectal oncogenesis. Previous studies have demonstrated that 40% (20-50%) of CRCs harbor a mutant allele of K-ras oncogene. The mutations are limited to codons 12, 13, and 61 of the gene, with a great incidence at codon 12. The localization of mutations has given mutated K-ras an advantage of sensitive and simple detection over APC or p53 in which mutations are spread in their whole DNA sequence. To determine the incidence of K-ras mutations in CRC in Iran, compared with other countries, DNA was isolated from a random collection of 55 colorectal carcinoma samples, and codon 12 K-ras mutations were detected by RFLP. K-ras mutations in sporadic colorectal cancer in Iran are relatively frequent, with an incidence of 65%. This may be attributed to variation in methodology and to characteristics of the population studied such as differences in genetic background and variability in environmental factors and epidemiologic parameters such as diet, social lifestyle status, and other parameters that could be specific to the Iranian population. Correlation between the presence of codon 12 mutation and various clincopathological parameters was also investigated. A significant correlation was found with poor tumor differentiation of tumor samples. This places much emphasis on the role of promotion of differentiation as the most prominent effect of Ras.

Keywords: PCR-RFLP, -ras, Colorectal cancer, codon-12, mutation detection

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