Mutation profile of KRAS and BRAF genes in patients with colorectal cancer: association with morphological and prognostic criteria.

KRAS and BRAF mutations are well-recognized molecular alterations during colorectal carcinogenesis, but there is little agreement on their effect on tumor characteristics. Therefore, we aimed to evaluate the distribution of the most common KRAS and BRAF mutations in Greek patients with colorectal cancer and their possible associations with clinical histopathological parameters. In this study, 322 and 188 colorectal carcinomas were used for the mutation analysis of KRAS (exon 2) and BRAF (exon 15) genes, respectively. The mutational status of both genes was evaluated by polymerase chain reaction and sequencing analysis. Although the overall frequency of KRAS mutations (36.6%) seemed to be similar to those reported for other populations, the rate of point mutations at codon 13 was significantly lower (12%) in Greek patients with colorectal cancer and associated with male gender (P < 0.05). Tumors with G>T codon 12 transversions and G>C transitions showed more frequent lymph node metastasis (P < 0.05, P < 0.005, respectively). The rate of KRAS mutations gradually decreased with increasing histological grade (P < 0.05), as opposed to BRAF mutations, which were strongly associated with poorly differentiated tumors (P < 0.005). Additionally, we found that the histological features of preexisting adenoma were associated with the absence of BRAF mutations, in contrast to KRAS (P < 0.05). Our data suggested that there seems to be a correlation between morphological criteria and discrete genetic pathways in colorectal carcinogenesis. Moreover, ethnic or geographic factors may have an impact on genetic background of colorectal carcinomas, and specific types of KRAS mutations may influence the metastatic potential of colorectal tumors.

Expression profile of the GA733 gene family in colorectal cancer: correlation with clinicopathological parameters.

GA733-1/-2/-3 genes have been detected in various types of cancer, although their role has not been fully clarified. GA733-2 and GA733-1 have been correlated with lymph node metastases in laryngeal cancer and liver metastases, respectively. Only a few studies have elucidated the mechanisms regulating GA733-1/-2 expression and their effect on colorectal cancer. Therefore, the expression pattern and the role of the aforementioned molecules in colorectal carcinogenesis were evaluated in this study. Tissue samples were obtained from 40 patients with colorectal cancer with no liver metastases. GA733-1/-2 mRNA levels were evaluated by quantitative real-time polymerase chain reaction. GA733-1/-2 gene expression in noncancerous/cancerous tissues was also correlated with clinicopathological parameters. The GA733-1 mRNA levels were very low; however, the GA733-1 mRNA transcripts were higher in cancerous tissues than in normal tissues (median ratio, 0.004391/0.00093; range, 0.000001- 0.025139/0.000001-0.007761), respectively (P = 0.012). GA733-2 gene expression was higher in noncancerous tissues than in cancerous tissues (median ratio 273.31/115.64; range, 65.24-1,486.41/11.58-1,189.14; P = 0.0000195). Lower GA733-2 expression in cancer tissues appeared to correlate with lymph node metastases (P < 0.05). GA733-1 gene expression was significantly higher in cancerous samples; conversely, the GA733-2 mRNA levels were higher in noncancerous tissues, and were significantly correlated with lymph node perforation in colorectal cancer (P < 0.05). Therefore, GA733-1/-2 mRNA expression levels appear to be a potential predictive marker of tumorigenesis.