n South African Medical Journal - codon 12 and not mutations are predominant in advanced colorectal cancers : research

Volume 105, Issue 8
  • ISSN : 0256-9574
  • E-ISSN: 2078-5135



Colorectal cancer (CRC) is one of the most common types of cancer, affecting 3 - 5% of the global population. proto-oncogene and tumour suppressor gene mutations are among the most common genetic alterations detected in advanced colorectal tumours.

To investigate the role of codon 12 and exons 5 - 9 mutations in late-stage CRC patients.
Blood samples were collected from 249 CRC patients, of whom 147 presented with advanced carcinoma. codon 12 mutations were analysed using polymerase chain reaction-restriction fragment length polymorphism, while direct sequencing was used in screening for exons 5 - 9 mutations.
No significant changes were observed in exons 5 - 9, except for two cases in which nucleotide replacements were observed in the non-coding regions in intron 4 (c.376-19C>T) and intron 9 (c.993+12T>C). Heterozygous mutations in codon 12 were observed in 79 individuals suffering from advanced CRC (53.7%). Colon and rectal tumours were equally distributed among the heterozygotes, but colon tumours were mostly present in wild-type homozygotes (84.6%). There was also a predominance of Caucasians among heterozygotes and a predominance of Asians among the wild-type homozygotes.
Analysis of peripheral blood samples of CRC patients suffering from advanced carcinoma has prognostic value only for codon 12 mutations, and not for mutations.

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