Transitions and transversions in Ki-ras gene in colorectal cancers in Mexican patients.
OBJECTIVE
An important increase in the incidence of colorectal cancers has been detected in the last 15 years in Mexico. This fact has been attributed to several causes, including the change in diet acquired from industrialized countries. Various groups have studied the mutational pattern of oncogenes, including Ki-ras gene, in colorectal cancers from different human populations. The aim of this work was to study the prevalence of mutations at codons 12, 13 and 61 of the Ki-ras gene in 37 colorectal tumors from Mexican patients and to correlate them with clinical data.


METHODS
Point mutations were studied in 37 colorectal cancers at codons 12 and 13 of the Ki-ras gene, using PCR followed by RFLP. We also performed PCR-SSCP to identify mutations at codon 61. We confirmed mutations by sequence analysis in all the altered codons.


RESULTS
Our results indicated that 24.3% of the tumors presented mutations at codon 12, 5.4% at codon 13, and 2.7% at codon 61 of the Ki-ras gene. We found that 75% of these mutations were transitions and 25% transversions. The overall results indicated that the frequency of Ki-ras mutations in colorectal cancers in a sample of a Mexican population (Mexico City) was 32.4%, which is similar to that reported in other populations. We did not find a correlation between the Ki-ras mutations and gender, location of the tumor, or Dukes' stage, but survival of the patient without recurrence was statistically significant.


CONCLUSIONS
The study of colorectal cancer indicated that in a Mexican population Ki-ras mutations were present in tumors of patients who survived without tumor recurrence. Most of them were transitions in the first and second base of codon 12.
Segura-Uribe
Julia
J
Facultad de Química, Universidad Nacional Autónoma de México, Cd Universitaria, Coyoacan, México. pache@servidor.unam.mx
Santiago-Payán
Hector
H
Quintero
Angelina
A
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015179:Colorectal Neoplasms / Q000453:epidemiology / Q000235:genetics* / Q000601:surgery; D004252:DNA Mutational Analysis; D017931:DNA Primers; D004273:DNA, Neoplasm / Q000235:genetics; D005260:Female; D011905:Genes, ras / Q000235:genetics*; D006801:Humans; D008297:Male; D008800:Mexico / Q000453:epidemiology; D008875:Middle Aged; D009367:Neoplasm Staging; D017354:Point Mutation / Q000235:genetics*; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D018807:Polymorphism, Single-Stranded Conformational; D015995:Prevalence
D017931:DNA Primers; D004273:DNA, Neoplasm