Polymorphism analysis of the CYP1A1 locus in Koreans: presence of the solitary m2 allele.

This study determined the complete genotype and the frequencies of all four mutations [T6235C (m1), A4889G (m2), T5639C (m3) and C4887A (m4)] of the CYP1A1 from 48 healthy Koreans and 17 Korean lung cancer patients. The mutations were analyzed by polymerase chain reaction (PCR)/restriction fragment length polymorphism (RFLP) and single stand conformation polymorphism (SSCP) simultaneously in order to improve accuracy as well as to screen for possible new alleles. Previously, the m2 mutation has always been linked to the m1 mutation. Also, the m1m2 double mutant allele (*2B) was thought to have a positive correlation with lung cancer susceptibility. Here we report the presence of the solitary m2 mutant allele without the m1 mutation (m1+m2) for the first time. This would be an evidence to support the theory of intragenic recombination in the CYP1A1 locus. The m1 mutation frequencies of healthy Koreans and lung cancer patients were 38.5% and 29.4%, respectively. The m2 mutation frequencies of healthy Koreans and lung cancer patients were 25.0% and 14.7%, respectively. Unlike the case for both Japanese and Caucasian lung cancer patients, neither m1 nor m2 mutations were overrepresented in Korean lung cancer patients. The m2 mutation frequency in Korean patients was significantly higher than those for Caucasians (2.7%) and the Japanese (19.8%). The African-American specific m3 mutation and m4 mutation found in Caucasians were not discovered in this study. The CYP1A1 allele with novel mutation was also not present.