Analysis of CYP1A1 exon 7 polymorphisms by PCR-SSCP in a Brazilian population and description of two novel gene variations.

CYP1A1 polymorphisms have been associated with a higher risk to develop lung cancer, particularly in Japanese. The type and the frequency of the polymorphisms can vary according to the ethnicity. In the present study, we aimed to determine the frequency of CYP1A1(*)2B and (*)4, and to look for other possible polymorphisms that may happen in exon 7 in individuals from Rio de Janeiro, an ethnic mixed population from Brazil. We developed a PCR-SSCP method for screening the genomic polymorphic region from 2289 to 2645 bp. Seven different migration patterns were found among 405 individuals, 130 healthy blood donors and 275 outpatients from Hospital Universitário Pedro Ernesto located in Rio de Janeiro. Five of the migration patterns corresponded to the genotypes: (*)1/(*)1 (the wild type); (*)1/(*)2B; (*)1/(*)4, (*)2B/(*)4 (heterozygous polymorphic) and (*)2B/(*)2B (homozygous polymorphic). Two other patterns corresponded to gene alterations not yet published: a C > T transition localized at the position 2461, and a C > T transition localized at position 2445. The genotype frequencies of the studied polymorphisms were: for CYP1A1(*)2B - 83.7% to (*)1/(*)1, 15.1% to (*)1/(*)2B and 1.2% to (*)2B/(*)2B; for CYP1A1(*)4 - 93.1% to (*)1/(*)1, 6.9% to (*)1/(*)4. The distribution of CYP1A1(*)2B and (*)4 genotypes combined were similar between white and non-white individuals. However, when the non-white individuals were stratified between blacks and mulattos, and then compared with white, black individuals showed a higher frequency of the wild type genotype (P = 0.008) and a lower frequency of genotype (*)1/(*)4 (P = 0.026). Additionally, when black and mulatto individuals were compared, blacks had a higher frequency of the wild type genotype (P = 0.008) and a lower frequency of the(*)1/(*)2B genotype (P = 0.0008), showing a different ethnic distribution of CYP1A1 polymorphisms.