Infrequent loss of heterozygosity at adenomatous polyposis coli gene locus in Indian oral cancers.

We have investigated loss of heterozygosity (LOH) of the adenomatous polyposis coli (APC) tumor suppressor gene using polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) in 86 untreated oral cancer patients, using matched oral cancer tissue and corresponding peripheral blood cell (PBC) DNA samples. PBC from 70 normal healthy individuals, were also analyzed for allelic distribution of APC gene. A 133 bp fragment, spanning exon 11 of the APC gene was amplified, and RsaI digestion of the PCR product defined the alleles as either homozygous 133 bp (Rsa(-/-)) or 87 and 46 bp (Rsa(+/+)) fragments, and heterozygous (Rsa(+/-)) exhibiting the three fragments. Distribution of the three alleles, Rsa(-/-), Rsa(+/+), and Rsa(+/-) in the oral cancer patients was observed as 10.5, 51.1 and 38.4%; whereas normal healthy individuals showed 11.4, 37.1 and 51.4%, respectively. In the informative heterozygous (Rsa(+/-)) oral cancer patients, LOH was infrequent, demonstrated in two of 33 (6%) samples. Thus, the APC gene was infrequently altered by LOH at the polymorphic RsaI locus in exon 11 in the tobacco associated Indian oral cancer, unlike the smoking tobacco/alcohol associated oral cancers from Western countries.