Patterns of tumorigenic markers and impact of N-acetylation polymorphism in a Lebanese bladder cancer cohort

Abstract

Urinary bladder cancer (UBC) is the seventh most frequent cancer worldwide in males with higher incidence in industrialized countries, and much lower in developing countries. However, this epidemiological pattern is not observed in Lebanon, a Mediterranean middleincome country, where UBC incidence marks the second highest incidence in the world and the second most incident cancer in males. Genetic polymorphisms affecting metabolism of carcinogens may influence mutagenic risk in regulatory genes, leading to cancer development. In this study, we investigated an association between N-Acetyltransferase NAT2 genetic polymorphism and mutations in key carcinogenesis biomarkers. A cohort of 250 Lebanese males with histologically confirmed urothelial bladder cancer was identified from two referral centers in the city of Beirut. Archival tumors were used to extract DNA. A TaqMan real-time PCR assay was used to genotype NAT2 for the following allelic variants: NAT2*4 (wild-type), NAT2*5, NAT2*6, and NAT2*7. PCR-RFLP was used to characterize tumors for p53 mutations at Codons 72 and 248, and RB1 162238C>T mutation at Exon 23. Patients’ clinical data were obtained from medical records including smoking status, along with tumor grade, stage, and invasiveness. Pearson chi-squared tests were used to check for associations. The analysis was adjusted for multiple testing using Bonferroni correction. Our results showed that homozygous mutants for p53 at Codon 72 were approximately 20% of the samples, while p53 Codon 248 and RB1 162238C>T were totally absent. NAT2*4 (wildtype), *5D, *5E, *5S, *6B, *6J, and *7A were found at frequencies of 21.4%, 23.4%, 15.2%, 4.2%, 20%, 3%, and 5%, in the total pool, respectively. Overall, there were no statistically significant differences in mutation frequencies of tested cancer biomarkers among carriers of the different NAT2 alleles. In addition, NAT2 polymorphism was not found to be associated with UBC muscle-invasiveness. Further studies are needed to examine the association of other drug-metabolizing enzymes with UBC.