Polymorphism analysis in cox-2 gene regulatory regions in non-melanoma skin cancer after transplantation

Over expression of cyclooxygenase-2 (COX-2), resulting in excessive prostaglandin production, has been observed in human epidermal keratinocytes after ultraviolet B (UVB) injury. The dysregulation of COX-2 expression can in part be due to functional changes affecting regulatory elements of the gene. Two common polymorphisms (-1195A>G and -765 G>C) in the promoter region of the COX-2 gene, and one common polymorphism in 3’UTR (8473T>C) have been described, and associated to various malignancies. This study was designed to determine if common known polymorphisms in the regulatory region of the COX-2 gene can be associated to non melanoma skin cancer (NMSC) predisposition after transplantation, and to identify possible new genetic polymorphisms in the proximal regulatory regions of the gene associated with disease. Frequency of the three known polymorphisms was determined in two hundred fourty North Italian transplant recipient patients (107 cases and 133 controls) by PCR-RFLP, and the proximal regulatory regions of the gene were screened by heteroduplex analysis to identify new variants. Allele –765C represented a protective factor in basal cell cancer (BCC) patients undergoing transplantation before 50 years of age (CC+CG vs GG Fisher exact test P=0.003). One novel polymorphism, -62C>G, was detected in the 5’flanking region; allele frequency was 0.019. Screening of the 3’ UTR region revealed the presence of one known polymorphism -8293G>, with a frequency of 0.02. Functional studies showed no effect of this variant, or of the common polymorphism 8473T>C, upon post-transcriptional regulation of gene expression. Haplotype analysis showed that the haplotype containing all major alleles represents a protective factor in squamous cell cancer (SCC) patients undergoing transplantation after 50 years of age [P=0.008; OR= 0.37 (0.18-0.79)] and that haplotype containing variant -1195G may represent a risk factor in this subgroup of patients [P=0.01; OR=3.92 (1.22- 12.46)]. Haplotype analysis in basal cell cancer (BCC) patients revealed that the haplotype containing variant –765C might be a protective factor in patients undergoing transplantation before 50 years of age (P=0.003). Conclusion: COX-2 common variants –1195A>G and –765G>C appear to be associated to SCC or BCC, respectively, indicating that the gene may be a risk factor for the development of NMSC after transplantation.