BIRC5 and nasopharyngeal carcinoma: In conclusion, our results reveal an association for the first time between the functional polymorphism -31C/G in the promoter of BIRC5 and susceptibility to NPC, and, the -31CC genotype, which are genetically predisposed to produce an increased expression level of BIRC5, seem to be a genetic risk factor for the NPC risk in a Chinese population.