DNA polymerase β gene mutations in human bladder cancer

We examined 24 human bladder cancer tissues for possible mutations in the entire coding region of the human DNA polymerase β gene using polymerase chain reaction analysis, single-strand conformational polymorphism analysis of RNA, and sequence analysis. DNA polymerase β gene mutations were observed in four of the 24 cases (16.7%) and included three missense point mutations and a single base insertion. The single base insertion was also observed in our previous study of human prostate cancer, suggesting that this region may be a hot spot for mutation of the DNA polymerase β gene. No clinical or pathological association was found among the four cases that contained the mutation. Three of the four cases with DNA polymerase β gene mutation had mutations of the p16 or RB genes or loss of heterozygosity of the p53 and APC gene loci. The results of the study presented here suggest that DNA polymerase β gene mutations, in combination with mutations of tumor suppressor genes, may be involved in certain cases of human bladder cancer.