Expression of orotate phosphoribosyl transferase in human pancreatic cancer: implication for the efficacy of uracil and tegafur-based adjuvant chemotherapy.

The enzyme orotate phosphoribosyl transferase (OPRT) is involved in the metabolism of the anticancer drug 5-fluorouracil (5-FU), and is a key enzyme for conversion of 5-FU to its active form in tumor tissue. Little is known regarding the significance of OPRT in human pancreatic cancer. The present study was designed to assess the association between the activity of OPRT in the tumor, and the clinicopathological status and prognosis of human resectable pancreatic cancer, especially regarding its relevance to the efficacy of adjuvant chemotherapy with uracil and tegafur (UFT), cyclophosphamide (CPA) and/or gemcitabine (GEM). The present study included 99 resectable pancreatic cancers, which were all invasive ductal tubular carcinomas. OPRT was immunostained with a rabbit anti-human OPRT polyclonal antibody. OPRT was positively stained in 54 (54.5%) of 99 pancreatic cancers. The post-surgical survival rate of the OPRT (+) pancreatic cancers was significantly higher than that of the OPRT (-) ones. In the OPRT (+) group, the survival rate of the patients, who received adjuvant chemotherapy (ACT) with UFT, CPA or GEM, was significantly higher than that of the patients without ACT; however, in the OPRT (-) group, there was no difference in the survival between the ACT (+) and (-) groups. Multivariate analyses demonstrated that for all patients, primary tumor, status of nodal involvement (pN), residual tumor, level of dissection and CPA were significant variables for the prognosis: in OPRT (+) groups, primary tumor, nodal involvement, GEM and CPA were significant variables. In contrast, in the OPRT (-) group, pN was the only significant variable. The present study is the first report on the significance of OPRT in human pancreatic cancer, and the results indicate that the expression of OPRT may be useful to predict the response to adjuvant chemotherapy in human pancreatic cancer.