Forced Expression of Cytidine Deaminase Confers Sensitivity to Capecitabine

Abstract

Objective: Cytidine deaminase (CDD) is involved in the metabolism of new pyrimidine analogues, capecitabine (N⁴-pentyloxycarbonyl-5′-deoxy-5-fluorocytidine) and gemcitabine (2′,2′-difluorodeoxycytidine). The purpose of the present study was to directly examine the role of CDD in tumor cells themselves in mediating the sensitivity to capecitabine compared with gemcitabine. Methods: The human bladder cancer cell line T24 was transfected with human CDD2 cDNA by the lipofectin method. Results: Transfection of CDD2 cDNA did not change the levels of thymidine phosphorylase, dihydropyrimidine dehydrogenase and thymidylate synthase (TS) but increased the CDD activity significantly (p < 0.01). Forced expression of CDD made T24 sensitive to 5′-deoxy-5-fluorocytidine (5′DFCR) in vitro and capecitabine in vivo, but resistant to gemcitabine both in vitro and in vivo. Tetrahydrouridine, a specific CDD inhibitor, abrogated the changes in the in vitro sensitivity to 5′DFCR and gemcitabine by transfection of CDD2 cDNA. Transfection of CDD2 cDNA resulted in a significant increase in cellular 5-fluorouracil level (p < 0.01) and inhibition of TS activity (p < 0.01) after treatment with 5′DFCR in vitro. Conclusions: The present study clearly showed direct evidence for the contribution of CDD in tumor cells themselves to the sensitivities to capecitabine and gemcitabine.

Genetic factors influencing Pyrimidine-antagonist chemotherapy

“…In vitro transfection of human bladder cancer cells with CDD2 cDNA did increase CDD activity, and indeed made the cells more sensitive to 5 0 dFUR and capecitabine, but resistant to dFdC. 61 This warrants further investigation of the possible role of the CDD genotype in fluoropyrimidine chemosensitivity.…”

Advances and Challenges in Fluoropyrimidine Pharmacogenomics and Pharmacogenetics

“…Other studies have begun to identify candidate response indicators that are specific to the newer FPs based upon knowledge of the additional steps unique to their activation and activity. These include TP:DPD ratio, human equilibrative nucleoside transporter 1, uridine phosphorylase, cytidine deaminase levels for capecitabine and CYP2A6 levels for tegafur [85][86][87][88][89]. Most of these observations have been made in preclinical models.…”

Development of gene therapy in association with clinically used cytotoxic deoxynucleoside analogues

“…[60][61][62] The relevance of this inactivation for the activity of these compounds has been shown both on cell models and in vivo using in particular the CDA inhibitor 3,4,5,6-tetrahydrouridine (THU). [63][64][65][66] Because of the high enzyme activity of CDA toward araC and gemcitabine in vitro and in vivo, this gene has been used to protect hematopoietic cells from the cytotoxic effect of these two drugs.…”

“…83 An additional advantage of the CDA system, is the fact that increased expression of CDA sensitizes cells to the cytotoxic effect of the pyrimidine analogue and precursor of 5-fluorouracil capecitabine. 66 CDA has also been used in a combination system with a double mutant of dihydrofolate reductase (DHFR) and treatment with both araC and methotrexate. This combination is widely used in the treatment of nonHodgkin's lymphoma.…”