Gene therapy for intraperitoneally disseminated pancreatic cancers by Escherichia coli uracil phosphoribosiltransferase (UPRT) gene mediated by restricted replication‐competent adenoviral vectors

Abstract

Although patients with unresectable pancreatic tumors have been treated with 5-fluorouracil (5FU)-based combination chemotherapy, the drug resistance of cancer cells presents a crucial therapeutic problem. It was reported that UPRT overcomes 5FU resistance. UPRT catalyzes the synthesis of 5-fluorouridine monophosphate (FUMP) from Uracil and phosphoribosylpyrophosphate (PRPP). The antitumor effect of 5FU is enhanced by augmenting 5-fluorodeoxyuridine monophosphate (FdUMP) converted from FUMP, which inhibits thymidylate synthetase (TS). We first demonstrated that injecting an E1-deficient adenoviral vector (Adv) expressing UPRT (AxCAUPRT) followed by 5-FU treatment resulted in a volume reduction of xenotransplanted human tumors. In examining the therapeutic effect of AxCAUPRT/ 5-FU against peritoneal dissemination, we found that nonselective gene transduction of AxCAUPRT caused severe adverse effects arising from the increase of F-dUMP in normal intestine. Because the therapeutic gene delivered by a restricted replication-competent Adv lacking 55 kDa E1B protein (AxE1AdB) is speculated to be expressed selectively in tumors, mice with established tumors were injected with AxE1AdB and E1-deleted Adv expressing the lacZ reporter gene (AxCAlacZ). The expression of the reporter gene (lacZ) was selectively enhanced in disseminated tumors. The therapeutic advantage of restricted replication competent Adv that expresses UPRT (AxE1AdB-UPRT) was evaluated in an intraperitoneal disseminated tumor model. To study the anti-tumor effect of AxE1AdB-UPRT/5FU, mice with disseminated AsPC-1 tumors were administered the Adv, followed by the 5FU treatment. It was shown that the treatment with AxE1AdB-UPRT/5FU caused a dramatic reduction of the disseminated tumor burden without toxicity in normal tissues. Our results showed that the AxE1AdB-UPRT/5FU system is a promising tool for intraperitoneal disseminated pancreatic cancer. © 2002 Wiley-Liss, Inc. Key words: gene therapy; UPRT; replicating adenovirus; pancreatic cancer; peritoneal disseminationPancreatic cancer is the fifth leading cause of cancer death in the United States. 1 The great majority of the patients present with the advanced disease when they are diagnosed. Consequently, many cases are unresectable at the time of diagnosis because of invasion to the retroperitoneal space together with the involvement of major vessels, lymph nodes, peritoneal dissemination and distant metastases. Although patients with unresectable pancreatic tumors are treated with 5-fluorouracil (5-FU) based-chemotherapy, the response rate of the agent against the disease is from 18 -28% and the median survival is only 6 months. Accordingly, conventional chemotherapy provides little survival benefit in patients with pancreatic cancer. 2 The drug resistance of cancer cells presents a crucial therapeutic problem. 5FU requires enzymatic conversion to the nucleotide to exert its cytotoxic activity: 1) incorporation of 5-fluorouridine triphosphate into RNA, 2) incorporation of 5-fluorodeoxyuridine triphosph...

Oncolytic replication-competent adenovirus suppresses tumor angiogenesis through preserved E1A region

“…As we previously described, the E1B mutant virus did replicate in pancreatic cancer cells in vitro and inhibited the tumor growth in vivo. 28,49,50 These data strongly suggested that the oncolytic replication-competent Adv is a promising tool for gene therapy against pancreatic cancer.…”

Human Adenovirus Replicates in Immunocompetent Models of Pancreatic Cancer in Syrian Hamsters

“…The feasibility and safety of CRAds in human patients have been demonstrated in many clinical trials (Aghi and Martuza, 2005). However, the promising results obtained with early-generation CRAds in animal models of liver and pancreatic cancer (Oonuma et al, 2002;Takahashi et al, 2002) have not been reproduced in humans, at least as single agents (Habib et al, 2002;Hecht et al, 2003;Makower et al, 2003). Improved versions of CRAds are being generated, but the preclinical evaluation of these viruses is still hampered by the fact that human adenovirus does not replicate efficiently in mice and rats.…”

Gene therapy developments for pancreatic cancer

“…In vivo gene transduction of UPRT, using a replication-incompetent adenovirus, resulted in the regression of intraperitoneal pancreatic tumours, although the high doses of adenovirus required to obtain a complete response produced severe dehydration and diarrhoea as adverse effects. 42 A replication-selective adenovirus expressing UPRT, AxE1 AdB-UPRT, was subsequently developed and evaluated in a disseminated intraperitoneal pancreatic cancer model. Combined treatment with 5-FU and the adenoviral agent dramatically reduced the tumour burden without adverse effects 42 and this may be a useful approach in overcoming drug resistance.…”

“…42 A replication-selective adenovirus expressing UPRT, AxE1 AdB-UPRT, was subsequently developed and evaluated in a disseminated intraperitoneal pancreatic cancer model. Combined treatment with 5-FU and the adenoviral agent dramatically reduced the tumour burden without adverse effects 42 and this may be a useful approach in overcoming drug resistance.…”