title: Hypoxia-targeted over-expression of carboxylesterase as a means of increasing tumour sensitivity to irinotecan (CPT-11).
abstract: The induced expression of carboxylesterase (CE) enzymes, which convert the prodrug irinotecan (CPT-11) into its active cytotoxic metabolite SN-38, constitutes a promising strategy for cancer gene therapy. By incorporating hypoxia-responsive elements (HREs) in conjunction with the transgene, expression can be targeted specifically to hypoxic tissues (such as solid tumours), expressing the hypoxia-inducible factor 1 (HIF-1). We have constructed a recombinant adenoviral vector, AdHRE-rCE, encoding the cDNA for the highly efficient rabbit liver CE (rCE), under the control of a HRE derived from the human phosphoglycerate kinase 1 (PGK-1) gene in conjunction with a minimal SV40 promoter. In vitro, HT1080 fibrosarcoma and SW480 colon carcinoma cells demonstrated an approximately 10-fold hypoxia-dependent induction in CE expression following pre-infection with AdHRE-rCE, which led to a15-30-fold increased sensitivity to CPT-11. Furthermore, in vivo, SW480 tumour xenografts infected with AdHRE-rCE demonstrated a 2-fold decrease in tumour doubling time, when combined with 7 days of CPT-11 treatment, in comparison to mock-infected controls, with rCE expression shown to be limited to hypoxic regions only. As the cytotoxicity of CPT-11 is reduced under hypoxic conditions, over-expression of a highly efficient CE such as rCE under hypoxia control within these hypoxic cells could reverse this effect and, therefore, form the basis for future clinical treatment strategies.
authors.affiliation: Paterson Institute for Cancer Research, Christie Hospital NHS Trust, and School of Pharmacy and Pharmaceutical Sciences, University of Manchester, UK.
authors.forename: Torkjel
authors.initials: T
authors.lastname: Matzow
authors.forename: Rachel L
authors.initials: RL
authors.lastname: Cowen
authors.forename: Kaye J
authors.initials: KJ
authors.lastname: Williams
authors.forename: Brian A
authors.initials: BA
authors.lastname: Telfer
authors.forename: Pamela J
authors.initials: PJ
authors.lastname: Flint
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Southgate
authors.forename: Mark P
authors.initials: MP
authors.lastname: Saunders
mesh_terms: D000256:Adenoviridae / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000627:therapeutic use*; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000627:therapeutic use; D043182:Carboxylesterase / Q000235:genetics / Q000378:metabolism*; D015687:Cell Hypoxia; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000627:therapeutic use*; D015972:Gene Expression Regulation, Neoplastic; D005822:Genetic Vectors; D006801:Humans; D000077146:Irinotecan; D009369:Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D011817:Rabbits; D014183:Transplantation, Heterologous
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D004791:Enzyme Inhibitors; D000077146:Irinotecan; D043182:Carboxylesterase; D002166:Camptothecin