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Hypoxia‐targeted over‐expression of carboxylesterase as a means of increasing tumour sensitivity to irinotecan (CPT‐11)
Author(s) -
Matzow Torkjel,
Cowen Rachel L.,
Williams Kaye J.,
Telfer Brian A.,
Flint Pamela J.,
Southgate Thomas D.,
Saunders Mark P.
Publication year - 2007
Publication title -
the journal of gene medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.689
H-Index - 91
eISSN - 1521-2254
pISSN - 1099-498X
DOI - 10.1002/jgm.1016
Subject(s) - carboxylesterase , hypoxia (environmental) , irinotecan , camptothecin , chemistry , pharmacology , biology , enzyme , medicine , biochemistry , oxygen , cancer , colorectal cancer , organic chemistry
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. Copyright © 2007 John Wiley & Sons, Ltd.