Antisense Bcl-xl Down-Regulation Switches the Response to Topoisomerase I Inhibition from Senescence to Apoptosis in Colorectal Cancer Cells, Enhancing Global Cytotoxicity

Purpose: To identify determinants of the effect of antisense-mediated Bcl-xl down-regulation (Bcl-xl knockdown) on the response of colorectal cancer cells to SN38, the active metabolite of irinotecan, a topoisomerase I inhibitor licensed for colorectal cancer chemotherapy. Experimental Design: Using...

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Bibliographic Details
Published in:Clinical cancer research 2003-07, Vol.9 (7), p.2856-2865
Main Authors: HAYWARD, Richard L, MACPHERSON, Janet S, CUMMINGS, Jeff, MONIA, Brett P, SMYTH, John F, JODRELL, Duncan I
Format: Article
Language:English
Subjects:
Annexin A5 - pharmacology
Antineoplastic agents
Antineoplastic Agents, Phytogenic - pharmacology
Apoptosis
bcl-2-Associated X Protein
bcl-X Protein
beta-Galactosidase - metabolism
Biological and medical sciences
Camptothecin - analogs & derivatives
Camptothecin - pharmacology
Cell Cycle
Cell Division
Cell Line, Tumor
Cellular Senescence
Chemotherapy
Colorectal Neoplasms - pathology
Cyclin-Dependent Kinase Inhibitor p21
Cyclins - genetics
Dose-Response Relationship, Drug
Down-Regulation
Enzyme Inhibitors - pharmacology
Fluorescent Dyes - pharmacology
Genes, p53 - genetics
Humans
Immunoblotting
Medical sciences
Oligonucleotides, Antisense - pharmacology
Pharmacology. Drug treatments
Proto-Oncogene Proteins - genetics
Proto-Oncogene Proteins c-bcl-2 - genetics
Proto-Oncogene Proteins c-bcl-2 - metabolism
Time Factors
Topoisomerase I Inhibitors
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Summary:Purpose: To identify determinants of the effect of antisense-mediated Bcl-xl down-regulation (Bcl-xl knockdown) on the response of colorectal cancer cells to SN38, the active metabolite of irinotecan, a topoisomerase I inhibitor licensed for colorectal cancer chemotherapy. Experimental Design: Using wild-type HCT116, p53 null, Bax null, or p21/WAF1 null isogenic derivatives, we measured expression of regulators of cellular response, and associated growth arrests or apoptosis, after SN38 treatment, with or without antisense-mediated Bcl-xl knockdown. Results: A modified phosphorothioate antisense oligonucleotide (ISIS15999) reduced Bcl-xl protein expression by ∼90%. SN38 induced p53, Bax, Bcl-xl, and p53-dependent p21/WAF1 protein accumulation. The Bax:Bcl-xl ratio changed little. In wild-type HCT116, but not in Bax null cells, Bcl-xl knockdown induced a shift in response from drug-induced senescence to apoptosis, and enhanced the global cytotoxicity of SN38. In p53 null or p21/WAF1 null cells marked apoptosis occurred after SN38 alone, and was additionally enhanced by Bcl-xl knockdown in p21/WAF1 null cells but not in p53 null cells. Conclusions: Drug-induced senescence is associated with late relapse after therapy in transgenic models of cancer in vivo . We have shown that abolition of p21/WAF1-mediated drug-induced senescence or antisense-mediated Bcl-xl knockdown can both, independently, enhance the apoptotic response of colorectal cancer cells to SN38 in vitro . The growth arrest suppresses a p53-independent apoptotic pathway, whereas Bcl-xl induction suppresses a p53 and Bax-dependent apoptotic pathway. The combination of irinotecan and Bcl-xL antisense merits testing in models of colorectal cancer in vivo .
ISSN:1078-0432
1557-3265