Antisense Bcl-xl down-regulation switches the response to topoisomerase I inhibition from senescence to apoptosis in colorectal cancer cells, enhancing global cytotoxicity.

Abstract

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 approximately 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.

• Authors: Richard L Hayward, Janet S Macpherson, Jeff Cummings, Brett P Monia, John F Smyth, Duncan I Jodrell
• Journal: Clinical cancer research : an official journal of the American Association for Cancer Research (Clin Cancer Res) Vol. 9 Issue 7 Pg. 2856-65 (Jul 2003) ISSN: 1078-0432 [Print] United States
• PMID: 12855666 (Publication Type: Journal Article)

Chemical References

• Annexin A5
• Antineoplastic Agents, Phytogenic
• BAX protein, human
• BCL2L1 protein, human
• CDKN1A protein, human
• Cyclin-Dependent Kinase Inhibitor p21
• Cyclins
• Enzyme Inhibitors
• Fluorescent Dyes
• Oligonucleotides, Antisense
• Proto-Oncogene Proteins
• Proto-Oncogene Proteins c-bcl-2
• Topoisomerase I Inhibitors
• bcl-2-Associated X Protein
• bcl-X Protein
• Irinotecan
• beta-Galactosidase
• Camptothecin

Topics

• Annexin A5 (pharmacology)
• Antineoplastic Agents, Phytogenic (pharmacology)
• Apoptosis
• Camptothecin (analogs & derivatives, pharmacology)
• Cell Cycle
• Cell Division
• Cell Line, Tumor
• Cellular Senescence
• 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
• Irinotecan
• Oligonucleotides, Antisense (pharmacology)
• Proto-Oncogene Proteins (genetics)
• Proto-Oncogene Proteins c-bcl-2 (genetics, metabolism)
• Time Factors
• Topoisomerase I Inhibitors
• bcl-2-Associated X Protein
• bcl-X Protein
• beta-Galactosidase (metabolism)