title: RU486-inducible retrovirus-mediated caspase-3 overexpression is cytotoxic to bcl-xL-expressing myeloma cells in vitro and in vivo.
abstract: The antiapoptotic protein bcl-x(L) is upregulated in a variety of solid tumors and in primary hematologic malignancies such as multiple myeloma. Activated caspase-3 cleaves proteins essential for cell survival, including bcl-x(L). To explore the potential of caspase-3 as a cytotoxic and immunostimulatory molecule in the treatment of malignancy, an RU486-inducible caspase-3 retrovirus was constructed, validated, and used to transduce first 3T3 and subsequently murine myeloma B9BM1 cells (creating the cell line B9BM-C3). After induction, apoptotic cell death of 3T3 and B9BM-C3 cells began by 4 h and was complete by 48 h postinduction, while nontransduced cells remained viable. Annexin V staining demonstrated 43, 76, and 98% apoptotic cell death at 12, 18, and 24 h postinduction. Activation of caspase-3 was evident in induced cells and cell death could be inhibited by the addition of a caspase-3-specific inhibitor. Overexpression of the myeloma-associated oncogene FGFR3, which upregulates bcl-x(L), delayed but did not prevent caspase-3-mediated killing. B9BM-C3 cells formed tumors after subcutaneous injection in mice. Early treatment with RU486 eradicated tumors; however, rechallenge of treated mice failed to demonstrate evidence of immunoprotection. These results indicate that therapeutic attempts to induce caspase-3 in malignant cells may prove useful in the treatment of bcl-x(L)-expressing tumors.
authors.affiliation: Division of Experimental Therapeutics, Toronto General Research Institute, and Department of Medical Oncology, Princess Margaret Hospital, M5G 2M9, Toronto, Ontario, Canada
authors.forename: Jonathan B
authors.initials: JB
authors.lastname: Pollett
authors.forename: Yuan Xiao
authors.initials: YX
authors.lastname: Zhu
authors.forename: Sonal
authors.initials: S
authors.lastname: Gandhi
authors.forename: Meena
authors.initials: M
authors.lastname: Bali
authors.forename: Esther
authors.initials: E
authors.lastname: Masih-Khan
authors.forename: Zhihua
authors.initials: Z
authors.lastname: Li
authors.forename: Xiao Yan
authors.initials: XY
authors.lastname: Wen
authors.forename: A Keith
authors.initials: AK
authors.lastname: Stewart
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3; D020169:Caspases / Q000235:genetics / Q000378:metabolism* / Q000633:toxicity; D045744:Cell Line, Tumor; D004790:Enzyme Induction / Q000187:drug effects; D015316:Genetic Therapy; D005822:Genetic Vectors / Q000235:genetics; D006801:Humans; D051379:Mice; D015735:Mifepristone / Q000494:pharmacology*; D009101:Multiple Myeloma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology* / Q000628:therapy; D041681:NIH 3T3 Cells; D009374:Neoplasms, Experimental; D011505:Protein-Tyrosine Kinases; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D051498:Receptor, Fibroblast Growth Factor, Type 3; D017468:Receptors, Fibroblast Growth Factor / Q000235:genetics / Q000378:metabolism; D012190:Retroviridae / Q000235:genetics*; D015996:Survival Rate; D013997:Time Factors; D051020:bcl-X Protein
chemical_list: C494811:BCL2L1 protein, human; C494812:Bcl2l1 protein, mouse; D019253:Proto-Oncogene Proteins c-bcl-2; D017468:Receptors, Fibroblast Growth Factor; D051020:bcl-X Protein; D015735:Mifepristone; C496365:FGFR3 protein, human; C496366:Fgfr3 protein, mouse; D011505:Protein-Tyrosine Kinases; D051498:Receptor, Fibroblast Growth Factor, Type 3; C505407:CASP3 protein, human; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases