title: The pro-apoptotic protein, Bik, exhibits potent antitumor activity that is dependent on its BH3 domain.
abstract: The Bcl-2 homology 3 (BH3) domain is present in most members of the Bcl-2 protein family and is required to confer the death-inducing properties of pro-apoptotic members, including Bax, Bak, Bad, and Bik, in cell-based assay systems. To determine whether the BH3 domain possesses a similar role in tumor tissues in vivo, we overexpressed the wild-type Bik protein and its BH3-deleted counterpart, using adenoviral technology, in chemoresistant human tumor prostate (PC-3) and colon (HT-29) cell lines growing in vitro and in vivo. Bik caused apoptosis in both PC-3 and HT-29 cells in vitro by inducing the release of cytochrome c from mitochondria to cytoplasm, resulting in the catalytic activation of caspases 9, 7, and 3 and cleavage of poly(ADP-ribose) polymerase and DNA fragmentation. When the BH3 domain was deleted from the Bik protein, no effect on mitochondrial activity or cell morphology could be observed. Furthermore, intratumoral injection of an adenovirus vector expressing the Bik gene, but not the deleted BH3 Bik gene, suppressed the growth of PC-3 and HT-29 xenografts established in nude mice. Histological examination of tumors from mice treated with the wild-type Bik adenoviral construct demonstrated cellular debris, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling positive staining, and morphological changes associated with apoptosis. In contrast, tissue sections obtained from tumors treated with the BH3-deleted Bik adenoviral construct showed no evidence of apoptosis. Thus, our results suggest that the BH3 domain is required for the antitumor activity of the Bik protein and provides a novel therapeutic approach for cancer therapy.
authors.affiliation: Shire BioChem, Inc., 275 Boulevard Armand-Frappier, Laval, Québec, H7V 4A7 Canada.
authors.forename: Y
authors.initials: Y
authors.lastname: Tong
authors.forename: Q
authors.initials: Q
authors.lastname: Yang
authors.forename: C
authors.initials: C
authors.lastname: Vater
authors.forename: L K
authors.initials: LK
authors.lastname: Venkatesh
authors.forename: D
authors.initials: D
authors.lastname: Custeau
authors.forename: T
authors.initials: T
authors.lastname: Chittenden
authors.forename: G
authors.initials: G
authors.lastname: Chinnadurai
authors.forename: H
authors.initials: H
authors.lastname: Gourdeau
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins; D015153:Blotting, Western; D020169:Caspases / Q000096:biosynthesis / Q000235:genetics; D002455:Cell Division / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000378:metabolism; D003574:Cytochrome c Group / Q000378:metabolism; D005260:Female; D005822:Genetic Vectors; D006801:Humans; D020287:In Situ Nick-End Labeling; D008297:Male; D008565:Membrane Proteins; D051379:Mice; D008819:Mice, Nude; D008928:Mitochondria / Q000187:drug effects; D024101:Mitochondrial Proteins; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000235:genetics / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects* / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; C096820:BIK protein, human; D003574:Cytochrome c Group; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D011506:Proteins; D020169:Caspases