title: Bozepinib, a novel small antitumor agent, induces PKR-mediated apoptosis and synergizes with IFNα triggering apoptosis, autophagy and senescence.
abstract: Bozepinib [(RS)-2,6-dichloro-9-[1-(p-nitrobenzenesulfonyl)-1,2,3,5-tetrahydro-4,1-benzoxazepin-3-yl]-9H-purine] is a potent antitumor compound that is able to induce apoptosis in breast cancer cells. In the present study, we show that bozepinib also has antitumor activity in colon cancer cells, showing 50% inhibitory concentration (IC50) values lower than those described for breast cancer cells and suggesting great potential of this synthetic drug in the treatment of cancer. We identified that the double-stranded RNA-dependent protein kinase (PKR) is a target of bozepinib, being upregulated and activated by the drug. However, p53 was not affected by bozepinib, and was not necessary for induction of apoptosis in either breast or colon cancer cells. In addition, the efficacy of bozepinib was improved when combined with the interferon-alpha (IFNα) cytokine, which enhanced bozepinib-induced apoptosis with involvement of protein kinase PKR. Moreover, we report here, for the first time, that in combined therapy, IFNα induces a clear process of autophagosome formation, and prior treatment with chloroquine, an autophagy inhibitor, is able to significantly reduce IFNα/bozepinib-induced cell death. Finally, we observed that a minor population of caspase 3-deficient MCF-7 cells persisted during long-term treatment with lower doses of bozepinib and the bozepinib/IFNα combination. Curiously, this population showed β-galactosidase activity and a percentage of cells arrested in S phase, that was more evident in cells treated with the bozepinib/IFNα combination than in cells treated with bozepinib or IFNα alone. Considering the resistance of some cancer cells to conventional chemotherapy, combinations enhancing the diversity of the cell death outcome might succeed in delivering more effective and less toxic chemotherapy.
authors.affiliation: Biopathology and Regenerative Medicine Institute, Centre for Biomedical Research, Spain ; Department of Human Anatomy and Embryology, Faculty of Medicine, University of Granada, Granada, Spain.
authors.forename: Juan Antonio
authors.initials: JA
authors.lastname: Marchal
authors.forename: Esther
authors.initials: E
authors.lastname: Carrasco
authors.forename: Alberto
authors.initials: A
authors.lastname: Ramirez
authors.forename: Gema
authors.initials: G
authors.lastname: Jiménez
authors.forename: Carmen
authors.initials: C
authors.lastname: Olmedo
authors.forename: Macarena
authors.initials: M
authors.lastname: Peran
authors.forename: Ahmad
authors.initials: A
authors.lastname: Agil
authors.forename: Ana
authors.initials: A
authors.lastname: Conejo-García
authors.forename: Olga
authors.initials: O
authors.lastname: Cruz-López
authors.forename: Joaquin María
authors.initials: JM
authors.lastname: Campos
authors.forename: María Ángel
authors.initials: MÁ
authors.lastname: García
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001343:Autophagy / Q000187:drug effects; D001943:Breast Neoplasms / Q000188:drug therapy / Q000473:pathology; D045744:Cell Line, Tumor; D016922:Cellular Senescence / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000473:pathology; D004357:Drug Synergism; D005260:Female; D006801:Humans; D020128:Inhibitory Concentration 50; D016898:Interferon-alpha / Q000008:administration & dosage / Q000494:pharmacology*; D061986:MCF-7 Cells; D051379:Mice; D010077:Oxazepines / Q000008:administration & dosage / Q000494:pharmacology*; D011687:Purines / Q000008:administration & dosage / Q000494:pharmacology*; D059807:S Phase Cell Cycle Checkpoints / Q000187:drug effects; D001616:beta-Galactosidase / Q000378:metabolism; D019892:eIF-2 Kinase / Q000378:metabolism
chemical_list: C556910:2,6-dichloro-9-(1-(p-nitrobenzenesulfonyl)-1,2,3,5-tetrahydro-4,1-benzoxazepin-3-yl)-9H-purine; D000970:Antineoplastic Agents; D016898:Interferon-alpha; D010077:Oxazepines; D011687:Purines; D019892:eIF-2 Kinase; D001616:beta-Galactosidase
keywords: IC50; breast and colon cancer cells; cell death; interferon cytokine; purines; seven-member heterocycles