title: Resistance mechanisms of cancer cells to the novel vacuolar H(+)-ATPase inhibitor archazolid B.
abstract: Resistance of cancer cells towards chemotherapy is the major cause of therapy failure. Hence, the evaluation of cellular defense mechanisms is essential in the establishment of new chemotherapeutics. Archazolid B, a novel vacuolar H(+)-ATPase inhibitor, displayed cytotoxicity in the low nanomolar range on a panel of different tumor cell lines. First, we investigated tumor-specific cytotoxicity of archazolid B by comparing cancer to non-cancer cells. Breast, liver and colon cancer cells displayed higher drug sensitivity than corresponding non-tumorous cells, whereas leukemia cell lines were as sensitive as peripheral mononuclear blood cells. Investigating classical drug resistance mechanisms, archazolid B was identified as a possible substrate of the ABC transporters ABCB1 (P-glycoprotein) and ABCG2 (BCRP), whereas collateral sensitivity was observed in ABCB5-expressing cells. Our results pointed to a possible binding competition of archazolid B with verapamil on P-glycoprotein. However, archazolid B did not reverse resistance towards doxorubicin indicating that it might be a substrate but not an inhibitor of P-glycoprotein mediated transport. Furthermore, the cytotoxicity of archazolid B was independent of the p53 status of the cell. Mechanisms of aquired resistance were investigated establishing an archazolid B-resistant MCF-7 cell line. Interestingly, drug resistance was not conferred by aberrant expression or DNA mutations of the gene encoding vacuolar H(+)-ATPase subunit c, the direct target of archazolids. Instead, long-term treatment with archazolid B led to a slight overexpression of ABCB1 and a significant overexpression of the epidermal growth factor receptor and reduced cell growth, all of which can be assumed to contribute to archazolid B resistance.
authors: Institute of Pharmacy and Biochemistry, Department of Pharmaceutical Biology, Johannes Gutenberg University, Staudinger Weg 5, 55128, Mainz, Germany.
authors: Rebecca
authors: R
authors: Hamm
authors: Yoshikazu
authors: Y
authors: Sugimoto
authors: Heinrich
authors: H
authors: Steinmetz
authors: Thomas
authors: T
authors: Efferth
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002460:Cell Line; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000502:physiology*; D066246:ErbB Receptors / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D018942:Macrolides / Q000494:pharmacology*; D062105:Molecular Docking Simulation; D017422:Sequence Analysis, DNA; D013844:Thiazoles / Q000494:pharmacology*; D016159:Tumor Suppressor Protein p53; D025262:Vacuolar Proton-Translocating ATPases / Q000037:antagonists & inhibitors* / Q000235:genetics
chemical_list: D018528:ATP-Binding Cassette Transporters; C541389:ATP6V0C protein, human; D000970:Antineoplastic Agents; D018942:Macrolides; D013844:Thiazoles; D016159:Tumor Suppressor Protein p53; C519728:archazolid B; C512478:EGFR protein, human; D066246:ErbB Receptors; D025262:Vacuolar Proton-Translocating ATPases