Hsu J.-L.Ho Y.-F.TSAI-KUN LIChen C.-S.LIH-CHING HSUJIH-HWA GUH2021-06-022021-06-02201262952https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860668140&doi=10.1016%2fj.bcp.2012.03.023&partnerID=40&md5=1cf983c51a28b06c6a0be318c2f605aehttps://scholars.lib.ntu.edu.tw/handle/123456789/564804Combination therapy, which can optimize killing activity to cancers and minimize drug resistance, is a mainstream therapy against hormone-refractory prostate cancers (HRPCs). Rottlerin, a natural polyphenolic component, synergistically increased PC-3 (a HRPC cell line) apoptosis induced by camptothecin (a topoisomerase I inhibitor). Using siRNA technique to knockdown protein kinase C-δ (PKCδ), the data showed that rottlerin-mediated synergistic effect was PKCδ-independent, although rottlerin has been used as a PKCδ inhibitor. Rottlerin potentiated camptothecin-induced DNA fragmentation at S phase and ATM phosphorylation at Ser 1981. The effect was correlated to apoptosis (r 2 = 0.9). To detect upstream signals, the data showed that camptothecin acted on and stabilized topoisomerase I-DNA complex, leading to the formation of camptothecin-trapped cleavage complexes (TOP1cc). The effect was potentiated by rottlerin. To determine DNA repair capability, the time-related γH 2A.X formation was examined after camptothecin removal. Consequently, rottlerin significantly inhibited camptothecin removal-mediated decline of γH 2A.X formation at S phase, indicating the impairment of DNA repair activity in the presence of rottlerin. The combinatory treatment of camptothecin and rottlerin induced conformational change and activation of Bax and formation of truncated Bad, suggesting the contribution of mitochondria stress to apoptosis. In summary, the data suggest that rottlerin-mediated camptothecin sensitization is through the augmented stabilization of TOP1cc, leading to an increase of DNA damage stress and, possibly, an impairment of DNA repair capability. Subsequently, mitochondria-involved apoptosis is triggered through Bax activation and truncated Bad formation. The novel discovery may provide an anticancer approach of combinatory use between rottlerin and camptothecin for the treatment of HRPCs. ? 2012 Elsevier Inc.[SDGs]SDG3ATM protein; camptothecin; DNA topoisomerase; protein BAD; protein Bax; protein kinase C delta; rottlerin; serine; small interfering RNA; article; cell cycle S phase; cell stress; chemosensitization; complex formation; conformational transition; controlled study; cytotoxicity; DNA cleavage; DNA fragmentation; DNA repair; drug potentiation; gene silencing; human; human cell; male; mitochondrial membrane potential; mitochondrion; priority journal; prostate cancer; protein phosphorylation; signal transduction; Acetophenones; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Benzopyrans; Blotting, Western; Camptothecin; Cell Culture Techniques; Cell Line, Tumor; Cell Survival; DNA Cleavage; DNA Topoisomerases, Type I; Drug Synergism; Flow Cytometry; Humans; In Situ Nick-End Labeling; Male; Neoplasms, Hormone-Dependent; Prostatic Neoplasms; Protein Kinase C-delta; RNA, Small Interfering; Topoisomerase I Inhibitors; Transfectionjournal article10.1016/j.bcp.2012.03.023224907012-s2.0-84860668140