Multidrug resistance (MDR) is a major challenge in cancer therapy. Apoptosis tolerance is one of the key mechanisms of MDR. Honokiol, a small-molecule pharmacologically active component, exhibits competent cytotoxicity in a variety of human cancer cells through apoptosis and other forms
of programmed cell death (such as programmed necrosis). Although much work has been done on its antitumor effects, little attention has been paid on systemic evaluation of efficacy of honokiol combined with other chemotherapeutic agents, especially in drugresistant cell lines. Here, we systematically
and quantitatively assess its combinational effect with different chemotherapeutic agents using the combination index (CI) equation. We found that honokiol synergized with chemotherapeutic agents both in sensitive and resistant, solid and non-solid (MCF-7, HL-60, MCF-7/ADR and HL-60/ADR) cell
lines. Honokiol (40 µg/ml) induced necrotic cell death in MCF-7/ADR cells with characterized morphological and biochemical features. Co-incubation with honokiol and etoposide (VP-16) activated a complex death modality, which was composed of necrotic cell death and apoptosis. This
dual-death pathway was shut down when pretreated with pan-caspase inhibitor (z-VAD-fmk) and cyclophilin D inhibitor (cyclosporin A). Western blot analysis results proved that honokiol also enhanced VP-16-induced apoptosis potentially via blocking nuclear factorκB (NF-κB)
activation. Our data for the first time quantitatively demonstrate that honokiol synergizes frequently-used chemotherapeutic agents via enhanced apoptosis and additional programmed necrotic death. These findings indicate a promising way to circumvent MDR and apoptosis tolerance.
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Document Type: Research Article
Department of Surgical Oncology, The Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang 310009, P.R. China
Division of Stem Cell and Leukemia Research, City of Hope National Medical Center, City of Hope, Duarte, CA 91010, USA
Zhejiang Youth College, Hangzhou, Zhejiang 310012, P.R. China
January 1, 2013
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The International Journal of Oncology provides an international forum for the publication of the latest, cutting-edge research in the broad area of oncology and cancer treatment. The journal accepts original high quality works and reviews on all aspects of oncology research including carcinogenesis, metastasis, epidemiology, chemotherapy and viral oncology. Through fair and efficient peer review, the journal is dedicated to publishing top tier research in the field, offering authors rapid publication as well as high standards of copy-editing and production. The International Journal of Oncology is published on a monthly basis in both print and early online.
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