Autophagy and Apoptosis in Hepatocellular Carcinoma Induced by EF25-(GSH)(2): A Novel Curcumin Analog

• Authors: Tao Zhou, Anhui University; Lili Ye, Anhui University; Yu Bai, Anhui University; Aiming Sun, Emory University; Dahai Liu, Anhui University; Yong Li, Anhui University; Dennis Liotta, Emory University; James P. Snyder, Emory University; Haian Fu, Emory University; Bei Huang, Anhui University; Bryan Cox, Emory University
• Journal Title: PLoS ONE
• Volume: Volume 9, Number 9
• Publisher: Public Library of Science | 2014-09-30, Pages e107876-e107876
• Type of Work: Article | Final Publisher PDF
• Publisher DOI: http://doi.org/10.1371/journal.pone.0107876
• Subjects: Health Sciences, Oncology; Health Sciences, Pharmacology; Chemistry, General
• Keywords: Science & Technology; Multidisciplinary Sciences; Science & Technology - Other Topics; MALIGNANT GLIOMA-CELLS; CANCER-CELLS; INDUCED CYTOTOXICITY; SIGNALING PATHWAYS; EF24; DEATH; ANGIOGENESIS; INHIBITION; ANTICANCER; INDUCTION; Autophagic cell death; Apoptosis; Cancer treatment; Cell cycle; Cell division; MTT assay; Cytotoxicity; Hepatocellular carcinoma; Light microscopy

Abstract

Curcumin, a spice component as well as a traditional Asian medicine, has been reported to inhibit proliferation of a variety of cancer cells but is limited in application due to its low potency and bioavailability. Here, we have assessed the therapeutic effects of a novel and water soluble curcumin analog, 3,5-bis(2-hydroxybenzylidene)tetrahydro-4H-pyran-4-one glutathione conjugate [EF25-(GSH) 2], on hepatoma cells. Using the MTT and colony formation assays, we determined that EF25-(GSH) 2 drastically inhibits the proliferation of hepatoma cell line HepG2 with minimal cytotoxicity for the immortalized human hepatic cell line HL-7702. Significantly, EF25-(GSH) 2 suppressed growth of HepG2 xenografts in mice with no observed toxicity to the animals. Mechanistic investigation revealed that EF25-(GSH)2 induces autophagy by means of a biphasic mechanism. Low concentrations (<5 mmol/L) induced autophagy with reversible and moderate cytoplasmic vacuolization, while high concentrations (>10 mmol/L) triggered an arrested autophagy process with irreversible and extensive cytoplasmic vacuolization. Prolonged treatment with EF25-(GSH)2 induced cell death through both an apoptosis-dependent and a non-apoptotic mechanism. Chloroquine, a late stage inhibitor of autophagy which promoted cytoplasmic vacuolization, led to significantly enhanced apoptosis and cytotoxicity when combined with EF25-(GSH)2. Taken together, these data imply a fail-safe mechanism regulated by autophagy in the action of EF25-(GSH)2, suggesting the therapeutic potential of the novel curcumin analog against hepatocellular carcinoma (HCC), while offering a novel and effective combination strategy with chloroquine for the treatment of patients with HCC.