title: Isomahanine induces endoplasmic reticulum stress and simultaneously triggers p38 MAPK-mediated apoptosis and autophagy in multidrug-resistant human oral squamous cell carcinoma cells.
abstract: Advanced oral squamous cell carcinoma (OSCC) is typically aggressive and closely correlated with disease recurrence and poor survival. Multidrug resistance (MDR) is the most critical problem leading to therapeutic failure. Investigation of novel anticancer candidates targeting multidrug-resistant OSCC cells may provide a basis for developing effective strategies for OSCC treatment. In the present study, we investigated the cytotoxic mechanism of a carbazole alkaloid, namely isomahanine, in a multidrug‑resistant OSCC cell line CLS-354/DX. We demonstrated that CLS-354/DX cells overexpressing multidrug resistance-associated protein 1 (MRP1) were resistant to anticancer drugs cisplatin and camptothecin. Isomahanine effectively induced cytotoxicity against CLS-354/DX cells regardless of resistance. Apoptosis as determined by FITC‑Annexin V/PI staining and western blot analysis of cleaved caspase-3 and cleaved poly(ADP‑ribose) polymerase (PARP) was significantly induced in a time-dependent manner upon isomahanine treatment. Isomahanine-induced caspase‑dependent apoptosis was determined using z-VAD‑fmk. The effects on autophagy in isomahanine-treated cells were investigated via conversion of LC3B and degradation of p62/SQSTM1 (p62). Isomahanine obviously induced autophagic flux as shown by an increase in punctate GFP-LC3B and the LC3B-II/LC3B-I ratio with a concomitant decrease in p62 levels. Autophagy inhibitors 3-methyladenine (3-MA) and chloroquine (CQ) protected isomahanine-induced cell death, indicating the activation of autophagic cell death. Endoplasmic reticulum (ER) stress and MAPK activation were examined to elucidate the mechanism underlying cell death. The expression levels of PERK, CHOP and phosphorylated MAPK (p38, ERK1/2 and JNK1/2) were upregulated following isomahanine treatment. We found that p38 MAPK inhibitor (SB203580) significantly attenuated isomahanine-induced apoptosis and autophagic flux and this prevented cell death. Collectively, the present study demonstrated that isomahanine was able to induce ER stress and trigger p38 MAPK-mediated apoptosis and autophagic cell death in multidrug-resistant OSCC cells. The potential cytotoxic action of isomahanine may provide the development of anticancer candidates for treating multidrug-resistant cancer.
authors.affiliation: School of Allied Health Sciences, Walailak University, Nakhon Si Thammarat 80161, Thailand.
authors.forename: Tanyarath
authors.initials: T
authors.lastname: Utaipan
authors.affiliation: Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ramkhamhaeng University, Bangkok 10240, Thailand.
authors.forename: Anan
authors.initials: A
authors.lastname: Athipornchai
authors.affiliation: Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ramkhamhaeng University, Bangkok 10240, Thailand.
authors.forename: Apichart
authors.initials: A
authors.lastname: Suksamrarn
authors.affiliation: Structural and Computational Biology Research Group and Department of Biochemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand.
authors.forename: Surasak
authors.initials: S
authors.lastname: Chunsrivirot
authors.affiliation: School of Allied Health Sciences, Walailak University, Nakhon Si Thammarat 80161, Thailand.
authors.forename: Warangkana
authors.initials: W
authors.lastname: Chunglok
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001343:Autophagy / Q000187:drug effects; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D018432:Drug Resistance, Multiple / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D006801:Humans; D009062:Mouth Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D020169:Caspases; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D048051:p38 Mitogen-Activated Protein Kinases; C421109:multidrug resistance-associated protein 1