title: Astaxanthin down-regulates Rad51 expression via inactivation of AKT kinase to enhance mitomycin C-induced cytotoxicity in human non-small cell lung cancer cells.
abstract: Astaxanthin has been demonstrated to exhibit a wide range of beneficial effects, including anti-inflammatory and anti-cancer properties. However, the molecular mechanism of astaxanthin-induced cytotoxicity in non-small cell lung cancer (NSCLC) cells has not been identified. Rad51 plays a central role in homologous recombination, and studies show that chemo-resistant carcinomas exhibit high levels of Rad51 expression. In this study, astaxanthin treatment inhibited cell viability and proliferation of two NSCLC cells, A549 and H1703. Astaxanthin treatment (2.5-20 μM) decreased Rad51 expression and phospho-AKT(Ser473) protein level in a time and dose-dependent manner. Furthermore, expression of constitutively active AKT (AKT-CA) vector rescued the decreased Rad51 mRNA and protein levels in astaxanthin-treated NSCLC cells. Combined treatment with phosphatidylinositol 3-kinase (PI3K) inhibitors (LY294002 or wortmannin) further decreased the Rad51 expression in astaxanthin-exposed A549 and H1703 cells. Knockdown of Rad51 expression by transfection with si-Rad51 RNA or cotreatment with LY294002 further enhanced the cytotoxicity and cell growth inhibition of astaxanthin. Additionally, mitomycin C (MMC) as an anti-tumor antibiotic is widely used in clinical NSCLC chemotherapy. Combination of MMC and astaxanthin synergistically resulted in cytotoxicity and cell growth inhibition in NSCLC cells, accompanied with reduced phospho-AKT(Ser473) level and Rad51 expression. Overexpression of AKT-CA or Flag-tagged Rad51 reversed the astaxanthin and MMC-induced synergistic cytotoxicity. In contrast, pretreatment with LY294002 further decreased the cell viability in astaxanthin and MMC co-treated cells. In conclusion, astaxanthin enhances MMC-induced cytotoxicity by decreasing Rad51 expression and AKT activation. These findings may provide rationale to combine astaxanthin with MMC for the treatment of NSCLC.
authors.affiliation: Department of Internal Medicine, National Taiwan University Hospital, Hsin-Chu Branch, Taiwan; Institute of Technology Law, National Chiao Tung University, Hsinchu, Taiwan.
authors.forename: Jen-Chung
authors.initials: JC
authors.lastname: Ko
authors.affiliation: Department of Food Science, National Chiayi University, Chiayi, Taiwan.
authors.forename: Jyh-Cheng
authors.initials: JC
authors.lastname: Chen
authors.affiliation: Department of Biochemical Science and Technology, National Chiayi University, Chiayi, Taiwan.
authors.forename: Tai-Jing
authors.initials: TJ
authors.lastname: Wang
authors.affiliation: Department of Biochemical Science and Technology, National Chiayi University, Chiayi, Taiwan.
authors.forename: Hao-Yu
authors.initials: HY
authors.lastname: Zheng
authors.affiliation: Department of Biochemical Science and Technology, National Chiayi University, Chiayi, Taiwan.
authors.forename: Wen-Ching
authors.initials: WC
authors.lastname: Chen
authors.affiliation: Department of Biochemical Science and Technology, National Chiayi University, Chiayi, Taiwan.
authors.forename: Po-Yuan
authors.initials: PY
authors.lastname: Chang
authors.affiliation: Department of Biochemical Science and Technology, National Chiayi University, Chiayi, Taiwan. Electronic address: linyw@mail.ncyu.edu.tw.
authors.forename: Yun-Wei
authors.initials: YW
authors.lastname: Lin
mesh_terms: D000903:Antibiotics, Antineoplastic / Q000633:toxicity; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy / Q000378:metabolism*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy / Q000378:metabolism*; D016685:Mitomycin / Q000627:therapeutic use / Q000633:toxicity*; D051058:Oncogene Protein v-akt / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051135:Rad51 Recombinase / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D024341:Xanthophylls / Q000633:toxicity
chemical_list: D000903:Antibiotics, Antineoplastic; D024341:Xanthophylls; D016685:Mitomycin; C005948:astaxanthine; D051058:Oncogene Protein v-akt; C495153:RAD51 protein, human; D051135:Rad51 Recombinase
keywords: AKT; Actinomycin D (PubChem CID: 2019); Astaxanthin; Astaxanthin (PubChem CID: 5281224); Crystal violet (PubChem CID: 11057); Cycloheximide (PubChem CID: 6197); LY294002 (PubChem CID: 3973); Leupeptin (PubChem CID: 72429); MG132 (PubChem CID: 462382); Mitomycin C; Mitomycin C (PubChem CID: 5746); Non-small cell lung cancer; Penicillin (PubChem CID: 5904); Sodium bicarbonate (PubChem CID: 516892); Streptomycin (PubChem CID: 19649); Trypan blue (PubChem CID: 9562061); Wortmannin (PubChem CID: 312145); l-Glutamine (PubChem CID: 5961)