title: C6 ceramide sensitizes pemetrexed-induced apoptosis and cytotoxicity in osteosarcoma cells.
abstract: Chemotherapy has significantly improved the prognosis of high-grade osteosarcoma (OS), but over 30% of OS patients can still not be cured. Pemetrexed, the newly-developed anti-folate chemotherapy drug, exerted lower efficacy against OS cells. Here, we aimed to increase pemetrexed efficiency, and found that the cell-permeable short-chain ceramide (C6) significantly enhanced pemetrexed-induced viability reduction and death in cultured OS cell lines (U2OS and MG-63). Pemetrexed induced moderate apoptosis in OS cells, which was dramatically augmented by C6 ceramide. The apoptosis inhibitor z-VAD-fmk largely inhibited C6 ceramide plus pemetrexed-induced cytotoxicity and apoptosis in OS cells. By using pharmacological and siRNA-knockdown strategies, we showed that Akt-mammalian TOR (mTOR) over-activation was an important pemetrexed resistance factor in OS cells, and C6 ceramide-mediated pemetrexed sensitization effect was mediated, at least in part, by Akt-mTOR inhibition. Finally, we found that Akt-S6 Kinase 1 (S6K1, an indicator of mTOR activation) was over-activated in human OS tissues. On the other hand, the osteoblastic MC3T3-E1 cells, which expressed lower Akt-S6K1 phosphorylation, were resistant to pemetrexed and/or C6 ceramide. Together, we conclude that C6 ceramide sensitizes pemetrexed-induced apoptosis and cytotoxicity in OS cells probably through in-activation of Akt-mTOR signaling.
authors.affiliation: Department of Orthopaedics, The Second Affiliated Hospital of Nantong University, Nantong 226001, People's Republic of China. Electronic address: zhuzhuyeah1981@yeah.net.
authors.forename: Xinhui
authors.initials: X
authors.lastname: Zhu
authors.affiliation: Department of Orthopaedics, Qi-Dong Hospital of Traditional Chinese Medicine, Nantong 226200, People's Republic of China.
authors.forename: Xueping
authors.initials: X
authors.lastname: Du
authors.affiliation: Department of Immunology, Medical College, Nantong University, Nantong 226001, People's Republic of China.
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Deng
authors.affiliation: Department of Orthopaedics, The Second Affiliated Hospital of Nantong University, Nantong 226001, People's Republic of China.
authors.forename: Hong
authors.initials: H
authors.lastname: Yi
authors.affiliation: Department of Orthopaedics, The Second Affiliated Hospital of Nantong University, Nantong 226001, People's Republic of China.
authors.forename: Shengyu
authors.initials: S
authors.lastname: Cui
authors.affiliation: Department of Orthopaedics, The Second Affiliated Hospital of Nantong University, Nantong 226001, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.affiliation: Department of Immunology, Medical College, Nantong University, Nantong 226001, People's Republic of China.
authors.forename: Aiguo
authors.initials: A
authors.lastname: Shen
authors.affiliation: Department of Orthopaedics, The Second Affiliated Hospital of Nantong University, Nantong 226001, People's Republic of China.
authors.forename: Zhiming
authors.initials: Z
authors.lastname: Cui
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D001483:Base Sequence; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002518:Ceramides / Q000494:pharmacology*; D005971:Glutamates / Q000494:pharmacology*; D006147:Guanine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D012516:Osteosarcoma / Q000473:pathology*; D000068437:Pemetrexed; D034741:RNA, Small Interfering / Q000235:genetics
chemical_list: D002518:Ceramides; D005971:Glutamates; D034741:RNA, Small Interfering; D000068437:Pemetrexed; D006147:Guanine
keywords: Akt–mTOR signaling and chemo-sensitization; C6 ceramide; Osteosarcoma; Pemetrexed