title: A sphingosine kinase inhibitor combined with temozolomide induces glioblastoma cell death through accumulation of dihydrosphingosine and dihydroceramide, endoplasmic reticulum stress and autophagy.
abstract: Glioblastomas (GBMs) are very aggressive tumors with low chemosensitivity. The DNA-alkylating agent temozolomide (TMZ) is currently the most efficient chemotoxic drug for GBM therapy; however, many patients develop resistance to TMZ. Combining TMZ with another agent could present an improved treatment option if it could overcome TMZ resistance and avoid side effects. Sphingosine kinase inhibitors (SKIs) have emerged as anticancer agents. Sphingosine kinases are often overexpressed in tumors where their activity of phosphorylating sphingosine (Sph) contributes to tumor growth and migration. They control the levels of the pro-apoptotic ceramide (Cer) and Sph and of the pro-survival sphingosine-1 phosphate. In the present work, TMZ was combined with a specific SKI, and the cytotoxic effect of each drug alone or in combination was tested on GBM cell lines. The combination of sublethal doses of both agents resulted in the cell death potentiation of GBM cell lines without affecting astrocyte viability. It triggered a caspase-3-dependent cell death that was preceded by accumulation of dihydrosphingosine (dhSph) and dihydroceramide (dhCer), oxidative stress, endoplasmic reticulum stress, and autophagy. Autophagy was identified as the crucial switch that facilitated induction of this cell death potentiation. The sublethal dose of the inhibitor induced these stress events, whereas that of TMZ induced the destructive autophagy switch. Remarkably, neither Cer nor Sph, but rather the Cer intermediates, dhSph and dhCer, was involved in the cytotoxicity from the combination. Cell lines sensitive to the combination expressed low levels of the antioxidant enzyme glutathione peroxidase-1, indicating this enzyme as a potential marker of sensitivity to such treatment. This work shows for the first time a strong interaction between a SKI and TMZ, leading to a tumor cell-specific death induction. It further demonstrates the biological relevance of dihydrosphingolipids in cell death mechanisms and emphasizes the potential of drugs that affect sphingolipid metabolism for cancer therapy.
authors.affiliation: German Cancer Research Centre, Program Infection and Cancer, Heidelberg, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Noack
authors.affiliation: 1] German Cancer Research Centre, Program Infection and Cancer, Heidelberg, Germany [2] University of Mainz, Institute of Molecular Cell Biology, Mainz, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Choi
authors.affiliation: German Cancer Research Centre, Program Imaging and Cytometry, Heidelberg, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Richter
authors.affiliation: German Cancer Research Centre, Biostatistics, Heidelberg, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Kopp-Schneider
authors.affiliation: 1] German Cancer Research Centre, Program Infection and Cancer, Heidelberg, Germany [2] University of Mainz, Institute of Molecular Cell Biology, Mainz, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Régnier-Vigouroux
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D001343:Autophagy / Q000187:drug effects; D001932:Brain Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology*; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D002518:Ceramides / Q000378:metabolism*; D003606:Dacarbazine / Q000031:analogs & derivatives* / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D004359:Drug Therapy, Combination; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005909:Glioblastoma / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology*; D006801:Humans; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000378:metabolism; D000077204:Temozolomide; D000099157:Sphingosine Kinase
chemical_list: D000970:Antineoplastic Agents; D002518:Ceramides; D003606:Dacarbazine; D004791:Enzyme Inhibitors; D017853:Phosphotransferases (Alcohol Group Acceptor); D013110:Sphingosine; D000077204:Temozolomide; D000099157:Sphingosine Kinase; C109343:dihydroceramide; C005682:safingol