title: Synergistic effect of targeting mTOR by rapamycin and depleting ATP by inhibition of glycolysis in lymphoma and leukemia cells.
abstract: The mammalian target of rapamycin (mTOR) pathway plays important roles in regulating nutrient metabolism and promoting the growth and survival of cancer cells, which exhibit increased glycolysis for ATP generation. In this study, we tested the hypothesis that inhibition of the mTOR pathway and glycolysis would synergistically impact the energy metabolism in cancer cells and may serve as an effective therapeutic strategy to kill malignant cells. Using human lymphoma cells and leukemia cells, we demonstrated that the combination of rapamycin, an mTOR inhibitor, with a glycolytic inhibitor produced synergistic cytotoxic effect, as evidenced by apoptosis and cell growth inhibition assays. Mechanistic studies showed that inhibition of the mTOR pathway by rapamycin alone sufficiently suppressed the phosphorylation of the downstream molecules p70S6K and 4E-BP-1, but only caused a moderate cytostatic effect. Combination of mTOR inhibition and blockage of glycolysis synergistically suppressed glucose uptake and severely depleted cellular ATP pools, leading to significant enhancement of cell killing. In contrast, combination of rapamycin and ara-C did not increase cytotoxicity in vitro. Our findings suggest that targeting mTOR pathway in combination with inhibition of glycolysis may be an effective therapeutic strategy for hematological malignancies. This mechanism-based drug combination warrants further investigation in preclinical and clinical settings.
authors.affiliation: Department of Molecular Pathology, The University of Texas, MD Anderson Cancer Center, Houston, TX, USA.
authors.forename: R-H
authors.initials: RH
authors.lastname: Xu
authors.forename: H
authors.initials: H
authors.lastname: Pelicano
authors.forename: H
authors.initials: H
authors.lastname: Zhang
authors.forename: F J
authors.initials: FJ
authors.lastname: Giles
authors.forename: M J
authors.initials: MJ
authors.lastname: Keating
authors.forename: P
authors.initials: P
authors.lastname: Huang
mesh_terms: D000255:Adenosine Triphosphate / Q000037:antagonists & inhibitors*; D017209:Apoptosis / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D003561:Cytarabine / Q000494:pharmacology; D004357:Drug Synergism; D004734:Energy Metabolism / Q000187:drug effects; D006019:Glycolysis / Q000187:drug effects; D006801:Humans; D007938:Leukemia / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D008223:Lymphoma / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D011494:Protein Kinases / Q000187:drug effects*; D020123:Sirolimus / Q000494:pharmacology*; D058570:TOR Serine-Threonine Kinases; D014407:Tumor Cells, Cultured
chemical_list: D003561:Cytarabine; D000255:Adenosine Triphosphate; D011494:Protein Kinases; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus