title: Leelamine mediates cancer cell death through inhibition of intracellular cholesterol transport.
abstract: Leelamine is a promising compound for the treatment of cancer; however, the molecular mechanisms leading to leelamine-mediated cell death have not been identified. This report shows that leelamine is a weakly basic amine with lysosomotropic properties, leading to its accumulation inside acidic organelles such as lysosomes. This accumulation leads to homeostatic imbalance in the lysosomal endosomal cell compartments that disrupts autophagic flux and intracellular cholesterol trafficking as well as receptor-mediated endocytosis. Electron micrographs of leelamine-treated cancer cells displayed accumulation of autophagosomes, membrane whorls, and lipofuscin-like structures, indicating disruption of lysosomal cell compartments. Early in the process, leelamine-mediated killing was a caspase-independent event triggered by cholesterol accumulation, as depletion of cholesterol using β-cyclodextrin treatment attenuated the cell death and restored the subcellular structures identified by electron microscopy. Protein microarray-based analyses of the intracellular signaling cascades showed alterations in RTK-AKT/STAT/MAPK signaling cascades, which was subsequently confirmed by Western blotting. Inhibition of Akt, Erk, and Stat signaling, together with abnormal deregulation of receptor tyrosine kinases, was caused by the inhibition of receptor-mediated endocytosis. This study is the first report demonstrating that leelamine is a lysosomotropic, intracellular cholesterol transport inhibitor with potential chemotherapeutic properties leading to inhibition of autophagic flux and induction of cholesterol accumulation in lysosomal/endosomal cell compartments. Importantly, the findings of this study show the potential of leelamine to disrupt cholesterol homeostasis for treatment of advanced-stage cancers.
authors.affiliation: Authors' Affiliations: Departments of Pharmacology, Penn State Hershey Melanoma Center;
authors.forename: Omer F
authors.initials: OF
authors.lastname: Kuzu
authors.affiliation: Authors' Affiliations: Departments of Pharmacology, Penn State Hershey Melanoma Center;
authors.forename: Raghavendra
authors.initials: R
authors.lastname: Gowda
authors.affiliation: Authors' Affiliations: Departments of Pharmacology, Penn State Hershey Melanoma Center; Penn State Melanoma Therapeutics Program; and.
authors.forename: Arati
authors.initials: A
authors.lastname: Sharma
authors.affiliation: Authors' Affiliations: Departments of Pharmacology, Pathology, Dermatology, and Surgery; Penn State Hershey Melanoma Center; Penn State Melanoma Therapeutics Program; and The Foreman Foundation for Melanoma Research, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania gprobertson@psu.edu.
authors.forename: Gavin P
authors.initials: GP
authors.lastname: Robertson
mesh_terms: D000818:Animals; D001343:Autophagy / Q000187:drug effects; D001692:Biological Transport / Q000187:drug effects; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D002784:Cholesterol / Q000378:metabolism*; D004224:Diterpenes / Q000493:pharmacokinetics / Q000494:pharmacology*; D004705:Endocytosis; D045325:HCT116 Cells; D006801:Humans; D008545:Melanoma / Q000188:drug therapy* / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D015398:Signal Transduction / Q000187:drug effects; D012878:Skin Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D014162:Transfection
chemical_list: D004224:Diterpenes; D002784:Cholesterol