title: Glucose Modulation Induces Lysosome Formation and Increases Lysosomotropic Drug Sequestration via the P-Glycoprotein Drug Transporter.
abstract: Pgp is functional on the plasma membrane and lysosomal membrane. Lysosomal-Pgp can pump substrates into the organelle, thereby trapping certain chemotherapeutics (e.g. doxorubicin; DOX). This mechanism serves as a "safe house" to protect cells against cytotoxic drugs. Interestingly, in contrast to DOX, lysosomal sequestration of the novel anti-tumor agent and P-glycoprotein (Pgp) substrate, di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT), induces lysosomal membrane permeabilization. This mechanism of lysosomal-Pgp utilization enhances cytotoxicity to multidrug-resistant cells. Consequently, Dp44mT has greater anti-tumor activity in drug-resistant relative to non-Pgp-expressing tumors. Interestingly, stressors in the tumor microenvironment trigger endocytosis for cell signaling to assist cell survival. Hence, this investigation examined how glucose variation-induced stress regulated early endosome and lysosome formation via endocytosis of the plasma membrane. Furthermore, the impact of glucose variation-induced stress on resistance to DOX was compared with Dp44mT and its structurally related analogue, di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC). These studies showed that glucose variation-induced stress-stimulated formation of early endosomes and lysosomes. In fact, through the process of fluid-phase endocytosis, Pgp was redistributed from the plasma membrane to the lysosomal membrane via early endosome formation. This lysosomal-Pgp actively transported the Pgp substrate, DOX, into the lysosome where it became trapped as a result of protonation at pH 5. Due to increased lysosomal DOX trapping, Pgp-expressing cells became more resistant to DOX. In contrast, cytotoxicity of Dp44mT and DpC was potentiated due to more lysosomes containing functional Pgp under glucose-induced stress. These thiosemicarbazones increased lysosomal membrane permeabilization and cell death. This mechanism has critical implications for drug-targeting in multidrug-resistant tumors where a stressful micro-environment exists.
authors.affiliation: From the Molecular Pharmacology and Pathology Program, Department of Pathology, Blackburn Building (D06), University of Sydney, New South Wales, Australia 2006.
authors.forename: Nicole A
authors.initials: NA
authors.lastname: Seebacher
authors.affiliation: From the Molecular Pharmacology and Pathology Program, Department of Pathology, Blackburn Building (D06), University of Sydney, New South Wales, Australia 2006.
authors.forename: Darius J R
authors.initials: DJ
authors.lastname: Lane
authors.affiliation: From the Molecular Pharmacology and Pathology Program, Department of Pathology, Blackburn Building (D06), University of Sydney, New South Wales, Australia 2006 patric.jansson@sydney.edu.au.
authors.forename: Patric J
authors.initials: PJ
authors.lastname: Jansson
authors.affiliation: From the Molecular Pharmacology and Pathology Program, Department of Pathology, Blackburn Building (D06), University of Sydney, New South Wales, Australia 2006 d.richardson@med.usyd.edu.au.
authors.forename: Des R
authors.initials: DR
authors.lastname: Richardson
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism*; D001693:Biological Transport, Active / Q000187:drug effects; D045744:Cell Line, Tumor; D004317:Doxorubicin / Q000493:pharmacokinetics* / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D004705:Endocytosis / Q000187:drug effects / Q000235:genetics; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007425:Intracellular Membranes / Q000378:metabolism; D008247:Lysosomes / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D013882:Thiosemicarbazones / Q000493:pharmacokinetics* / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D013882:Thiosemicarbazones; C539263:di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone; D004317:Doxorubicin; D005947:Glucose
keywords: drug delivery; drug resistance; drug transport; endocytosis; glucose; glucose-induced stress; lysosome