title: Increased calcium influx and ribosomal content correlate with resistance to endoplasmic reticulum stress-induced cell death in mutant leukemia cell lines.
abstract: Cell clones were derived by treatment of HL-60 cells with stepwise increasing concentrations of econazole (Ec), an imidazole antifungal that blocks Ca2+ influx and induces endoplasmic reticulum (ER) stress-related cell death in multiple mammalian cell types. Clones exhibit 20- to more than 300-fold greater resistance to Ec. Unexpectedly, they also display stable cross-resistance to tunicamycin, thapsigargin, dithiothreitol, and cycloheximide but not doxorubicin, etoposide, or Fas ligand. Phenotypic analysis indicates that the cells display increased store-operated calcium influx and resistance to ER Ca2+ store depletion by Ec. E2R2, the most resistant clone, was observed to maintain protein synthesis levels after treatment with Ec or thapsigargin. Expression of GRP78, an ER-based chaperone, was induced by these ER stress treatments but to equal degrees in HL-60 and E2R2 cells. By using microarray analysis, at least 15 ribosomal protein genes were found to be overexpressed in E2R2 compared with HL-60 cells. We also found that ribosomal protein content was increased by 30% in E2R2 as well as other clones. The resistance phenotype was partially reversed by the ribosome-inactivating protein saporin. Therefore, increased store-operated calcium influx, resistance to ER Ca2+ store depletion, and overexpression of ribosomal proteins define a novel phenotype of ER stress-associated multidrug resistance.
authors.affiliation: Arthritis and Immune Disorder Research Centre, University Health Network and the Department of Immunology, University of Toronto, Toronto, Ontario M5G 2M9, Canada.
authors.forename: Yicheng
authors.initials: Y
authors.lastname: Zhang
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Berger
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D019540:Area Under Curve; D002118:Calcium / Q000378:metabolism*; D016923:Cell Death; D045744:Cell Line, Tumor; D003513:Cycloheximide / Q000494:pharmacology; D004229:Dithiothreitol / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004317:Doxorubicin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D004464:Econazole / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D000091342:Endoplasmic Reticulum Chaperone BiP; D005047:Etoposide / Q000494:pharmacology; D053222:Fas Ligand Protein; D005434:Flow Cytometry; D018922:HL-60 Cells; D006801:Humans; D007938:Leukemia / Q000378:metabolism / Q000473:pathology*; D008562:Membrane Glycoproteins / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D012270:Ribosomes / Q000378:metabolism*; D019284:Thapsigargin / Q000494:pharmacology; D013997:Time Factors; D014415:Tunicamycin / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D000903:Antibiotics, Antineoplastic; D000972:Antineoplastic Agents, Phytogenic; D000091342:Endoplasmic Reticulum Chaperone BiP; C505661:FASLG protein, human; D053222:Fas Ligand Protein; C000717247:HSPA5 protein, human; D008562:Membrane Glycoproteins; D014415:Tunicamycin; D019284:Thapsigargin; D005047:Etoposide; D004464:Econazole; D004317:Doxorubicin; D003513:Cycloheximide; D002118:Calcium; D004229:Dithiothreitol