title: Tunicamycin-induced endoplasmic reticulum stress reduces in vitro subpopulation and invasion of CD44+/CD24- phenotype breast cancer stem cells.
abstract: Tunicamycin is an inhibitor of glycosylation that disturbs protein folding machinery in eukaryotic cells. Tunicamycin causes accumulation of unfolded proteins in cell endoplasmic reticulum (ER) and induces ER stress. ER stress is an essential mechanism for cellular homeostasis has role in cell death via reprogramming of protein processing, regulation of autophagy and apoptosis. In this study we show effect of tunicamycin on subpopulation and invasion of CD44+/CD24- MCF7 breast cancer stem cells. CD44+/CD24- cells were isolated from MCF7 cell line by fluorescence activated cell sorting (FACS) and treated with tunicamycin. ER stress was monitored by evaluation of X-box binding protein 1(XBP-1) mRNA splicing, cleaved activating transcription factor 6 (ATF6) nuclear translocation and CCAAT/enhancer-binding protein homologous protein (CHOP) expression. CD44+/CD24- subpopulation was analyzed using flow cytometry. Invasion was investigated by scratch assay, trypan blue staining, 3-(4,5-dimethylthiazol-2-Yl)-2,5-diphenyltetrazolium bromide (MTT) proliferation and in vitro migration assays. Increased level of spliced XBP-1, ATF6 nuclear translocation and CHOP protein expression were detected in CD44+/CD24- and original MCF7 cells treated with tunicamycin. Also, a significant decline in CD44+/CD24- cell subpopulation was determined in the cells treated with tunicamycin. The results also showed inhibited invasion, increased cell death, suppressed proliferation and reduced migration in the CD44+/CD24- and CD44+/CD24- rich MCF7 cell culture, under effect of tunicamycin. Our results indicate that CD44+/CD24- phenotype MCF7 cells are susceptible to tunicamycin. The results showed that tunicamycin-induced ER stress suppresses CD44+/CD24- phenotype cell subpopulation and in vitro invasion and accelerates tumorosphore formation. These results suggest that tunicamycin-induced ER stress inhibits CD44+/CD24- phenotype MCF7 breast cancer stem cells. We conclude that using ER-targeting chemicals like tunicamycin is an interesting approach to target breast cancer stem cells inside tumor.
authors.affiliation: Department of Medical Genetics and Women and Children's Health Research Institute (WCHRI), University of Alberta, Edmonton, Canada. Electronic address: namimoll@ualberta.ca.
authors.forename: Babak
authors.initials: B
authors.lastname: Nami
authors.affiliation: Department of Medical Genetics, Selcuk University Medical Faculty, Konya, Turkey. Electronic address: dr.huseyin.donmez@gmail.com.
authors.forename: Huseyin
authors.initials: H
authors.lastname: Donmez
authors.affiliation: Department of Medical Genetics, Selcuk University Medical Faculty, Konya, Turkey. Electronic address: nkocak@selcuk.edu.tr.
authors.forename: Nadir
authors.initials: N
authors.lastname: Kocak
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000473:pathology*; D051927:CD24 Antigen / Q000378:metabolism*; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D006801:Humans; D018960:Hyaluronan Receptors / Q000378:metabolism*; D061986:MCF-7 Cells; D009361:Neoplasm Invasiveness; D014411:Neoplastic Stem Cells / Q000187:drug effects* / Q000378:metabolism; D014415:Tunicamycin / Q000494:pharmacology*
chemical_list: D000970:Antineoplastic Agents; D051927:CD24 Antigen; C497889:CD24 protein, human; C497483:CD44 protein, human; D018960:Hyaluronan Receptors; D014415:Tunicamycin
keywords: Breast cancer; CD24; CD44; Cancer stem cells; Endoplasmic reticulum stress; Tunicamycin