title: Inhibition of the autophagic flux by salinomycin in breast cancer stem-like/progenitor cells interferes with their maintenance.
abstract: Breast cancer tissue contains a small population of cells that have the ability to self-renew; these cells are known as cancer stem-like cells (CSCs). We have recently shown that autophagy is essential for the tumorigenicity of these CSCs. Salinomycin (Sal), a K (+) /H (+) ionophore, has recently been shown to be at least 100 times more effective than paclitaxel in reducing the proportion of breast CSCs. However, its mechanisms of action are still unclear. We show here that Sal blocked both autophagy flux and lysosomal proteolytic activity in both CSCs and non-CSCs derived from breast cancer cells. GFP-LC3 staining combined with fluorescent dextran uptake and LysoTracker-Red staining showed that autophagosome/lysosome fusion was not altered by Sal treatment. Acridine orange staining provided evidence that lysosomes display the characteristics of acidic compartments in Sal-treated cells. However, tandem mCherry-GFP-LC3 assay indicated that the degradation of mCherry-GFP-LC3 is blocked by Sal. Furthermore, the protein degradation activity of lysosomes was inhibited, as demonstrated by the rate of long-lived protein degradation, DQ-BSA assay and measurement of cathepsin activity. Our data indicated that Sal has a relatively greater suppressant effect on autophagic flux in the ALDH (+) population in HMLER cells than in the ALDH (-) population; moreover, this differential effect on autophagic flux correlated with an increase in apoptosis in the ALDH (+) population. ATG7 depletion accelerated the proapoptotic capacity of Sal in the ALDH (+) population. Our findings provide new insights into how the autophagy-lysosomal pathway contributes to the ability of Sal to target CSCs in vitro.
authors.affiliation: INSERM U984, Faculté de Pharmacie, Chatenay Malabry, France.
authors.forename: Wen
authors.initials: W
authors.lastname: Yue
authors.forename: Ahmed
authors.initials: A
authors.lastname: Hamaï
authors.forename: Giovanni
authors.initials: G
authors.lastname: Tonelli
authors.forename: Chantal
authors.initials: C
authors.lastname: Bauvy
authors.forename: Valérie
authors.initials: V
authors.lastname: Nicolas
authors.forename: Hugo
authors.initials: H
authors.lastname: Tharinger
authors.forename: Patrice
authors.initials: P
authors.lastname: Codogno
authors.forename: Maryam
authors.initials: M
authors.lastname: Mehrpour
mesh_terms: D000165:Acridine Orange / Q000378:metabolism; D000444:Aldehyde Dehydrogenase / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D001343:Autophagy / Q000187:drug effects*; D000071193:Autophagy-Related Protein 7; D001943:Breast Neoplasms / Q000473:pathology*; D049109:Cell Proliferation / Q000187:drug effects; D015536:Down-Regulation / Q000187:drug effects; D005260:Female; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism; D061986:MCF-7 Cells; D008561:Membrane Fusion / Q000187:drug effects; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008954:Models, Biological; D014411:Neoplastic Stem Cells / Q000187:drug effects / Q000201:enzymology / Q000473:pathology*; D010588:Phagosomes / Q000187:drug effects / Q000378:metabolism; D059748:Proteolysis / Q000187:drug effects; D011714:Pyrans / Q000494:pharmacology*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013194:Staining and Labeling; D044764:Ubiquitin-Activating Enzymes / Q000378:metabolism; D000095662:Polyether Polyketides
chemical_list: D000165:Acridine Orange; D000444:Aldehyde Dehydrogenase; D000071193:Autophagy-Related Protein 7; D049452:Green Fluorescent Proteins; D008869:Microtubule-Associated Proteins; D011714:Pyrans; D011993:Recombinant Fusion Proteins; D044764:Ubiquitin-Activating Enzymes; C477012:MAP1LC3A protein, human; C010327:salinomycin; D000095662:Polyether Polyketides; C509349:ATG7 protein, human
keywords: autophagy; breast cancer stem-like/progenitor cell; cell death; lysosome; salinomycin