title: Autophagy Supports Breast Cancer Stem Cell Maintenance by Regulating IL6 Secretion.
abstract: Autophagy is a mechanism by which cells degrade cellular material to provide nutrients and energy for survival during stress. The autophagy is thought to be a critical process for cancer stem cell (CSC) or tumor-initiating cell maintenance but the mechanisms by which autophagy supports survival of CSCs remain poorly understood. In this study, inhibition of autophagy by knockdown of ATG7 or BECN1 modified the CD44(+)/CD24(low/-) population in breast cancer cells by regulating CD24 and IL6 secretion. In a breast cancer cell line that is independent of autophagy for survival, autophagy inhibition increased IL6 secretion to the media. On the other hand, in an autophagy-dependent cell line, autophagy inhibition decreased IL6 secretion, cell survival, and mammosphere formation. In these cells, IL6 treatment or conditioned media from autophagy-competent cells rescued the deficiency in mammosphere formation induced by autophagy inhibition. These results reveal that autophagy regulates breast CSC maintenance in autophagy-dependent breast cancer cells by modulating IL6 secretion implicating autophagy as a potential therapeutic target in breast cancer.
  
  
  CONCLUSIONS
  Modulation of autophagy in breast cancer has different and even opposite effects, indicating the need for a selection strategy when trying to manipulate autophagy in the context of cancer therapy.
authors.affiliation: Department of Pharmacology, University of Colorado School of Medicine, Aurora, Colorado.
authors.forename: Paola
authors.initials: P
authors.lastname: Maycotte
authors.affiliation: Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, Colorado.
authors.forename: Kenneth L
authors.initials: KL
authors.lastname: Jones
authors.affiliation: Department of Pharmacology, University of Colorado School of Medicine, Aurora, Colorado.
authors.forename: Megan L
authors.initials: ML
authors.lastname: Goodall
authors.affiliation: Department of Pharmacology, University of Colorado School of Medicine, Aurora, Colorado.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Thorburn
authors.affiliation: Department of Pharmacology, University of Colorado School of Medicine, Aurora, Colorado. Andrew.Thorburn@ucdenver.edu.
authors.forename: Andrew
authors.initials: A
authors.lastname: Thorburn
mesh_terms: D051017:Apoptosis Regulatory Proteins / Q000037:antagonists & inhibitors; D001343:Autophagy; D000071193:Autophagy-Related Protein 7; D000071186:Beclin-1; D001943:Breast Neoplasms / Q000276:immunology / Q000473:pathology*; D051927:CD24 Antigen / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002470:Cell Survival; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D055785:Gene Knockdown Techniques; D006801:Humans; D018960:Hyaluronan Receptors / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism*; D061986:MCF-7 Cells; D008565:Membrane Proteins / Q000037:antagonists & inhibitors; D014411:Neoplastic Stem Cells / Q000276:immunology / Q000473:pathology*; D017423:Sequence Analysis, RNA; D044764:Ubiquitin-Activating Enzymes / Q000037:antagonists & inhibitors
chemical_list: D051017:Apoptosis Regulatory Proteins; C491997:BECN1 protein, human; D000071186:Beclin-1; D051927:CD24 Antigen; D018960:Hyaluronan Receptors; C508600:IL6 protein, human; D015850:Interleukin-6; D008565:Membrane Proteins; C509349:ATG7 protein, human; D000071193:Autophagy-Related Protein 7; D044764:Ubiquitin-Activating Enzymes