American Association for Cancer Research
00085472can133470-sup-supplementary_information.pdf (996.27 kB)

Supplementary Methods, Figures 1 - 4 from STAT3-Mediated Autophagy Dependence Identifies Subtypes of Breast Cancer Where Autophagy Inhibition Can Be Efficacious

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journal contribution
posted on 2023-03-30, 23:10 authored by Paola Maycotte, Christy M. Gearheart, Rebecca Barnard, Suraj Aryal, Jean M. Mulcahy Levy, Susan P. Fosmire, Ryan J. Hansen, Michael J. Morgan, Christopher C. Porter, Daniel L. Gustafson, Andrew Thorburn

PDF file - 1806K, Supplementary Figure S1. Hierarchical clustering of breast cancer cell lines transduced with an autophagy-focused shRNA library produced two main clusters. Supplementary Figure S2. ATG5, ATG7 and BECN1 shRNAs decreased protein levels in all cell lines tested. Supplementary Figure S3. Autophagy inhibition induces cell death in some cell lines but not others. MCF7, MDAMB231 and MDAMB468 cells were transduced with a lentivirus expressing shRNAs against ATG7 or BECN1, plated and evaluated for cell death with propidium iodide (red) staining after 48 h. Supplementary Figure S4. Triple negative cell lines have constitutively activated JAK/STAT pathway and autophagy regulates their STAT3 phosphorylation status.



Autophagy is a protein and organelle degradation pathway that is involved in diverse diseases, including cancer. Recent evidence suggests that autophagy is a cell survival mechanism in tumor cells and that its inhibition, especially in combination with other therapy, could be beneficial but it remains unclear if all cancer cells behave the same way when autophagy is inhibited. We inhibited autophagy in a panel of breast cancer cell lines and found that some of them are dependent on autophagy for survival even in nutrient rich conditions without any additional stress, whereas others need autophagy only when stressed. Survival under unstressed conditions is due to cell type–specific autophagy regulation of STAT3 activity and this phenotype is enriched in triple-negative cell lines. This autophagy-dependency affects response to therapy because autophagy inhibition reduced tumor growth in vivo in autophagy-dependent but not in autophagy-independent breast tumors, whereas combination treatment with autophagy inhibitors and other agent was preferentially synergistic in autophagy-dependent cells. These results imply that autophagy-dependence represents a tumor cell–specific characteristic where autophagy inhibition will be more effective. Moreover, our results suggest that autophagy inhibition might be a potential therapeutic strategy for triple-negative breast cancers, which currently lack an effective targeted treatment. Cancer Res; 74(9); 2579–90. ©2014 AACR.

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