Supplementary Figure 5 from miR-34a Silences c-SRC to Attenuate Tumor Growth in Triple-Negative Breast Cancer
Figure S5, Related to Figure 6. A, Assessment of SRC mRNA levels in MDA-MB-231 SRC-ORF, EMPTY-ORF, or parental cell lines. Data is normalized in RPL19 levels. B, Crystal violet staining assays on day 5 post-transfection confirms the ability of c-SRC to rescue miR-34a-induced anti-tumor growth. C-D, Examples of Pearson correlation analysis indicating MDA-MB-231 cells were not similar to BT-549 and MDA-MB-436 cells, and therefore were not included in the initial K-Means clustering analysis (results shown in D). E, The fold knockdown by miR-34a as compared to the miR-Scr treatments of the indicated genes in Clusters 1-3 in both BT-549 and MDA-MB-436 cells using a 2-fold change cut-off. None of the genes in Cluster 4 were downregulated by miR-34a (data not shown). F, Schematic of the KEGG pathway (hsa04510: Focal Adhesion) with miR-34a downregulated genes highlighted in red. G-H, Represents further analysis of the miR-34a gene signature in breast cancer. G, Indicates correlation analyses of miR-34a target genes in TNBC patients from Metabric data. H, Confirmation of prognostic importance of mIR-34a gene signature using a PROGgeneV2 algorithm on the TCGA data set.
Funding
Yale Cancer Center and NIH
Breast Cancer Research Foundation Award
OTKA
AIRC
History
ARTICLE ABSTRACT
Triple-negative breast cancer (TNBC) is an aggressive subtype with no clinically proven biologically targeted treatment options. The molecular heterogeneity of TNBC and lack of high frequency driver mutations other than TP53 have hindered the development of new and effective therapies that significantly improve patient outcomes. miRNAs, global regulators of survival and proliferation pathways important in tumor development and maintenance, are becoming promising therapeutic agents. We performed miRNA-profiling studies in different TNBC subtypes to identify miRNAs that significantly contribute to disease progression. We found that miR-34a was lost in TNBC, specifically within mesenchymal and mesenchymal stem cell–like subtypes, whereas expression of miR-34a targets was significantly enriched. Furthermore, restoration of miR-34a in cell lines representing these subtypes inhibited proliferation and invasion, activated senescence, and promoted sensitivity to dasatinib by targeting the proto-oncogene c-SRC. Notably, SRC depletion in TNBC cell lines phenocopied the effects of miR-34a reintroduction, whereas SRC overexpression rescued the antitumorigenic properties mediated by miR-34a. miR-34a levels also increased when cells were treated with c-SRC inhibitors, suggesting a negative feedback exists between miR-34a and c-SRC. Moreover, miR-34a administration significantly delayed tumor growth of subcutaneously and orthotopically implanted tumors in nude mice, and was accompanied by c-SRC downregulation. Finally, we found that miR-34a and SRC levels were inversely correlated in human tumor specimens. Together, our results demonstrate that miR-34a exerts potent antitumorigenic effects in vitro and in vivo and suggests that miR-34a replacement therapy, which is currently being tested in human clinical trials, represents a promising therapeutic strategy for TNBC. Cancer Res; 76(4); 927–39. ©2015 AACR.Usage metrics
