miR-34a Silences c-SRC to Attenuate Tumor Growth in Triple-Negative Breast Cancer

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. MicroRNAs (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 were 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 re-introduction, while SRC overexpression rescued the anti-tumorigenic 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 anti-tumorigenic 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.

MiR-34a Promotes Apoptosis and Inhibits Autophagy by Targeting HMGB1 in Acute Myeloid Leukemia Cells

“…showed that miR-519 enhanced cell proliferation and induced cell apoptosis in AML HL-60 cell line by decreasing the level of RNA-binding protein human antigen R [14]. MiR-34a is the first identified tumor suppressor gene that is lower expressed in many forms of tumors, including breast cancer, lung cancer and AML [15-17]. MiR-34a plays a critical role in many cellular processes including p53-induced cell cycle arrest, apoptosis and other biological behaviors by negatively regulating its target genes [18, 19].…”

cel-mir-237 and its homologue, hsa-miR-125b, modulate the cellular response to ionizing radiation

“…Since proper development of C. elegans vulval precursor cells depend upon EGFR and NOTCH1 signaling, two aberrantly activated pathways in human breast cancer, we profiled both normal and breast cancer cell lines. In a vast majority of breast cancer lines miR-125b was downregulated compared to HMECs, MCF-10As, and a panel of conditionally reprogrammed normal breast cells (CRCs) 36 (Fig. 3B & Fig.…”

“…For cytotoxicity assessment and development of IC 50 curves, Sulforhodamine Blue (SRB) assays were performed as previously described 36 . Briefly, transfected or drug treated cells were seeded into 24-well plates, HMECs were additionally treated with γ-irradiation, and at indicated times cells were fixed, stained, and dye intensity quantified.…”

“…Briefly, transfected or drug treated cells were seeded into 24-well plates, HMECs were additionally treated with γ-irradiation, and at indicated times cells were fixed, stained, and dye intensity quantified. Additionally, transfected cells underwent γ-irradiation treatment and were analyzed for presence of apoptosis by the Annexin V Apoptosis Detection Kit (BD Pharmigen), presence of senescence by the SA-β-Galactosidase Staining Kit (Cell Signaling Technology) 36,76 , and for cell cycle analysis as previously described 36 . Unless otherwise stated, data was made relative to the initial time point for each treatment condition and presented as the average of at least two independent experiments ±/- SD.…”

The role of long noncoding RNAs in cancer metastasis

“…One class of ncRNA includes microRNAs (miRNAs), which are short 22-nucleotide (nt) ncRNAs that undergo biochemical processing from a longer primary miRNA (pri-miRNA) transcript via a series of interactions with RNase-III type proteins that include DROSHA and DICER. miRNAs operate via a distinct mechanism of action that relies upon imperfect complementarity or Watson-Crick base-pairing between a miRNA and the 3' untranslated region (3' UTR) of a target messenger RNA (mRNA) [34] . miRNAs therefore serve as guides that recruit RNA binding proteins (RBPs) such as AGO2 to specific mRNA targets resulting in reduced gene expression either via translational inhibition or via RNA degradation [25,[35][36][37] .…”