MicroRNA profiling of the pubertal mouse mammary gland identifies miR-184 as a candidate breast tumour suppressor gene

Abstract

IntroductionThe study of mammalian development has offered many insights into the molecular aetiology of cancer. We previously used analysis of mammary morphogenesis to discover a critical role for GATA-3 in mammary developmental and carcinogenesis. In recent years an important role for microRNAs (miRNAs) in a myriad of cellular processes in development and in oncogenesis has emerged.MethodsmicroRNA profiling was conducted on stromal and epithelial cellular subsets microdissected from the pubertal mouse mammary gland. miR-184 was reactivated by transient or stable overexpression in breast cancer cell lines and examined using a series of in vitro (proliferation, tumour-sphere and protein synthesis) assays. Orthotopic xenografts of breast cancer cells were used to assess the effect of miR-184 on tumourigenesis as well as distant metastasis. Interactions between miR-184 and its putative targets were assessed by quantitative PCR, microarray, bioinformatics and 3′ untranslated region Luciferase reporter assay. The methylation status of primary patient samples was determined by MBD-Cap sequencing. Lastly, the clinical prognostic significance of miR-184 putative targets was assessed using publicly available datasets.ResultsA large number of microRNA were restricted in their expression to specific tissue subsets. MicroRNA-184 (miR-184) was exclusively expressed in epithelial cells and markedly upregulated during differentiation of the proliferative, invasive cells of the pubertal terminal end bud (TEB) into ductal epithelial cells in vivo. miR-184 expression was silenced in mouse tumour models compared to non-transformed epithelium and in a majority of breast cancer cell line models. Ectopic reactivation of miR-184 inhibited the proliferation and self-renewal of triple negative breast cancer (TNBC) cell lines in vitro and delayed primary tumour formation and reduced metastatic burden in vivo. Gene expression studies uncovered multi-factorial regulation of genes in the AKT/mTORC1 pathway by miR-184. In clinical breast cancer tissues, expression of miR-184 is lost in primary TNBCs while the miR-184 promoter is methylated in a subset of lymph node metastases from TNBC patients.ConclusionsThese studies elucidate a new layer of regulation in the PI3K/AKT/mTOR pathway with relevance to mammary development and tumour progression and identify miR-184 as a putative breast tumour suppressor.Electronic supplementary materialThe online version of this article (doi:10.1186/s13058-015-0593-0) contains supplementary material, which is available to authorized users.

RETRACTED: miR‐655 suppresses epithelial‐to‐mesenchymal transition by targeting Prrx1 in triple‐negative breast cancer

“…It has been demonstrated that miRNAs play crucial roles in cell biology such as proliferation, apoptosis, cell cycle, migration and invasion 13, 14, 15. Increasing evidence shows the potential involvement of miRNAs in the development of various human cancers such as gastric cancer, bladder cancer, lung cancer, hepatocellular carcinoma, and breast cancer 16, 17, 18, 19.…”

Identification of microRNA expression profile related to lymph node status in women with early-stage grade 1–2 endometrial cancer

“…41 As suggested by various studies, miR-184 might be a useful diagnostic and therapeutic tool for malignant diseases. 38,39 However, to the best of our knowledge, ours is the first study to provide data about miR-184 expression in EC.…”

“…In the same way, miR-184 functions as a tumor suppressor in various cancers (renal carcinoma, 36 glioma, 37,38 non-small-cell lung cancer, 39 oral squamous cell carcinoma, 40 breast cancer 41 ) by repressing oncogenes such as TNFAIP2, 37 SND1, 38 CDC25A, c-MYC, 39 and regulating the AKT/mTORC1 pathway. 41 As suggested by various studies, miR-184 might be a useful diagnostic and therapeutic tool for malignant diseases.…”

MicroRNAs in the development and neoplasia of the mammary gland

“…There may be a possibility of increased miR-206 levels due to BRCA1 loss, culminating in mammary gland remodeling and tumour development 20 . miR-184 is found to be a tumour suppressor by regulating the number of genes in the PI3K/AKT/mTOR pathway, as observed by miR profiling of the pubertal mouse mammary gland 21 . This pathway is important in mammary gland development and lactation 22 .…”

“…This pathway is important in mammary gland development and lactation 22 . miR-184 is only expressed in epithelial cells, and the level increases during differentiation of cells from terminal end bud into ductal epithelial cells 21 .…”