miR-424/503 modulates Wnt/β-catenin signaling in the mammary epithelium by targeting LRP6

MicroRNAs: The key players regulating the crosstalk between Hippo and Wnt/β-catenin pathways in breast cancer

Breast Cancer has the highest burden in females worldwide and is predicted to increase by many folds with increasing lifestyle related risk factors, genetic mutations, and an aging population. The Hippo signalling and Wnt signalling pathways were identified as important signal transducers involved in maintaining organ development, tissue homeostasis, cell proliferation and apoptosis. microRNAs are short nucleotide sequences which act as regulatory components driving signal transductions in most cancers and can serve as both diagnostic and prognostic markers. Several reports have implicated that deregulated Hippo as well as Wnt signalling mediated by miRNAs together drive tumorigenesis, metastases and chemoresistance in breast cancer. Recent evidences on a crosstalk between Hippo and Wnt components elucidated how these pathways might be synchronized to have overlapping functions to promote tumorigenesis. Since miRNAs are demonstrated to target most of the components in both the pathways, in this review, we talk about the crosstalk between Hippo and Wnt signalling pathways and the potential microRNAs that might regulate the interplay between the two pathways in breast cancer, which has not been explored earlier.

Down-regulation of miR-424 inhibited the metastasis of endometrial carcinoma via targeting PTEN/PI3K/AKT signaling pathway

Background: The incidence of endometrial carcinoma (EC) has been increasing annually, and treatment of advanced cases remains challenging. MicroRNA-424 (miR-424) was reported to affect several types of tumors, but its role in EC has not been studied. Methods: We generated transient knockdown models of miR-424 and PTEN in EC cells. We measured mRNA and protein expression using RT-PCR and western blotting. We evaluated cell proliferation, invasion, migration, and apoptosis using CCK8, Transwell, wound healing, and flow cytometry assays. We also investigated the effect of miR-424 and PTEN on tumor growth using a metastatic tumor model in nude mice. Results: The expression of miR-424 was significantly elevated in EC tissues and cell lines. MiR-424 inhibitor significantly restrained PTEN/PI3K/AKT signaling, while miR-424 mimic activated this pathway. Knockdown of PTEN significantly reversed the effects of miR-424 inhibitor on cell proliferation, invasion, migration, and apoptosis in EC cells. The significant inhibition of tumor growth and ki67 expression caused by miR-424 inhibitor were markedly promoted by sh-PTEN. Conclusions: Our findings suggest that miR-424 inhibitor could inhibit cell proliferation, invasion, migration, epithelial-mesenchymal transition (EMT) process, and tumor growth, while promoting apoptosis in EC. However, the effects of miR-424 inhibitor were markedly reversed by sh-PTEN. This study provides a potential novel therapeutic strategy for the prevention and treatment of EC by targeting miR-424.

MicroRNAs in Molecular Classification and Pathogenesis of Breast Tumors

The current clinical practice of breast tumor classification relies on the routine immunohistochemistry-based expression analysis of hormone receptors, which is inadequate in addressing breast tumor heterogeneity and drug resistance. MicroRNA expression profiling in tumor tissue and in the circulation is an efficient alternative to intrinsic molecular subtyping that enables precise molecular classification of breast tumor variants, the prediction of tumor progression, risk stratification and also identifies critical regulators of the tumor microenvironment. This review integrates data from protein, gene and miRNA expression studies to elaborate on a unique miRNA-based 10-subtype taxonomy, which we propose as the current gold standard to allow appropriate classification and separation of breast cancer into a targetable strategy for therapy.