Estrogen plays a critical role in breast cancer (BC) progression through estrogen receptor (ER)-mediated gene regulation. Emerging studies suggest that the malignant progress of BC cells is influenced by the cross talk between microRNAs (miRNAs) and ER-α signaling. However, the mechanism and functional linkage between estrogen and miRNAs remain unclear. The expression levels of miR-196a and SPRED1 in BC were tested by qRT-PCR in 46 paired BC and adjacent tissues and by the GEO datasets. The role of miR-196a in estrogen-induced BC development was examined by CCK-8 assay, wound healing assay, Matrigel invasion assay and tumorigenicity assay in nude mice. The binding site of ER-α in miR-196a promoter region was analyzed by ChIP-seq, ChIP assay and luciferase reporter assay. The potential targets of miR-196a in BC cells were explored using the luciferase reporter assay and western blot analysis, and the correlation between miR-196a and SPRED1 was analyzed by Spearman’s correlation analysis in BC specimens and GEO dataset. TCGA BRCA data was used to characterize the ESR1 signatures according to MSigDB gene set. The expression levels of miR-196a were higher in ER-positive (ER+) breast tumors compared to ER-negative (ER-) tumor tissue samples. Besides, miR-196a was involved in estrogen-induced BC cell proliferation, migration and invasion. Notably, the up-regulation of miR-196a was mediated by a direct interaction with estrogen receptor α (ER-α) but not estrogen receptor β (ER-β) in its promoter region, and miR-196a expression levels were positively correlated to ER-α signature scores. Furthermore, SPRED1 was a new direct target of miR-196a which participated in miR-196a-promoted BC development and was suppressed by ligand-activated ER-α signal pathway. Finally, forced expression of miR-196a induced tumor growth of MCF7 cells, while inhibition of miR-196a significantly suppressed the tumor progress in vivo. Overall, the identification of estrogen/miR-196a/SPRED1 cascade will shed light on new molecular mechanism of estrogen signaling in BC development and therapy.

Tumor-derived nanovesicles have been widely used as a biomarker or therapeutic target in various tumor types. However, these nanovesicles have limited use in therapy due to the risk of advancing tumor development.

MicroRNA-30e (miR-30e) is downregulated in various tumor types. However, its mechanism in inhibiting tumor growth of breast cancer remains to be elucidated. In this study, we found that miR-30e was significantly downregulated in tumor tissues of breast cancer (BC) patients and cell lines, and overexpression of miR-30e inhibited cell proliferation, migration and invasion. To understand the potential mechanism of miR-30e in inhibiting tumor growth, we showed that miR-30e blocked the activation of AKT and ERK1/2 pathways, and the expression of HIF-1α and VEGF via directly targeting IRS1. Moreover, miR-30e regulates cell proliferation, migration, invasion and increases chemosensitivity of MDA-MB-231 cells to paclitaxel by inhibiting its target IRS1. MiR-30e also inhibited tumor growth and suppressed expression of IRS1, AKT, ERK1/2 and HIF-1α in mouse xenograft tumors. To test the clinical relevance of these results, we used 40 pairs of BC tissues and adjacent normal tissues, analyzed the levels of miR-30e and IRS1 expression in these tissues, and found that miR-30e levels were significantly inversely correlated with IRS1 levels in these BC tissues, suggesting the important implication of our findings in translational application for BC diagnostics and treatment in the future.

Background: Recent therapeutic approaches have improved survival rate for women with breast cancer, but the survival rate for metastatic breast cancer is still low. Exosomes released by various cells are involved in all steps of breast cancer development.Methods: We established the multimodal imaging report expression in breast cancer cells with lentivirus vectors pGluc and pBirA to investigate the secreted exosomes. Comparative microRNA (miRNA) analysis was performed with miRNA qPCR array in mice with breast cancer lung metastasis. The co-immunoprecipitation and chromatin immunoprecipitation assays were used to identify the mechanism of miRNA sorting to exosomes. The potential therapeutic strategy using an anti-sorting antibody was used to investigate breast cancer lung metastasis.Results: We identified 26 high-and 32 low-expression level miRNAs in exosomes from metastasis compared to those from primary tumors and normal tissues. The tumor suppressors, including miR-200c and let-7a, were reduced in tumor tissues and metastasis but increased in the respective exosomes compared to normal tissues. Furthermore, the Ras-related protein (Rab1A) facilitated miR-200c sorting to exosomes circumventing the influence of tumor suppressor miR-200c on tumor cells, while the metastatic exosome cargo miR-200c inhibited F4/80+ macrophage immune response. Administration of anti-Rab1A antibody significantly repressed the trafficking of miR-200c to exosomes and breast cancer lung metastasis.Conclusion: Our study has identified a novel molecular mechanism for breast cancer lung metastasis mediated by exosome cargo miRNAs and provided a new therapeutic strategy for cancer immunotherapy.