Recently, novel mechanisms underlying the pro-tumorigenic effects of cancer-associated fibroblasts (CAFs) have been identified in several cancers, including breast cancer. CAFs can secrete exosomes that are loaded with proteins, lipids, and RNAs to affect tumor microenvironment. Herein, we identify CAF-derived exosomes that can transfer miR-181d-5p to enhance the aggressiveness of breast cancer. Cancerous tissues and matched paracancerous tissues were surgically resected from 122 patients with breast cancer. Chromatin immunoprecipitation (ChIP) and dual luciferase reporter assays were employed to identify interaction between homeobox A5 (HOXA5) and caudal-related homeobox 2 (CDX2), as well as between CDX2 and miR-181d-5p, respectively. Human breast cancer Michigan Cancer Foundation-7 (MCF-7) cells were cocultured with CAF-derived exosomes. 5-Ethynyl-2 0 -deoxyuridine (EdU) assay, TUNEL staining, Transwell invasion assays, and scratch tests were carried out to evaluate MCF-7 cell functions. Nude mice bearing xenografted MCF-7 cells were injected with CAF-derived exosomes, and the tumor formation was evaluated. HOXA5 expressed at a poor level in breast cancer tissues, and its overexpression retarded MCF-7 cell proliferation, invasion, migration, and epithelial-mesenchymal transition (EMT) and facilitated its apoptosis in vitro. miR-181d-5p targets CDX2, a transcription factor binding to HOXA5 promoter. Coculture of CAFs and MCF-7 cells showed that CAFs prolonged proliferation and antagonized apoptosis of MCF-7 cells via release of exosomes. Coculture of MCF-7 cells and exosomes derived from CAFs identified miR-181d-5p as a mediator of the exosomal effects on MCF-7 cells, in part, via downregulation of CDX2 and HOXA5. CAF-derived exosomes containing miR-181d-5p promoted the tumor growth of nude mice bearing xenografted MCF-7 cells. In conclusion, exosomal miR-181d-5p plays a key role in CAF-mediated effects on tumor environment in breast cancer, likely via CDX2 and HOXA5.

Objectives Long non‐coding RNAs (lncRNAs) have been demonstrated as crucial regulators in cancer, but whether they are involved in the immune response of cancer cells remains largely undiscovered. GATA3‐AS1 is a novel lncRNA that was upregulated in breast cancer (BC) according to online databases. However, its role in triple‐negative breast cancer (TNBC) was elusive. Methods GATA3‐AS1 expression in BC tissues and adjacent normal tissues was obtained from online databases. Loss‐of‐function assays were designed and conducted to verify the functional role of GATA3‐AS1 in TNBC cells. Bioinformatic analysis and mechanism experiments were applied to explore the downstream molecular mechanism of GATA3‐AS1. Similarly, the upstream mechanism which led to the upregulation of GATA3‐AS1 in TNBC cells was also investigated. Results GATA3‐AS1 was markedly overexpressed in TNBC tissues and cells. Knockdown of GATA3‐AS1 suppressed TNBC cell growth and enhanced the resistance of TNBC cells to immune response. GATA3‐AS1 induced the deubiquitination of PD‐L1 through miR‐676‐3p/COPS5 axis. GATA3‐AS1 destabilized GATA3 protein by promoting GATA3 ubiquitination. Conclusion GATA3‐AS1 contributed to TNBC progression and immune evasion through stabilizing PD‐L1 protein and degrading GATA3 protein, offering a new target for the treatment of TNBC.

The tumor microenvironment is composed of tumor cells, fibroblasts, endothelial cells and infiltrating immune cells, which may inhibit or promote tumor growth and progression. The objectives of this retrospective study were to characterize the density of tumor-associated macrophages (TAMs) in breast cancer, and to correlate the density of TAMs with clinicopathological parameters. Paraffin-embedded specimens and clinicopathological data, including up to 5 years follow-up information, were obtained from 172 breast cancer patients. Immunohistochemical staining for CD68 (marker for macrophages) was performed and evaluated in a blinded fashion. We found that TAMs were significantly frequent in high histopathological grade breast cancer patients. Breast cancer patients with a high density of TAMs had significantly lower rates of disease-free survival and 5-year overall survival than patients with low density of TAMs. Furthermore, high-infiltration of TAMs indicated worse survival rate for patients with node-negative breast cancer. In conclusion, the number of TAMs in the tumor stroma is an independent predictor of survival time for breast cancer patients. High-infiltration of TAMs is a significant unfavorable prognostic factor for patients with invasive breast cancer and, as such, is a potentially useful prognostic marker for breast cancer.

No abstract

TGF-β1-induced epithelial-mesenchymal transition (EMT) has been proved to be associated with metastasis of breast cancer cells. We attempted to detect a novel mechanism that microRNAs mediated the TGF-β1-induced EMT in the process of breast cancer metastasis. Here we reported that the expression of miR-23a was higher in breast cancer cells with high metastasis ability and patients with lymph node metastasis and the treatment of TGF-β1 significantly upregulated the expression of miR-23a in breast cancer cells. We found that miR-23a was upregulated by TGF-β1 post-transcriptionally and Smads directly bound the RNA Smad binding element (R-SBE) of miR-23a. Functional studies showed that inhibition of miR-23a suppressed the TGF-β1-induced EMT, migration, invasion and metastasis of breast cancer both in vitro and in vivo. In addition, we determined that miR-23a directly targeted and suppressed CDH1, one important gene in EMT phenomenon. Notably, Wnt/β-catenin signaling was activated by the suppression of CDH1 in the miR-23a mediated process of TGF-β1-induced EMT and tumor invasion. These results demonstrate that miR-23a promotes TGF-β1-induced tumor metastasis in breast cancer by targeting CDH1 and activating Wnt/β-catenin signaling. Taken together, our results indicate a novel regulatory mechanism of TGF-β1-induced EMT and suggest that miR-23a might be a potential target in breast cancer therapy.