Exosomal Wnt7a from a low metastatic subclone promotes lung metastasis of a highly metastatic subclone in the murine 4t1 breast cancer

Abstract

Background Patients with triple-negative breast cancer (TNBC) often have poorer prognosis than those with other subtypes because of its aggressive behaviors. Cancer cells are heterogeneous, and only a few highly metastatic subclones metastasize. Although the majority of subclones may not metastasize, they could contribute by releasing factors that increase the capacity of highly metastatic cells and/or provide a favorable tumor microenvironment (TME). Here, we analyzed the interclonal communication in TNBC which leads to efficient cancer progression, particularly lung metastasis, using the polyclonal murine 4T1 BC model. Methods We isolated two 4T1 subclones, LM.4T1 and HM.4T1 cells with a low and a high metastatic potential, respectively, and examined the effects of LM.4T1 cells on the behaviors of HM.4T1 cells using the cell scratch assay, sphere-forming assay, sphere invasion assay, RT-qPCR, and western blotting in vitro. We also examined the contribution of LM.4T1 cells to the lung metastasis of HM.4T1 cells and TME in vivo. To identify a critical factor which may be responsible for the effects by LM.4T1 cells, we analyzed the data obtained from the GEO database. Results Co-injection of LM.4T1 cells significantly augmented lung metastases by HM.4T1 cells. LM.4T1-derived exosomes promoted the migration and invasion of HM.4T1 cells in vitro, and blocking the secretion of exosome abrogated their effects on HM.4T1 cells. Analyses of data obtained from the GEO database suggested that Wnt7a might be a critical factor responsible for the enhancing effects. In fact, a higher level of Wnt7a was detected in LM.4T1 cells, especially in exosomes, than in HM.4T1 cells, and deletion of Wnt7a in LM.4T1 cells significantly decreased the lung metastasis of HM.4T1 cells. Further, treatment with Wnt7a increased the spheroid formation by HM.4T1 cells via activation of the PI3K/Akt/mTOR signaling pathway. Finally, infiltration of αSMA-positive fibroblasts and angiogenesis was more prominent in tumors of LM.4T1 cells and deletion of Wnt7a in LM.4T1 cells markedly reduced angiogenesis. Conclusions We demonstrated, for the first time, that a low metastatic subclone can enhance lung metastasis of highly metastatic subclone via exosomal Wnt7a and propose Wnt7a as a molecular target to treat TNBC patients.

Critical Review on the Different Roles of Exosomes in TNBC and Exosomal-Mediated Delivery of microRNA/siRNA/lncRNA and Drug Targeting Signalling Pathways in Triple-Negative Breast Cancer

“…Macrophage-derived exosomes containing Wnt5a initiate the Wnt/β-catenin signalling pathway in breast cancer cells [ 52 ]. Exosomal Wnt7a is accountable for the metastasis of breast tumours to the lungs [ 53 ]. In human breast fibroblasts, the exosome-mediated release of miR-9 produces cancer-associated fibroblast-like characteristics.…”

Perspective Chapter: Clinical Application of Exosome Components

“…Among them, exosomal glucose transporter 1 (GLUT-1), glypican 1 (GPC-1), and a disintegrin and metalloproteinase 10 (ADAM10) may be served as BC potential biomarkers [23]. Exosomes carrying proteins, including Anx II, Wnt7a, and ephrin type-A receptor 2 (EPHA2) could stimulate BC's invasive, angiogenesis, and metastasis abilities [24][25][26]. Exosomal Anx II has stimulated angiogenesis and BC metastasis [24].…”

“…Exosomal Anx II has stimulated angiogenesis and BC metastasis [24]. Further, exosomal Wnt7a has been found to promote lung metastasis of BC [25]. Exosomal EPHA2 has also been found to activate the AMP-activated protein kinase (AMPK) signal pathway via the Ephrin A1-EPHA2 forward signal that promoted the angiogenesis and metastasis of BC [26].…”

Listen to the WNT; It Talks: WNT7A Drives Epithelial–Mesenchymal Cross-Talk within the Fibrotic Niche in Idiopathic Pulmonary Fibrosis

“…It is intriguing that WNT proteins, such as WNT5A, have been identified as extracellular vesicle cargo eliciting profibrotic actions ( 19 ). Similarly, WNT7A is expressed on extracellular vesicles promoting lung metastasis ( 20 ). Transport via extracellular vesicles is of particular interest for WNT proteins, which are modified by lipids and known for their short-ranging effects, as it might significantly expand their range of action in vivo ( 21 ).…”