Triple-negative breast cancer (TNBC) is the most aggressive breast cancer subtype. TNBC progression is sustained by recruitment of a strong tumor microenvironment (TME) mainly composed of cancer-associated fibroblasts (CAFs) able to endorse tumor hallmarks. Increasing evidences demonstrate that exosomes mediate the crosstalk between cancer cells and the TME.
Researchers from the University of Naples Federico II examined TNBC-derived exosomes and their microRNA (miRNA) cargo in activation of normal fibroblasts (NFs) toward CAFs. They demonstrated that TNBC cell-derived exosomes increased NF collagen contraction and migration alongside CAF molecular markers. Exosome-activated fibroblasts promoted the invasion potential of normal breast epithelial cells, as assessed by an organotypic co-culture assay that resembled the in vivo context. The researchers also investigated TNBC cell-derived exosome cargo in activating NFs to CAFs by performing small RNA sequencing. They found that the synergistic action of miR-185-5p, miR-652-5p, and miR-1246 boosted fibroblast migration and contraction, promoting specific CAF subspecialization toward a pro-migratory functional state. These data highlight the role of breast cancer cells in re-education of the TME and their contribution to tumor evolution.
Differentially expressed miRNAs in fibroblasts upon exposure
to MDA-MB-231 cell-derived exosomes
(A) Heatmap of data from small RNA sequencing analysis, showing miRNAs differentially expressed in NFs (pt. #1) incubated with MDA-MB-231 cell-derived exosomes (+exosomes) and PBS (NT). (B) Histograms of qRT-PCR results showing the expression levels of miR-185-5p, miR-652-5p, and miR-1246 in NFs (pt. #1) incubated with exosomes compared with NT. (C) Histograms of qRT-PCR results showing the basal expression levels of miR-185-5p, miR-652-5p, and miR-1246 in NFs compared with CAFs. (D) Representative images of the EXOmotif analysis with MDS software showing a short motif (3–5 nt) in miR-185-5p, miR-652-5p, and miR-1246 sequences, predictive of their active loading into exosomes. (E) Western blot showing overexpression of FAP, Caveolin-1, and MCT4 proteins in NFs (pt. #1, #2, and #3) transfected with combo miRs compared with control (scrambled [Scra]) after 72 h. (F) Histogram of densitometric measurement of bands, obtained with ImageJ.