Exosomes secreted from human colon cancer cells influence the adhesion of neighboring metastatic cells: Role of microRNA-210

Abstract

Cancer-secreted exosomes influence tumor microenvironment and support cancer growth and metastasis. MiR-210 is frequently up-regulated in colorectal cancer tissues and correlates with metastatic disease. We investigated whether exosomes are actively released by HCT-8 colon cancer cells, the role of exosomal miR-210 in the cross-talk between primary cancer cells and neighboring metastatic cells and its contribution in regulating epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET).After 7 d of culture, a subpopulation of viable HCT-8 cells detached the monolayer and started to grow in suspension, suggesting anoikis resistance and a metastatic potential. The expression of key proteins of EMT revealed that these cells were E-cadherin negative and vimentin positive further confirming their metastatic phenotype and the acquisition of anoikis resistance. Metastatic cells, in the presence of adherently growing HCT-8, continued to grow in suspension whereas only if seeded in cell-free wells, were able to adhere again and to form E-cadherin positive and vimentin negative new colonies, suggesting the occurrence of MET.The chemosensitivity to 5 fluorouracil and to FOLFOX-like treatment of metastatic cells was significantly diminished compared to adherent HCT-8 cells. Of note, adherent new colonies undergoing MET, were insensitive to both chemotherapeutic strategies. Electron microscopy analysis demonstrated that adherently growing HCT-8, actually secreted exosomes and that exosomes in turn were taken up by metastatic cells. When exosomes secreted by adherently growing HCT-8 were administered to metastatic cells, MET was significantly inhibited. miR-210 was significantly upregulated in exosomes compared to its intracellular levels in adherently growing HCT-8 cells and correlated to anoikis resistance and EMT markers.Exosomes containing miR-210 might be considered as EMT promoting signals that preserve the local cancer-growth permissive milieu and also guide metastatic cells to free, new sites of dissemination.

A microRNA Signature of Metastatic Colorectal Cancer

“…Higher Mir-210 levels were also reported to enhance invasion and metastasis in cell lines (Mudduluru et al 2015) . We did not observe up-regulation of Mir-210_3p in pCRC compared to nCR; rather, our results show up-regulation at the metastatic sites, which is in accordance with several non-NGS studies in CRC [68][69][70] . Our finding of increased Mir-210_3p expression at all mCRC sites, suggest that hypoxic stress is a common occurrence at the metastatic sites, and that up-regulation of Mir-210_3p may be a consequence of this hypoxic microenvironment.…”

Exosomal miR‐221 derived from hydroquinone‐transformed malignant human bronchial epithelial cells is involved in cell viability of recipient cells

“…For example, exosomes derived from breast cancer cells can transmit miRNAs to normal recipient cells to induce their malignant transformation (Li, Ren, Tang, & Yu, 2017). Exosomes secreted by human colon cancer cells can transmit miR-210 to neighboring metastatic cells to influence their adhesion (Bigagli, Luceri, Guasti, & Cinci, 2016). Similarly, exosome-transmitted long ncRNA PTENP1 participates in normal-cell-to-bladder-cell communication during the carcinogenesis of bladder cancer (Zheng et al, 2018).…”

Exosomes and their importance in metastasis, diagnosis, and therapy of colorectal cancer

“…In other words, miR‐215 could be used as a potential therapeutic target for prevention of metastasis and also as a new main biomarker in the pathogenesis of CRC . In contrast, a study on HCT‐8 cell line has shown that miR‐210 was upregulated in exosomes derived from these cells and this miRNA resulted in cancer cell metastasis and homing processes (Table ). Furthermore, it is shown that exosomal CRNDE‐h lncRNA levels in patients with CRC were higher and it was positively associated with distant metastasis and especially regional lymph node metastasis (Table ) …”