Table 1.

MicroRNA	Cell type released by	Cell type taken up by	Extracellular Role	Ref.
Angiogenesis
miR-16	MSCs	Tumour cells	Suppression of angiogenesis by downregulating VEGF.	[40]
miR-92a	Tumour cells MSCs	MSC Endothelial cells	Pro-angiogenic role Anti-angiogenic role.	[46], [47]
miR-21	Tumour cells	Bronchial epithelial cells	Increase in VEGF production and promotion of angiogenesis	[49]
miR-494	Tumour cells	Endothelial cells	Suppression of PTEN and Akt/eNos pathway activation, enhancing angiogenesis.	[50]
Migration and metastasis
miR-200	Metastatic tumour cells	Non-metastatic tumour cells	Promoting mesenchymal-to-epithelial transition and colonisation of metastatic sites.	[52]
miR-10b	Metastatic tumour cells	Non-malignant cells	Induction of invasive properties	[53]
miR-21	Tumour cells	Tumour cells	Promoting migration and invasion by targeting PDCD4 for downregulation.	[54]
miR-105	Metastatic tumour cells	Endothelial cells	Promoting vascular permeability by downregulating ZO-1.	[55]
Modulation of tumour-immune response
miR-9	Tumour cells	Tumour cells	Inhibits expression of MHC class I, preventing recognition of tumour cells by the immune system.	[57]
miR-21	Tumour cells	Macrophages Myoblasts	Binds to TLRs, inducing the secretion of inflammatory cytokines. Induction of cell-death through activation of the JNK pathway.	[58], [60]
miR-223	Macrophages	Tumour cells	Promotion of tumour cell invasion.	[59]
miR-203	Tumour cells	Dendritic cells	Downregulation of TLR4 expression and decreased production of cytokines TNF-α and IL-12.	[61]
miR-23	Tumour cells	NK cells	Downregulation of CD107a leading to immunosuppression.	[62]
miR-24-3p, miR-891a, miR-106a-5p, miR-20a-5p, miR-1908	Tumour cells	T-cells	Promotes Treg differentiation leading to suppression of anti-tumour immunity.	[63]