Table 1.

TME-associated cells.

Cell type	Identification markers	Normal activity	Prometastatic activity	References
CSC	Nanog Oct-4 SOX-2 Lgr-5 CD133 CD24 CD29 ALDH1 EpCAM CD44 CD166 CD26	Not present in healthy tissues	Tumor development, chemoattractant activity (SDF-1/CXCL12)	(6)
CAFs	CD44 a-SMA PDGFR-b Desmin FAP FSP MFAP5 TN-C PDPN NG2	Extracellular matrix synthesis of collagen and elastin.	Secretion of growth factors EGF, IL-6, ILGF, HGF, improve angiogenesis, and remodel of ECM	(7–12)
MSCs	CD105 CD73 CD44 CD90	Components of stroma, immunomodulatory functions	Improve cell proliferation, angiogenesis, and metastasis by the secretion of CXCL12, IL-6, IL-8, and differentiation in CAFs	(11, 13, 14)
Pericytes	PDGFRβ CD13 NG2 CSPG4 a-SMA Desmin RGS5 CFTR/MRP SUR2 ALP Vimentin CD133 CD146.	Protection of endothelial cells in capillaries, blood flow regulation, and inflammatory cell trafficking	Secretion of growth factors HGF, FGFs, and CXCL12 that promote the growth, survival of malignant cells, and function as a chemoattractant	(5, 15–17)
Tregs	CD4 CD25 FoxP3 CD127	Maintenance of immune tolerance	Inactivation of CD8+ T-cells' cytotoxic activities, improvement of angiogenesis, and myeloid cell recruitment. Bad prognostic indicator	(11, 18–20)
Tumor-associated macrophages (TAM) -M1 -M2	CD14, CD16, CD64, CD68, CD71 CCR5	Proinflammatory cells specialized in pathogen destruction and enhancing activation of cytotoxic lymphocytes Anti-inflammatory cells that stimulate a CD4+ and regulatory T-cell response	Elimination of malignant cells. High production of NO TNFα, CXCL9, and CXCL10 Activate secretion of IL-6, TGFβ, EGF, bFGF, and IL-10, and VEGF to enhance tumor growth	(3, 11)