ECM:	extracellular matrix
PMN:	pre-metastatic niche
BMDC:	bone marrow-derived cells
MDSC:	myeloid-derived suppressor cells
TAM:	tumor-associated macrophage
EV:	extracellular vesicles
EMT:	epithelial-to-mesenchymal transition
CAF:	cancer associated fibroblast
HSC:	hematopoietic stem cell
BBB:	blood–brain barrier
IL-6:	interleukin 6
IL-1β:	interleukin-1β
CXCL12/SDF-1 α:	stromal cell-derived factor 1
IL-8:	interleukin 8
VEGF:	vascular endothelial growth factor
G-CSF:	granulocyte-colony stimulating factor
MIF:	macrophage migration inhibitory factor
TIMP-1:	tissue inhibitor of metalloproteinases 1
GM-CSF:	granulocyte–macrophage colony-stimulating factor
SAA:	serum amyloid A
TGF-β:	transforming growth factor beta
HIF-1:	hypoxia-inducible factor 1
CCL2:	CC-chemokine ligand 2
CCL5:	chemokine ligand 5
CXCL1:	C–X–C motif ligand 1
JAK:	Janus kinase
STAT3:	signal transducer and activator of transcription 3
AKT:	protein kinase B
MAPK:	mitogen-activated protein kinase
IDO:	indoleamine 2,3-dioxygenase
PD-L1:	programmed death ligand 1