Chemotherapy-elicited EVs are enriched in annexin A6 (ANXA6), a Ca<sup>2+</sup>-dependent protein that promotes NF-κB-dependent endothelial cell activation, Ccl2 induction and Ly6C<sup>+</sup>CCR2<sup>+</sup> monocyte expansion in the pulmonary pre-metastatic niche to facilitate the establishment of lung metastasis.
Thus, AMs can be recruited under the guidance of IM-derived CCL2 into metastatic lungs and can eventually contribute to the progression of lung metastasis by providing a potent arachidonic acid-derived tumor growth promoting mediator, LTB<sub>4</sub>.
Deficiency in MCP-1 reduced lung metastases by 37% in high-fat diet-fed mice; it reduced metastatic cross-sectional area by 46% and volume by 69% compared to wild-type mice.
Knockdown of the combination of CXCR1 and CCL2 reduced the invasive activities of HCC cells that overexpress FOXC1 and formation of lung metastases in mice, and transgenic overexpression of CXCR1 increased cell's invasive and metastatic abilities after knockdown of FOXC1.
Transplantation of MCP-1(-/-) bone marrow cells into WT mice did not alter the incidence of lung metastasis, whereas transplantation of WT bone marrow cells into MCP-1(-/-) mice increased lung metastasis.
We report here that miR-126/miR-126(*), a microRNA pair derived from a single precursor, independently suppress the sequential recruitment of mesenchymal stem cells and inflammatory monocytes into the tumour stroma to inhibit lung metastasis by breast tumour cells in a mouse xenograft model. miR-126/miR-126(*) directly inhibit stromal cell-derived factor-1 alpha (SDF-1α) expression, and indirectly suppress the expression of chemokine (C-C motif) ligand 2 (Ccl2) by cancer cells in an SDF-1α-dependent manner. miR-126/miR-126(*) expression is downregulated in cancer cells by promoter methylation of their host gene Egfl7.
Moreover, the spontaneous lung metastases were augmented in the animals injected with MCAF-transfectants compared to those injected with parental cells with a concomitant increase of angiogenesis.