CCL2 and cancer: Tumor cells and non-malignant tumor-associated cells (e.g., cancer-associated fibroblasts, stromal cells) secrete a variety of inflammatory factors (IL-6, IL-34, IL-17, M-CSF), chemokines (CCL2, CCL7, CXCL8, CX3CL1) and miRs involved in the recruitment of surrounding macrophages and blood monocytes into the tumor site [40,98].