CCL2 and cancer: Tumors lacking PTEN are characterized by reduced levels of helper T cells, natural killer cells, and cytotoxic lymphocytes [44], along with increased levels of inflammatory cytokines that promote cancer, particularly C-C motif chemokine ligand 2 (CCL2), and an increase in immune-suppressive cells such as myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs) [1].