Tumor cell-derived CCL2 binds to its corresponding chemokine receptor CCR2 on endothelial cells, which in turn activates the Janus kinase 2 (JAK2)-signal transducer and activator of transcription protein 5 (STAT5) and p38 mitogen-activated protein kinase (MAPK) signaling pathways, resulting in enhanced vascular permeability and effective extravasation of tumor cells by recruitment of monocytes (41). The gene discussed is JAK2; the disease is neoplasm.