CCR1 and neoplasm: With regard to chemokine receptors, PGK1 had the strongest correlation with CCR1, the ligands of which include myeloid progenitor inhibitory factor-1 (MPIF-1), monocyte chemoattractant protein 3 (MCP-3), macrophage inflammatory protein 1 alpha (MIP-1 alpha), and regulated on activation normal T expressed and secreted protein (RANTES), implying that it plays an important role in recruiting immune cells to tumor sites.