CD47 and neoplasm: Under hypoxic condition, the activation of HIFs and their downstream signaling cascades, such as C-X-C chemokine receptor (CXCR)4, macrophage colony-stimulating factor receptor (M-CSFR) and CD47, modulates tumor-specific immune responses by inducing the production of immunosuppressive cytokines and growth factors, promoting tumor immune evasion and ultimately stimulating tumorigenesis (8, 9).