This myeloid-specific PD-1-SHP-2 axis might be particularly important in the context of cancer, where growth factors released by cancer cells induce emergency myelopoiesis, and directly upregulate PD-1 and PD-L1 expression in myeloid progenitors and their progeny, thereby posing a signaling restrain to their effector differentiation. This evidence concerns the gene PDCD1 and cancer.