In contrast, blockade of the CXCL12-CXCR4 axis by a CXCR4 inhibitor (which supports the mobilization of non-aged neutrophils from the bone marrow into the systemic circulation, interferes with the recruitment of aged neutrophils back to bone marrow, liver, and spleen as well as directly promotes neutrophil aging13 39) even slightly enhanced tumor growth, again without altering neutrophil infiltration of the neoplasms or directly affecting tumor cell proliferation. The gene discussed is CXCL12; the disease is neoplasm.