As mentioned above, CXCR4 is a member of ALARM genes, indicating a likely mechanism of signaling from the graft via CXCL12 and recruitment of ALARM cells expressing CXCR4. This cytokine receptor pair has been previously described as a homing mechanism in various distinct tissues, such as bone marrow32,33 and in cancer.34 The gene discussed is CXCL12; the disease is cancer.