The CXCR4 chemokine receptor has been found to be overexpressed in different tumors, including breast cancer, gastric cancer, ovarian cancer, glioma, pancreatic cancer, prostate cancer, acute myeloid leukemia, chronic lymphoblastic leukemia (CLL), B-CLL, melanoma, cervical cancer, colon carcinoma, rhabdomyosarcoma, astrocytoma, small-cell lung carcinoma, renal cancer, and non-Hodgkin's lymphoma, as compared to normal cells which show little or no CXCR4 expression [13,22,40,47-49]. The gene discussed is CXCR4; the disease is small cell lung carcinoma.