Chemokine expression in tumor-to-tumor metastasis.

Chemokines play an important role in cancer metastasis by modulating the directional cell movement and migration of tumor cells. The most commonly overexpressed chemokine receptor in human cancer is CXCR4. Once activated by its ligand CXCL12 (stromal cell-derived factor-1 ligand/SDF1), CXCR4 stimulates several key migratory, proliferative and survival signaling cellular pathways. CXCR4 is expressed in small-cell lung carcinoma (SCLC) cells and other tumors. To further characterize the role of chemokines in tumor-to-tumor metastasis, we analyzed the tissue expression of CXCR4 and CXCL12 in the surgical specimen of a patient with this phenomenon. We performed immunohistochemical analysis for the expression of CXCR4 and CXCL12 in metastatic tumor tissue of a 69-year-old Caucasian male with extensive SCLC metastatic to a renal oncocytoma. The oncocytoma tissue harboring SCLC showed CXCL12 expression, but not CXCR4. A high expression of the two molecules was found in a normal renal parenchymal control. Our results suggest that CXCR4 and CXCL12 plays a role in this condition, but their expression may be affected by the microenvironment of the harboring malignancy. Further characterization of these phenomena is needed to shed light on the biological mechanisms of tumor metastasis.