Cocaine modulates cytokine and enhances tumor growth through sigma receptors.

Sigma receptors are intracellular receptors that interact with a variety of psychotropic ligands, including cocaine. Administration of cocaine to mice promoted the in vivo growth of a syngeneic lung cancer cell line and identical effects were observed with PRE 084, a selective sigma(1) receptor agonist. Increased tumor growth was accompanied by an increase in IL-10 and a decrease in IFN-gamma production in splenocytes and at the tumor site. The tumor-promoting effects produced by both cocaine and PRE 084 were abrogated by administration of specific antibodies to IL-10, or by administration of a sigma(1) receptor antagonist. We conclude that sigma(1) receptor ligands, including cocaine, augment tumor growth via a cytokine-dependent, receptor-mediated mechanism that involves regulation of T helper 1/T helper 2 cytokine balance.