Mahajan et al. found that addition of morphine in vitro to the astrocytoma cell line U87 or to primary human astrocytes resulted in a dose-dependent reduction in mRNA and protein production of the chemokines CXCL1/IL-8/KC, CCL4/MIP-1β, and CCL2/MCP-1 (95, 96). This evidence concerns the gene CCL4 and astrocytoma (excluding glioblastoma).