To gain insight into the tumor-promoting effects of CX3CR1-deficient cells in the tumor microenvironment, the expression levels of TNF-α, iNOS, IL6 and IL1β, which each have altered expression due to loss of CX3CR1 in different CNS diseases [18, 20], were examined by quantitative RT-PCR. The gene discussed is IL1B; the disease is neoplasm.