Investigation of molecular events underlying the IL-6-mediated Th1 inhibition in tumor-bearing mice

To understand the molecular mechanism underlying the IL-6-mediated attenuation of Th1 differentiation in tumor-bearing animals, we have employed whole genome microarray expression profiling of CD4+ T cells isolated from tumor-bearing mice. In order to distingish the effect of IL-6/sIL-6R signaling augmented in tumor-bearing mice from the effecct of other tumor-derived signals, we isolated CD4+ T cells that were primed in tumor free-mice and in the mice inoculated with ovalbumin (OVA)-expressing MCA205 fibrosamcoma, in conjunction of anti-IL-6R Ab injection. We found that Th2-like gene signature such as Il4, IL10, Ccr4, and c-maf was up-regulated in CD4+ T cells primed in tumor-bearing mice. However,the expression of other Th2 master regulator Gata3 gene, or Tfh-related genes (Bcl6, Cxcr5, and Batf) was not substantially augmented in tumor-bearing mice as compared with those in tumor-free mice. These expressions were abrogated by IL-6R blockade, suggesting that the expression of these Th2-like gene set and the other IL-6 signal-dependent genes like Klf1, Bcl11a, and Klf4 are candidate regulators responsible for IL-6 signaling-mediated Th1 inhibition in tumor-bearing animals. The differential gene expressions in CD4+ T cells primed in tumor-free vs MCA205-OVA-bearing mice, and in control Ab-treated vs anti-IL-6R Ab-treated MCA-OVA tumor-bearing mice were measured. Two independent experiments were performed in each condition.