TNF and central nervous system cancer: RT-PCR results showed that the level of Il-6 mRNA in U373-MG glioma cells was elevated approximately 1-, 2-, and 10-fold by IL-6, a combination of IL-6 and soluble IL-6 receptor (IL-6/sIL-6R), and TNF-α plus IL-6 and soluble IL-6 receptor (TNF-α/IL-6/sIL-6R), respectively [28].