IL6 and renal cell carcinoma: Despite this evidence, IL-6 inhibitors did not improve outcomes in various types of cancer (myeloid myeloma, prostate cancer, and renal cell carcinoma), possibly due to the high heterogeneity of cancer cells—some of them are IL-6-sensitive, but others are stimulated by additional growth factors [88,89], or a higher IL-6 level is a biomarker but not a reason for a worse prognosis.