Interleukin-6 signaling pathway in targeted therapy for cancer

Interleukin-6 (IL-6) is a multifunctional cytokine which plays an important role in a wide range of biologic activities in different types of cell including tumor cells. IL-6 is involved in the host immune defense mechanism as well as the modulation of growth and differentiation in various malignancies. These effects are mediated by several signaling pathways, in particular the signal transducer and transcription activator 3 (Stat3). There exists abundant evidence demonstrating that deregulated overexpression of IL-6 was associated with tumor progression through inhibition of cancer cell apoptosis, stimulation of angiogenesis, and drug resistance. Clinical studies have revealed that increased serum IL-6 concentrations in patients are associated with advanced tumor stages of various cancers (e.g., multiple myeloma, non-small cell lung carcinoma, colorectal cancer, renal cell carcinoma, prostate cancer, breast cancer and ovarian cancer) and short survival in patients. Therefore, blocking IL-6 signaling is a potential therapeutic strategy for cancer (i.e., anti-IL-6 therapy) characterized by pathological IL-6 overproduction. Preliminary clinical evidence has shown that antibody targeted IL-6 therapy was well tolerated in cancer patients. In this review, we detail the progress of the current understanding of IL-6 signaling pathway in cancer as well as an antibody targeted IL-6 therapy for human cancer.