Cytokine disbalance in common human cancers.

Interleukin (IL)-6, -4, and -8 levels have been elevated in most patients suffering from prostate, breast, or colon cancer. There is a large body of evidence suggesting that chronic inflammation is one of the etiologic factors in these tumors. IL-6 is a multifunctional cytokine which is known to influence proliferation, apoptosis, and angiogenesis in cancer. Its transcription factor STAT3 is known as an oncogene that is constitutively phosphorylated in these malignancies. However, IL-6-induced STAT3 phosphorylation may result in growth arrest. IL-6 activation of androgen receptor in prostate cancer may yield either tumor cell proliferation or differentiation. Prolonged treatment with IL-6 results in generation of sublines which express a more malignant phenotype. Therapy options against IL-6 have been established and the antibody siltuximab has been applied in preclinical and clinical studies. Recently, investigations of the role of suppressors of cytokine signaling have been carried out. IL-4 and -8 are implicated in regulation of apoptosis, migration, and angiogenesis in cancers associated with chronic inflammation. All cytokines mentioned above regulate cellular events in stem cells. These cells could not be targeted by most conventional cancer therapies. 2010 Elsevier B.V. All rights reserved.