Doping and Cancer

Anabolic steroids and peptides are utilized to increase the performance of athletes of professional or amateur sports. The use of some of these agents has significantly grown and has been extended also to non athletes with the aim to improve appearance or to counteract ageing. Besides the well documented side effects of hormones or growth factors, experimental evidences have warned about the potential risk of cancer development and progression. Anabolic steroids have been described to provoke serious adverse effects to the liver, including tumors; treatment with growth hormone (GH) and high levels of its mediator insulin-like growth factor-1 (IGF-1) have been associated with colon, breast, and prostate cancers. Actually, IGF-1 promotes cell cycle progression and inhibits apoptosis either by triggering other growth factors or by interacting with pathways which have an established role in carcinogenesis and cancer promotion. Thus, it is likely that GH/IGF-1 might accelerate carcinogenesis, although a direct cause-effect relationship has not been proven, yet. Circumstantial evidences in support to this fear come from in vitro and/or animal studies, but also from epidemiological observations within the general population in patients with an excess of production of GH or in patients chronically treated with GH/IGF-1 for various pathologies. More recently the finding of the expression of erythropoietin (Epo) receptor (R) in cancer cells has suggested the possibility that recombinant Epo may exert direct effects on tumor cells such as stimulation of proliferation and angiogenesis or inhibition of apoptosis. The presence of an autocrine-paracrine Epo/EpoR loop in tumors and the possible effects of Epo on tumor microenvironment and angiogenesis are consistent with the involvement of Epo/EpoR signalling in cancer. Therefore, the potential risk of developing cancer after treatment with hormone/growth factors deserves careful evaluation and further studies are requested.