Mystery Story about Erythropoietin (Epo) and Erythropoietin Receptor (EpoR) are Disguised?

In this review we would like to focus our attention upon very controversial reports on Erythropoietin (Epo) and Erythropoietin Receptor (EpoR) expression in cancer patients. The effects of Epo on cancerous tissues are poorly understood. Hypoxia results in an increase in the level of the production of both Epo and EpoR via activation of the hypoxia-inducible factor 1 (HIF-1) pathway. HIF-1α, promotes the expression of vascular endothelial growth factor (VEGF). The signaling through VEGF in both a paracrine and an autocrine manner is required for the homeostasis of adult vessels. Macrophages stimulate vessel sprouting via a soluble factor other than VEGF, rather than through direct contact with endothelial cells. The intriguing questions are set about many researches to link Epo/EpoR expression and function in order to establish one of the mechanisms of tumor growth, disease progression of cancer patient. However, it is uncertain role in tumour angiogenesis as promoter and stimulator of tumour growth which should need to be furtherly validated.