EPO and chronic kidney disease: This inconsistency might be due to other potential risk factors or molecular mechanisms in CKD patients, which we would discuss later in this review, and might be resulted from the potential effects or impacts of common application of other drugs in these CKD patients such as erythropoietin (EPO) for the treatment of anemia in CRF patients, which has been implicated to be related to promotion of tumor growth with undetermined mechanisms (González Vitores et al., 1999; Ribatti, 2010).