EPO and neoplasm: Moreover, in the dual EPO and EPOR positive tumor cells the tumor-derived EPO was functionally active that was evidenced by: (1) the blockage of EPO or knockdown of EPOR diminished the growth promotion effects of the NSCLC patients’ sera in vitro, and (2) the xenograft tumors of stable EPOR knocked-down cells or with local administration of EPO-NA exhibited delayed growth in vivo.