Recombinant human (rh) erythropoietin (EPO) is attracting increasing interest as an agent for treating cancer-related anemia. Thus, we have tested the effects of rhEPO on the clonal growth of 22 different cell lines derived from a wide range of human solid tumors (head and neck 3, lung 2, breast 2, stomach 1, colorectal 3, hepatocellular 1, pancreas 1, ovary 1, choriocarcinoma 1, osteogenic sarcoma 1, glioblastoma 2, neuroblastoma 1, prostate 1, renal 2) in vitro. RhEPO (dose range 0.01-100 U/ml) caused no significant and reproducible stimulation of clonal growth as measured by a capillary modification of the human tumor cloning assay in agar in any of the cell lines tested. In particular, there was no sensitivity for rhEPO of those cell lines which were shown to be responsive to interleukin-3 and GM-CSF. On the other hand, there were no growth inhibitory effects of rhEPO on the cell lines of this study. Finally, neutralizing anti-human EPO antibody had no effect on the clonal growth of two kidney carcinoma cell lines, making autocrine growth regulation by hEPO in these lines unlikely.
