Erythropoietin Receptor in Human Tumor Cells: Expression and Aspects Regarding Functionality

Recombinant human erythropoietin (Epo)and granu l o cy t e - c o l o ny - s t i mulating factor (G-CSF) are used to stimulate hematopoiesis in patients with malignant dise a s e s . These cytokines transduce their biological signal via the Epo receptor (EpoR) and G-CSF receptor (G-CSF-R) into the cell. We therefore investigated in human tumor cell lines the expression of these receptors in tumor cells as well as their response to Epo and G-CSF. Methods and study design: The expression of EpoR and G-CSF-R mRNA was analy zed with rev e rse transcription-poly m e r a s e chain reaction (RT-PCR). EpoR protein expression was further monitored with Western blot and immunocytochemistry analys i s . The cellular response to various concentrations of Epo was evaluated using 3[H]-thymidine uptake, Northern blot of cfos expression and tyrosine kinase activity assay. The proliferation after G-CSF incubation was analyzed with the MTS assay. Results: In this study EpoR mRNA and protein were detected in various human tumor cell lines. Treatment with Epo did not influence the pro l i feration rate of examined EpoR-positive tumor cell lines.Epo did not stimulate the tyrosine kinase activity nor did it affect the c-fos mRNA in these cell lines.G-CSF-R mRNA was only detected in two myeloid cell lines. Treatment with G-CSF did not increase the proliferation of these cells. C o n c l u s i o n s : These results demonstrate that Epo and G-CSF did not modulate the growth rate of examined receptor-positive tumor cell lines; the presence of the Epo receptor seems not essential for cell growth of these tumor cells in cell culture.