Erythropoietin increases the radioresistance of a clonal hematopoietic progenitor cell line expressing a transgene for the erythropoietin receptor.

Erythropoietin (Epo) is a serum glycoprotein growth factor required for the survival, proliferation and differentiation of committed erythroid progenitor cells. In the present study, we sought to determine whether the action of Epo via its receptor is also implicated in the repair of radiation-induced cell damage. Overexpression of the Epo receptor (Epo-R) was achieved as a result of transfection of the 32D cl 3 clonal hematopoietic cell line. These clonal lines allowed us to investigate the effects of Epo on the radiation sensitivity in vitro of a clonal murine hematopoietic progenitor cell line. Low level expression of Epo-R on many hematopoietic cell types was thus circumvented. Ligand binding of Epo resulted in increased radioresistance of 32D cl 3 subclonal lines expressing the Epo-R transgene. The D0 of 32D Epo-R cells at 1.49 Gy/min was 1.33 Gy and n was 1.39. The D0 of parental clonal cell line 32D cl 3 cells at 1.49 Gy/min was 1.36 Gy and n was 1.39. In contrast, at the low dose rate of 0.0595 Gy/min, the D0 of 32D Epo-R cells was 2.0 Gy and n was 1.24, while parental clonal line 32D cl 3 showed a D0 of 1.35 Gy and n was 1.39. The increased radioresistance was statistically significant at low dose rate (p < 0.05). Combined exposure to Epo and interleukin 3 (IL-3) increased proliferation of 32D Epo-R cells but did not induce a detectable further increase in radioresistance. Temporal dissociation between growth factor-activated tyrosine phosphorylation of intracellular substrates, and the radioprotective effect was observed.(ABSTRACT TRUNCATED AT 250 WORDS)