Suppression of mouse erythroid colony formation by L1210 leukemia cells.

: The effect of L1210 transplantable leukemic cells on in vitro formation of erythroid colonies from CD2F1 mouse bone marrow progenitor cells (CFU-E) was investigated. Clonal cell culture was carried out by a methylcellulose technique. Human urinary erythropoietin served as the stimulator. After 44 hours of incubation aggregates of eight or more erythroid cells were scored as colonies. The number of CFU-E which could be demonstrated in marrow cells from mice that had been injected intravenously 6 days before with 5 x 10(4) L1210 cells was far below that obtained from normal marrow cells. When 1.3 x 10(5) marrow cells from leukemic mice or L1210 ascites cells were cultured with an equal amount of normal cells, the number of CFU-E expressed was reduced by 51% and by 86%, respectively, relative to controls with normal cells only. Neither lethally irradiated L1210 cells (4500 rad) nor L1210 cell conditioned media suppressed erythroid colony formation. It is suggested that in L1210 leukemia erythropoiesis is decreased because of a cell-to-cell inhibitory action of the leukemia cells on CFU-E.