The human promyelocyte leukemic cell line HL-60 secretes a glycoprotein factor which stimulates HL-60 and myeloid cell growth and colony formation in vitro. Functional and biochemical studies indicate this autostimulatory activity (ASA) is distinct from colony-stimulating factor (CSF) activities reported previously. Human CSF I, CSF II, and HL-60 ASA stimulated HL-60 growth and colony formation. The ASA also demonstrated CSF activity for both granulocyte and macrophage colonies when assayed on normal mouse and human bone marrow cells. The ASA glycoprotein was partially purified 1200-fold to an apparent molecular weight of 25,000 on G-75 filtration and a pl of 4.9 after neuraminidase treatment. Serological cross-reactivity between human CSF I and HL-60 ASA was detectable by immune precipitation and neutralization of biological activity with rabbit anti-CSF I antibodies. The cross-reactive anti-CSF I antibodies also inhibited spontaneous HL-60 colony formation in vitro in the absence of exogenous CSF, ASA, or anti-HL-60 antibody activity. These results indicate that HL-60 ASA is an endogenous growth factor similar to CSF that may be required for HL-60 growth in vitro.

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Supported in part by Rachelle Wilderman Memorial Grant CH-280 from the American Cancer Society and by a gift from Mr. Issam Fares.

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