Production of multilineage hemopoietic growth-stimulating activities by a human melanoma cell line

In this study we report that conditioned medium (CM) from the human melanoma cell line Hs0294 contains growth-stimulating activity for human and murine hemopoietic progenitor cells of multiple lineages. Crude CM was assayed for hemopoietic progenitor cell growth-stimulating activity (HP-GSA) in plasma clot cultures of 10⁵ C57Bl/6J mouse bone marrow cells or 10⁵ light-density, nonadherent human peripheral blood mononuclear cells. CM concentrations as low as 0.2% had demonstrable HP-GSA for murine and human hemopoietic progenitor cells, although peak activity for all hemopoietic progenitor cell types assayed (murine CFU-Mix, BFU-E, CFU-GM, and CFU-M and human BFU-E) was observed with 5%-10% Hs0294-CM. Growth-stimulating activity for human erythroid progenitors (BFU-E) was comparable to that produced by phytohemagglutinin-stimulated human mononuclear cell CM. Stimulation of murine hemopoietic progenitors by Hs0294-CM was comparable to the activity in pokeweed mitogen-stimulated mouse spleen cell CM. The Hs0294-CM did not contain detectable quantities of erythropoietin or interleukin 3. Human burst-promoting activity was stable through sequential freezing and thawing, heating to 50°C for 1 h or 100°C for 5 min, and incubation at pH 9.8 for 1 h, but lost 70% of its activity when incubated at pH 2.2 for 1 h. More than 95% of the HP-GSA was recovered in the 50%-80% fraction by (NH₄)₂SO₄ precipitation. The HP-GSA had an estimated molecular weight of approximately 21,000. In conclusion, we have shown that a human melanoma cell line, Hs0294, produces multilineage HP-GSA.