A VINCRISTINE-RESISTANT MURINE ERYTHROLEUKEMIA CELL-LINE SECRETES - A DIFFERENTIATION ENHANCING FACTOR

A clone of vincristine resistant murine erythroleukemia cells V3.17[44], characterized by high sensitivity to terminal erythroid differenitation induced by hexamethylene bisacetamide, secretes into the extracellular medium a protein factor which partially reduces the latent period before commitment and accelerates the expression of the terminal differentiated phenotype in a slow responding murine erythroleukemia N23 cell variant. This differentiation enhancing factor increases the rate of protein kinase C down-regulation which occurs at slower rate during cell differentiation. The activity of the factor is detected either by co-culture of the two cell line variants or by addition of conditioned medium from V3.17[44] cells to a culture of N23 cells in the presence of the inducer. In addition to being secreted by V3.17[44] cells, this factor can also be detected in the cytoplasm of both V3.17[44] and N23 cells, associated with a particulate fraction from which it can be released by sonication.