Screening method for colony-stimulating factor inducers using a human bone marrow stromal cell line, KM-102

A new screening method for inducers of colony-stimulating factors (CSFs) was established using KM-102, a human bone marrow stromal cell line as the producer. In this method, the assay system which uses CSF dependent cell lines is combined with the CSF production system. Interleukin-1 (IL-1), which is known to upregulate CSF production in many cell populations, was used as a positive control for production of granulocyte CSF (G-CSF) and granulocyte-macrophage CSF (GM-CSF). Induction in the positive controls was clearly detected within 24 hours. Activators of protein kinase C (PKC), protein phosphatase inhibitors and lipopolysaccharide (LPS) were positive in this assay system, but muramyl dipeptide (MDP) and Bestatin which are known macrophage activators, were negative. Inducers of CSFs were successfully detected using this assay method. Among 1,600 microbial strains tested, 2 actinomycete strains were found to produce active substances. One strain produces teleocidin-A, a strong activator of PKC, and the other strain produces a mixture of active compounds including three novel compounds. These three compounds do not induce terminal differentiation of HL-60 cells, suggesting that they are not teleocidin-like substances and form a new class of CSF inducers.