ENHANCEMENT OF FIBROBLAST-DEPENDENT MAST-CELL GROWTH IN MICE BY A CONDITIONED MEDIUM OF KERATINOCYTE-DERIVED SQUAMOUS-CELL CARCINOMA-CELLS

We investigated the increase in mast cell numbers at the sites of inoc ulation of keratinocyte-derived squamous cell carcinoma cell line (KCM H-1) cells in mice. A significant increase in the number of mast cells was observed at the sites of tumours developed at the sites of inocul ation of the KCMH-1 cells. Enhancement of mast cell growth was observe d by culturing bone marrow-derived mast cells (BMMC) on NIH/3T3 fibrob last monolayers in the presence of conditioned medium (TCM) obtained f rom KCMH-1. Activities of known factors for mast cell growth, such as interleukin-3 (IL-3), IL-4, IL-9, IL-10 and stem cell factor (SCF), we re not detected in the TCM. Nerve growth factor (NGF) did not induce m ast cell growth. Mast cell growth induced by the TCM needed 3T3 fibrob lasts. These results suggest that KCMH-1 cells may produce a factor wh ich induces mast cell growth with 3T3 fibroblasts, other than the alre ady known mast cell growth factors. This may be the mechanism of mast cell accumulation at sites of tumours.