EXOGENOUS THROMBOSPONDIN STIMULATES THE PROLIFERATION OF NON-THROMBOSPONDIN-PRODUCING CELLS

The effects of thrombospondin (TSP) on the proliferation of two differ ent human carcinoma cell lines (KIM-1 and CW-2) were investigated. The characterization of these two carcinoma cells by immunohistochemistry using anti-TSP antibody and anti-TSP-receptor antibody showed that th e KLM-1 had TSP-receptors and TSP, while the CW-2 had only TSP-recepto rs. The addition of exogenous TSP (10 or 20 mu g/ml) to culture medium stimulated the cell proliferation of CW-2 but not that of KIM-1. The cell count for CW-2 was increased dosage-dependently from 10.3+/-0.6x1 0(4)/ml at zero TSP concentration to 12.9+/-0.6x10(4)/ml at 10 mu g/ml TSP concentration and to 14.7+/-0.4x10(4)/ml at 20 mu g/ml TSP (each p<0.0001). In conclusion, though TSP promoted the proliferation of non -TSP-producing cells, it did not promote proliferation of TSP-producin g cells. Therefore, it is predicted that TSP was already at saturated activity concentration in the TSP-producing cell line (KIM-1).