Suppression of granulocyte-macrophage colony formation in vitro by conditioned medium derived from human bladder cancer cells.

Media conditioned with 8 cell lines were assayed for stimulating and inhibiting activities on granulocyte-macrophage colony formation from bone marrow cells in soft agar (CFUc). Conditioned media from 3 human bladder cancer cell lines (EJ, T24 and KK47) and a rat bladder cancer cell line (BC50-TC) showed marked inhibition of mouse CFUc. Conditioned medium from normal human bladder cells showed a weak colony-stimulating activity, and only a slight inhibition when added to CFUc culture. Conditioned media from mouse or rat fibroblast cell lines (BLP and 3Y1) showed no colony-inhibiting activity, and the conditioned media from human lymphoblastoid cell line (Raji) and human epithelia-like cell line from amniotic membrane (FL) showed moderate inhibitory activity. No colony-stimulating activity was detected in any of the cell lines tested. EJ-conditioned medium inhibited human CFUc, but not erythroid progenitors. Colony-inhibiting activity in EJ-conditioned medium appears not to be prostaglandins; it needs more than 3 hr to inhibit CFUc, is stable at 56 degrees for 30 min but not at 75 degrees for 20 min, and is susceptible to proteolytic enzymes.