TRANSFORMING GROWTH FACTOR-BETA-INDUCED CELL-GROWTH INHIBITION IN HUMAN BREAST-CANCER CELLS IS MEDIATED THROUGH INSULIN-LIKE GROWTH FACTOR-BINDING PROTEIN-3 ACTION

Most estrogen receptor-negative breast cancer cells, including Hs578T cells, express mRNAs encoding insulin-like growth factor-binding prote in (IGFBP)-3, as well as transforming growth factor (TGF)-beta recepto rs. Our previous studies (Oh, Y., Muller, H. L., Lamson, G., and Rosen feld, R. G. (1993) J. Biol. Chem, 268, 14964-14971; Oh, Y., Muller, H. L., Pham, H. M., and Rosenfeld, R. G. (1993) J. Biol. Chem. 268, 2604 5-26048) have demonstrated a significant inhibitory effect of exogenou s IGFBP-3- on Hs578T cell growth and existence of IGFBP-3-specific rec eptors that may mediate those direct inhibitory effect of IGFBP-3. TGF -beta is also a potent growth inhibitor in human breast cancer cells i n vitro and regulates IGFBP-3 production in different cell systems, su ggesting that IGFBP-3 is a major anti-proliferative factor and a key e lement for TGF-beta-induced growth inhibition in human breast cancer c ells. In support of this hypothesis, we have demonstrated using Hs578T cells that: 1) TGF-beta stimulates IGFBP-3 gene expression and produc tion prior to its inhibition of cell growth, 2) treatment with an IGFB P-3 antisense oligodeoxynucleotide selectively inhibits TGF-beta-induc ed IGFBP-3 synthesis and cell growth inhibition, and 3) treatment with IGF-II and IGF-II analogs diminish TGF-beta effects by blocking TGF-b eta-induced binding of IGFBP-3 to the cell surface. These findings sug gest that IGFBP-3 is a major anti-proliferative factor and a key eleme nt in TGF-beta-induced growth inhibition in human breast cancer cells.