Inhibitory effect of recombinant TGF alpha-PE40 on vascular smooth muscle cell proliferation

AIM: To study inhibitory effect of recombinant transforming growth factor a lpha-Pseudomonas exotoxin fusion protein (TP40) on proliferation of the cul tured vascular smooth muscle cells (SMC). METHODS: Expression of epidermal growth factor receptor (EGFR) mRNA and EGER in cultured proliferating and q uiescent SMC was analyzed with Northern blot and immunohistochemistry. Inhi bitory effects of TP40 on SMC proliferation and protein synthesis were anal yzed with crystal violet staining and [H-3]leucine incorporation. Competiti on assays were performed by the addition of 100-fold excess of EGF. RESULTS : Expression of EGFR mRNA and EGFR in rapidly proliferating SMC increased t han that in quiescent SMC. When the concentration of TP40 was 10 or 100 mu g.L-1 inhibitory effects of TP40 on rapidly proliferating SMC proliferation and protein synthesis were much higher than that on quiescent SMC (P < 0.0 1), and the IC50 of [H-3]leucine incorporation against rapidly proliferatin g and quiescent SMC were 8.01 (5.05 - 12.69) and 121.95 (90.98 - 163.47) mu g.L-1. Excess EGF completely blocked inhibitory effects of TP40. CONCLUSIO N: The rapidly proliferating SMC express EGFR at a high level. TP40 selecti vely inhibited the proliferation of rapidly proliferating SMC. The cytotoxi c effects of TP40 were specifically mediated by EGFR.