Sustained Down-regulation of the Epidermal Growth Factor Receptor by Decorin

The small leucine-rich proteoglycan decorin interacts with the epidermal growth factor receptor (EGFR) and triggers a signaling cascade that leads to elevation of endogenous p21 and growth suppression. We demonstrate that decorin causes a sustained down-regulation of the EGFR. Upon stable expression of decorin, the EGFR number is reduced by approximately 40%, without changes in EGFR expression. However, EGFR phosphorylation is nearly completely abolished. Concurrently, decorin attenuates the EGFR-mediated mobilization of intracellular calcium and blocks the growth of tumor xenografts by down-regulating the EGFR kinase in vivo. Thus, decorin acts as an autocrine and paracrine regulator of tumor growth and could be utilized as an effective anti-cancer agent.