Anti-Epidermal Growth Factor Receptor Monoclonal Antibody 225 Upregulates p27<sup>KIP1</sup> and p15<sup>INK4B</sup> and Induces G1 Arrest in Oral Squamous Carcinoma Cell Lines

Abstract

Epidermal growth factor receptor (EGFR) regulates the growth and progression of human oral squamous cell carcinoma (SCC). Recently, the link between EGFR signaling and the cell cycle has been identified. Some reports have described that EGFR-blocking monoclonal antibody 225 (mAb225) induced G1 arrest and inhibited the growth of various cancer cells. The purpose of this study was to evaluate the effect of mAb225 on human oral SCC cell lines. Exposure to mAb225 in culture inhibited the growth of oral SCC cell lines in an EGFR number-independent manner, with the percent inhibition ranging from 13.8 to 76.6%. Flow-cytometric analysis demonstrated that treatment with mAb225 induced cell accumulation in G1 phase, accompanied by a decrease in the percentage of cells in the S phase. Apoptosis was not seen in this study. G1 arrest was accompanied by a decrease in CDK2-, CDK4-, and CDK6-associated histone H1 kinase activities, and an increase in the expression levels of cell cycle inhibitors p27(KIP1) and p15(INK4B). These results suggested that the antiproliferative effect of EGFR blockade by mAb225 in oral SCC may be mediated by p27(KIP1) and p15(INK4B).