Proliferation of squamous cell carcinoma of the head and neck (SCCHN) depends on epidermal growth factor receptor (EGFR) expression. As STAT 3 activation as well contributes to the cell growth in SCCHN, the interaction of STAT 3 and the EGFR is of great interest when considering treatment options through inhibition of STAT 3. We, therefore, evaluated the influence of blocking or activating the EGFR in human SCCHN cell lines and in vivo tumors on STAT 3 activation. We compared the effects on STAT 3 activation with the regulation of MAP Kinase under these conditions. We found that STAT 3 can be strongly inhibited via EGFR blocking in vitro as well as in vivo. However, the influence of EGFR regulation on the MAP Kinase pathway seemed to be very slight. These findings provide evidence that STAT 3 signal activity in head and neck carcinomas, which is partially responsible for proliferative activity, can be controlled via the EGFR.
