Tumor Growth and Prognosis of Squamous Cell Carcinoma of the Head and Neck is Linked to Protein Kinase C Alpha

Protein Kinase C alpha (PKC) is a critical mediator of cell signaling and cancer growth. We show that PKC inhibitors decrease proliferation in squamous cell carcinoma of the head and neck (SCCHN) cells and abrogate growth of SCCHN tumors in mouse xenografts. Analysis of gene expression arrays reveals that PKC regulates cell cycle genes required for DNA synthesis. In particular, PKC increases cyclin E protein expression, cyclinE/cdk2 complex formation, and transcription of cyclin E and E2F target genes. Consistent with this mechanism, expression of cyclin E rescues the block in DNA synthesis caused by PKC inhibition. In SCCHN tissue, PKC and cyclin E expression increase progressively from normal and dysplastic to malignant human head and neck tissue. Furthermore, PKC  expression correlates with poor prognosis in SCCHN. These results demonstrate that PKC regulates growth by stimulating DNA synthesis through cyclin E and E2F and identify PKC as a therapeutic target that is highly expressed in aggressive SCCHN. Keywords: time course; dose response 9 samples composed of treated replicates at three time points