H-7 stimulates desmosome formation and inhibits growth in KB oral carcinoma cells

Protein kinase inhibitor H-7 was reported to stimulate desmosome formation in normal keratinocytes and to inhibit proliferation of neural cell lines. In the present study, the effects of this inhibitor on adhesion and growth of KB human oral carcinoma cells were investigated. H-7 was found to enhance desmosome assembly, as evidenced by an increased punctate labeling for the major desmosomal markers. Immunogold labeling confirmed the formation of desmosomes both at the cell surface and in the cytoplasm. In order to assess cell proliferation and possible correlation with adhesion, confluent cultures were treated and both adherert and detached cell fractions were counted. Under serum-free conditions, H-7 significantly reduced cell detachment. In contrast, EGF stimulated cell detachment, and this effect was abolished when cells were simultaneously treated with both EGF and H-7. Total cell counts were also significantly reduced by H-7, both in the presence and absence of EGF. Using the TUNEL technique, labeled cells were increased after H-7 treatment, thus implicating protein kinase inhibition in cell death. These results indicate that H-7 inhibits growth and stimulates adhesion of KB carcinoma cells.