H-7 STIMULATES DESMOSOME FORMATION AND INHIBITS GROWTH IN KB ORAL-CARCINOMA CELLS

Protein kinase inhibitor H-7 was reported to stimulate desmosome forma tion in normal keratinocytes and to inhibit proliferation of neural ce ll lines. In the present study, the effects of this inhibitor on adhes ion 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 labeli ng confirmed the formation of desmosomes both at the cell surface and in the cytoplasm. In order to assess cell proliferation and possible c orrelation with adhesion, confluent cultures were treated and both adh erent and detached cell fractions were counted. Under serum-free condi tions, H-7 significantly reduced cell detachment. In contrast, EGF sti mulated 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 adhesi on of KB carcinoma cells. (C) 1998 Wiley-Liss, Inc.