H-7 and fetal calf serum (FCS) act synergistically to increase apoptosis in the KB line of human oral carcinoma cells

There is a high incidence of oral squamous cell carcinoma (SCC) worldwide. The survival rate is among the lowest of the major cancers and has not impr oved significantly over the past two decades. The KB line of human oral car cinoma cells is a useful experimental system for studies of the biology of oral SCC. In a previous study, we reported inhibition of KB cell proliferat ion and stimulation of desmosome formation in confluent cultures treated wi th 20 muM H-7 (1-(5-isoquinolinylsulfonyl)-2-methylpiperazine). In the pres ent study, the effects of this protein kinase C (PKC) inhibitor on the surv ival of KB cells were investigated. Apoptotic cells were detected using a c ombination of Hoechst 33258 nuclear stain, TUNEL technique and ultrastructu ral analysis. Our results indicated that H-7 significantly increased apopto sis in KB cells in a dose-dependent manner. Maximal stimulation occurred at 100 muM, the highest dose of H-7 tested. Apoptotic cells exhibited nuclear fragmentation, chromatin condensation and apoptotic bodies. Interestingly, H-7 and fetal calf serum (FCS) acted synergistically to increase apoptosis in KB cells, suggesting that there is a serum activated subpopulation of H -7 target cells in the cultures. The underlying mechanism of activation rem ains to be elucidated. Our study suggests that the PKC inhibitor H-7 is a p otentially useful cytostatic agent for oral carcinoma cells. (C) 2001 Harco urt Publishers Ltd.