Differential effect of TPA on cell growth and Epstein-Barr virus reactivation in epithelial cell lines derived from gastric tissues and B cell line Raji

We characterized the cell growth and Epstein-Barr virus (EBV) reactivation for EBV infected epithelial cell lines, GT38, GT39, and GTC-4 using 12-O-te tradecanoylphorbol-13-acetate (TPA). These cell lines grew similarly in liq uid medium, and formed colonies in soft agar. The cell growth was inhibited with TPA, dose-dependently in liquid medium. The colony formation was enha nced with low concentrations of TPA, but was inhibited with high concentrat ions. The latent EBV was reactivated with high concentrations of TPA as sho wn by the expression of EBV BZLF1 gene product ZEBRA. The effects of TPA on GTC-4 were compared with a Burkitt's lymphoma cell line Raji. The mode of actions of TPA in GTC-4 was different from Raji in terms of cell growth and EBV reactivation. The effective concentrations of TPA for cell growth inhi bition and EBV reactivation were higher in Raji than GTC-4. Cell cycle anal ysis showed that TPA (20 ng/ml) induced cell cycle arrest to Raji but not t o GTC-4; however, the rate of trypan blue stained cells increased in the TP A treated GTC-4 but not Raji. These results demonstrated that TPA affects d ifferentially for the stimulation and inhibition of cell growth, and also E BV reactivation depends on TPA concentrations and cell types.