Effects of 12 beticolins, Cercospora beticola toxins, on proliferation of ras-transformed adrenocortical cell

AIM: To explore different effects of 12 beticolins, Cercospora beticola tox ins, on ras-transformed adrenocortical cell growth inhibition and their fun ctional mechanism. METHODS: Beticolin-induced inhibition was measured with survival cell number determined by an automated photocolorimetric method. T he penetration of beticolin was examined by confocal microscopy. Ras protei n determined by Lowry method were separated by 14 % SDS-PAGE and electroblo tted to Immobilon-P transfer membrane and detected with pan-Ras (Ab-3) mono clonal antibody. The Ca2+ chelation by beticolin was investigated using a c alcium ionophore. RESULTS: Cell growth inhibition was found dose- and time- dependently at submicromolar level for beticolin-1, -2, and -13 (IC50 less than or equal to 250 nmol/L) and for beticolin-0, 6, and -11 (400 nmol/L < IC50 less than or equal to 500 nmol/L). The inhibition by beticolin-1 was i mmediate, independent of cell culture step and not reversible for 3-day tre atment. Beticolin-3 and -4 were slightly active (1 mu mol/L < IC50 less tha n or equal to 2 mu mol/L) and beticolin-7, -9, -12, and -5 were inactive at micromolar level. The beticolin-induced cell growth inhibition was con-ela ted with the hydrophobicity of these compounds. Beticolin-1. fluorescence i n RTAC cells was detected by confocal microscopy whereas beticolin-3 and 12 were not even after a 24 b incubation period. Beticolin-1-induced cell gro wth inhibition was partially reverted by calcium ionophore suggesting a rol e of intracellular Ca2+ chelation by beticolin-1 on cell growth inhibition. Furthermore, beticolin-1 blocked up Ras p21 translocation to membrane and induced accumulation of Ras in the cytosol as an inactive form by different ways. CONCLUSION: Beticolins with high hydrophobicity inhibit tumorigenic cell proliferation by different ways.