MODULATION OF THE SPONTANEOUS G2 PHASE BLOCKAGE IN FANCONI-ANEMIA CELLS BY CAFFEINE - DIFFERENCES FROM CELLS ARRESTED BY X-IRRADIATION

The effect of caffeine on the endogenous G2 phase cell cycle blockage of Fanconi anemia (FA) cells was compared with the effect of caffeine on the G2 phase blockage induced in control cells by X-irradiation. Th e G2 phase accumulations in FA cells could be completely resolved by e xposure to 1.5 mM caffeine. This was also observed in three brothers w ith endogenous G2 phase blockage due to unusual BrdU sensitivity. In c ontrast, G2 phase blockage induced by X-irradiation was only partially resolved by exposure to caffeine. The rescued G2 phase cells from FA patients were arrested within the following G1 phase compartments. Thi s was not seen in X-irradiated cells from control donors. These result s point towards a different nature and/or repair mechanism of the endo genous G2 phase lesion in FA cells compared to that induced by X-irrad iation in control cells.