The in vitro modulation of apoptosis and cell proliferation by modified in comparison with non-modified ribonucleosides was investigated for the first time using peripheral blood lymphoeytes, HL-60 cells and Caco-2 cells as human cell culture models. Modulating effects of several ribonucleosides were found in the range of 10-~-10 s mol/i. The following ribonuclensides induced significant apoptosis of HL-60 cells: adenosine, N6-dimethyladenosine, N~-(2-isopentenyl)-adenosine, N2-dimethylguanosine. A significant apoptotic effect on PBL was found with N6-dimethyladenosine and N°-(2 -isopentenyl)-adenosine. N6-Dimethyladenosine, N6-(2-isopentenyl)-adenosine and guanosine had a pronounced inhibitory effect on Caco-2 cell apoptosis. Regarding the known function of ribonucleosides as pathobiochemical marker molecules for cancer, the possibility of a selective apoptotic effect against malignant cells is discussed.

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