G(1) phase-specific suppression of the Cdk2 activity by ginsenoside Rh-2 in cultured murine cells

Ginsenoside Rh-2, a plant glycoside with a dammarane skeleton resembling a steroid skeleton as an aglycone, has anticancer potentials in vitro or in vivo. To elucidate the molecular mechanisms of the effects of Rh-2, we have examined the Cyclin-dependent kinase-2 (Cdk2) activity in G(1) arrested B16 melanoma cells and in S phase-arrested Meth-A sarcoma cells, that have been treated with Rh-2. The kinase activity was suppressed in B16 cells but not in Meth-A cells. In addition, Rh-2 was found to induce G(1) arrest and concomitantly suppress the Cdk2 activity in carcinogen-susceptible BALB/c 3T3 A31-1-1 and A31-1-13 cell lines. Thus, Rh-2 has a G(1) phase-specific suppressive effect on the Cdk2 activity, supporting further evaluation of Rh-2 and its related compounds in cancer chemoprevention studies.