Anti-tumor activity of the ginsenoside Rk1 in human hepatocellular carcinoma cells through inhibition of telomerase activity and induction of apoptosis

The ginsenoside Rk1 is one of major components of heat-processed Panax ginseng C. A. MEYER, Sun Ginseng (SG). Here, we investigated the mechanisms underlying the anti-tumor activity of Rk1 in human hepatocellular carcinoma HepG2 cells in vitro. Rk1 markedly inhibited telomerase activity and cell growth along with significant morphological change. The expression levels of telomerase reverse transcriptase (hTERT) and c-Myc mRNA were obviously decreased with Rk1 treatment, while that of telomerase RNA (hTR) was not. Furthermore, Rk1 induced apoptosis through activation of caspases-8 and -3. However, Fas-associated death domain (FADD) expression decreased with Rk1 treatment, though it was known that the signaling cascade of FADD was associated with caspase-8 activity. Interestingly, activation of extracellular-regulated kinase (ERK) increased with Rk1 treatment. In conclusion, these results represent the first identification of the biological activity of Rk1 against HepG2 cell growth and show that the mechanism underlying the anti-tumor activity of Rk1 involves coordination between inhibition of telomerase activity and induction of apoptosis.