Abstract: Objective To investigate the effects of Panax notoginseng saponins (PNS) on the proliferation, apoptosis and cell cycle
of K562 cells and explore the molecular mechanisms underlying these effects. Methods PNS-induced growth inhibition of
K562 cells was detected by MTT assay; the cell apoptosis was evaluated by AO/EB staining and Annexin V-FITC/ PI staining;
flow cytometry was used to detect cell cycle changes in the treated cells. The mRNA expressions of the molecules in mTOR
signaling pathway were examined by RT-PCR, and the cellular expressions of cleaved caspeas-3, cyclin D1 and major
proteins in mTOR signaling pathway were detected using Western blotting. Results MTT assay showed that treatment with
100-800 μg/mL PNS significantly inhibited the proliferation, promoted the cell apoptosis, and caused cell cycle arrest in G0/G1
phase in K562 cells. Western blotting revealed increased protein expression of cleaved caspase-3 and decreased expression of
cyclin D1 in PNS-treated cells, in which the proteins expressions of mTOR, p-mTOR, p-p70S6K and p-4E-BP 1 and the mRNA
expression of mTOR were all decreased. Conclusion PNS can inhibit the proliferation, induce apoptosis and cause cell cycle
arrest in K562 cells possibly by up-regulating cleaved caspase 3 and down-regulating cyclin D1 and mTOR signaling pathway.