Baicalin Induces Apoptosis in Leukemia HL-60/ADR Cells via Possible Down-regulation of the PI3K/Akt Signaling Pathway

Background: The effect and possible mechanism of traditional Chinese medicine, baicalin, on the PI3K/Akt signaling pathway in drug-resistant human myeloid leukemia HL-60/ADR cells have been investigated in this current study. Methods: HL-60/ADR cells were treated by 20, 40, $80\;{\mu}mol/L$ baicalin followed by cell cycle analysis at 24h. The mRNA expression level of the apoptosis related gene, Bcl-2 and bad, were measured by RT-PCR on cells treated with $80\;{\mu}mol/L$ baicalin at 12, 24 and 48hr. Western blot was performed to detect the changes in the expression of the proteins related to HL-60/ADR cell apoptosis and the signaling pathway before and after baicalin treatment, including Bcl-2, PARP, Bad, Caspase 3, Akt, p-Akt, NF-${\kappa}B$, p-NF-${\kappa}B$, mTOR and p-mTOR. Results: Sub-G1 peak of HL-60/ADR cells appeared 24 h after $20\;{\mu}mol/L$ baicalin treatment, and the ratio increased as baicalin concentration increased. Cell cycle analysis showed 44.9% G0/G1 phase cells 24 h after baicalin treatment compared to 39.6% in the control group. Cells treated with $80\;{\mu}mol/L$ baicalin displayed a trend in decreasing of Bcl-2 mRNA expression over time. Expression level of the Bcl-2 and PARP proteins decreased significantly while that of the PARP, Caspase-3, and Bad proteins gradually increased. No significant difference in Akt expression was observed between treated and the control groups. However, the expression levels of p-Akt, NF-${\kappa}B$, p-NF-${\kappa}B$, mTOR and p-mTOR decreased significantly in a time-dependent manner. Conclusions: We conclude that baicalin may induce HL-60/ADR cell apoptosis through the PI3K/AKT signaling pathway.