Saikosaponin B4 Suppression Cancer Progression by Inhibiting SW480 and SW620 Cells Proliferation via the PI3K/AKT/mTOR Pathway in Colon Cancer

Background: Colon cancer is a gastrointestinal malignancy with high incidence and poor prognosis. Objective: Saikosaponin B4 (SSB4) is a monomeric component of the Traditional Chinese medicine (TCM), Bupleurum. The current study investigates the therapeutic effect and mechanisms of SSB4 in colon cancer. Methods: The proliferation of two colon cancer cell lines, SW480 and SW620, were assessed using CCK8 and expression of regulatory molecules, including Bax, Caspase3, Caspase9, Cleaved Caspase3, Cleaved Caspase9 and Bcl2 by flow cytometry and Western blotting. Results: Survival rates, assessed by CCK8, of SW480 and SW620 cells decreased significantly when the SSB4 concentration was in the range 12.5–50 μg/ml. Flow cytometry measurements indicated apoptosis rates of 55.07% ± 1.63% for SW480 cells and 33.07% ± 1.28% for SW620 cells treated with 25 μg/ml SSB4. Western blotting revealed upregulation of the proapoptotic proteins, Bax, Caspase3, Caspase9, Cleaved Caspase3 and Cleaved Caspase9, and downregulation of the anti-apoptotic protein, Bcl2, in the presence of SSB4. Network pharmacology and molecular docking predicted that the PI3K/Akt/mTOR pathway might be the main regulatory target for the antitumor effect of SSB4. Further Western blotting experiments showed that SSB4 downregulated (p < 0.01) expression of PI3K, Akt, mTOR and the phosphorylated proteins, P-PI3K, P-Akt and P-MTOR. Expression of PI3K, Akt and mTOR mRNA was found to be downregulated by SSB4 (P < 0.01) as the result of RT-PCR measurements. Conclusion: SSB4 is a potent anti-colon cancer agent. Its effects are likely to be mediated by suppression of the PI3K/AKT/mTOR pathway.