Saikosaponin-d Enhances the Anticancer Potency of TNF-α via Overcoming Its Undesirable Response of Activating NF-Kappa B Signalling in Cancer Cells

Tumor necrosis factor-alpha (TNF-α) was reported as anticancer therapy due to its cytotoxic effect against an array of tumor cells. However, its undesirable responses of TNF-α on activating NF-κB signaling and pro-metastatic property limit its clinical application in treating cancers. Therefore, sensitizing agents capable of overcoming this undesirable effect must be valuable for facilitating the usage of TNF-α-mediated apoptosis therapy for cancer patients. Previously, saikosaponin-d (Ssd), a triterpene saponin derived from the medicinal plant, Bupleurum falcatum L. (Umbelliferae), showed to exhibit a variety of pharmacological activities such as antiinflammation, antibacteria, antivirus and anticancer. Recently, we found that Ssd could inhibit the activated T lymphocytes via suppression of NF-κB, NF-AT and AP-1 signaling. Here, we showed that Ssd significantly potentiated TNF-α-mediated cell death in HeLa and HepG2 cancer cells via suppression of TNF-α-induced NF-κB activation and its target genes expression involving cancer cell proliferation, invasion, angiogenesis and survival. Also, Ssd revealed a significant potency of abolishing TNF-α-induced cancer cell invasion and angiogenesis in HUVECs while inducing apoptosis via enhancing the loss of mitochondrial membrane potential in HeLa cells. Collectively, these findings indicate that Ssd has a significant potential to be developed as a combined adjuvant remedy with TNF-α for cancer patients.