Tenuigenin inhibits osteosarcoma growth via CIP2A/PP2A/NF-κB axis

Background: Polygala tenuifolia and its active components have been revealed to possess anti-tumor activities. However, the role of Tenuigenin (TEN), a bioactive ingredient from Polygala tenuifolia, in tumors such as osteosarcoma (OS) remains unclear. The present research intended to explore the efficacy and underlying mechanism of TEN on OS.

Methods: OS cells were administrated with different concentrations of TEN. Cell viability, proliferation, invasion, and migration were assessed with CCK-8 assay, colony formation assay, transwell assay, and wound healing assay, respectively. Protein and mRNA levels were determined with western blot and qRT-PCR, while protein Phosphatase 2A (PP2A) activity was tested with PP2A Phosphatase assay kit. The interaction between PP2A and cancerous inhibitor of protein Phosphatase 2A (CIP2A) or nuclear factor kappaB (NF-κB) signaling was detected using co-immunoprecipitation. p-p65 expression in the nucleus was determined with immunofluorescence. The efficacy of TEN in vivo was also explored in a xenograft tumor model. Immunohistochemistry was performed to detect CIP2A and Ki67 in mice.

Results: TEN treatment or CIP2A depletion repressed cell viability, proliferation, invasion, and migration in OS cells. Additionally, TEN reduced CIP2A, increased PP2A activity, and inactivated NF-κB signaling. PP2A directly interacted with CIP2A or NF-κB signaling, and PP2A inhibition reversed CIP2A knockdown-induced repression of NF-κB signaling. CIP2A overexpression overturned the efficacy of TEN, which was reversed by NF-κB inhibition. TEN decreased CIP2A, elevated PP2A activity, inactivated NF-κB signaling, and inhibited tumor growth in vivo, which was antagonized by CIP2A overexpression.

Conclusion: TEN suppressed OS growth via CIP2A/PP2A/NF-κB axis, indicating that it would be a novel drug for treating OS.

CIP2A; NF-κB; Osteosarcoma; PP2A; Tenuigenin.