Arjunolic acid inhibits Wnt3a-mediated macrophage M2 polarization to suppress osteosarcoma progression.

Background: Osteosarcoma (OS) is a bone tumor characterized by a high recurrence rate and poor prognosis. Arjunolic acid (AA), the most abundant triterpene component in Cyclocarya paliurus, is reported to have anti-tumor effects. Its specific role in OS is still unknown, which we aim to investigate in our study.

Methods: An OS mouse model was established to investigate the effects of AA. Subsequently, M2 macrophages and M0 macrophages pretreated with AA were co-cultured with OS cells. The impact of AA on OS cell behavior (proliferation, apoptosis, migration, and invasion) was evaluated via EdU staining, flow cytometry, and Transwell assays. Concurrently, the expression of M1- and M2-associated genes (CD86, CD163, IL-6, Arg1) was quantified to assess AA's regulatory role in macrophages within the tumor microenvironment (TME). Knockdown or overexpression of Wnt3a in AA-treated M0 macrophages to determine whether AA modulates Wnt3a-mediated M2 polarization, which was further validated in vivo.

Results: In vivo, AA inhibited tumor progression in OS mice. Concurrently, AA-treated macrophages inhibited OS cell malignant behavior, and AA inhibited OS cell-mediated macrophage M2-type polarization. Mechanistically, AA inhibits the malignant behavior of OS cells and inhibits tumor progression in OS mice by suppressing Wnt3a-mediated macrophage M2 polarization. Additionally, AA-induced macrophage conversion to a pro-inflammatory phenotype in the TME of OS mice.

Conclusion: Our experiment demonstrated that AA from Cyclocarya paliurus inhibits Wnt3a-mediated M2 macrophage polarization to suppress the progression of osteosarcoma, providing a pharmacological foundation for developing therapies against OS.