Synergistic Anti‐Tumor Effect of Toosendanin and Paclitaxel on Triple‐Negative Breast Cancer via Regulating ADORA2A‐EMT Related Signaling

Abstract Triple negative breast cancer (TNBC) is an aggressive cancer with very poor prognosis. Combination therapy has proven to be a promising strategy for enhancing TNBC treatment efficacy. Toosendanin (TSN), a plant‐derived triterpenoid, has shown pleiotropic effects against a variety of tumors. Herein, it is evaluated whether TSN can enhance the efficacy of paclitaxel (PTX), a common chemotherapeutic agent, against TNBC. It is found that TSN and PTX synergistically suppress the proliferation of TNBC cell lines such as MDA‐MB‐231 and BT‐549, and the combined treatment also inhibits the colony formation and induces cell apoptosis. Furthermore, this combination shows more marked migratory inhibition when compared to PTX alone. Mechanistic study shows that the ADORA2A pathway in TNBC is down‐regulated by the combination treatment via mediating epithelial‐to‐mesenchymal transition (EMT) process. In addition, the combined treatment of TSN and PTX significantly attenuates the tumor growth when compared to PTX monotherapy in a mouse model bearing 4T1 tumor. The results suggest that combination of TSN and PTX is superior to PTX alone, suggesting that it may be a promising alternative adjuvant chemotherapy strategy for patients with TNBC, especially those with metastatic TNBC.