Brusatol

Osteosarcoma (OS) is a rare primary malignant bone tumor. Despite ongoing research efforts, improvements in the five-year survival rate of OS patients remain limited. Therefore, there is an urgent need to identify novel therapeutic agents to improve OS prognosis. Brusatol (Bru), a quassinoid extracted from the seeds of Brucea javanica and Brucea sumatrana, has been shown to possess the potential to inhibit tumor metastasis and proliferation. In recent years, increasing evidence has highlighted the critical role of ferroptosis-a distinct form of regulated cell death-in cancer therapy. However, whether Bru exerts its anti-OS effects by modulating ferroptosis in OS cells remains unexplored. Our study demonstrates that Bru exhibits significant anti-OS activity. In vivo, Bru inhibited the proliferation of subcutaneous OS cells, prevented OS cell-induced tibial and fibular osteolysis, and prolonged the survival of nude mice. In vitro, Bru suppressed OS cell migration and proliferation in a dose-dependent manner. Additionally, Bru induced mitochondrial dysfunction and a marked increase in reactive oxygen species in OS cells. Integrating RNA-seq analysis, our findings indicate that Bru exerts its anti-OS effects by inducing ferroptosis through the regulation of the Keap1/Nrf2/SLC7A11 signaling pathway. Notably, the Keap1 inhibitor KI696 reversed Bru-induced ferroptosis. Importantly, we found that the combination of Bru and the chemotherapeutic agent doxorubicin (DOX) significantly enhanced DOX's anti-OS efficacy by activating apoptotic pathways. Our study reveals that Bru, as a potent ferroptosis inducer in OS cells, holds promise as a potential therapeutic agent for the treatment of OS.

Photodynamic therapy (PDT) remains underutilized as a primary cancer treatment due to the limited lethality of reactive oxygen species (ROS) and poor targeting efficiency of traditional photosensitizers. This the aim of the study is to develop a Fe₃O₄@ZnO nanoparticle photosensitizer co-loaded with anti-EGFR antibody, brusatol, and Nrf2-siRNA to improve the therapeutic effect of PDT. This system can be guided to tumors by a magnetic field and further targets cancer cells through EGFR-specific binding. Under UVA light, brusatol and Nrf2-siRNA are released, enabling combined chemo-, gene, and photodynamic therapy. With the photosensitizer treatment, ROS levels in cutaneous squamous cell carcinoma cells were elevated by 191.09 ± 10.02 % through suppression of Nrf2 and its associated antioxidant defenses, significantly enhancing cell lethality and reducing cell viability by 80.43 ± 9.37 %. In vivo studies further demonstrated a tumor suppression rate of 76.30 ± 5.12 % in nude mice, highlighting the robust anti-tumor efficacy of the photosensitizer and its potential for clinical application in targeted cancer therapy. The biocompatibility and high therapeutic efficacy of this photosensitizer highlight its promise as a safer and more effective option for treating cutaneous squamous cell carcinoma.