Ganoderic acid A regulates CSF1R to reprogram tumor-associated macrophages for immune therapy of hepatocellular carcinoma.

BACKGROUND: The tumor microenvironment (TME) plays a crucial role in cancer progression, with tumor-associated macrophages (TAMs) constituting the core cell population of the tumor immune microenvironment. TAMs can differentiate into M1 or M2 types based on the TME, either inhibiting or promoting tumor development. Ganoderma lucidum, a medicinal and edible fungus, has a long history of use for extending lifespan and improving health. Ganoderic acid A (GAA), a bioactive compound extracted from G. lucidum, is considered the most abundant monomer among ganoderic acids and has wide applications in clinical anti-tumor therapies.

METHODS: In this study, the effects of GAA against hepatocellular carcinoma (HCC) by modulating TAMs were investigated. The orthotopic and subcutaneous HCC mouse models were established and administrated with GAA at doses of 30 mg/kg/day and 60 mg/kg/day. Additionally, the toxicity of GAA towards tumor cells and macrophages in vitro at concentrations ranging from 25 to 100 μM were evaluated and the phagocytic capacity of macrophages against HCC cells were assessed. The polarization of macrophages was analyzed, along with the expression of CSF1R.

RESULTS: Our data demonstrated that GAA could suppress the growth of both orthotopic and subcutaneous HCC, which was closely associated with macrophage modulation, confirming that its anti-HCC activity was mediated by enhancing macrophage efficacy. GAA exhibited no significant toxicity to tumor cells and macrophages in vitro while enhancing the phagocytic capacity of macrophages against HCC cells. Furthermore, GAA promoted M1 polarization of macrophages while inhibiting M2 polarization. These effects were mechanistically linked to the suppression of CSF1R expression on macrophages, both in vivo and in vitro.

CONCLUSION: Our findings suggest that GAA exerts immunotherapeutic effects in HCC by regulating macrophage polarization through CSF1R inhibition. As a promising natural bioactive compound with the potential to modulate the TME of HCC, GAA may provide novel insights into HCC immunotherapy through the reprogramming of TAMs.