Scutellaria barbata D.Don suppresses SPP1+ polarization in tumor-associated macrophages via the HIF-1α/STAT3 signaling to attenuate hepatocellular carcinoma progression.

ETHNOPHARMACOLOGICAL RELEVANCE: Scutellaria barbata D.Don (SBD) is used for the treatment of hepatocellular carcinoma (HCC) as an alternative therapy in East Asia. Previous studies have shown that SBD can suppress the progression of HCC. However, the precise mechanism of SBD, particularly within the tumor immune microenvironment (TME), remains unclear. AIM OF THE STUDY: This study aims to evaluate the effect of SBD on HCC and elucidate its immunomodulatory mechanisms. MATERIALS AND METHODS: Orthotopic and subcutaneous HCC murine models were established to evaluate the antitumor effects of SBD. In addition, tumor-associated macrophages (TAMs) were cultured in vitro, and a cell-conditioned culture system was used. RESULTS: We found that SBD suppressed tumor growth and Ki-67+ proliferating tumor cells. Moreover, SBD upregulated the anti-tumor factors GZMB and IFN-γ. Importantly, SBD reduced the population of SPP1+ TAMs and increased the ratio of CXCL9+/SPP1+ TAMs, accompanied by an increase in CD8+ T cells. Macrophage depletion weakened the antitumor effect of SBD. Furthermore, SBD inhibited the polarization of TAMs toward the SPP1+ phenotype in vitro and indirectly suppressed TAM-induced tumor growth and CD8+ T cell exhaustion. Mechanistically, SBD inhibited the HIF-1α/STAT3/SPP1 signaling axis. SBD blocked the interaction between HIF-1α and STAT3, thereby suppressing STAT3 phosphorylation. Knockdown of HIF-1α abolished the effect of SBD on TAMs. A 14-day high-dose regimen of SBD was well tolerated in vivo. Additionally, in vitro screening based on SPP1 polarization in TAMs identified baicalin, luteolin, naringenin, and wogonin as the active ingredients of SBD. CONCLUSIONS: These findings indicate that SBD inhibits HCC progression. SBD suppresses the polarization of TAMs toward the SPP1+ phenotype via inhibition of the HIF-1α/STAT3/SPP1 signaling pathway. We suggest that SBD may serve as a potential alternative therapy for HCC.