TU-100 Antagonizes the M2 Polarization Phenotype of Macrophages in the Tumor Microenvironment by Suppressing the TLR4/NF-B/STAT3 Axis

Abstract

Background/aim: Macrophages are the most abundant immune cells in the tumor stroma, and their polarization states within the tumor microenvironment (TME) exert critical roles in tumorigenesis. TU-100 (Daikenchuto) is a commonly prescribed Japanese herbal medicine that has shown anti-cancer effects by regulating cancer-associated fibroblasts (CAFs) in the TME. However, its effects on tumor-associated macrophages (TAMs) remain unclear.

Materials and methods: TAMs were generated by macrophage exposure to tumor-conditioned medium (CM), and their polarization states were evaluated after TU-100 treatment. The underlying mechanism was further studied.

Results: TU-100 exhibited little cytotoxicity over a range of doses in M0 macrophages and TAMs. However, it could antagonize the M2-like polarization of macrophages evoked by tumor-CM exposure. These effects might be caused by the inhibition of TLR4/NF-B/STAT3 signaling in the M2-like phenotype of macrophages. Interestingly, TU-100 antagonized the malignancy promoting effects of M2 macrophages on hepatocellular carcinoma cell lines in vitro. Mechanistically, the administration of TU-100 restrained the high expression of MMP-2, COX-2, and VEGF in TAMs.

Conclusion: TU-100 may alleviate the progression of cancer by regulating the M2 polarization of macrophages within the TME, suggesting a viable therapeutic approach.

Keywords: M2 polarization; Toll-like receptor 4; Tumor-associated macrophages; nuclear factor-B; tumor microenvironment.