Dihydroartemisinin Prevents Progression and Metastasis of Head and Neck Squamous Cell Carcinoma by Inhibiting Polarization of Macrophages in Tumor Microenvironment.

BACKGROUND

Polarized M2 macrophages are an important type of tumor-associated macrophage (TAM), with roles in the growth, invasion, and migration of cancer cells in the tumor microenvironment. Dihydroartemisinin (DHA), a traditional Chinese medicine extract, has been shown to inhibit the progression and metastasis of head and neck squamous cell carcinoma (HNSCC); however, the effect of DHA on cancer prevention, and the associated mechanism, has not been investigated in the tumor microenvironment.

MATERIALS AND METHODS

First, human Thp-1 monocytes were induced and differentiated into M2 macrophages using phorbol 12-myristate 13-acetate (PMA), interleukin-6 (IL-6), and interleukin-4 (IL-4). Induction success was confirmed by cell morphology evaluation, flow cytometry, and quantitative real-time polymerase chain reaction (qRT-PCR). Then, DHA was applied to interfere with M2 macrophage polarization, and conditioned medium (CM), including conditioned medium from M2 macrophages (M2-CM) and conditioned medium from M2 macrophages with DHA (M2-DHA-CM), was obtained. CM was applied to Fadu or Cal-27 cells, and its effects on cancer invasion, migration, and angiogenesis were evaluated using transwell, wound-healing, and tube formation assays, respectively. Finally, Western blotting was used to evaluate the relationship between signal transducer and activator of transcription 3 (STAT3) signaling pathway activation and M2 macrophage polarization.

RESULTS

Human Thp-1 monocytes were successfully polarized into M2-like TAMs using PMA, IL-6, and IL-4. We found that M2-like TAMs promoted the invasion, migration, and angiogenesis of HNSCC cells; however, DHA significantly inhibited IL-4/IL-6-induced M2 macrophage polarization. Additionally, as DHA induced a decrease in the number of M2-like TAMs, M2-DHA-CM inhibited the induction of invasion, migration, and angiogenesis of Fadu and Cal-27 cells. Finally, DHA inhibited M2 macrophage polarization by blocking STAT3 pathway activation in macrophages.

CONCLUSION

DHA inhibits the invasion, migration, and angiogenesis of HNSCC by preventing M2 macrophage polarization via blocking STAT3 phosphorylation.