Abstract
Preclinical and clinical data show a close relationship between high infiltration of tumor-associated macrophages (TAMs) and a poor prognosis in most types of tumors, thus targeting TAMs stands out as promising anticancer immunotherapies. Recent studies have demonstrated the anti-tumor effects of artemisinin via enhancing anti-tumor immunity within tumor microenvironment, but the underlying mechanism is still not clear. In the present study we uncovered an important role of dihydroartemisinin (DHA) in regulating intratumoral TAM polarization and anti-tumor immune responses in mouse Lewis Lung carcinoma model. We found that DHA inhibited Lewis Lung carcinoma progress, moderately decreased the frequencies of TAMs within tumor stroma, and significantly increased CD86 expression while decreased CD206 expression on TAMs which indicates the role of DHA in polarizing TAMs into a M1-like phenotype. Then, our in vitro data confirmed that DHA dose-dependently promoted macrophage M1 phenotype transition by increasing M1 phenotype-related molecules, meanwhile decreasing the expression of M2 phenotype-related molecules. In addition, DHA increased proinflammatory cytokine production, enhanced the phagocytic capacity while decreased anti-inflammatory cytokine production. Finally, in order to prove that AKT/mTOR signaling potentially mediated DHA-induced macrophage differentiation, we used rapamycin to specifically block the activity of mTOR and stimulated macrophages under M1 stimuli. Our data clearly showed that rapamycin significantly decreased DHA-induced M1-related phenotypes and proinflammatory cytokine expression. In summary, our study highlighted DHA as one of future potential therapeutic options for the development of novel anticancer immunotherapies in lung cancer.