Puerarin inhibits M2 polarization and metastasis of tumor-associated macrophages from NSCLC xenograft model via inactivating MEK/ERK 1/2 pathway

Non-small cell lung carcinoma (NSCLC) metastasis is responsible for most of cancer-related mortality. The tumor associated macrophages (TAMs) are known to be crucial cells in lung cancer and are usually divided into two antagonistic types, M1 and M2. Puerarin has a wide spectrum of pharmacological properties. The present study explores puerarin on macrophage polarization and metastasis of NSCLC. The results demonstrated that puerarin inhibited tumor growth and tumor volumes in NSCLC xenograft model, increased M1 markers [CD197(+), inducible nitric oxide synthase (iNOS)(+), CD40(+))] and reduced M2 markers (CD206(+), Arg-1(+) and CD163(+)). Besides, puerarin elevated the level of pro-inflammatory cytokine interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha and interleukin (IL)-12, decreased the expression of pro-tumor cytokines IL-10, IL-4 and transforming growth factor (TGF)-beta. To explore whether puerarin directly acts on macrophages, we purified macrophages from NSCLC model, the results showed that puerarin inhibited macrophages polarized to M2 phenotype and did not require the auxiliary of other cells. In addition, puerarin suppressed the invasion and migration of NSCLC macrophages, restrained the expression of angiogenesis factors. Puerarin also inhibited the activation of mitogen-activated extracellular signal-regulated kinase (MEK)/extracellular signal-regulated kinase (ERK) 1/2 pathway through inhibition of ERK nucleus translocation. Finally, IL-4 induced M2 macrophage polarization and metastasis were partially offset by puerarin through inactivating the MEK/ERK 1/2 pathway. Taken together, this study validated that puerarin is able to skew macrophage populations back to M1 subsets to stimulate antitumor effects and suggests puerarin is a negative metastatic regulator of NSCLC.