Lung cancer remains the most common cause of cancer-related deaths, with a high incidence and mortality in both sexes worldwide. Chemoprevention has been the most effective strategy for lung cancer prevention. Thus, exploring novel and effective candidate agents with low toxicity for chemoprevention is essential and urgent. Houttuynia cordata Thunb. (Saururaceae) (H. cordata), which is a widely used herbal medicine and is also popularly consumed as a healthy vegetable, exhibits anti-inflammatory, antioxidant and antitumor activity. However, the chemopreventive effect of H. cordata against benzo(a)pyrene (B[a]P)-initiated lung tumorigenesis and the underlying mechanism remain unclear. A B[a]P-stimulated lung adenocarcinoma animal model in A/J mice in vivo and a normal lung cell model (BEAS.2B) in vitro were established to investigate the chemopreventive effects of H. cordata and its bioactive compound 2-undecanone against lung tumorigenesis and to clarify the underlying mechanisms. H. cordata and 2-undecanone significantly suppressed B[a]P-induced lung tumorigenesis without causing obvious systemic toxicity in mice in vivo. Moreover, H. cordata and 2-undecanone effectively decreased B[a]P-induced intracellular reactive oxygen species (ROS) overproduction and further notably protected BEAS.2B cells from B[a]P-induced DNA damage and inflammation by significantly inhibiting phosphorylated H2A.X overexpression and interleukin-1β secretion. In addition, H. cordata and 2-undecanone markedly activated the Nrf2 pathway to induce the expression of the antioxidative enzymes heme oxygenase-1 (HO-1) and NAD(P)H: quinone oxidoreductase 1 (NQO-1). Nrf2 silencing by transfection with Nrf2 siRNA markedly decreased the expression of HO-1 and NQO-1 to diminish the reductions in B[a]P-induced ROS overproduction, DNA damage and inflammation mediated by H. cordata and 2-undecanone. H. cordata and 2-undecanone could effectively activate the Nrf2-HO-1/NQO-1 signaling pathway to counteract intracellular ROS generation, thereby attenuating DNA damage and inflammation induced by B[a]P stimulation and playing a role in the chemoprevention of B[a]P-induced lung tumorigenesis. These findings provide new insight into the pharmacological action of H. cordata and indicate that H. cordata is a novel candidate agent for the chemoprevention of lung cancer.

Introduction: Brain metastasis (BM) is the most common and serious complication of breast cancer (BC). There is significant interest in investigating the crosstalk between BC cells and immune cells. β-elemene is the main pharmacodynamic component of Curcumae Rhizoma, a traditional Chinese medicine that is commonly used for the clinical treatment and prevention of various tumors. However, the specific underlying mechanism of β-elemene in BC-BM is still unclear.Methods: An intracardiac (ICT) injection model was used to establish specific BC-BM cells, then an intracarotid (ICD) injection model was used to verify the inhibitory effect of β-elemene in BC-BM. Tumor-cell-conditioned media, a primary microglia co-culture model, and an in vitro recruitment experiment were used to explore crosstalk between BC cells and immune cells. TMT-based quantitative proteomic, ELISA, IF, and other molecular biotechnologies were used to investigate the mechanisms.Results: The BC-BM cells established in our study not only increased BM rates but also exhibit mesenchymal phenotype and activated the JAK–STAT signaling pathway. Microglia, particularly M2 microglia, were enriched in BM lesions and secreted high levels of both IL6 and CCL2. Hypersecretory IL6 reversed the MET process of BC cells by regulating the JAK2/STAT3 signaling pathway to promote colonization in the brain. Increased levels of CCL2 significantly recruited monocytic myeloid-derived suppressor cells (M-MDSCs) to induce an immunosuppressive brain microenvironment. β-elemene could significantly inhibit BC-BM in mice by regulating the IL6/STAT3 signaling pathway and suppressing the M-MDSC recruitment.Conclusion: Our work first demonstrated that β-elemene regulated the IL6/STAT3 axis and M-MDSC recruitment to reconstruct immunosuppressive brain microenvironment to suppress BC-BM.