Modified Bu-Fei decoction inhibits lung metastasis via suppressing angiopoietin-like 4

Background: Modified Bu-Fei decoction (MBFD), a formula of traditional Chinese medicine, is used for treating lung cancer in clinic. The actions and mechanisms of MBFD on modulating lung microenvironment is not clear.

Purpose: Lung microenvironment is rich in vascular endothelial cells (ECs). This study is aimed to examine the actions of MBFD on tumor biology, and to uncover the underlying mechanisms by focusing on pulmonary ECs.

Methods: The Lewis lung carcinoma (LLC) xenograft model and the metastatic cancer model were used to determine the efficacy of MBFD on inhibiting tumor growth and metastasis. Flow cytometry and trans-well analysis were used to determine the role of ECs in anti-metastatic actions of MBFD. The in silico analysis and function assays were used to identify the mechanisms of MBFD in retarding lung metastasis. Plasma from lung cancer patients were used to verify the effects of MBFD on angiogenin-like protein 4 (ANGPTL4) in clinical conditions.

Results: MBFD significantly suppressed spontaneous lung metastasis of LLC tumors, but not tumor growth, at clinically relevant concentrations. The anti-metastatic effects of MBFD were verified in metastatic cancer models created by intravenous injection of LLC or 4T1 cells. MBFD inhibited lung infiltration of circulating tumor cells, without reducing tumor cell proliferations in lung. In vitro, MBFD dose-dependently inhibited trans-endothelial migrations of tumor cells. RNA-seq assay and verification experiments confirmed that MBFD potently depressed endothelial ANGPTL4 which is able to broke endothelial barrier and protect tumor cells from anoikis. Database analysis revealed that high ANGPTL4 levels is negatively correlated with overall survival of cancer patients. Importantly, MBFD therapy reduced plasma levels of ANGPTL4 in lung cancer patients. Finally, MBFD was revealed to inhibit ANGPTL4 expressions in a hypoxia inducible factor-1α (HIF-1α)-dependent manner, based on results from specific signaling inhibitors and network pharmacology analysis.

Conclusion: MBFD, at clinically relevant concentrations, inhibits cancer lung metastasis via suppressing endothelial ANGPTL4. These results revealed novel effects and mechanisms of MBFD in treating cancer, and have a significant clinical implication of MBFD therapy in combating metastasis.