Betulin, an active component from Chinese herb birch bark, suppresses tumor angiogenesis and tumor growth by inhibiting the PAX2/VEGF-A/VEGR2 signaling pathway in non-small cell lung cancer.

[INTRODUCTION] Angiogenesis inhibition is an effective therapeutic strategy for patients with non-small cell lung cancer (NSCLC). Natural products serve as critical sources of antiangiogenic inhibitors. Betula platyphylla Suk (birch bark) is a Chinese medicine that can clear heat, detoxify, relieve cough and resolve phlegm. This herb has attracted increasing attention because of its antitumor effects. Betulin is a crucial active ingredient of Betula platyphylla Suk and has been shown to have antitumor effects through the induction of apoptosis and ferroptosis. However, its antiangiogenic effect remains unclear.

[OBJECTIVES] This study aimed to investigate the antiangiogenic of betulin in NSCLC and elucidate the underlying mechanism.

[METHODS] Endothelial cell, pericyte, aortic ring, chorioallantoic membrane, zebrafish and xenograft models were used to evaluate the antiangiogenic effect of betulin. RNA- sequencing, RT-qPCR, and western blotting were employed for target validation. RNA stability assays, methylated RNA immunoprecipitation-PCR, luciferase reporter assays and chromatin immunoprecipitation assays were performed to explore the underlying mechanism.

[RESULTS] Betulin obviously suppressed tumor angiogenesis and tumor growth in both lung adenocarcinoma and lung squamous carcinoma models. Further research revealed that betulin suppressed angiogenesis by inhibiting N6-methyladenosine of paired box 2 (PAX2) mRNA and subsequently reducing PAX2 mRNA stability. Betulin also dissociated PAX2 from the VEGF-A promoter and subsequently reduced VEGF-A expression, leading to the blockade of VEGF-A/VEGFR2 signaling.

[CONCLUSION] These results suggest that betulin is a novel angiogenesis inhibitor with potential clinical application for NSCLC therapy. Our study also suggested that PAX2 is a potential therapeutic target for tumor angiogenesis.