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.

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