小细胞肺癌（SCLC）是一种高度致命的肺癌亚型，治疗选择有限，因此寻找新的靶点和具有强力联合治疗效果的药物是可取的。我们先前从天然产物库中筛选了BH3模拟物，本研究验证了柚皮素作为一种BH3模拟物。具体而言，我们观察了柚皮素与沃里诺斯塔联合应用在SCLC体内外的潜力和机制。结果显示，柚皮素和沃里诺斯塔的联合治疗减少了SCLC H82细胞的增殖，并增加了cleaved caspase-9和cleaved PARP等凋亡相关蛋白的水平。联合治疗提高了LC3-II的表达并诱导自噬细胞死亡。此外，该治疗显著抑制了H82细胞异种移植的SCLC肿瘤在裸鼠体内的生长。柚皮素和沃里诺斯塔的联合治疗通过抑制PI3K-AKT-mTOR通路、促进BCL-2和Beclin 1复合物解离来有效增加自噬，并增加孤立的Beclin 1水平来刺激自噬。分子对接和表面等离子共振分析表明，柚皮素以浓度依赖的方式稳定地结合于BCL-2、BCL-XL和MCL-1蛋白。这些结果表明柚皮素是一种仅包含BH3蛋白的模拟物。此外，柚皮素与沃里诺斯塔的联合治疗增加了SCLC鼠肿瘤组织中组蛋白H3K9和H3K27的乙酰化水平，并增加了BH3蛋白BIM和BID的表达。我们得出结论，柚皮素是一种新型的天然BH3模拟物，可以与沃里诺斯塔协同诱导SCLC的凋亡和自噬。版权所有 © 2023. Elsevier Inc.发表。

Small cell lung cancer (SCLC) is a highly lethal subtype of lung cancer with few therapeutic options; therefore, the identification of new targets and drugs with potent combination therapy is desirable. We previously screened BH3 mimetics from a natural product library, and in this study, we validated nobiletin as a BH3 mimetic. Specifically, we observed its combination potential and mechanism with vorinostat in SCLC in vitro and in vivo. The results showed that combination treatment with nobiletin and vorinostat reduced the proliferation of SCLC H82 cells and increased the levels of apoptotic proteins such as cleaved caspase-9 and cleaved PARP. The combination treatment increased LC3-II expression and induced autophagic cell death. In addition, this treatment significantly inhibited H82 cell xenograft SCLC tumor growth in nude mice. The combination treatment with nobiletin and vorinostat efficiently increased autophagy by inhibiting the PI3K-AKT-mTOR pathway and promoting dissociation of the BCL-2 and Beclin 1 complex, increasing the level of isolated Beclin 1 to stimulate autophagy. Molecular docking and surface plasmon resonance analysis showed that nobiletin stably bound to the BCL-2, BCL-XL and MCL-1 proteins with high affinity in a concentration-dependent manner. These results suggest that nobiletin is a BH3-only protein mimetic. Furthermore, the combination of nobiletin with vorinostat increased histone H3K9 and H3K27 acetylation levels in SCLC mouse tumor tissue and enhanced the expression of the BH3-only proteins BIM and BID. We conclude that nobiletin is a novel natural BH3 mimetic that can cooperate with vorinostat to induce apoptosis and autophagy in SCLC.Copyright © 2023. Published by Elsevier Inc.