Hypertrophic lysosomes are critical for tumor progression and drug resistance; however, effective and specific lysosome-targeting compounds for cancer therapy are lacking. Here we conducted a lysosomotropic pharmacophore-based in silico screen in a natural product library (2,212 compounds), and identified polyphyllin D (PD) as a novel lysosome-targeted compound. PD treatment was found to cause lysosomal damage, as evidenced by the blockade of autophagic flux, loss of lysophagy, and the release of lysosomal contents, thus exhibiting anticancer effects on hepatocellular carcinoma (HCC) cell both in vitro and in vivo. Closer mechanistic examination revealed that PD suppressed the activity of acid sphingomyelinase (SMPD1), a lysosomal phosphodieserase that catalyzes the hydrolysis of sphingomyelin to produce ceramide and phosphocholine, by directly occupying its surface groove, with Trp148 in SMPD1 acting as a major binding residue; this suppression of SMPD1 activity irreversibly triggers lysosomal injury and initiates lysosome-dependent cell death. Furthermore, PD-enhanced lysosomal membrane permeabilization to release sorafenib, augmenting the anticancer effect of sorafenib both in vivo and in vitro. Overall, our study suggests that PD can potentially be further developed as a novel autophagy inhibitor, and a combination of PD with classical chemotherapeutic anticancer drugs could represent a novel therapeutic strategy for HCC intervention.

肥大的溶酶体对于肿瘤进展和耐药性至关重要；然而，目前尚缺乏用于癌症治疗的有效且特异性的溶酶体靶向化合物。在这里，我们在天然产物库（2,212 种化合物）中进行了基于溶酶体药效团的计算机筛选，并将多茶素 D (PD) 鉴定为一种新型溶酶体靶向化合物。 PD 治疗被发现会引起溶酶体损伤，表现为自噬流受阻、溶酶体丧失和溶酶体内容物释放，从而在体外和体内对肝细胞癌细胞 (HCC) 表现出抗癌作用。更仔细的机制检查发现，PD通过直接占据其表面凹槽来抑制酸性鞘磷脂酶（SMPD1）的活性，SMPD1是一种溶酶体磷酸二酯酶，催化鞘磷脂水解产生神经酰胺和磷酸胆碱，SMPD1中的Trp148是主要的结合残基。 SMPD1 活性的这种抑制不可逆地触发溶酶体损伤并引发溶酶体依赖性细胞死亡。此外，PD增强溶酶体膜通透性以释放索拉非尼，增强索拉非尼在体内和体外的抗癌作用。总的来说，我们的研究表明PD有可能被进一步开发为一种新型自噬抑制剂，并且PD与经典化疗抗癌药物的组合可能代表一种新的HCC干预治疗策略。