Phytochemical library screening reveals betulinic acid as a novel Skp2‐SCF E3 ligase inhibitor in non–small cell lung cancer

• Published in: Cancer science 2021-08, Vol.112 (8), p.3218-3232
• Main Authors: He, Dan‐Hua, Chen, Yu‐Fei, Zhou, Yi‐Le, Zhang, Shi‐Bing, Hong, Ming, Yu, Xianjun, Wei, Su‐Fen, Fan, Xiang‐Zhen, Li, Si‐Yi, Wang, Qi, Lu, Yongzhi, Liu, Yong‐Qiang
• Format: Article
• Language: English
• Subjects: A549 Cells; Acids; Animals; Antibodies; Antineoplastic Agents, Phytogenic - administration & dosage; Antineoplastic Agents, Phytogenic - pharmacology; Antitumor activity; Betulinic Acid; Binding Sites; Calcium phosphates; Cancer; Cancer therapies; Carcinoma, Non-Small-Cell Lung - drug therapy; Carcinoma, Non-Small-Cell Lung - metabolism; Care and treatment; Cell culture; Cell Line, Tumor; Cell migration; Cell Proliferation - drug effects; Cell Survival - drug effects; Drug delivery; Drug development; Drug Screening Assays, Antitumor; Early Detection of Cancer; Enzyme Inhibitors - administration & dosage; Enzyme Inhibitors - pharmacology; Ethylenediaminetetraacetic acid; Experiments; E‐cadherin; Health aspects; High-Throughput Screening Assays; Humans; Ligases; Lung cancer; Lung cancer, Non-small cell; Lung cancer, Small cell; Lung Neoplasms - drug therapy; Lung Neoplasms - metabolism; Male; Metastases; Metastasis; Mice; Non-small cell lung carcinoma; NSCLC; Original; Pentacyclic Triterpenes - administration & dosage; Pentacyclic Triterpenes - pharmacology; Phytochemicals; Proteasomes; Protein Binding - drug effects; Proteins; S-Phase Kinase-Associated Proteins - chemistry; S-Phase Kinase-Associated Proteins - metabolism; Skp2; Skp2 protein; Small cell lung carcinoma; Ubiquitin; Ubiquitin-protein ligase; Wound healing; Xenograft Model Antitumor Assays; Xenografts
• ISSN: 1347-9032; 1349-7006
• DOI: 10.1111/cas.15005

Skp2 is overexpressed in multiple cancers and plays a critical role in tumor development through ubiquitin/proteasome‐dependent degradation of its substrate proteins. Drugs targeting Skp2 have exhibited promising anticancer activity. Here, we identified a plant‐derived Skp2 inhibitor, betulinic acid (BA), via high‐throughput structure‐based virtual screening of a phytochemical library. BA significantly inhibited the proliferation and migration of non–small cell lung cancer (NSCLC) through targeting Skp2‐SCF E3 ligase both in vitro and in vivo. Mechanistically, BA binding to Skp2, especially forming H‐bonds with residue Lys145, decreases its stability by disrupting Skp1‐Skp2 interactions, thereby inhibiting the Skp2‐SCF E3 ligase and promoting the accumulation of its substrates; that is, E‐cadherin and p27. In both subcutaneous and orthotopic xenografts, BA significantly inhibited the proliferation and metastasis of NSCLC through targeting Skp2‐SCF E3 ligase and upregulating p27 and E‐cadherin protein levels. Taken together, BA can be considered a valuable therapeutic candidate to inhibit metastasis of NSCLC. By screening a phytochemical library via high‐throughput molecular docking, we identified that betulinic acid is capable of binding to Skp2 at residue Lys145, leading to decreased protein stability of Skp2 and the accumulation of its substrate protein p27 and E‐cadherin. Betulinic acid significantly inhibited the proliferation and migration of NSCLC through downregulating Skp2 both in vitro and in vivo.