Ginsenoside Rg5's Enhancement of Radiosensitivity of Lung Adenocarcinoma via Reducing HSP90 CDC37 Interaction and Promoting Client Protein Degradation

Abstract

Ginsenoside Rg5 is a rare ginsenoside showing promising tumor-suppressive effects. This study aimed to explore its radio-sensitizing effects and the underlying mechanisms. Human lung adenocarcinoma cell lines A549 and H460 were used for in vitro and in vivo analysis. Bioinformatic molecular docking prediction and following validation by surface plasmon resonance (SPR) technology and cellular thermal shift assay (CETSA) were conducted to explore the binding between ginsenoside Rg5 and HSP90α. The effects of ginsenoside Rg5 on HSP90-CDC37 interaction, the client protein stability and the downstream regulations were further explored. ginsenoside Rg5 can induce cell cycle arrest at the G1 phase and enhance radiation-induced cell apoptosis. Ginsenoside Rg5 could bind to HSP90α with a high affinity. ginsenoside Rg5 might interfere in the HSP90-CDC37-client interaction. Co-IP assays confirmed that ginsenoside Rg5 weakened the HSP90-CDC37 interaction in a dose-dependent manner. Ginsenoside Rg5 reduced irradiation-induced upregulation of the HSP90-CDC37 client proteins, including SRC, CDK4, RAF1 and ULK1 in A549 cell derived xenograft (CDX) tumors. Ginsenoside Rg5 or MRT67307 pre-treatment suppressed irradiation-induced elevation of the LC3-II/β ratio and restored irradiation-induced downregulation of p62 expression. In A549 CDX tumors, ginsenoside Rg5 treatment suppressed LC3 expression and enhanced irradiation-induced DNA damage. ginsenoside Rg5 may be a potential radiosensitizer for lung adenocarcinoma. It interacts with HSP90 and reduces the binding between HSP90 and CDC37, thereby increasing the ubiquitin-mediated proteasomal degradation of the HSP90-CDC37 client proteins.