Discovery of Urea Derivatives of Celastrol as Selective Peroxiredoxin 1 Inhibitors against Colorectal Cancer Cells.

Peroxiredoxin (PRDX1) is a tumor-overexpressed antioxidant enzyme for eliminating excessive reactive oxygen species (ROS) to protect tumor cells from oxidative damage. Herein, a series of celastrol urea derivatives were developed based on its cocrystal structure with PRDX1, with the aim of pursuing a PRDX1-specific inhibitor. Among them, derivative 15 displayed potent anti-PRDX1 activity (IC50 = 0.35 µM) and antiproliferative potency against colon cancer cells. It covalently bound to Cys-173 of PRDX1 (KD = 0.37 µM), which was secured by the cocrystal structure of PRDX1 with an analogue of 15 while exhibiting weak inhibitory effects on PRDX2-PRDX6 (IC50 > 50 µM), indicating excellent PRDX1 selectivity. Treatment with 15 dose-dependently decreased the mitochondria membrane potential of SW620 cells, probably due to ROS induced by PRDX1 inhibition, leading to cell apoptosis. In colorectal cancer cell xenograft model, it displayed potent antitumor efficacy with superior safety to celastrol. Collectively, 15 represents a promising PRDX1 selective inhibitor for the development of anticolorectal cancer agents.

Celastrol suppresses colorectal cancer via covalent targeting peroxiredoxin 1.

As a terpenoids natural product isolated from the plant Thunder God Vine, Celastrol is widely studied for its pharmacological activities, including anti-tumor activities. The clinical application of Celastrol is strictly limited due to its severe side effects, whereas previously revealed targets and mechanism of Celastrol seldom reduce its in vivo toxicity via structural optimization. Target identification has a far-reaching influence on the development of innovative drugs, and omics data has been widely used for unbiased target prediction. However, it is difficult to enrich target of specific phenotype from thousands of genes or proteins, especially for natural products with broad promising activities. Here, we developed a text-mining-based web-server tool to enrich targets from omics data of inquired compounds. Then peroxiredoxin 1 (PRDX1) was identified as the ROS-manipulating target protein of Celastrol in colorectal cancer. Our solved high-resolution crystal structure revealed the unique covalent binding mode of Celastrol with PRDX1. New derivative compound 19-048 with improved potency against PRDX1 and selectivity towards PRDX2~PRDX6 were synthesized based on crystal structure analysis. Both Celastrol and 19-048 effectively suppressed the proliferation of colorectal cancer cells. The anti-tumor efficacy of Celastrol and 19-048 was significantly diminished on xenograft nude mice bearing PRDX1 knock-down colorectal cancer cells. Several downstream genes of p53 signaling pathway were dramatically up-regulated with Celastrol or 19-048 treatment. Our findings reveal that the side effects of Celastrol could be reduced via structural modification, and PRDX1 inhibition is promising for the treatment of colorectal cancer.