Small molecule RL71 targets SERCA2 at a novel site in the treatment of human colorectal cancer.

Baofang Yang,Xuefeng Wu,Guang Liang,Jian Gao,Qiang Xu,Lu Fan,Yan Shen,Jiahuang Li,Yang Sun,Xudong Wu,Xingqi Wang,Minxia Zhang,Gang Xiang,Xiaoning Wang

doi:10.18632/oncotarget.6068

Abstract

While targeted agents are an important part of the treatment arsenal for colorectal cancer, there is still a lack of efficient small-molecule targeted agents based on the understanding of pathogenic molecular mechanisms. In this study, curcumin analog RL71 displayed potent cytotoxicity towards human colon cancer cells with an IC50 of 0.8 µM in SW480 cells and inhibited xenotransplanted tumor growth in a dose-dependent manner. Using affinity chromatography, we identified sarco/endoplasmic reticulum calcium-ATPase (SERCA) 2 as the binding target of RL71. Most notably, RL71 demonstrated special binding to SERCA2 at a novel site with the lowest estimated free energy -8.89 kcal mol(-1), and the SERCA2 residues critical for RL71 binding were identified. RL71 suppressed the Ca(2+)-ATPase activity of SERCA2 both in vitro and in vivo, accompanied by the induction of endoplasmic reticulum stress leading to apoptosis and G2/M cycle arrest in SW480 cells. In addition, RL71 showed synergistic cytotoxicity with the pan-SERCA inhibitor thapsigargin. These results suggest that RL71 could be a selective small-molecule inhibitor of SERCA2, and that it may serve as a lead compound for the study of targeted colorectal cancer therapy.

Highlights

Colorectal cancer (CRC) is one of the most important causes of cancer mortality [1]
These results indicate that RL71 can potentially target SERCA2 in the Endoplasmic reticulum (ER)
We report the discovery of the small molecule RL71 as a potent anti-CRC compound and identified SERCA2 as the direct target of RL71

Summary

Introduction

Current therapy for CRC mainly relies on traditional cytotoxic agents with limited effects. These considerations highlight the importance of developing new treatments based on the understanding of pathogenic molecular mechanisms. SERCA2 mRNA overexpression has been found both in cancerous tissues of CRC patients and in circulating tumor cells of relapsed CRC patients [8, 9]. Increased SERCA2 protein expression is significantly correlated with serosal invasion, lymph node metastasis, and advanced tumor stage. Our previous study demonstrates www.impactjournals.com/oncotarget that increased SERCA2 protein levels correlate strongly with tumor progression in patients with CRC [10]. Increased SERCA2 expression could be a rational and feasible target for anti-CRC drug development

Methods

Results

Conclusion