Jolkinolide B induces apoptosis of colorectal carcinoma through ROS-ER stress-Ca2+-mitochondria dependent pathway.

Jing Zhang,Yang Wang,Ye Zhou,Qing-Yu He

doi:10.18632/oncotarget.20077

Abstract

Colorectal carcinoma (CRC) remains one of the leading causes of death in cancer-related diseases. In this study, we aimed to investigate the anticancer effect of Jolkinolide B (JB), a bioactive diterpenoid component isolated from the dried roots of Euphorbia fischeriana Steud, on CRC cells and its underlying mechanisms. We found that JB suppressed the cell viability and colony formation of CRC cells, HT29 and SW620. Annexin V/PI assay revealed that JB induced apoptosis in CRC cells, which was further confirmed by the increased expression of cleaved-caspase3 and cleaved-PARP. iTRAQ-based quantitative proteomics was performed to identify JB-regulated proteins in CRC cells. Gene Ontology (GO) analysis revealed that these JB-regulated proteins were mainly involved in ER stress response, which was evidenced by the expression of ER stress marker proteins, HSP90, Bip and PDI. Moreover, we found that JB provoked the generation of reactive oxygen species (ROS), and that inhibition of the ROS generation with N-acetyl L-cysteine could reverse the JB-induced apoptosis. Confocal microscopy and flow cytometry showed that JB treatment enhanced intracellular and mitochondrial Ca2+ level and JC-1 assay revealed a loss of mitochondrial membrane potential in CRC after JB treatment. The mitochondrial Ca2+ uptake and depolarization can be blocked by Ruthenium Red (RuRed), an inhibitor of mitochondrial Ca2+ uniporter. Taken together, we demonstrated that JB exerts its anticancer effect by ER stress-Ca2+-mitochondria signaling, suggesting the promising chemotherapeutic potential of JB for the treatment of CRC.

Highlights

Colorectal carcinoma (CRC) is one of the most prevalent malignant cancers and the third leading cause of cancer-related deaths in the world [1]
We aimed to investigate the anticancer effect of Jolkinolide B (JB), a bioactive diterpenoid component isolated from the dried roots of Euphorbia fischeriana Steud, on CRC cells and its underlying mechanisms
It is well recognized that reactive oxygen species (ROS) is involved in endoplasmic reticulum (ER) stress and cell death [18], we examined whether JB can induce ROS generation in CRC cells

Summary

Introduction

Colorectal carcinoma (CRC) is one of the most prevalent malignant cancers and the third leading cause of cancer-related deaths in the world [1]. A critical need is to identify promising therapeutic molecules and to understand their action mechanisms against CRC for the further development of the potential drugs associated with a favorable clinical outcome. Oxidative injury, or cytotoxic conditions can trigger ER stress responses by inducing the unfolded protein response (UPR) to maintain ER homeostasis; and when the stress signals are prolonged and unresolved, ER can initiate mitochondrial apoptosis [4]. As one of the most important second messengers in multiple cellular activities, calcium (Ca2+) released from the ER induces cell death mainly through the mitochondria-dependent apoptosis [5]. The strategy of inducting UPR to target cancer cells has attracted great of interest, many potential www.impactjournals.com/oncotarget drugs have shown promising outcome in inducing UPR and some of these drugs are under clinical trials [7]

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