Choline kinase inhibition induces exacerbated endoplasmic reticulum stress and triggers apoptosis via CHOP in cancer cells

Abstract

Endoplasmic reticulum (ER) is a central organelle in eukaryotic cells that regulates protein synthesis and maturation. Perturbation of ER functions leads to ER stress, which has been previously associated with a broad variety of diseases. ER stress is generally regarded as compensatory, but prolonged ER stress has been involved in apoptosis induced by several cytotoxic agents. Choline kinase α (ChoKα), the first enzyme in the Kennedy pathway, is responsible for the generation of phosphorylcholine (PCho) that ultimately renders phosphatidylcholine. ChoKα overexpression and high PCho levels have been detected in several cancer types. Inhibition of ChoKα has demonstrated antiproliferative and antitumor properties; however, the mechanisms underlying these activities remain poorly understood. Here, we demonstrate that ChoKα inhibitors (ChoKIs), MN58b and RSM932A, induce cell death in cancer cells (T47D, MCF7, MDA-MB231, SW620 and H460), through the prolonged activation of ER stress response. Evidence of ChoKIs-induced ER stress includes enhanced production of glucose-regulated protein, 78 kDa (GRP78), protein disulfide isomerase, IRE1α, CHOP, CCAAT/enhancer-binding protein beta (C/EBPβ) and TRB3. Although partial reduction of ChoKα levels by small interfering RNA was not sufficient to increase the production of ER stress proteins, silencing of ChoKα levels also show a decrease in CHOP overproduction induced by ChoKIs, which suggests that ER stress induction is due to a change in ChoKα protein folding after binding to ChoKIs. Silencing of CHOP expression leads to a reduction in C/EBPβ, ATF3 and GRP78 protein levels and abrogates apoptosis in tumor cells after treatment with ChoKIs, suggesting that CHOP maintains ER stress responses and triggers the pro-apoptotic signal. Consistent with the differential effect of ChoKIs in cancer and primary cells previously described, ChoKIs only promoted a transient and moderated ER stress response in the non-tumorogenic cells MCF10A. In conclusion, pharmacological inhibition of ChoKα induces cancer cell death through a mechanism that involves the activation of exaggerated and persistent ER stress supported by CHOP overproduction.

Disruption of mitochondrial fission in the liver protects mice from diet-induced obesity and metabolic deterioration

“…The top five upregulated genes are shown in Table 1. Among these, P8, Atf3 and Trb3 (also known as Trib3) are known to be ER stress-response genes [17][18][19], indicating that Drp1 defects induce ER stress. Meg3, a maternally expressed imprinted gene, has a function of tumour suppression by activation of P53 [20].…”

The roles of oxidative stress, endoplasmic reticulum stress, and autophagy in aldosterone/mineralocorticoid receptor-induced podocyte injury

“…Increasing evidence supports that ER stressinduced apoptosis is an important pathogenic factor in a vast number of diseases. 36 Chop is the major proapoptotic transcription factor upregulated by ER stress. 37 Chop is ubiquitously expressed at very low levels, but is robustly expressed by perturbations that induce stress in a wide variety of cells.…”

Alterations of Choline Phospholipid Metabolism in Endometrial Cancer Are Caused by Choline Kinase Alpha Overexpression and a Hyperactivated Deacylation Pathway

“…Furthermore, overexpression of CHKA (6)(7)(8) and abundance of choline metabolites (13)(14)(15) have been shown to be prognostic in a number of cancers including prostate, breast, lung, and ovarian cancer. More recently inhibition of CHKA, both by shRNA and small-molecule inhibitors, has been shown to have both an antimitogenic and antiproliferative effects in vitro and in vivo (16)(17)(18)(19)(20)(21).…”