A novel copper(I) complex induces ER-stress-mediated apoptosis and sensitizes B-acute lymphoblastic leukemia cells to chemotherapeutic agents.

Roberta Bortolozzi,Valentina Gandin,Elena Porcù,Giuseppe Basso,Maura Pellei,Francesca Consolaro,Cristina Marzano,Giampietro Viola

doi:10.18632/oncotarget.2027

Roberta Bortolozzi, Valentina Gandin + Show 6 more

Open Access

https://doi.org/10.18632/oncotarget.2027

Copy DOI

Journal: Oncotarget	Publication Date: May 27, 2014
Citations: 26	License type: cc-by

Affiliation: University of Padua, Università di Camerino

Abstract

A phosphine copper(I) complex [Cu(thp)4][PF6] (CP) was recently identified as an efficient in vitro antitumor agent. In this study, we evaluated the antiproliferative activity of CP in leukemia cell lines finding a significant efficacy, especially against SEM and RS4;11 cells. Immunoblot analysis showed the activation of caspase-12 and caspase-9 and of the two effector caspase-3 and -7, suggesting that cell death occurred in a caspase-dependent manner. Interestingly we did not observe mitochondrial involvement in the process of cell death. Measures on semipurified proteasome from RS4;11 and SEM cell extracts demonstrated that chymotrypsin-, trypsin- and caspase-like activity decreased in the presence of CP. Moreover, we found an accumulation of ubiquitinated proteins and a remarkable increase of ER stress markers: GRP78, CHOP, and the spliced form of XBP1. Accordingly, the protein synthesis inhibitor cycloheximide significantly protected cancer cells from CP-induced cell death, suggesting that protein synthesis machinery was involved. In well agreement with results obtained on stabilized cell lines, CP induced ER-stress and apoptosis also in primary cells from B-acute lymphoblastic leukemia patients. Importantly, we showed that the combination of CP with some chemotherapeutic drugs displayed a good synergy that strongly affected the survival of both RS4;11 and SEM cells.

Highlights

Many studies have shown that several chemotherapeutics drive cell death through the activation of ER stress
PERK is activated to block protein synthesis, followed by activating transcription factor 6 (ATF6) to restore ER homeostasis and inositol-requiring enzyme 1 (IRE1) is activated with function of Unfolding Protein Response (UPR) mediator and of ER stress-apoptosis inducer [4]
We showed that CP had a strong growth inhibitory activity on several leukemia cell lines of different lineage and phenotype and it preferentially killed B-lymphoblastic leukemia cells

Summary

Introduction

Many studies have shown that several chemotherapeutics drive cell death through the activation of ER stress. In response to ER stress and accumulation of unfolded proteins, cells activate a process known as Unfolding Protein Response (UPR). UPR integrates many signalling pathways to restore ER stability through the attenuation of protein synthesis and the upregulation of chaperones that facilitate protein folding. The main activator of UPR is the chaperon GRP78 which functions as a inhibitor of three ER transmembrane receptors: (PKR)-like ER kinase (PERK), inositol-requiring enzyme 1 (IRE1) and activating transcription factor 6 (ATF6) [3]. GRP78 is required to target proteins for degradation and its release from ER membrane allows the activation of the three receptors. PERK is activated to block protein synthesis, followed by ATF6 to restore ER homeostasis and IRE1 is activated with function of UPR mediator and of ER stress-apoptosis inducer [4]

Methods

Results

Conclusion