Etoposide-Induced Apoptosis in Cancer Cells Can Be Reinforced by an Uncoupled Link between Hsp70 and Caspase-3

Dmitry Sverchinsky,Vladimir Mitkevich,Irina Guzhova,Elena Komarova,Dmitry Druzhilovskiy,Vladimir Lazarev,Alina Nikotina,Vladimir Poroikov,Elena Mikhaylova,Roman Suezov,Nikolay Aksenov,Boris Margulis

doi:10.3390/ijms19092519

Abstract

The Hsp70 chaperone binds and inhibits proteins implicated in apoptotic signaling including Caspase-3. Induction of apoptosis is an important mechanism of anti-cancer drugs, therefore Hsp70 can act as a protective system in tumor cells against therapeutic agents. In this study we present an assessment of candidate compounds that are able to dissociate the complex of Hsp70 with Caspase-3, and thus sensitize cells to drug-induced apoptosis. Using the PASS program for prediction of biological activity we selected a derivative of benzodioxol (BT44) that is known to affect molecular chaperones and caspases. Drug affinity responsive target stability and microscale thermophoresis assays indicated that BT44 bound to Hsp70 and reduced the chaperone activity. When etoposide was administered, heat shock accompanied with an accumulation of Hsp70 led to an inhibition of etoposide-induced apoptosis. The number of apoptotic cells increased following BT44 administration, and forced Caspase-3 processing. Competitive protein–protein interaction and immunoprecipitation assays showed that BT44 caused dissociation of the Hsp70–Caspase-3 complex, thus augmenting the anti-tumor activity of etoposide and highlighting the potential role of molecular separators in cancer therapy.

Highlights

The most common anti-tumor drugs target a great variety of proteins implicated in programmed cell death
The chaperone protein Hsp70 can interfere with many steps of the apoptotic pathway, inactivating signal messenger molecules and impeding death for hours or days, giving tumor cells a chance to survive and divide [1]
Preventing the binding of Hsp70 to apoptotic enzymes may be an approach to inhibit the protective mechanisms of cancer cells and so increase their sensitivity to anti-cancer drugs

Summary

Introduction

The most common anti-tumor drugs target a great variety of proteins implicated in programmed cell death. They cause inhibition of the cell cycle, followed by the activation of apoptotic pathways [1]. The high expression of Hsp in cancerous cells often correlates with reduced sensitivity to anti-cancer drugs [5,6]. While this protective effect is desirable for normal cells in response to physiological stress, clinically it impedes the development of antitumor therapeutic strategies

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