Snake venom toxin from Vipera lebetina turanica induces apoptosis of colon cancer cells via upregulation of ROS- and JNK-mediated death receptor expression.

Mi Hee Park,Miran Jo,Ho Sueb Song,Sang Bae Han,Min Jong Song,Jin Tae Hong,Dohee Won

doi:10.1186/1471-2407-12-228

Abstract

BackgroundAbundant research suggested that the cancer cells avoid destruction by the immune system through down-regulation or mutation of death receptors. Therefore, it is very important that finding the agents that increase the death receptors of cancer cells. In this study, we demonstrated that the snake venom toxin from Vipera lebetina turanica induce the apoptosis of colon cancer cells through reactive oxygen species (ROS) and c-Jun N-terminal kinases (JNK) dependent death receptor (DR4 and DR5) expression.MethodsWe used cell viability assays, DAPI/TUNEL assays, as well as western blot for detection of apoptosis related proteins and DRs to demonstrate that snake venom toxin-induced apoptosis is DR4 and DR5 dependent. We carried out transient siRNA knockdowns of DR4 and DR5 in colon cancer cells.ResultsWe showed that snake venom toxin inhibited growth of colon cancer cells through induction of apoptosis. We also showed that the expression of DR4 and DR5 was increased by treatment of snake venom toxin. Moreover, knockdown of DR4 or DR5 reversed the effect of snake venom toxin. Snake venom toxin also induced JNK phosphorylation and ROS generation, however, pretreatment of JNK inhibitor and ROS scavenger reversed the inhibitory effect of snake venom toxin on cancer cell proliferation, and reduced the snake venom toxin-induced upregulation of DR4 and DR5 expression.ConclusionsOur results indicated that snake venom toxin could inhibit human colon cancer cell growth, and these effects may be related to ROS and JNK mediated activation of death receptor (DR4 and DR5) signals.

Highlights

Abundant research suggested that the cancer cells avoid destruction by the immune system through down-regulation or mutation of death receptors
Effect of snake venom toxin on the growth of human colon cancer cells To evaluate an effect of the snake venom toxin from Vipera lebetina turanica on the growth of colon cancer cells, we analyzed the cell viability by direct counting viable cells in Neubauer chamber
To determine if the inhibition of cell viability by snake venom toxin was due to the induction of apoptosis, we evaluated the changes in the chromatin morphology of cells by using DAPI staining followed by TdT-mediated dUTP nick and labeling (TUNEL) staining assays, and the double labeled cells were analyzed by fluorescence microscope

Summary

Introduction

Abundant research suggested that the cancer cells avoid destruction by the immune system through down-regulation or mutation of death receptors. Apoptosis is the best characterized form of programmed cell death and is an intracellular suicide program possessing morphologic characteristics and biochemical features, including chromatin condensation, nuclear DNA fragmentation, cell shrinkage, membrane blebbing, and the formation of apoptotic bodies [10,11]. It is an important process in maintaining homeostasis which can be triggered by many factors like radiation and chemotherapeutics drugs [12]. The use of death receptor ligands as therapeutic agents has come under scrutiny [17,18,19,20,21]

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Conclusion