The present study was carried out to elucidate the mechanisms underlying Verrucarin A (VA)-induced cytotoxicity in human breast cancer cell line MDA-MB-231. VA inhibited the growth of MDA-MB-231 cells by induction of ROS-dependent mitochondrial apoptosis. Elevation of reactive oxygen species (ROS) production, associated with changes in Bax/Bcl-2 ratio, led to loss of mitochondrial membrane potential (Δφm) and cytochrome c release in VA treated cells. Release of cytochrome c from mitochondria to cytosol triggered activation of caspase-3, PARP cleavage, DNA fragmentation and finally apoptotic cell death. Furthermore, VA-induced apoptosis was accompanied by the activation of p38MAPK and inhibition of pho... More
The present study was carried out to elucidate the mechanisms underlying Verrucarin A (VA)-induced cytotoxicity in human breast cancer cell line MDA-MB-231. VA inhibited the growth of MDA-MB-231 cells by induction of ROS-dependent mitochondrial apoptosis. Elevation of reactive oxygen species (ROS) production, associated with changes in Bax/Bcl-2 ratio, led to loss of mitochondrial membrane potential (Δφm) and cytochrome c release in VA treated cells. Release of cytochrome c from mitochondria to cytosol triggered activation of caspase-3, PARP cleavage, DNA fragmentation and finally apoptotic cell death. Furthermore, VA-induced apoptosis was accompanied by the activation of p38MAPK and inhibition of phosphorylation of EGFR as well as of Akt and ERK1/2. However, pretreatment with n-acetyl cysteine, an ROS scavenger, and SB202190, a p38MAPK inhibitor, significantly inhibited VA-induced ROS generation, EGFR inhibition, p38MAPK activation and apoptosis. Moreover, pharmacological inhibition of EGFR and ERK1/2 significantly accelerated the VA-induced apoptosis in MDA-MB-231 cells. Collectively, these results indicate that VA-induces ROS elevation in cancer cells, which results in the activation of p38MAPK and inhibition of EGFR/Akt/ERK signaling cascade and, ultimately, cancer cell death.
