Molecular targeting of breast and colon cancer cells by PAR1 mediated apoptosis through a novel pro-apoptotic peptide.

A novel activating peptide was designed and synthesized from V. cholerae hemagglutinine protease (HAP) mediated cleavage site of mouse PAR1. The peptide "PFISED" interacts with PAR1 in a new site which is different from its thrombin mediated conventional activation site and induced a series of new downstream signaling pathways. The peptide showed apoptosis in human and mouse breast (MCF-7 and EAC) and colon (HT29 and CT26) cancer cells where as in the same peptide concentration in normal human breast epithelial cells (MCF-10A), normal human fibroblast cells (MRC-5), normal mouse peritoneal macrophage cells and normal mouse breast and colon tissues did not show any effect. Treatment with this peptide enhanced the survival kinetics of EAC induced mice. The peptide mediated apoptosis was inhibited in presence of PAR1 inhibitor and was significantly reduced in si-PAR1 treated cells that indicate the activating peptide "PFISED" induced PAR1 mediated apoptosis of colon and breast cancer cells. This peptide induced over expression and activation of PAR1 and its downstream MAP kinase and NFκB signaling pathways. These signaling pathways enhanced the cellular ROS level to kill malignant cells. We report a novel pro-apoptotic peptide which can selectively kill malignant cells via its specific target receptor PAR1 which is over expressed in the malignant cells and can be used as a molecular target therapy for cancer treatment.