Piperine Induces Apoptosis and Cell Cycle Arrest via Multiple Oxidative Stress Mechanisms and Regulation of PI3K/Akt and MAPK Signaling in Colorectal Cancer Cells

Piperine, a phytochemical alkaloid, exhibits anticancer properties on several cancer cells. The present study explored the important oxidative stress and signaling mechanisms by which piperine provokes cell death and apoptosis in colorectal DLD-1 cancer cells. We investigated the cell viability, cell cycle, and apoptosis-inducing of piperine by performing MTT assay, flow cytometry, gene overexpression, and Western blot analysis. Piperine treatment of DLD-1 cells diminished cell viability, and stimulated cell cycle G1 arrest and apoptosis. Piperine induced intracellular reactive oxygen species (ROS) generation by regulating mitochondrial complex III, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, and xanthine oxidase. Piperine inhibited the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) pathway and activated the p-38 and p-extracellular signal-regulated kinase (ERK) pathways. Pretreatment with antimycin A (a mitochondrial complex III inhibitor), apocynin (an NADPH oxidase inhibitor), allopurinol (a xanthine oxidase inhibitor), and PD98059 (an ERK inhibitor) and the overexpression of p-Akt significantly recovered cell viability and reduced apoptosis. This study was the first to demonstrate a multiple oxidative stress mechanism and the critical regulating PI3K/Akt and ERK signaling pathways of piperine, inducing apoptosis on colorectal cancer cells.