Piper nigrum Extract Inhibits the Growth of Human Colorectal Cancer HT-29 Cells by Inducing p53-Mediated Apoptosis

Colorectal cancer (CRC) is a prevalent malignancy of the digestive tract with the second highest mortality rate globally. Piper nigrum is a widely used traditional medicinal plant, exhibiting antitumor activity against various tumor cells. At present, research on the effect of Piper nigrum on CRC is limited to in vitro cytotoxicity, lacking comprehensive mechanism investigations. This study aimed to explore the inhibitory effect and mechanism of Piper nigrum extract (PNE) on HT-29 cells. Firstly, we identified the chemical components of PNE. Then, MTT assay, colony formation assay, JC-1 staining, and flow cytometry were used to analyze the effect of PNE on HT-29 cells in vitro. A xenograft model, histopathological examination, immunohistochemistry, and western blot were used to evaluate the tumor growth inhibitory activity and mechanism of PNE in vivo. The results indicated that PNE could inhibit cell proliferation and colony formation, reduce mitochondrial membrane potential, induce cell apoptosis in vitro, and inhibit tumor growth in vivo. Furthermore, PNE could regulate p53 and its downstream proteins, and subsequently activate the caspase-3 pathway. In summary, PNE probably induced apoptosis of HT-29 cells through the mitochondrial pathway mediated by p53. All these results suggested that PNE might be a potential natural-origin anti-CRC drug candidate.