Bryophyllum pinnatum Induces p53-Dependent Apoptosis of Colorectal Cancer Cells via Increased Intracellular ROS and G2/M Cell-Cycle Arrest In Vitro and Validated in Silico by Molecular Docking

Abstract

Chemotherapy, radiotherapy and surgical treatments of cancer having several limitations and toxic side-effects, have led researchers to focus towards development of alternative natural plant-based therapeutics that can reduce disease severity. The present research work is mainly focussed towards identifying molecular mechanisms of apoptosis of colorectal cancer cells (HCT116) by perennial herb Bryophyllum pinnatum leaf-extract via both in vitro experimentations and in silico analysis. B. pinnatum leaf extract induced highest cytotoxicity at lowest dose (IC₅₀:0.01 mg/mL) against HCT116 cells with 49.5% (p < 0.0001) cellular death, in comparison to other cancer cell lines. It has arrested HCT116 cell populations at G2/M cell-cycle phase and led to 10 folds (p < 0.0001) and 5.5 folds (p < 0.0001) increased intracellular ROS production in treated groups. ROS production might have led to significant 34.23% and 21.03% (p < 0.0001) apoptosis in treated cells, proved in vitro and in silico, with significant upregulation of p53 (p < 0.0001), BAX (p = 0.0252), CASPASE3 (p < 0.0001) and downregulation of BCL2 (p = 0.0058), leading to increased nuclear p53 (p = 0.0002) accumulation in treated cells, suggesting that the leaf-extract might have induced p53-dependent apoptosis of colorectal cancer cells. The phyto-extract also possess significant gene-modulatory potential as evident from qRT-PCR analysis of oncogenes and tumor suppressor genes. Leaf's bioactive phyto-constituents were elucidated by GC-MS and HPLC-ESI/MS analysis. In silico STITCH analysis provided significant network interactions between these bioactive phyto-compounds and studied proteins. Further Molecular Docking studies revealed strong binding between such docked complexes. Also, predicted major bioactive phyto-constituents of B. pinnatum leaf-extract such as Quercetin, Morin and β-Sitosterol have induced significant (p < 0.0001) apoptosis and increased intracellular ROS, validating their in silico interactions with studied proteins of HCT116 cells. All these studies together demonstrated ability of B. pinnatum to be used as a suitable natural phyto-therapeutic agent for development of chemo-preventive medications against colorectal cancer.