Synergystic Interaction of Common Bean (Phaseolus vulgaris L.) Peptides and Oxaliplatin on Proliferation of HCT116 Colorectal Cancer Cells through Mitochondrial Depolarization and DNA Damage

Abstract

The objectives of this study were to evaluate the antiproliferative effect of common bean (Phaseolus vulgaris L.) peptides on HCT116 human colorectal cancer cells and their interaction with oxaliplatin; furthermore, to determine their potential mechanisms of action. Pure peptides GLTSK, LSGNK, GEGSGA, MTEEY and MPACGS and the peptides in the non‐digestible fraction from common bean cultivars Azufrado Higuera (AH) and Bayo Madero (BM) were tested for cytotoxic effects on HCT116, and also on CCD‐33Co human normal colon cells. None of the peptides were toxic to normal cells at concentrations up to 1 mM. GLTSK (IC50=134.6 μM). On the contrary, according to MTS assay, GEGSGA (IC50=156.7 μM) exerted antiproliferative effects on HCT116 cells.. Based on the combination indexes (γ) of the isobolographic analysis, GLTSK (γ=0.64) and GEGSGA (γ=0.78) interacted synergistically (p < 0.05) with oxaliplatin inhibiting HCT116 cells. Using flow cytometry, it was determined that GLTSK caused loss of mitochondrial membrane potential (Δψm) (16% of cells), increased (p < 0.05) in intracellular reactive oxygen species (ROS) (12.1‐fold compared with untreated cells), cell cycle arrest in G2 (54% of cells) and induced apoptosis (33% of cells). GEGSGA had a limited effect on Δψm and intracellular ROS, but caused arrest in G1 phase (64% of cell population) and promoted increase (p < 0.05) in p53 (290%) and cleavage of PARP (184%) compared to untreated cells, promoting DNA damage. The different mechanisms of action were further established by confocal microscopy. An increase (p < 0.05) in the expression and activation of nuclear p53 (145% of fluorescence intensity/μm2) was observed in response to GEGSGA treatment compared to untreated cells in a time‐frame of 3 to 8 h. Moreover, GLTSK depolarized the cells (38% decrease of fluorescence intensity/μm2) and increased (p < 0.05) intracellular ROS (180% of fluorescence intensity/μm2). In addition, peptide fractions from bean cultivar Azufrado Higuera interacted synergistically with oxaliplatin inducing apoptosis (49% of cells), loss of Δψm (21.7% of cells) and increase of intracellular ROS (13.1‐fold compared to untreated cells). This is the first report demonstrating that dietary peptides from common bean interact synergistically with oxaliplatin inhibiting HCT116 human cancer cells. These results support the hypothesis that physicochemical properties of peptides would determine their mechanism of action.Support or Funding InformationBasic Science, National Council for Science and Technology, Mexico CONACyT‐grant number 220924