Selective mechanism of action of dietary peptides from common bean on HCT116 human colorectal cancer cells through loss of mitochondrial membrane potential and DNA damage

• Dietary peptides GLTSK and GEGSGA inhibited selectively human colon cancer cells.
• Peptides from common bean enhanced oxaliplatin effects on HCT116 cells.
• GLTSK caused loss in mitochondrial potential and GEGSGA DNA damage.
• GEGSGA activated p53, increased p21, and decreased p-Rb inducing cell cycle arrest.

The inhibitory effect of pure peptides from common bean on human colorectal cancer cells, their ability to enhance oxaliplatin effects, and mechanisms of action were evaluated. Peptides GLTSK, LSGNK, GEGSGA, MTEEY, and MPACGSS were tested for cytotoxic effects on HCT116 and CCD-33Co human normal colon cells; no peptide was toxic to normal cells. GLTSK (IC50 = 134.6 µM) and GEGSGA (IC50 = 156.7 µM) exerted anti-proliferative effects on HCT116 cells; LSGNK, MTEEY, and MPACGSS were less potent. GLTSK (γ = 0.64) and GEGSGA (γ = 0.78) interacted synergistically with oxaliplatin inhibiting HCT116 cells. GLTSK caused loss of mitochondrial potential (Δψm) (15.8%) and increased intracellular ROS (12.1-fold) suggesting mitochondrial membrane disruption. GEGSGA caused arrest in G1 phase (63.6% of cell population) and promoted cleavage of PARP (183.7%) suggesting DNA damage. GEGSGA and oxaliplatin caused activation and nuclear translocation of p53. Thus, peptides from common beans selectively induced apoptosis through loss of Δψm and DNA damage on human colorectal cancer cells.