title: Events associated with apoptotic effect of p-Coumaric acid in HCT-15 colon cancer cells.
abstract: OBJECTIVE
  To investigate the events associated with the apoptotic effect of p-Coumaric acid, one of the phenolic components of honey, in human colorectal carcinoma (HCT-15) cells.
  
  
  METHODS
  3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tertazolium-bromide assay was performed to determine the antiproliferative effect of p-Coumaric acid against colon cancer cells. Colony forming assay was conducted to quantify the colony inhibition in HCT 15 and HT 29 colon cancer cells after p-Coumaric acid treatment. Propidium Iodide staining of the HCT 15 cells using flow cytometry was done to study the changes in the cell cycle of treated cells. Identification of apoptosis was done using scanning electron microscope and photomicrograph evaluation of HCT 15 cells after exposing to p-Coumaric acid. Levels of reactive oxygen species (ROS) of HCT 15 cells exposed to p-Coumaric acid was evaluated using 2', 7'-dichlorfluorescein-diacetate. Mitochondrial membrane potential of HCT-15 was assessed using rhodamine-123 with the help of flow cytometry. Lipid layer breaks associated with p-Coumaric acid treatment was quantified using the dye merocyanine 540. Apoptosis was confirmed and quantified using flow cytometric analysis of HCT 15 cells subjected to p-Coumaric acid treatment after staining with YO-PRO-1.
  
  
  RESULTS
  Antiproliferative test showed p-Coumaric acid has an inhibitory effect on HCT 15 and HT 29 cells with an IC₅₀ (concentration for 50% inhibition) value of 1400 and 1600 μmol/L respectively. Colony forming assay revealed the time-dependent inhibition of HCT 15 and HT 29 cells subjected to p-Coumaric acid treatment. Propidium iodide staining of treated HCT 15 cells showed increasing accumulation of apoptotic cells (37.45 ± 1.98 vs 1.07 ± 1.01) at sub-G1 phase of the cell cycle after p-Coumaric acid treatment. HCT-15 cells observed with photomicrograph and scanning electron microscope showed the signs of apoptosis like blebbing and shrinkage after p-Coumaric acid exposure. Evaluation of the lipid layer showed increasing lipid layer breaks was associated with the growth inhibition of p-Coumaric acid. A fall in mitochondrial membrane potential and increasing ROS generation was observed in the p-Coumaric acid treated cells. Further apoptosis evaluated by YO-PRO-1 staining also showed the time-dependent increase of apoptotic cells after treatment.
  
  
  CONCLUSIONS
  These results depicted that p-Coumaric acid inhibited the growth of colon cancer cells by inducing apoptosis through ROS-mitochondrial pathway.
authors.affiliation: Saravana Kumar Jaganathan, Eko Supriyanto, IJ N-UTM Cardiovascular Engineering Centre, Faculty of Bioscience and Medical Engineering, Universiti Teknologi Malaysia, Johor Bahru 81310, Malaysia.
authors.forename: Saravana Kumar
authors.initials: SK
authors.lastname: Jaganathan
authors.forename: Eko
authors.initials: E
authors.lastname: Supriyanto
authors.forename: Mahitosh
authors.initials: M
authors.lastname: Mandal
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003110:Colonic Neoplasms / Q000378:metabolism / Q000473:pathology*; D003373:Coumaric Acids / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D019073:HT29 Cells; D006801:Humans; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D011422:Propionates; D017382:Reactive Oxygen Species / Q000378:metabolism; D013997:Time Factors
chemical_list: D000970:Antineoplastic Agents; D000975:Antioxidants; D003373:Coumaric Acids; D011422:Propionates; D017382:Reactive Oxygen Species; C495469:p-coumaric acid
keywords: Apoptosis; Honey; Merocyanine; Reactive oxygen species; Rhodamine-123; Sub-G1; p-Coumaric acid