title: Effect of light irradiation by light emitting diode on colon cancer cells.
abstract: OBJECTIVE
  Recent studies have demonstrated the efficacy of irradiation from light emitting diodes (LED) for wound healing, anti-inflammation and anticancer therapies. However, little is known about the effects of visible light in colon cancer cells. The purpose of this study was to evaluate the biological response (including gene expression changes) of human colon cancer cells to different wavelengths of LED irradiation.
  
  
  METHODS
  Human colon cancer cells (HT29 or HCT116) were seeded onto laboratory dishes that were then put on LED irradiation equipment with a 465 nm-, 525 nm-, or 635 nm-LED. Irradiation at 15 or 30 mW was performed 10 min/day, each day for 5 days. The cell counting kit8 was then used to measure cell viability. Apoptosis and expression of several mRNAs (caspase, MAPK and autophagy pathway) in HT29 cultures irradiated with 465 nm LED were evaluated via AnnexinV/PI and RT-PCR, respectively.
  
  
  RESULTS
  Viability of HT29 and HCT116 cells was lower in 465 nm-LED irradiated cultures than in control cultures, but viability of HT29 cells did not differ between control cultures and 525 nm-LED or 635 nm-LED irradiated cultures. Moreover, the expression of FAS, caspase-3, capase-8, and JUK were significantly higher in 465 nm-LED irradiated cultures than in control cultures, and expression of ERK1/2 and LC3 was lower in blue-irradiated cells.
  
  
  CONCLUSIONS
  LED irradiation at 465 nm inhibited the proliferation of HT29 cells and of HCT116 cells. Notably, LED irradiation at 465 nm promoted apoptosis inHT29 cultures via the extrinsic apoptosis pathway and the MAPK pathway.
authors.affiliation: Department of Surgery, Institute of Health Biosciences, The University of Tokushima, Tokushima, Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Matsumoto
authors.affiliation: Department of Surgery, Institute of Health Biosciences, The University of Tokushima, Tokushima, Japan yoshikawa.kozo@tokushima-u.ac.jp.
authors.forename: Kozo
authors.initials: K
authors.lastname: Yoshikawa
authors.affiliation: Department of Surgery, Institute of Health Biosciences, The University of Tokushima, Tokushima, Japan.
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Shimada
authors.affiliation: Department of Surgery, Institute of Health Biosciences, The University of Tokushima, Tokushima, Japan.
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Kurita
authors.affiliation: Department of Surgery, Institute of Health Biosciences, The University of Tokushima, Tokushima, Japan.
authors.forename: Hirohiko
authors.initials: H
authors.lastname: Sato
authors.affiliation: Department of Surgery, Institute of Health Biosciences, The University of Tokushima, Tokushima, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Iwata
authors.affiliation: Department of Surgery, Institute of Health Biosciences, The University of Tokushima, Tokushima, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Higashijima
authors.affiliation: Department of Surgery, Institute of Health Biosciences, The University of Tokushima, Tokushima, Japan.
authors.forename: Motoya
authors.initials: M
authors.lastname: Chikakiyo
authors.affiliation: Department of Surgery, Institute of Health Biosciences, The University of Tokushima, Tokushima, Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Nishi
authors.affiliation: Department of Surgery, Institute of Health Biosciences, The University of Tokushima, Tokushima, Japan.
authors.forename: Hideya
authors.initials: H
authors.lastname: Kashihara
authors.affiliation: Department of Surgery, Institute of Health Biosciences, The University of Tokushima, Tokushima, Japan.
authors.forename: Chie
authors.initials: C
authors.lastname: Takasu
authors.affiliation: Department of Surgery, Institute of Health Biosciences, The University of Tokushima, Tokushima, Japan.
authors.forename: Shohei
authors.initials: S
authors.lastname: Eto
authors.affiliation: Department of Preventive Environment and Nutrition, Institute of Health Biosciences, The University of Tokushima, Tokushima, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Takahashi
authors.affiliation: Department of Life system, Institute of Technology and Science, The University of Tokushima, Tokushima, Japan.
authors.forename: Masatake
authors.initials: M
authors.lastname: Akutagawa
authors.affiliation: Department of Life system, Institute of Technology and Science, The University of Tokushima, Tokushima, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Emoto
mesh_terms: D017209:Apoptosis / Q000528:radiation effects; D059447:Cell Cycle Checkpoints / Q000528:radiation effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000528:radiation effects; D002470:Cell Survival / Q000528:radiation effects; D003110:Colonic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D004307:Dose-Response Relationship, Radiation; D015972:Gene Expression Regulation, Neoplastic / Q000528:radiation effects; D045325:HCT116 Cells; D019073:HT29 Cells; D006801:Humans; D054023:Lasers, Semiconductor; D008027:Light; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000528:radiation effects
chemical_list: D020928:Mitogen-Activated Protein Kinases
keywords: HCT116 cells; HT29; Light-emitting diode; colon cancer