271 Background: Recent studies demonstrate the efficacy of irradiation from light emitting diodes (LED) for wound healing and anti-inflammation and anti-cancertherapies. However, little is known about the effects of LED in colon cancer cells. Furthermore, most solid cancers are believed to be initiated from and maintained by cancer stem cells (CSCs). The purpose of this study was to evaluate the biological response of human colon cancer cells and CSCs to LED irradiation. Methods: <Experiment 1, Effect of LED on normal cancer cells> Human colon cancer cells (HT29 or HCT116) were seeded onto laboratory dishes that were 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. 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. <Experiment 2, Effect of LED on CSCs> HCT-116 cell line was cultured with fetal bovine serum in RPMI-1640 medium and its sphere was grown in serum-free non-adherent culture. Cancer sphere were seeded onto laboratory dishes that were then put on LED irradiation equipment with a 465 nm-LED. Stemness gene and cell surface markers of CSCs expressions (Oct4, CD44, Nanog, EPCAM) were analyzed by RT-PCR. Results: <Experiment 1> 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, caspase3, capase8, 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. <Experiment 2> Cell viability of cancer sphere were significantly decreased by LED irradiation(p<0.05). And, stemness gene and cell surface markers of CSCs expressions (Oct4, CD44, Nanog, EPCAM) were significantly decreased by LED irradiation (p<0.05) Conclusions: LED irradiation at 465 nm inhibited the proliferation of both normal colon cancer cell lines and CSCs.
Efficacy of 5-aminolevulinic acid-mediated photodynamic therapy using light-emitting diodes in human colon cancer cells
