Background: Photodynamic therapy (PDT) is a relatively new approach for the treatment of biliary tract carcinoma, and its effects have not been investigated in detail to date. This study investigated the mechanisms of human biliary cancer cell death by PDT by focusing on apoptosis induction in vitro and in vivo.
Materials and methods: In vitro, NOZ cells were incubated with porfimer sodium (Photofrin) for up to 24 hours before exposure to laser light. Cell viability was assessed using a methyltetrazolium assay after PDT. DNA fragmentation, cell cycle analysis and caspase-3 activity assay were performed to evaluate apoptotic cells induced by PDT. In vivo, DNA fragmentation was detected by TUNEL assay.
Results: DNA ladder formation and activation of caspase-3 were observed within 24 hours. The proportion of cells with DNA fragmentation on flow cytometric analysis was increased significantly to 22.2% at 24 hours after PDT. In the in vivo model, TUNEL-positive cells began to increase in the implanted tumour from 6 hours after PDT, and peaked 12 hours later.
Conclusion: PDT with Photofrin in this human biliary cancer cell line has antitumor effects and induces apoptotic cell death after PDT.