Therapeutic effect of photodynamic therapy using hematoporphyrin monomethyl ether (HMME) on human cholangiocarcinoma cell line QBC939

Photodynamic therapy (PDT) is an effective local cancer treatment when a photosensitizer is administered and the tumor is irradiated with light. We examined the effect of PDT using HMME as the photosensitizer, and the 630nm diode laser on human cholangiocarcinoma cell line QBC939. Cell viability was determined by MTT assay. The percentage of apoptotic cell was determined by flow cytometry following annexin V/PI staining. Two methods were used for the determination of apoptosis: terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling assay and laser scanning confocal microscope detection. The procaspase-3 and cytochrome c were measured by western blot. In vitro PDT showed excellent cytotoxicity that was a function of laser energy and drug concentration to the QBC939 cell lines. PDT-mediated cell death occurred predominantly by apoptosis in vitro. Furthermore, this treatment initiates early cytochrome c release, followed by late procaspase-3 activation. Our study demonstrates that PDT using HMME and the diode laser induces apoptosis that is mediated by cytochrome c release and caspase activation in human cholangiocarcinoma cell lines. It is expected that this therapy would be clinically useful for the treatment of patients with cholangiocarcinoma.