Photodynamic therapy (
PDT) has been developed as an effective treatment for malignant disease.
Carboplatin (
CBDCA), a less nephrotoxic analog of cisdiamminedichloroplatinum (
cisplatin), has been widely used for the treatment of multiple
malignancies. In this study, we investigated the cytotoxic and apoptotic effect of combined modality of
9-hydroxypheophorbide alpha (9-HPbD)-mediated
PDT and
CBDCA on AMC-HN-3 human
head and neck cancer cell line in vitro. The attached AMC-HN-3 cells were incubated with
CBDCA (0.04 mg/ml) for 24 h at 37 degrees C and followed by
photosensitization with 9-HPbD for 6 h and
laser irradiation with 670 nm
diode laser at an intensity of 2.0 J/cm(2) for activating 9-HPbD for 15 min. Then MTT reduction assay and
Hoechst 33342 and
propidium iodide (PI) double staining were used respectively to measure the cytotoxicity and nuclear morphology at 24 h after
PDT. Expression of
caspase-3, -9 and
poly(ADP-ribose) polymerase (PARP) was detected at 0, 3, 6 and 12 h after irradiation through Western blotting techniques. Compared with
PDT and
CBDCA alone groups, there was more cytotoxicity and enhanced apoptotic cell death in combination groups. The peaked expression of cleaved form of
caspase-3, -9 and PARP occurred approximately 3 h after
PDT. There was stronger expression of cleaved
caspase-3, -9 and PARP in combination groups than that in
PDT or
CBDCA alone groups. This study demonstrates that the combined modality resulted in enhanced apoptotic cell death as well as cytotoxic effect on AMC-HN-3 cells in vitro, which suggests the feasibility of combined modality and the possibility of reducing the effective dosage of 9-HPbD and
CBDCA and lowering the side effects on normal cells.