Hyperthermic photodynamic therapy combined with topical administration of OK-432 in the mouse carcinoma

Expression of vascular endothelial growth factor by photodynamic therapy with mono-l-aspartyl chlorin e6 (NPe6) in oral squamous cell carcinoma

Photodynamic therapy (PDT) is a method for treating pre-cancerous and cancerous lesions of the skin, bladder and oral cavity. However, tumour recurrence after PDT remains problematic despite good initial response. Some studies have shown that PDT induces vascular endothelial growth factor (VEGF) expression in human oral squamous cell carcinoma and other organs. However, little is known about VEGF expression applied to PDT in human carcinoma cell lines. No studies have been conducted of PDT using Npe6 (Npe6-mediated PDT), a second-generation photosensitizer, in the human oral carcinoma cell line, HSC-3 cells. We investigated the expression of VEGF, c-jun and c-fos proto-oncogenes in HSC-3 cells in response to Npe6-mediated PDT. We also addressed the possibility that oxidative damage induced by PDT could lead to an angiogenic response, via VEGF expression. Reverse transcription polymerase chain reaction (RT-PCR) analysis revealed that Npe6-mediated PDT induced the expression of mRNAs for VEGF, c-jun and c-fos in time- and concentration-dependent manners. Desferrioxamine (DFX), an iron chelator, induced VEGF expression, but the expression pattern was different to that of Npe6-mediated PDT. The expression mRNAs for VEGF, c-jun and c-fos induced by Npe6-mediated PDT were inhibited by SB203580, p38 MAPK inhibitors, and the expression of VEGF mRNA was inhibited by cycloheximide (CHX), a protein synthesis inhibitor. The c-jun mRNA expression was inhibited, whereas the c-fos mRNA expression was enhanced by N-acetyl-L-cysteine (NAC), a free radical scavenger. We conclude that Npe6-mediated PDT induces the expression of VEGF, c-jun and c-fos in human oral carcinoma cell line, HSC-3 cell, and at least partly, through the activation of p38 MAPK.

Fractionated photodynamic therapy for a human oral squamous cell carcinoma xenograft

The aim of this study was to define the appropriate fractionation interval between photodynamic therapies (PDTs) for enhanced anti-tumour effects on human oral squamous cell carcinoma (HOSCC). Reoxygenation of HOSCC and the proliferative kinetics of the tumour cells following PDT exposure were evaluated in terms of immunohistochemical expression of vascular endothelial growth factor (VEGF) and the proliferating cell nuclear antigen (PCNA). The immunohistochemical expression of VEGF was quantitatively determined by computer-assisted image analysis. The VEGF expression and the PCNA labeling indices (LIs) of the tumour cells were assessed at varying time intervals after PDT. No significant differences were observed in PCNA LIs between the control group and experimental groups at 24, 48, and 72 h after PDT. The expression of VEGF after PDT exposure was demonstrated to be higher in the experimental group at 6 h than the control group, and then was comparable at 24 h between the both groups. These results indicate that the tumour cells surviving from PDT have proliferative potential, and that oxygenation in tumours subjected to PDT may be recovered after 24 h. In the next experiment, two protocols of laser irradiation in PDT were assessed on the basis of tumour volume between fractionated exposure with a 24-h interval and continuous exposure. Regrowth of the tumour was significantly suppressed by fractionated PDT. We propose here that fractionated light exposure with a 24-h interval should be utilized in PDT for an enhanced anti-tumour effect.

Enhanced Susceptibility of Mouse Squamous Cell Carcinoma to Photodynamic Therapy Combined With Low-Dose Administration of Cisplatin

PURPOSE

We have investigated the antitumor effect of photodynamic therapy (PDT), using Photofrin as the photosensitizer, combined with low-dose cisplatin (CDDP) on NR-S1 mouse squamous cell carcinoma.

MATERIALS AND METHODS

CDDP (5 mg/kg body weight) was injected intraperitoneally either 1 hour or 3 hours prior to PDT or immediately afterward. Twenty-four hours after each protocol, the antitumor effects were evaluated by percentage area of the tumor necrosis in hematoxylin-eosin stained specimens as well as terminal deoxynucleotidyl transferase-mediated d-UTP nick-end labeling indices. Furthermore, the tumor sizes were evaluated at 3, 7, and 10 days after each protocol.

RESULTS

The antitumor effect of PDT was enhanced by administration of CDDP 3 hours before PDT, whereas the administration of CDDP 1 hour before PDT or immediately after PDT did not potentiate a PDT antitumor effect.

CONCLUSION

Administration of low-dose CDDP 3 hours before PDT appears to be a useful treatment modality.