Treatment of Lewis lung carcinoma by photodynamic therapy and glucan from barley.

Objective. During the photodynamic treatment, complement system is activated and tumor cells are opsonized with iC3b fragment. beta-glucans can enhance cytotoxicity of iC3b-opsonized cells due to their specific interaction with complement receptor 3 (CR3; CD11b/CD18) on the surface of the effector cells. In contrast to microorganisms, tumor cells lack beta-glucan as a surface component and cannot trigger complement receptor 3-dependent cellular cytotoxicity and initiate tumor-killing activity. This mechanism could be induced in the presence of beta-glucans. This study aimed at determining the influence of coadministration of beta-glucan from barley on the efficacy of photodynamic tumor therapy (PDT). Material and methods. C57 Bl/16 female mice bearing Lewis lung carcinoma were used throughout the study. Mice were randomized into groups (15 in each group) and exposed to the treatment with intravenous Photofrin injection (dose, 10 mg/kg) and after 24 h following laser illumination, or with oral administration of beta-glucan from barley at a dose of 400 mu g/mouse per day up to 5 days, or with their combination. Tumor growth dynamics and survival of the treated and untreated mice were monitored. Results. Tumor volume in all treated groups was significantly lower (P<0.001) than that in the control group. The most effective tumor growth suppression (P=0.033) was achieved in mice treated with combination of PDT and beta-glucan from barley as compared with PDT alone. The best survival was achieved in the same group, but difference was not significant as compared to the control group (P=0.143) and to PDT alone group (P=0.319). Conclusions. The present study demonstrates that coadministration of beta-glucan from barley can enhance efficacy of photodynamic therapy.