Potentiation of photodynamic therapy by immunotherapy: the effect of schizophyllan (SPG).

Treatment of squamous cell carcinoma (SCCVII) bearing mice with the immunostimulant schizophyllan (SPG) raised the relative content of Mac-1 positive host cells infiltrating the tumor and increased photofrin retention in these tumors. In vitro colony formation assay following photofrin-based photodynamic therapy (PDT) in vivo revealed a greater killing of tumor cells in the SPG pre-treated group, particularly pronounced when the tumor excision was delayed for 8 h after PDT. The tumor cure rate increased approximately three times when PDT was preceded by the SPG therapy. In contrast, the administration of SPG after PDT was of no benefit for tumor control.