Anti-tumor immune response in glioblastoma induced by 5-ALA-based PDT? (Invited Paper)

Longtime survivals have been observed after 5-ALA-based PDT of glioblastoma patients. This may partly be attributed to immune response stimulation. Oligonucleotide microarray analyses after sub-lethal in vitro PDT revealed upregulation of chemokine genes, known to support anti-tumor immune response. 5-ALA was more effective in this regard than Photofrin. Expression of transfected ABCG2 modulates photosensitizer concentration more strongly than PDT efficiency. We hypothesize that mitochondrial PpIX is less influenced but decisive for PDT-efficiency. Blocking of (also mitochondrial) ABCG2 led to an increase in phototoxicity. The efficiency of 5-ALA based PDT may be enhanced by immune modifiers and ABCG2 blockers.