Comparison of ALA and Photofrin in two rat glioma models

Photodynamic therapy (PDT) shows good promise as an adjuvant therapy for the treatment of gliomas. PDT requires the use of a photosensitizer but there have been few studies in which they have been directly compared. Two rat brain glioma cell lines, BT4C and F98 were used to study the effects of Photofrin (PF) and aminolevulinic acid (ALA) as photosensitizers. Both compounds were able to sensitize cells to red light (635nm) however, PF treated (2.5 &mgr;g/ml) cells displayed more cell death than ALA treated (1 mM) cells. ALA-PDT treated cells did not have a block in the cell cycle while PF-PDT treated cells had a fluence dependent G1 block 24 hrs after treatment. The BT4C cell line also displayed a G2 cell cycle block. Both photosensitizers were able to induce apoptosis as measured by flow cytometry but only PF-PDT was able to induce necrosis at the fluence rates investigated (1-20 J/cm2). These differences in cellular responses to ALA and