Cellular distribution and phototoxicity of Benzoporphyrin derivative and Photofrin

Abstract

Photodynamic therapy (PDT) induces cell-membrane damage and alterations in cancer-cell adhesiveness, an important parameter in cancer metastasis. These alterations result from cell sensitivity to photosensitizers and the distribution of photosensitizers in cells. The efficacy of photosensitizers depends on their close proximity to targets and thus on their pharmacokinetics at the cellular level. We studied the cellular distribution of photosensitizers with a confocal microspectrofluorimeter by analysing the fluorescence emitted by benzoporphyrin derivative-monoacid ring A (BPD-MA) and Photofrin relative to their cell sensitivity. Two cancer cell lines of colonic origin, but with different metastatic properties, were used: PROb (progressive) and REGb (regressive). For BPD-MA (1.75 microg/ml), maximal fluorescence intensity (8,300 cts) was reached after 2 h for PROb and after 1 h (4,900 cts) for REGb. For Photofrin (10 microg/ml), maximal fluorescence intensity (467 cts) was reached after 5 h for PROb and after 3 h (404 cts) for REGb. Intracellular studies revealed stronger cytoplasmic than nuclear fluorescence for both BPD and Photofrin. Both of the sensitizers induced a dose-dependent phototoxicity; LD50 with BPD-MA was 93.3 ng/ml for PROb and 71.1 ng/ml for REGb, under an irradiation of 10 J/cm2. With Photofrin, LD50 was 1,270 ng/ml for PROb and 1,200 ng/ml for REGb under an irradiation of 25 J/cm2. The photosensitizer effect within PROb and REGb cancer cells was assessed by incorporation kinetics and toxicity-phototoxicity tests. The intracellular concentration of the photosensitive agent was one important factor in the effectiveness of PDT, but not the only one contributing to the photodynamic effect. In conclusion, this study showed that there was a clear difference between sensitizer uptake and phototoxicity, even in cancer cells of the same origin. This could induce cell-killing heterogeneity in clinics.

Mitochondrion‐Targeted Photosensitizer Enhances the Photodynamic Effect‐Induced Mitochondrial Dysfunction and Apoptosis

“…For instance, photosensitizers that localized to plasma membrane, lysosome, and Golgi apparatus resulted in a different photo‐killing effect 26. Intracellular studies carried by Rousset et al has revealed stronger cytoplasmic than nuclear fluorescence for both BPD and Photofrin 27,28. Because mitochondria play a pivotal role in arbitrating apoptosis, we focused on whether the BPD‐MA can localize to the mitochondrial area by time‐lapse imaging the emitted red fluorescence of BPD‐MA after cells were loaded with BPD‐MA.…”

Subcellular localization of Photofrin® determines the death phenotype of human epidermoid carcinoma A431 cells triggered by photodynamic therapy: When plasma membranes are the main targets

“…In addition to apoptosis and necrosis, cell death shared with both apoptotic and necrotic characteristics, the mixed type of cell death, has also been described (Formigli et al, 2000;Denecker et al, 2001). Previous studies have pointed out the complexity of cell death induced by PDT, which can be affected by the nature of sensitizers, the dose of light energy, the incubation protocol, and the cell type (Dellinger, 1996;Chan et al, 2000;Rousset et al, 2000;Fabris et al, 2001;Wyld et al, 2001). In this report, we have analyzed the subcellular localization of Photofrin in A431 cells and characterized the Photofrin-PDT-induced cell death when plasma membranes are the main targets.…”

Purging of murine erythroblastic leukemia by ZnPcS2P2-based-photodynamic therapy

“…The intracellular concentrations of photosensitizers were important factors in the effectiveness of PDT. 25 Therefore, PDT requires essentially high contrast between malignant cells and surrounding normal cells as well as sufficient concentration of photosensitizer in malignant cells. On the basis of our previous studies, there were different kinetic changes of ZnPcS 2 P 2 concentration between leukemic cell lines and normal BMC.…”