Expression of Fas antigen and apoptosis caused by 5,10,15,20-tetra(4-methoxyphenyl)porphyrin (TMP) on carcinoma cells: implication for photodynamic therapy

The photodynamic effects of 5,10,15,20-tetra(4-methoxyphenyl)porphyrin (TMP ) on a Hep-2 cell line were investigated. TMP toxicity in the dark and in r elation to illumination with visible light was examined. Hep-2 cells were t reated with different TMP concentrations (1, 5 and 10 mu M). The uptake of TMP by Hep-2 cells increased with TMP concentration and an increase of the initial uptake rate was observed with increasing TMP concentrations. Howeve r, after 24 h of incubation, a similar value of intracellular TMP concentra tion was reached at all three concentrations of TMP added. Cell toxicity in duced by TMP was analyzed in the dark at different concentrations of the ph otosensitizer and at several incubation periods. The cell mortality obtaine d after exposure of the cell cultures to visible light was exclusively due to the photosensitization effect of TMP produced by light irradiation. Stai ning with the hematoxylin-eosin method demonstrated that treatment with TMP , followed by exposure to visible light, notably increased the apoptotic fi gures. Fas antigen was only expressed in these conditions. The results cont ribute to the understanding of the photodynamic therapy (PDT) mechanism pro duced by TMP on Hep-2 carcinoma cell line. (C) 2000 Elsevier Science Irelan d Ltd. All rights reserved.