Apoptosis Mechanisms Related to the Increased Sensitivity of Jurkat T‐cells versus A431 Epidermoid Cells to Photodynamic Therapy with the Phthalocyanine Pc 4

Abstract

In this article, Photochemistry and Photobiology, 2008, 84(2), 407–411, there was an omission of data from Fig. 4. The correct figure is shown: Sensitivity to Pc 4-PDT. (a) Example of a cell cytotoxicity study using the MTT assay. Cells of each line were plated in 96-well plates, exposed to a series of Pc 4 concentrations followed by red light at 200 mJ/cm2, and returned to the 37°C incubator for 24 hours. Cytotoxicity was assayed with MTT, and the LD50 determined (in this case, 20 nM for Jurkat cells and 140 nM for A431 cells). (b) Plot of LD50 of Pc 4 plotted versus fluence, for experiments on A431 (diamonds) and Jurkat (squares) cell lines. Solid and dashed lines are least-squares regression lines obtained by regressing Ln(LD50) vs Ln(Fluence) for A431 and Jurkat cells, respectively. (c) Quantification of Pc 4-PDT induced apoptosis. A431 cells (left) and Jurkat cells (right) were incubated with Pc 4-loaded growth medium for two h, followed by irradiation with 200 mJ/cm2 red light. After further incubation for 4 (open bars) or 18 (hatched bars) h, cells were fixed in 3.7% formaldehyde for 30 min at room temperature, followed by staining with Hoechst 33342 (Molecular Probes, Eugene, OR) for 30 min at room temperature. Slides were viewed under a fluorescence microscope. Cells displaying morphological apoptosis were quantified and normalized to untreated control cells. Data represent an average of 2–3 independent experiments ± standard error or range, except for A431 cells at 100 nM Pc 4, which are from single experiments.