Photodynamic Effects of mTHPC on Human Colon Adenocarcinoma Cells: Photocytotoxicity, Subcellular Localization and Apoptosis¶

Abstract

The photodynamic properties of meta‐tetra(hydroxy‐phenyl)chlorin (mTHPC), a promising second‐generation photosensitizer, were investigated using a human colon adenocarcinoma cell line (Colo 201 cells). The study on photocytotoxicity using 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide reduction assay showed that mTHPC was an effective photosensitizer on Colo 201 cells. The photocytotoxicity of mTHPC showed both drug and light dose–dependent characteristics. To reach LD50, namely, the dose at which 50% of the cells were killed, only 0.45 ± 0.15 μg/mL of mTHPC and 3 J/cm2 of light dose were required. The presence of 10% fetal calf serum in culture medium significantly decreased the incorporation of mTHPC into cells and resulted in the reduction of photodynamic efficacy. Using confocal laser scanning microscopy, mTHPC was first shown to localize in lysosomes rather than in mitochondria. Furthermore, nuclear stainings demonstrated that photodynamic therapy with mTHPC induced apoptosis in Colo 201 cells.

2-Bromo-5-hydroxyphenylporphyrins for photodynamic therapy: Photosensitization efficiency, subcellular localization and in vivo studies

“…Photodynamic reaction depends largely of uptake, retention and accumulation of sensitizers in tumour tissue. Subcellular localization of sensitizers defines the site of primary damage since the first places to suffer the damage of photodynamic reaction is the closest to the place of singlet oxygen formation [31][32][33]. As described [34], mitochondria of WiDr cell line show a granular appearance that, as we can see in Fig.…”

Photophysical Parameters, Photosensitizer Retention and Tissue Optical Properties Completely Account for the Higher Photodynamic Efficacy of meso‐Tetra‐Hydroxyphenyl‐Chlorin vs Photofrin¶

“…It was clear from the comparison that while the '02-mediated fit captured all the essential features of the 302 distribution, the predictions from the simple exponential description of photobleaching were not in good agreement with the experimental data. Detailed analysis of 18 experiments using irradiances of 5, 10 and 20 mW cm-' showed a similar pattern, suggesting that mTHPC bleaching is consistent with a predominantly '02-mediated reaction process. The fits to the data also yielded the ratio k,,Jko,[A], which was found to be 29.7 i: 4.6 M-' for mTHPC.…”

Targeted photodynamic therapy as potential treatment modality for the eradication of colon cancer and colon cancer stem cells

“…In CRC cell lines Colo-201 and PDT, phototoxicity was noted, PS localized in the liposomes and apoptotic cell death was induced Leung et al 104 Lysosome localizing chlorin e 6 (Ce6) ATX-S10Na(II)…”