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Updated: Sep 25, 2026
An Automated Differential Nuclear Staining Assay for Accurate Determination of Mitocan Cytotoxicity
Published on: May 12, 2020
Comparison of photodynamic targets in a carcinoma cell line and its mitochondrial DNA-deficient derivative
J Morgan1, W R Potter, A R Oseroff
1Department of Dermatology, Roswell Park Cancer Institute, Buffalo, NY 14222, USA. jamorgan@acsu.buffalo.edu
Abstract:
The relative contribution, to cell death, of photodynamic damage to respiratory proteins (known targets of photodynamic therapy with many photosensitizers) and other cellular sites was examined. The models were a human ovarian carcinoma cell line 2008, and its mitochondrial DNA-deficient derivative ET3, which lacks several key respiratory protein subunits. Phototoxicity was compared in the two cell lines with photosensitizers that localized to different cellular compartments. Photosensitizers included Victoria Blue BO (VBBO; mitochondria); Photofrin with a short incubation, (plasma membrane) or a long incubation (intracellular membranes including mitochondria); and Nile Blue A (NBA; lysosomes). Photosensitizer content and localization did not differ between the 2008 and ET3 cells. For sensitizers without a primary mitochondrial localization (NBA and Photofrin with a short incubation), there was no significant difference between 2008 and ET3 toxicity. Consistent with a mitochondrial localization of VBBO and independence from respiratory-chain damage, ET3 cells were less susceptible than 2008 to both dark- and light-activated VBBO-mediated damage. Statistical analysis of the data demonstrated minimal photobleaching of VBBO and a significant difference between the phototoxicity curves of ET3 and 2008. For Photofrin with a long incubation, dark- and phototoxicity effects were similar for both cell lines. Inhibition of respiratory enzymes is thus only a minor component of Photofrin-mediated (long incubation) phototoxicity in these cell lines and is overwhelmed by more significant damage elsewhere, whereas it is a major but not the exclusive element of death mediated by VBBO.
Insights
Photodynamic therapy
Area of Science:
- Biochemistry
- Cell Biology
- Oncology
Background:
- Photodynamic therapy (PDT) utilizes photosensitizers to induce cell death.
- The precise cellular targets of PDT-induced damage remain under investigation.
- Respiratory proteins are known targets for some photosensitizers.
Purpose of the Study:
- To determine the contribution of damage to respiratory proteins versus other cellular sites in PDT-induced cell death.
- To compare the efficacy of photosensitizers targeting different cellular compartments.
Main Methods:
- Utilized human ovarian carcinoma cell line 2008 and its mitochondrial DNA-deficient derivative ET3.
- Administered photosensitizers Victoria Blue BO (mitochondria), Photofrin (plasma membrane/intracellular membranes), and Nile Blue A (lysosomes).
- Compared phototoxicity between cell lines with varying photosensitizer localizations.
Main Results:
- ET3 cells showed less susceptibility to Victoria Blue BO, indicating mitochondrial damage is significant but not exclusive.
- Nile Blue A and short-incubation Photofrin showed similar toxicity in both cell lines, suggesting non-mitochondrial targets.
- Long-incubation Photofrin toxicity was similar in both cell lines, indicating damage to respiratory enzymes is a minor component.
Conclusions:
- Damage to respiratory proteins is a major, but not sole, contributor to cell death mediated by mitochondrial-localized photosensitizers like Victoria Blue BO.
- For photosensitizers like Photofrin, damage to other cellular sites overwhelms the contribution of respiratory enzyme inhibition.
