Heterogeneity in DNA damage using the comet assay

Abstract

The single-cell gel electrophoresis or ''comet'' assay was developed many years ago to analyze DNA damage in individual cells. It is a powerful and versatile technique that relies on microscopic visualization or imaging of DNA after single cells are embedded in agarose, lysed, and electrophoresed. In addition, the basic methodology has been extended to permit the detection of a variety of classes of DNA damage with good sensitivity in virtually any single-cell type. A unique but understudied property of the comet assay is its ability to detect and quantify cellular heterogeneity in response to DNA-damaging agents. This review outlines the considerations in producing and analyzing comet data when heterogeneity in induction of or cellular response to DNA damage is the major consideration. Examples are presented to emphasize the heterogeneity of tumor response to ionizing radiation and cytotoxic drugs.

In vitro cytotoxicity and genotoxicity studies of titanium dioxide (TiO2) nanoparticles in Chinese hamster lung fibroblast cells

“…Our genotoxicity findings agree with earlier studies in the induction of DNA damage in cells after exposure to nano-TiO 2 , and a stronger induction was observed in nano-sized anatase compared to rutile. The olive tail moment and the percentage of DNA in the tail (% tail DNA), which are the most informative and reliable measurements (Kumaravel and Jha, 2006;Olive and Durand, 2005), were used as DNA damage indicators in our study. Neither the % tail DNA nor the olive tail moment was shown to be significantly different in cells exposed to Vive Nano Titania compared to negative control groups (Fig.…”

“…5f). The percentage of DNA in the comet tail (% Tail DNA) and the olive tail moment (OTM) from 50 cells in each of two replicate samples were used to measure DNA damage; these two parameters are considered as the most informative and reliable measurements (Kumaravel and Jha, 2006;Olive and Durand, 2005). A large tail was detected in the nucleus of each cell treated with the 100 μM hydrogen peroxide positive control group (data not shown).…”

Potent antileukemic action of naphthoquinoidal compounds: evidence for an intrinsic death mechanism based on oxidative stress and inhibition of DNA repair

“…All compounds elicited significant antiproliferative effects in all myeloid human leukemia cells examined after 72 h of exposure. Among the four leukemia cell lines evaluated, the chronic myelogenous leukemia cells (K562) were slightly less sensitive (slightly greater IC 50 values in relation to the other cell lines) to treatment with the tested compounds.…”

“…50,75,76 Because many chemotherapeutic drugs have been shown to induce apoptosis in malignant Figure 6. Effects of nor-β-lapachone (a) and its semisynthetic derivatives 1 (b), 2 (c), 3 (d), 4 (e) and β-lapachone (f) on HL-60 cell viability, mitochondrial transmembrane potential (DYm) and internucleosomal DNA fragmentation.…”

“…At such low levels of damage, the fragments and breaks would be of such a size that migration in an agarose gel becomes difficult to visualize. 50 Therefore, it was performed the modified comet assay in the presence of the endonucleases FPG and ENDOIII, which specifically recognize oxidized purine and pyrimidine bases in DNA, respectively. In our experiments, cultures treated with DMSO (0.1%) or buffer solution does not increase the DNA migration pattern in modified comet assay, in agreement with our previously publication.…”