PREDICTION OF RADIOSENSITIVITY INHUMAN BLADDER CELL-LINES USINGNUCLEAR CHROMATIN PHENOTYPE

Nuclear chromatin organisation can provide subtle cluesto the underlying patho-biology of the cell. Nucleartexture analysis is a method that quantitatively measuresphenotypic changes in chromatin distribution within acell nucleus whilst the alkaline Comet assay is a sensitivemethod for measuring the extent of DNA breakage inindividual cells. Both these methods can provide usefulinformation about the sensitivity of cells to DNAdamaging agents, such as ionising radiation.In the current study, the alkaline Comet assay wasperformed on 6 human bladder carcinoma cell-lines and1 human urothelial cell-line exposed to γ-radiation dosesfrom 0 – 10 Gy. Nuclear chromatin texture analysis of 40features was then performed in the same cell-linesexposed to 0, 2 and 6 Gy to investigate if chromatinphenotype was related to radiation sensitivity.Based on the extent of DNA damage measured by theComet assay, we demonstrated that these 7 cell-linesexhibit different levels of radiosensitivity and can bedivided into a radiosensitive group or a radioresistantgroup. Identification of a subset of important texturefeatures using discriminant analysis and the definition ofa classification function showed that 81.75% of all cellscould be correctly identified as radiosensitive orradioresistant based on their pre-treatment chromatinphenotype. We also observed changes in chromatintexture features in the same cell-lines exposed toincreasing doses of γ-radiation, indicating how chromatinorganisation within the nucleus is altered by DNAdamage.We conclude that both the alkaline Comet assay andnuclear texture methodologies may prove to be valuableaids in predicting