Measurements using the alkaline comet assay predict bladder cancer cell radiosensitivity - PubMed (original) (raw)

Measurements using the alkaline comet assay predict bladder cancer cell radiosensitivity

M A L Moneef et al. Br J Cancer. 2003.

Abstract

In the UK, the two main treatments of invasive bladder cancer are radiotherapy or cystectomy. However, approximately 50% of patients undergoing radiotherapy fail to respond. If tumour radiosensitivity could be predicted in advance, it may be possible to improve control rates significantly by selecting for radiotherapy those patients whose tumours are radiosensitive. Additionally, patients who would benefit from surgery would be identified earlier. The alkaline comet assay (ACA) is a sensitive method for the detection of DNA strand break damage in cells. In the present study, using six bladder cancer cell lines of differing radiosensitivities, cell survival was compared to the manifestation of radiogenic DNA damage as assessed by ACA. For all the cell lines, the extent of comet formation strongly correlates with cell killing (R2>0.96), with a greater response being noted in radiosensitive cells. In repair studies, measures of residual damage correlate with survival fraction at 2 Gy (R2>0.96), but for only five of the cell lines. Finally, cells from human bladder tumour biopsies reveal a wide range of predicted radiosensitivies as determined by ACA. Overall, these studies demonstrate ACA to be a good predictive measure of bladder cancer cell radiosensitivity at low dose, with potential clinical application.

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Figures

Figure 1

Figure 1

(A) The radiation cell survival curve responses for the six bladder cancer cell lines investigated, over a dose range of 0–6 Gy, as determined by clonogenic assay. Survival was determined as the number of colonies formed following X-ray exposure. (B) The extent of initial comet formation, as measured by mean OTM, for the six bladder cancer cell lines, over a dose range of 0–6 Gy, as determined by ACA. For (A and B) each data point is the mean of three independent experiments±s.e. (C) The relationship between the measures of mean OTM for initial comet formation, as measured by ACA, and the measures of clonogenic cell survival, for all six bladder cancer cell lines at 0, 2, 4 and 6 Gy. The data are fitted with an exponential trend line and the slope and correlation coefficient are deduced.

Figure 2

Figure 2

(A) The extent of damage repair as determined by ACA, after irradiation with 2.5 Gy of X-rays. Each data point is the mean or three independent experiments±s.e. The dashed line represents the mean ‘background’ level for unirradiated/control cells. (B and C) The correlation between the measures of residual damage at (B) 15 and (C) 30 min, as determined by ACA, and the determined SF2 values for the five cell lines J82, RT112, UM-UC-3, HT1376 and RT4. Data points for T24 (open grey triangles) were excluded from the analysis.

Figure 3

Figure 3

Extent of initial comet formation, as measured by mean OTM, for epithelial cells prepared from invasive bladder tumour biopsies, over a dose range of 0–6 Gy, as determined by ACA. Each data point is the mean of duplicate or triplicate irradiations±s.e. Also shown is the extent of initial comet formation for the bladder cancer cell lines J82 and RT4.

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