Detection of DNA damage in sonochemotherapy against cisplatin-resistant human ovarian cancer cells using the modified comet assay.

PURPOSE: To explore methodological modifications in the detection of DNA damage in sonochemotherapy for cisplatin-resistant human ovarian cancer cells using the comet assays.

MATERIALS AND

METHODS

Chemoresistant cells COC1/DDP were subjected to sonochemotherapy and DNA damage detected with the alkaline and neutral comet assays.

RESULTS

In the alkaline assay, the percentage of comets formed was less than that of dead cells, and most values for the percentage of comets formed were < 5% when using the default value to identify comets, showing an underestimation. These values were corrected when adjusting the threshold to the 95th percentile in control cells. In the neutral assay, this modification was not needed. Tail length (TL), tail moment (TM) and Olive tail moment (OTM) dramatically varied between comets. The 75th percentiles of TL, TM and OTM in the alkaline assay, and 90th percentiles in the neutral assay, correlated with the percentage of comets formed, thereby reflecting the temporal shift in DNA damage. Quantification of the interaction using the percentage of comets formed was consistent with that using the percentage of dead cells.

CONCLUSIONS

The percentage of comets formed can be used to assess DNA damage in sonochemotherapy against chemoresistant cells when adjusting the threshold.