Comet assay measures of DNA damage are predictive of bladder cancer cell treatment sensitivity in vitro and outcome in vivo

Abstract

Bladder cancer patients suffer significant treatment failure, including high rates of recurrence and poor outcomes for advanced disease. If mechanisms to improve tumour cell treatment sensitivity could be identified and/or if tumour response could be predicted, it should be possible to improve local-control and survival. Previously, we have shown that radiation-induced DNA damage, measured by alkaline Comet assay (ACA), correlates bladder cancer cell radiosensitivity in vitro. In this study we first show that modified-ACA measures of cisplatin and mitomycin-C-induced damage also correlate bladder cancer cell chemosensitivity in vitro, with essentially the same rank order for chemosensitivity as for radiosensitivity. Furthermore, ACA studies of radiation-induced damage in different cell-DNA substrates (nuclei, nucleoids and intact parent cells) suggest that it is a feature retained in the prepared nucleoids that is responsible for the relative damage sensitivity of bladder cancer cells, suggestive of differences in the organisation of DNA within resistant vs. sensitive cells. Second, we show that ACA analysis of biopsies from bladder tumours reveal that reduced DNA damage sensitivity associates with poorer treatment outcomes, notably that tumours with a reduced damage response show a significant association with local recurrence of non-invasive disease and that reduced damage response was a better predictor of recurrence than the presence of high-risk histology in this cohort. In conclusion, this study demonstrates that mechanisms governing treatment-induced DNA damage are both central to and predictive of bladder cancer cell treatment sensitivity and exemplifies a link between DNA damage resistance and both treatment response and tumour aggression.

New insight for metformin against bladder cancer

“…Mechanisms governing treatment-induced DNA damage are both central to and predictive of bladder cancer cell treatment sensitivity and exemplify a link between DNA damage resistance and both treatment response and tumour aggression [71]. On the other hand, study conducted by Camargo et al , indicated that no relationship was observed between the amount of DNA damage and the level of hMLH1 (a gene involved in the mismatch repair pathway) and RASSF1 (a tumor suppressor gene) in bladder cancer cells treated with cisplatin and gemcitabine.…”

Phase I study of LY2603618, a CHK1 inhibitor, in combination with gemcitabine in Japanese patients with solid tumors

“…Moreover, in bladder cancer, a link has been identified between both DNA damage resistance and tumor aggressiveness in response to treatment [36]. In this study, two of the three patients diagnosed with urinary tract cancer showed a PR and experienced durable disease control for 176 and 387 days.…”

Dynamic In Vivo Profiling of DNA Damage and Repair after Radiotherapy Using Canine Patients as a Model

“…DNA damage detection from patient samples has been performed for various tumor groups irradiated ex vivo, resulting in robust correlations with radio-responsiveness, as known from clinical behavior [2,5]. Furthermore, monitoring the responses towards damage formation and repair from individual tumors may offer a legitimate chance to monitor cancer treatment and even a possibility to predict clinical response to treatment [6,7]. This is thought to hold true even in spite of the high inter-tumoral and inter-patient heterogeneity that is to be expected from patient samples [6,7].…”

“…Furthermore, monitoring the responses towards damage formation and repair from individual tumors may offer a legitimate chance to monitor cancer treatment and even a possibility to predict clinical response to treatment [6,7]. This is thought to hold true even in spite of the high inter-tumoral and inter-patient heterogeneity that is to be expected from patient samples [6,7]. …”

“…While the time-courses in responses to different DNA damaging agents have been well characterized in cultured tumor cells in vitro, little is known about the time-course of DNA damage response in tumor and normal tissues sampled from individual tumor patients [2,5,6,8,9,10]. Specifically, actual time-courses from patients undergoing radiation therapy are lacking.…”