Severe normal tissue complication correlates with increased in vitro fibroblast radiosensitivity in radical prostate radiotherapy: A case report

DNA strand breaks and hypoxia response inhibition mediate the radiosensitisation effect of nitric oxide donors on prostate cancer under varying oxygen conditions

Prostate cancer cells can exist in a hypoxic microenvironment, causing radioresistance. Nitric oxide (NO) is a radiosensitiser of mammalian cells. NO-NSAIDs are a potential means of delivering NO to prostate cancer cells. This study aimed to determine the effect and mechanism of action of NO-sulindac and radiation, on prostate cancer cells and stroma, under normoxia (21% oxygen) and chronic hypoxia (0.2% oxygen). Using clonogenic assays, at a surviving fraction of 10% the sensitisation enhancement ratios of radiation plus NO-sulindac over radiation alone on PC-3 cells were 1.22 and 1.42 under normoxia and hypoxia, respectively. 3D culture of PC-3 cells revealed significantly reduced sphere diameter in irradiated spheres treated with NO-sulindac. Neither NO-sulindac nor sulindac radiosensitised prostate stromal cells under normoxia or hypoxia. HIF-1α protein levels were reduced by NO-sulindac exposure and radiation at 21 and 0.2% oxygen. Alkaline Comet assay analysis suggested an increased rate of single strand DNA breaks and slower repair of these lesions in PC-3 cells treated with NO-sulindac prior to irradiation. There was a higher level of γ-H2AX production and hence double strand DNA breaks following irradiation of NO-sulindac treated PC-3 cells. At all radiation doses and oxygen levels tested, treatment of 2D and 3D cultures of PC-3 cells with NO-sulindac prior to irradiation radiosensitised PC-3, with minimal effect on stromal cells. Hypoxia response inhibition and increased DNA double strand breaks are potential mechanisms of action. Neoadjuvent and concurrent use of NO-NSAIDs have the potential to improve radiotherapy treatment of prostate cancer under normoxia and hypoxia.

Adaptive responses in human glioma cells assessed by clonogenic survival and DNA strand break analysis

PURPOSE

Human gliomas are known to be radioresistant and the aim was to determine if this resistance in part could be due to an adaptive response.

MATERIALS AND METHODS

Human U-87MG glioma cells were used. Three different radiation regimens that could be related to clinical treatments were tested for their ability to cause an adaptive response. Cell survival and DNA double-strand breakage were the measured endpoints.

RESULTS

All three regimens caused an adaptive response in terms of cell survival when given priming doses of radiation. The DNA double-strand break endpoint also showed fewer breaks when the adaptive response occurred.

CONCLUSIONS

Using irradiation regimens that closely resembled clinical applications, in vitro data are presented that show an adaptive response in human glioma cells. This effect in part could be responsible for the radioresistance of human gliomas.

Skin fibroblasts in vitro radiosensitivity can predict for late complications following AVM radiosurgery

BACKGROUND AND PURPOSE

A small proportion of patients undergoing radiotherapy display heightened normal tissue reactions. We have set out to determine whether this sensitivity is genetic in nature and can be assessed using an in vitro skin fibroblast assay in order to predict and avoid excessive normal tissue complications.

PATIENTS AND METHODS

In this study we compared five arteriovenous malformation (AVM) patients who were treated with radiotherapy and showed severe normal tissue reactions (necrosis) to two AVM patients who showed normal reactions. Fibroblasts taken from patients were cultured in vitro and irradiated.

RESULTS

The results showed that the fibroblasts from the sensitive patients were also more radiosensitive in vitro than the cells from the normally responding patients.

CONCLUSIONS

The results suggest underlying genetic radiosensitivity and that such an assay may be used for prediction of severe radiosensitivity in AVM patients.