P53 INDUCTION AS A PREDICTOR OF RADIATION COMPLICATIONS

The ability to predict the response of normal tissues to a given course of radiation might allow a clinician to anticipate and avoid undue toxicity. Recent studies have demonstrated that the intrinsic radiosensitivity of skin fibroblasts from individual patients is predictive of the severity of acute and late radiation reactions experienced by these patients. While radiosensitivity assays are cumbersome, newer techniques which measure DNA double strand breaks (dsb) or the level of p53 induction (a central molecule involved in radiation-induced apoptosis) following irradiation may prove to be useful as predictive assays. The primary goal of this project will be to assess whether these assays performed on skin fibroblasts obtained form patients treated with radiation are predictive for acute or late skin reactions. Early passage fibroblast cell lines will be established from 26 breast cancer patients exhibiting severe skin reactions and from case-matched controls treated on a prospective radiation fractionation trial at the Royal Marsden Hospital. DNA dsb will be measured with pulse-field gel electrophoresis or single- cell gel electrophoresis. The levels of p53 and WAF1 (a downstream effector of p53) induction will be measured by various methods including Western blotting, enzyme linked immunosorbent assay, electrophoretic mobility shift assay and Northern blotting. We hypothesize that the level of DNA dsb induction following in vitro irradiation of skin fibroblasts should correlate with p53 induction, and that higher levels of p53 and DNA dsb induciton may predict for more severe acute or late normal tissue reactions in patients. The ability to accurately predict the severity of radiation reactions can potentially aid the clinician in planning a course of radiotherapy.