Browsing Clinical Oncology by Subjects
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Aberrant CDKN1A transcriptional response associates with abnormal sensitivity to radiation treatment.Normal tissue reactions to radiation therapy vary in severity among patients and cannot be accurately predicted, limiting treatment doses. The existence of heritable radiosensitivity syndromes suggests that normal tissue reaction severity is determined, at least in part, by genetic factors and these may be revealed by differences in gene expression. To test this hypothesis, peripheral blood lymphocyte cultures from 22 breast cancer patients with either minimal (11) or very severe acute skin reactions (11) have been used to analyse gene expression. Basal and post-irradiation expression of four radiation-responsive genes (CDKN1A, GADD45A, CCNB1, and BBC3) was determined by quantitative real-time PCR in T-cell cultures established from the two patient groups before radiotherapy. Relative expression levels of BBC3, CCNB1, and GADD45A 2 h following 2 Gy X-rays did not discriminate between groups. However, post-irradiation expression response was significantly reduced for CDKN1A (P<0.002) in severe reactors compared to normal. Prediction of reaction severity of approximately 91% of individuals sampled was achieved using this end point. Analysis of TP53 Arg72Pro and CDKN1A Ser31Arg single nucleotide polymorphisms did not show any significant association with reaction sensitivity. Although these results require confirmation and extension, this study demonstrates the possibility of predicting the severity of acute skin radiation toxicity in simple tests.
Lymphocyte telomere length correlates with in vitro radiosensitivity in breast cancer cases but is not predictive of acute normal tissue reactions to radiotherapy.PURPOSE: To examine the hypothesis that lymphocyte telomere length may be predictive of both breast cancer susceptibility and severity of acute reactions to radiotherapy. MATERIALS AND METHODS: Peripheral blood lymphocyte cultures from breast cancer patients (with normal or severe skin reactions to radiotherapy) and normal individuals were assessed for in vitro radiosensitivity as measured by apoptosis, cell cycle delay and cytotoxicity. Telomere lengths were determined by a flow cytometric fluorescence in situ hybridization assay (FLOW-FISH). RESULTS: Female breast cancer cases (n = 24) had reduced lymphocyte telomere lengths by comparison with healthy controls (n = 20, p < 0.04). However, the average age of healthy controls was less (45.4) than cases (53). When the control group was modified to give a better age match (51.5, n = 13) the reduced telomere length in cases was not significantly different from controls. Lymphocytes from breast cancer cases also showed reduced cell cycle delay (p < 0.001) and increased apoptosis (p < 0.01) following irradiation in vitro at 3 and 5 Gy respectively, compared to healthy controls. Statistical significance was maintained with the improved age matching of groups. Comparison of lymphocytes from breast cancer patients with normal (n = 11) and severe (n = 13) skin reactions to radiotherapy failed to identify differences in telomere length or cellular radiosensitivity in this limited sample. CONCLUSIONS: This study adds to the evidence suggesting a correlation between altered cellular radiosensitivity and breast cancer. However, in the cases investigated, telomere length does not appear to be predictive of acute skin reactions to radiotherapy.