Abstract 4640: Quantification of gamma-H2AX expression in whole blood culture as a risk predictor for renal cell carcinoma

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Purpose: Individual's susceptibility to DNA damage has been associated with increased risk of many cancers. The detection of gamma-H2AX (γH2AX) foci can serve as a sensitive marker for DNA double-strand breaks (DSB) induced by ionizing radiation or other genotoxic agents. Although the quantification of γH2AX foci has been widely investigated, its application in population studies to assess individual susceptibility to cancer has not been established. Here we developed a high throughput method to quantify γH2AX foci in whole blood culture using laser scanning cytometry. This immunofluorescence based assay enables easy, fast, sensitive, and inexpensive detection of DSB in different individuals. Materials and Methods: We included 93 subjects with previously untreated renal cell carcinoma (RCC) and 117 age, gender, and ethnicity matched controls. For each subject, we fluorescently labeled γH2AX signal in peripheral blood lymphocytes at baseline and 1.5 hour after exposure to gamma irradiation. The fluorescence signal was measured by laser scanning cytometry. At least 5000 cells were measured per sample. The γH2AX fluorescence signal was defined as the mean fluorescence signal in cells from each sample. The relative γH2AX expression was calculated as the ratio of γH2AX signal after gamma irradiation to that of the baseline. Results: The inductivity of γH2AX expression by gamma irradiation was significantly higher in cancer patients (1.39 ± 0.15) than in healthy controls (1.33 ± 0.15) (p < 0.005), especially in younger subjects and in white subjects. When subjects were categorized into γH2AX expression tertiles defined by the distribution of relative γH2AX expression in control subjects, a significant dose-effect relationship was observed between γH2AX level and risk of RCC. Compared to subjects in the lowest tertile of γH2AX expression, those in the middle and the highest tertiles exhibited increased risk of RCC with odd ratios (ORs) of of 1.49 (95% confidence intervals [CI], 0.65-3.41) and 2.42 (95% CI, 1.05-5.34), respectively (P for trend =0.026). The increased risk was more evident in ever-smokers, with the highest OR of 4.24 (95% CI, 1.17-15.23) (P for trend=0.029). Additionally, the induction of γH2AX expression by gamma radiation is significantly higher in female than in male individuals (p<0.01). Conclusions: The pilot case-control study suggests that γH2AX expression induced by gamma radiation is significantly associated with an increased risk of developing RCC. The simplicity, sensitivity, and reproducibility of this γH2AX detection assay enables its application in epidemiologic studies and gamma radiation induced γH2AX expression may become a valuable marker of renal cancer susceptibility. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4640. doi:10.1158/1538-7445.AM2011-4640