Lack of inverse dose-rate effect and binding of the @entity995 gene product in the nucleus of XXXX cancer T-47D cells arrested in G2 by ionizing radiation.

@entity1 @entity0 @entity2455 @entity996 @entity995
PURPOSE: To investigate the radiosensitivity of @entity1 @entity0 cells, T-47D, irradiated with low dose-rates and to study activation of the @entity995 gene product in the G1 and G2 phases during irradiation. MATERIALS AND METHODS: Cells were irradiated with (60)Co gamma-rays with dose-rates of 0.37 and 0.94 Gy h(-1). Cell survival was measured as the ability of cells to form colonies. Cells were extracted, fixed and stained for simultaneous measurements of nuclear-bound @entity996 content and DNA content. Cell nuclei were stained with monoclonal antibody PMG3-245 and @entity2455 was used for additional staining of DNA. Two-parametric flow cytometry measurements of @entity996 and DNA content were performed using a FACSTAR(PLUS) flow cytometer. RESULTS: It was observed that irradiated cells were arrested in G2. No increase in radiation sensitivity was observed when the cells accumulated in G2. Irradiation of cells at both 0.37 and 0.94 Gy h(-1) resulted in exponential dose-survival curves with nearly equal alpha values, i.e. the same radiosensitivity. However, the @entity995 gene product was bound in the nucleus, i.e. hypophosphorylated, in about 15% of the cells arrested in G2. CONCLUSIONS: T47-D cells accumulate in G2 during low dose irradiation, but no inverse dose-rate effect, i.e. a more efficient inactivation of cells at lower than at higher dose-rates, was observed. A population of arrested G2 cells has @entity996 protein bound in the nucleus, and @entity996 therefore could play a role in protecting cells against radiation-induced cell death in G2.
