Radiosensitivity of human breast cancer cell lines expressing the breast tumor kinase (Brk)

Abstract

The breast tumor kinase (Brk) is over-expressed in 80% of all breast cancers and we sought to determine the influence of this oncogene on radiation sensitivity in breast cancer cell lines. Since radiotherapy is a routinely used method of treatment for early and intermediate stage breast cancer, the alteration of clinical radiosensitivity in breast cancer by an oncogene over-expression would have important implications in radiotherapy management. To address this question, we conducted an in vitro study of radiation sensitivity in two breast cancer cell lines, MDA-MB-157 and MDA-MB-468 transfected with cDNA constructs to over-express the following genes: Brk wild type (WT); Brk with an inactivating mutation in the kinase domain (KM) and vector only. Gamma H2AX foci assays by imaging flow cytometry were used to measure DNA double strand break (DSB) repair after radiation exposure. Total ataxia telangiectasia (ATM) and activated phospho794-ATM protein was measured by imaging flow cytometry. In all cell lines tested there was a proportionate decline in cell survival following gamma radiation exposure. Radiation sensitivity of the cell lines in clonogenic assays and repair of DNA double strand breaks were similar and independent of Brk expression status. We conclude that over-expression of the Brk proto-oncogene in breast cancer cell lines does not appear to influence radiation sensitivity or affect DNA DSB repair.