Radiation induced molecular modulations in human breast adenocarcinoma cells after single (10Gy) and fractionated (2Gy x 5) dose irradiation.

Abstract

Abstract Abstract #5133 Background: Radiotherapy a recognized treatment modality for breast cancer patients is now considered mandatory for most patients undergoing conservative surgery and is considered appropriate for women at high risk of recurrence after mastectomy. However, relapse due to radio-resistance of cancer cells significantly affects the success of radiotherapy and cancer patient survival. Ascertaining the fractionated irradiation (FIR) modulated molecular targets is important to make tumors more susceptible to molecular targeted therapy. Accordingly, we investigated the (i) expression of 84 genes representing 6 functional pathways including Cell cycle and DNA damage repair, Apoptosis and cell senescence, Signal transduction and transcription, Adhesion, Invasion and metastasis and Angiogenesis; (ii) nuclear translocation and DNA-binding activity of NFκB and; (iii) expression of radio-responsive TNFα, IL-1α, pAKT, cIAP1, cIAP2 and survivin molecules after single dose (SDR) radiation and FIR protocols in human breast adenocarcinoma cells.
 Methods: MCF-7 cells exposed to either SDR (10Gy) or FIR (2Gy x 5 days) and harvested after 24h were analyzed for alterations in gene expression using real-time Q-PCR-profiling. NFκB-DNA binding activity was analyzed using electrophoretic mobility shift assay and pIκB levels was measured using immunoblotting. Relative changes in the expression patterns of TNFα, IL-1α, pAKT, cIAP1, cIAP2 and survivin were determined using Q-PCR analysis and immunoblotting.
 Results: Compared to the SDR, FIR treated cells showed an induced expression 61 (Cell cycle & DNA damage repair - 12, Apoptosis & cell senescence - 10, Signal transduction & transcription - 7, Adhesion - 8, Invasion & metastasis – 11 and Angiogenesis – 13) genes. Furthermore, we observed a relatively induced DNA binding activity of NFκB and phosphorylation of IκBα after FIR. Like-wise, we observed an induced expression of TNFα, IL-1α, pAKT, cIAP1, cIAP2 and survivin mRNA in cells exposed to FIR. The changes in these genes were confirmed at the protein level.
 Discussion: These results along with the differential gene expression pattern support our hypothesis that FIR can induce molecular targets. In this initial analysis, NFκB and known NFκB regulated radio-responsive genes were found to be modulated. Currently, we are in the process of identifying similar FIR-induced targets and evaluate their potential for selective drug-targeted manipulation. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 5133.