Gene expression studies in radiation-sensitive cell lines

Background

Repair of damaged DNA is a highly regulated process in normal tissue. Several human genetic diseases are known to be or suspected to be due to defects in DNA repair or cell cycle control. Some of these patients are radiation sensitive and/or predisposed for cancer as a cause of mutations in genes involved in these cellular pathways. A well-known group of radiation-sensitive patients is the ataxia-telangiectasia (A-T) patients. This disease is caused by mutations in the ATM (A-T mutated) gene, whose gene product is involved in detecting double-strand breaks. In this study we are trying to reveal the cause of radiation sensitivity in a group of radiation-sensitive patients having an A-T phenotype without mutations in ATM.

Methods

Gene expression studies were conducted using 15 k cDNA (NRH) microarrays on lymphoblastoid cell lines obtained from four control individuals ('normal'), four A-T patients and 10 radiation-sensitive patients, before and after radiation. Cells were harvested prior to radiation (0 hours) and at 2 hours, 8 hours and 24 hours, respectively, after exposure to ionizing radiation. The cell lines were irradiated with a dose of 2.0 Gy. To be able to study possible similarities and differences in the expression patterns between the three groups of cell lines, we used cluster analyses.

Preliminary results

The preliminary results suggest that the radiation-sensitive patients constitute a heterogeneous group, and that the cause of their radiation sensitivity may be diverse. Conversely, several samples showed consistency in their gene expression patterns, which might reveal relevant genes and unknown pathways. To understand the biological context we need a broader base of comparison. Ongoing experiments include more samples in this study and will hopefully enable us to reveal the cause of the radiation sensitivity in these patients and bring us a step closer to the understanding of early malignancy development.