ATM protein overexpression in prostate tumors: possible role in telomere maintenance

It has been postulated that telomere dysfunction and telomerase activation have important roles in prostate tumorigenesis. Since the ataxia-telangiectasia mutated gene product (ATM protein) is involved in maintaining telomere length and integrity, we hypothesized that its expression might be altered in prostate tumors and, thus, examined its profile in 49 tumor samples. The majority (32/49) had ATM protein levels higher than those observed in normal tissues, with only 5 of 49 tissue samples showing reduced or absent ATM levels. Three of these were from the group of 6 young-onset or sibling-pair tumors. There was a trend toward higher ATM expression in tumors with a higher Gleason score (23/32 [72%] for grade 8-10 vs 9/17 [53%] for grades 5-7), although this difference was not statistically significant. These findings support our hypothesis that the presence of the ATM protein at the same or a higher level than that in normal prostate cells might have an important role in the maintenance of the shortened telomeres commonly found in prostate cancer cells.