The Mre11-Rad50-NBS1 complex plays an important role in telomere maintenance. Recently, it has been proposed that alterations in Mre11 function may be contributing factors in the development of some tumors. Moreover, mutations of Mre11 have been demonstrated to cause reduced Mre11 immunostaining.
To investigate Mre11 in atypical adenomatous hyperplasia (AAH) and nonmucinous bronchioloalveolar carcinoma (NMBAC), an issue not previously explored.
We examined (1) the expression of Mre11 protein in 27 AAHs (9 lesions interpreted as low-grade AAH and 18 as high-grade AAH) and 40 NMBACs (using immunohistochemistry) and (2) Mre11 mRNA expression in 1 high-grade AAH and 6 NMBACs (using reverse transcription polymerase chain reaction). For the analysis of immunoreactivity, the intensity and extent of staining were each scored from 0 to 3. These 2 scores were summed to give in each case a final score of 0 to 6.
Scores for Mre11 expression were 5.0 +/- 2.1 for low-grade AAH, 5.4 +/- 1.2 for high-grade AAH, and 5.5 +/- 0.9 for NMBAC, and there was no statistically significant difference among these 3 types of lesions. In the reverse transcription polymerase chain reaction for Mre11 mRNA, polymerase chain reaction products were detected in all samples.
On this basis, we suggest that the part played by Mre11 in telomere maintenance may not be important for the progression of the adenoma-carcinoma (AAH-NMBAC) sequence in the lung, although some role for it in carcinogenesis cannot be completely ruled out.