Amplification and specific expression of T-bet gene in nasal NK/T-cell lymphoma

To define the specific genetic alterations in nasal natural killer/T-cell lymphoma (N-NK/T-L), the assay of restriction landmark genomic scanning (RLGS), a genome-wide method, was used to investigate a pair of genomic DNA from N-NK/T-L cells and peripheral blood leukocytes of the same patient. The intensified spots in displayed N-NK/T-L gel of RLGS were subjected to bioinformatic analysis by virtual genome scan (VGS) and one of candidate spots proved to be T-bet gene (T-box expressed in T-cell). The pair of samples was consequently analysed by Southern hybridization, revealing genomic amplification of T-bet but not different status of DNA methylation. The amplification of T-bet was also discovered in other cases of N-NK/T-L by dot blotting. The expression of T-bet was investigated by in situ hybridization (ISH) and immunohistochemistry (IHC). The results showed that T-bet predominantly expressed in N-NK/T-L (ISH: 90.0%, 18/20; IHC: 80%, 16/20), while few cases of B-cell lymphoma (ISH: 11.8%, 2/17; IHC: 17.6%, 3/17) or T-cell lymphoma (ISH: 33.3%, 2/6; IHC: 16.7%, 1/6) were positive. The difference of T-bet expression in either ISH or IHC between N-NK/T-L and B-cell lymphoma or T-cell lymphoma was statistically significant (P < 0.05). Moreover, the expression of T-bet was not detected in normal spleen tissue and chronic inflammatory nasal mucosa. The results suggested that the amplification of T-bet gene or resulting its over-expression of T-bet gene might be involved in the development of N-NK/T-L and thus it should be worth confirming whether the over-expression of T-bet be helpful to the diagnosis of N-NK/T-L in further study.