[Study on expression of natural killer (NK) cell C-type lectin-like receptors in nasal NK/T-cell lymphomas]

To investigate the expression and possible role of C-type lectin-like natural killer cell receptors, including CD94 and NKG2s, in extranodal NK/T-cell lymphoma, nasal type (EN-NK/T-NT).

Reverse transcriptase polymerase chain reaction (RT-PCR) was used to detect the expression of CD94 and NKG2s in tissue sections of 21 cases of EN-NK/T-NT(confirmed by histology, immunohistochemistry, in-situ hybridization for Epstein-Barr virus(EBV) and PCR for T-cell receptor genes), eight midline B cell lymphomas (BCL), 10 peripheral T cell lymphoma of lymph nodes (PTCL), five spleens, five thymuses and five chronic nasopharyngitis.

All 21 cases of EN-NK/T-NT showed typical histological features, with expression of CD3epsilon, CD56, cytotoxic granules and positivity of EBV in 20 cases. The RT-PCR results showed a high level expression of CD94 (85.7%) and NKG2 members (95.2% totally, with NKG2A/2B in 85.7%, NKG2D in 61.9%, NKG2F in 14.3%, NKG2C/2E in 4.8%, respectively and sequentially) in EN-NK/T-NT. But in the controls, none of the receptors were detected in TCL (0%) and BCL (0%), while only a few cases of lymphoid tissues expressed one or two of these receptors (two spleens and two chronic nasopharyngitis mucosa for CD94, one spleen for NKG2A/2B and one thymus for NKG2D). The differences of CD94 and NKG2 expression between EN-NK/T-NT and BCL or TCL were statistically significant (P<0.01). Co-expression of CD94 and NKG2 was found in 17 out of 21 EN-NK/T-NT cases (81.0%).

The specific and sequential expression nature of CD94 and NKG2 in EN-NK/T-NT, mimics the developmental expression model in their normal counterparts, and suggests that the tumor cells of most cases are being activated and keeping in a stage as the functional NK cells. Detection of these molecules may provide a useful tool to confirm the diagnosis of NK cell lymphoma.