Glutathione-S-Transferase π Expression Helps for Differential Diagnosis between Mantle Cell Lymphoma and Marginal Zone Lymphoma with t(11;14).

Glutathione-S-transferase π (GSTπ), whose gene is located in 11q13, is belonging to a complex multigene family of enzymes that may detoxify electrophilic xenobiotics. Recent gene expression profiling analysis showed that GSTπ transcript is belonging to the mantle cell lymphoma (MCL) signature and constitutes one of the most expressed mRNA in MCL^*. Furthermore it has been reported by immunohistochemistry that overexpression of cyclin D1 in MCL was associated with a high level of GSTπ protein expression. We then looked for the specificity of a high level of GSTπ protein expression in MCL, and particularly when comparing to marginal zone lymphoma (MZL) with t(11;14). Material and Methods: Immunochemistry analysis of GSTπ and cyclinD1 expression was performed 111 non Hodgkin’s lymphoma including MCL, MZL, small lymphocytic lymphoma (SLL), follicular lymphoma (FL), and diffuse large B-cell lymphoma (DLBCL) cases with or without t(11;14). Results: A strong GSTπ expression in more than 50% of the cells was observed in 98% of the MCL. None of the MZL cases with t(11;14) expressed GSTπ, except one case that expressed a weak signal in less than 20% of the cells. None of the MZL without t(11;14) expressed GSTpi. Only two (13%) FL graded 3 according to OMS classification expressed GSTπ in less than 50% of the cells. A high GSTπ expression (>50% cells stained) was detected in 29% of the DLBCL and 43% of the SLL.

In conclusion, 98% of the MCL with t(11;14) expressed high level of GSTπ whereas none of our MZL with t(11;14) and high transcriptional cyclinD1 expression expressed GSTπ. This results may help for differential diagnosis between MCL and MZL with t(11;14) and suggest different transcriptional regulation of GSTπ in lymphoma subtypes with t(11;14), contributing possibly to the chemoresistant phenotype of MCL. Finally, this confirmed our previous work on MZL with t(11;14).