Absence of Mutations of the Histone Methyltransferase Gene EZH2 In Splenic B-Cell Marginal Zone Lymphoma

Splenic marginal zone lymphoma (SMZL) is a rare low-grade B-cell lymphoproliferative disorder with characteristic clinical, cytological, histological and immunophenotypical features. The most common cytogenetic abnormality, present in 30–40% of the patients is the 7q deletion, that extends from 7q21 to 7q36. This aberration may represent a primary pathogenic event in SMZL. Recently, mutations in the EZH2 gene, located at 7q36.1, have been described in different hematological malignancies including B-cell lymphomas. However, the role of the EZH2 gene in SMZL has to be elucidated.

To determine the prevalence of EZH2 mutations in a cohort of SMZL patients.

Twenty-nine patients with SMZL were screened for mutations in the EZH2 gene. From the whole cohort, 11 patients presented 7q deletion (three of them as a single anomaly), 11 had a normal karyotype and 7 had other cytogenetic aberrations. The mutational analysis of the EZH2 gene was performed by direct sequencing using primers covering the whole exome of the gene. DNA was extracted from CD19 isolated B-cells from peripheral blood or from total lymphocytes if the percentage of pathologic B-cell was higher than 50%.

From the whole cohort of 29 SMZL patients, no pathogenic mutations (frameshift or nonsense mutations) were detected in the EZH2 gene in any of the patients analyzed. Five patients harboured the missense mutation D185H in exon 6, that has been previously described as a single nucleotide polymorphism (SNP).

In conclusion, the EZH2 gene is not mutated in our series of SMZL patients suggesting that this gene is not involved in the pathogeny of this entity.

Fellowship FI2008 (AGAUR) to LMA, This work was supported (in part) by grants from Instituto de Salud Carlos III FEDER; Red Temática de Investigación Cooperativa en Cáncer (RTICC, FEDER): RD06/0020/0031 and RD07/0020/2004; Ministerio de Sanidad y Consumo (Spain): PI07/0586.

No relevant conflicts of interest to declare.