Differences between BCL2-break positive and negative follicular lymphoma unraveled by whole exome sequencing

Depending on disease stage follicular lymphoma (FL) lack the t(14;18) in ~15-~50% of cases. Nevertheless, most of these cases express BCL2.To elucidate mechanisms triggering BCL2-expression and promoting pathogenesis in t(14;18)-negative FL, exonic single nucleotide variant (SNV)-profiles of 28 t(14;18)-positive and 13 t(14;18)-negative FL were analysed, followed by the integration of copy-number changes, copy neutral LOH and published gene-expression data as well as the assessment of immunoglobulin N-glycosylation sites. Typical FL-mutations also affected t(14;18)-negative FL. Curated gene set/pathway-annotation of genes mutated in either t(14;18)-positive or t(14;18)-negative FL revealed a strong enrichment of same or similar gene sets but also a more prominent or exclusive enrichment of immune-response and N-glycosylation signatures in t(14;18)-negative FL. Mutated genes showed high BCL2-association in both subgroups. Among the genes mutated in t(14;18)-negative FL 555 were affected by copy-number alterations and/or copy-neutral LOH and 96 were differently expressed between t(14;18)-positive and t(14;18)-negative FL (P<0.01). N-glycosylation sites were detected considerably less frequently in t(14;18)-negative FL. These results suggest a diverse portfolio of genetic alterations that may induce or regulate BCL2-expression or promote pathogenesis of t(14;18)-negative FL as well as a less specific but increased crosstalk with the microenvironment that may compensate for the lack of N-glycosylation.Leukemia accepted article preview online, 21 August 2017. doi:10.1038/leu.2017.270.