Yusuke Okuno

Epstein-Barr virus (EBV)+ nodal T- and NK-cell lymphoma (EBV+ nPTCL) is a peripheral T-cell lymphoma (PTCL) that presents as a primary nodal disease with T-cell phenotype and EBV harboring on tumor cells. To date, the genetic aspect of EBV+ nPTCL has not been fully investigated. In this study, whole-exome and/or genome sequencing was performed on 22 cases of EBV+ nPTCL. TET2 (68%) and DNMT3A (32%) were observed to be the most frequently mutated genes whose presence was associated with poor overall survival (p = 0.004). The RHOA p.Gly17Val mutation was identified in two patients who had TET2 and/or DNMT3A mutations. In four patients with TET2/DNMT3A alterations, blood cell-rich tissues (bone marrow [BM] or spleen) were available as paired normal samples. Three out of these four cases had at least one identical TET2/DNMT3A mutation in the BM or spleen. Additionally, the whole part of the EBV genome was sequenced and structural variations (SVs) were found frequent among the EBV genomes (63%). The most frequently identified type of SV was deletion. In one patient, four pieces of human chromosome 9, including PD-L1 were identified to be tandemly incorporated into the EBV genome. The 3'-untranslated region of PD-L1 was truncated, causing a high-level of PD-L1 protein expression. Overall, the frequent TET2 and DNMT3A mutations in EBV+ nPTCL seem to be closely associated with clonal hematopoiesis and, together with the EBV genome deletions, may contribute to the pathogenesis of this intractable lymphoma.