Recurrent mutations in epigenetic regulators, RHOA and FYN kinase in peripheral T cell lymphomas

Peripheral T-cell lymphomas (PTCLs) are a heterogeneous and poorly understood group of non Hodgkin lymphomas(1,2). Here we combined whole exome sequencing of 12 tumor-normal DNA pairs, RNAseq analysis and targeted deep sequencing to identify new genetic alterations in PTCL transformation. These analyses identified highly recurrent epigenetic factor mutations in TET2, DNMT3A and IDH2 as well as a new highly prevalent RHOA p.Gly17Val (NM_001664) mutation present in 22/35 (67%) of angioimmunoblastic T-cell lymphomas (AITL) and in 8/44 (18%) not otherwise specified PTCL (PTCL NOS) samples. Mechanistically, the RHOA Gly17Val protein interferes with RHOA signaling in biochemical and cellular assays, an effect potentially mediated by the sequestration of activated Guanine Exchange Factor (GEF) proteins. In addition, we describe new and recurrent, albeit less frequent, genetic defects including mutations in FYN, ATM, B2M and CD58 implicating SRC signaling, impaired DNA damage response and escape from immune surveillance mechanisms in the pathogenesis of PTCL.