Activating mutations and translocations in the guanine exchange factor VAV1 in peripheral T-cell lymphomas

Significance Guanine nucleotide exchange factor VAV1 encodes an adaptor and signal transduction factor with important roles in T-cell receptor signaling. This study identifies activating VAV1 recurrent mutations and VAV1 fusions in peripheral T-cell lymphomas, directly establishing an oncogenic role for constitutive VAV1 signaling in the pathogenesis of this disease. Peripheral T-cell lymphomas (PTCLs) are a heterogeneous group of non-Hodgkin lymphomas frequently associated with poor prognosis and for which genetic mechanisms of transformation remain incompletely understood. Using RNA sequencing and targeted sequencing, here we identify a recurrent in-frame deletion (VAV1 Δ778–786) generated by a focal deletion-driven alternative splicing mechanism as well as novel VAV1 gene fusions (VAV1-THAP4, VAV1-MYO1F, and VAV1-S100A7) in PTCL. Mechanistically these genetic lesions result in increased activation of VAV1 catalytic-dependent (MAPK, JNK) and non–catalytic-dependent (nuclear factor of activated T cells, NFAT) VAV1 effector pathways. These results support a driver oncogenic role for VAV1 signaling in the pathogenesis of PTCL.