FYN-TRAF3IP2 activating fusion oncogene in peripheral T-cell lymphoma

FYN-TRAF3IP2 expression in hematopoietic progenitors induces T cell transformation in mice and cooperates with loss of the Tet2 tumor suppressor in PTCL development. To investigate the oncogenic activity of FYN-TRAF3IP2, we analyzed the lymphomagenic effects of expressing this gene fusion alone and in cooperation with loss of the Tet2 tumor suppressor gene in vivo. In these experiments, we first infected hematopoietic progenitors from CD4-specific tamoxifen-inducible Cre Tet2 conditional knockout mice (CD4 Cre-ERT2, Tet2fl/fl) with bicistronic retroviruses expressing wild type TRAF3IP2 and GFP, FYN-TRAF3IP2 and GFP, or GFP alone and injected these intravenously into isogenic recipients. Transplanted mice were then treated with vehicle only, to test the oncogenic effects of TRAF3IP2, FYN-TRAF3IP2 or GFP expression; or with tamoxifen, to evaluate the effects of TRAF3IP2, FYN-TRAF3IP2 or GFP expression in concert with genetic loss of Tet2 in CD4 T cells. In this setting, all animals transplanted with GFP-expressing progenitors remained lymphoma free at the end of follow up and one animal transplanted with wild type TRAF3IP2 GFP expressing cells developed a CD8+ T cell lymphoma. In contrast, 4/10 (40%) vehicle treated mice transplanted with FYN-TRAF3IP2-expressing cells and 5/10 (50%) tamoxifen treated mice transplanted with FYN-TRAF3IP2-expressing cells developed clonal CD4-restricted mature T cell lymphomas. To further analyze the lymphomagenic effect of the fusion gene, we performed transcriptomic profiling of FYN-TRAF3IP2-induced mouse CD4+ GFP+ PTCL tumor lymphocytes compared with normal mouse CD4+ T cells by RNAseq. We performed RNAseq on nine FYN-TRAF3IP2-induced mouse tumor samples of CD4+ GFP+ FACS-sorted lymphoma cells (six independent primary tumors and three independent secondary transplanted tumors) and three independent wild type normal mouse CD4+ T cell samples using Illumina HiSeq 4000. (average depth of 30 million, 150 base pair, paired-end reads per sample)