IRF4 drives clonal evolution and lineage choice in a zebrafish model of T-cell lymphoma

IRF4 is a master regulator of immunity and is also frequently overexpressed in mature lymphoid neoplasms. Here, we demonstrate the oncogenicity of IRF4 in vivo, its potential effects on T-cell development and clonal evolution using a zebrafish model. IRF4-transgenic zebrafish develop aggressive tumors with massive infiltration of abnormal lymphocytes that spread to distal organs. Many late-stage tumors are mono- or oligoclonal, and tumor cells can expand in recipient animals after transplantation, demonstrating their malignancy. Mutation of p53 accelerates tumor onset, increases penetrance, and results in tumor heterogeneity. Surprisingly, single-cell RNA-sequencing reveals that the majority of tumor cells are double-negative T-cells, many of which express tcr-gamma that became dominant as the tumors progress, whereas double-positive T-cells are largely diminished. Gene expression and epigenetic profiling demonstrates that gata3, mycb, lrrn1, patl1 and psip1 are specifically activated in tumors, while genes responsible for T-cell differentiation including id3 are repressed. IRF4-driven tumors are sensitive to the BRD inhibitor. IRF4 is a regulator of immune function, and is overexpressed in lymphoid neoplasms. Here, the authors utilise single cell RNA-seq to show the abundance of double-negative T cells in IRF4 driven zebrafish tumour models, and identify sensitivity of these tumours to BRD inhibition.

Automated summary

This study demonstrates the oncogenicity of IRF4 in zebrafish models and its potential effects on T-cell development and clonal evolution. The majority of IRF4-driven tumors are composed of double-negative T cells and show sensitivity to a BRD inhibitor.