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Abstract

Diffuse large B cell lymphoma (DLBCL) and classic Hodgkin lymphoma (cHL) are two distinct lymphoma entities characterized by vastly different tumour microenvironments. Recurrent mutations in oncogenic signaling pathways, such as NF-κB and JAK-STAT, play key roles in driving the pathogenesis and shaping the microenvironments of these lymphomas. In this thesis, I describe the discovery and functional characterization of somatic loss of the NF-κB regulator TRAF3, and truncating mutations of the cytokine receptor IL4R. Focal deletions of TRAF3 were found in 24/324 DLBCL cases (~7.4%) by high-resolution SNP arrays. CRISPR-mediated knockout of TRAF3 in DLBCL-derived cell lines culminated in constitutive non-canonical (NC) NF-κB pathway activation, rendering these cells sensitive to knockdown or pharmacological inhibition of the central NC NF-κB kinase NIK. TRAF3 ablation further led to exacerbated secretion of the immunosuppressive cytokine IL-10, which impaired induction of Granzyme B and IFNγ of co-cultured CD8+ T cells and restored upon neutralization of IL-10. Additionally, in collaboration, genomic profiling of cHL by deep sequencing of liquid biopsy-derived cell-free DNA identified a novel class of recurrent frameshifting mutations predicted to truncate the IL4R protein in approximately 10% of cHL patients. These mutations clustered around the cytoplasmic tail of the receptor, wherein the immunoreceptor tyrosine-based inhibitor motif (ITIM) resides. HL cells engineered with IL4R truncating mutations exhibited IL-13-dependent upregulation of STAT6 transcription factor phosphorylation and CCL17 chemokine secretion compared to wildtype (WT) controls, which were fully reversible with surface receptor-targeting IL4R neutralizing antibodies. Taken together, our results suggest TRAF3 and IL4R mutations as novel drivers of NC NF-κB and JAK-STAT signaling in DLBCL and cHL, respectively. We further provide proof-of-concept evidence for the targetability of these oncogenic signaling pathways with implications for future therapeutic strategies.