Pb2397: transcriptome analysis of diffuse large b-cell lymphoma cells expressing myd88 l265p reveals cd44, lgals3, nfkbiz and batf as downstream targets of oncogenic nf-κb signaling.

Topic: 20. Lymphoma Biology & Translational Research Background: Myeloid differentiation primary response 88 (MyD88) serves as a crucial signaling adaptor protein during innate immune responses, integrating stimuli from the Toll-like receptors (TLR) and Interleukin-1 receptor (IL-1R) family and translating them into specific cellular outcomes. In B cells, somatic mutations of MyD88 induce oncogenic NF-κB signaling independently of receptor stimulation, resulting in the onset of B-cell malignancies. However, the precise molecular mechanisms and downstream signaling targets remain unresolved. Aims: This study aims to investigate the impact of MyD88L265P oncogenic signaling on lymphoma cells by analyzing the transcriptomic response of model cell lines. Specifically, we aim to identify the downstream targets of MyD88L265P signaling that are either upregulated or downregulated and may play a role in cellular transformation. Methods: Our study utilized an inducible expression system to introduce MyD88 into lymphoma cell lines acutely. We performed transcriptomic analysis (RNA-seq) to identify genes differentially expressed due to the MyD88 L265P oncogenic mutation. To validate the RNA-seq hits, we employed additional experimental techniques such as qPCR, flow cytometry, and immunoblotting. Furthermore, we conducted database searches to support our findings and strengthen the relevance of the identified targets in the context of cellular transformation. Results: We show that MyD88L265P activates the NF-κB signaling pathway and upregulates genes that might contribute to lymphomagenesis, including membrane receptors CD44 and LGALS3 (coding Galectin-3), and transcription factors NFKBIZ (coding IkBƺ) and BATF. Moreover, we demonstrate that CD44 can serve as a novel biomarker of the activated B cell (ABC) subtype of diffuse large B cell lymphoma (DLBCL). Finally, we show that CD44 expression negatively correlates with overall survival in DLBCL patients using publicly available datasets. Summary/Conclusion: Our results shed new light on downstream outcomes of MyD88L265P oncogenic signaling that might be involved in cellular transformation, thus providing novel biomarkers and potential therapeutical targets.Keywords: Signaling, CD44, Oncogene, DLBCL