The IL32/BAFF axis supports prosurvival dialogs in the lymphoma ecosystem and is disrupted by NIK inhibition

Aggressive B-cell malignancies, such as mantle cell lymphoma (MCL), are microenvironment-dependent tumors and a better understanding of the dialogs occurring in lymphoma-protective ecosystems will provide new perspectives to in-crease treatment efficiency. To identify novel molecular regulations, we performed a transcriptomic analysis based on the comparison of circulating MCL cells (n=77) versus MCL lymph nodes (n=107) together with RNA sequencing of malignant (n=8) versus normal B-cell (n=6) samples. This integrated analysis led to the discovery of microenvironment-dependent and tumor-specific secretion of interleukin-32 beta (IL3213), whose expression was confirmed in situ within MCL lymph nodes by multiplex immunohistochemistry. Using ex vivo models of primary MCL cells (n=23), we demonstrated that, through the secretion of IL3213, the tumor was able to polarize monocytes into specific MCL-associated macrophages, which in turn favor tumor survival. We highlighted that while IL3213-stimulated macrophages secreted several protumoral factors, they supported tumor survival through a soluble dialog, mostly driven by BAFF. Finally, we demonstrated the ef-ficacy of selective NIK/alternative-NF kappa B inhibition to counteract microenvironment-dependent induction of IL3213 and BAFF-dependent survival of MCL cells. These data uncovered the IL3213/BAFF axis as a previously undescribed pathway involved in lymphoma-associated macrophage polarization and tumor survival, which could be counteracted through se-lective NIK inhibition.