Gene-expression profiling of a polyostotic-DLBCL and primary bone-DLBCL cohort compared to a nodal DLBCL GCB.

This study performed an in-depth investigation of the immune-molecular profiles of an unique cohort of extranodal diffuse large B-cell lymphoma (DLBCL) of the bone, with single primary bone (PB-)DLBCL and multiple localizations (polyostotic-DLBCL). A similar DLBCL cohort with nodal localizations only and germinal center B-cell (GCB) phenotype (nodal-DLBCL-GCB) was used as comparator. With comprehensive genomic mutational and gene gene-expression profiling (GEP), in total 103 DLBCLS were analyzed. Both molecular techniques revealed a shared mutational genomic and gene-expression transcriptomic profile for PB-DLBCL (n=51) and polyostotic-DLBCL (n=18), justifying a collective analysis as bone-DLBCL. Differential incidences of EZH2, IRF8, and HIST1H1E, and MYC mutations/rearrangements (p<0.05) confirmed the distinct oncogenic evolution of bone-DLBCL and nodal-DLBCL-GCB (n=34). Bone-DLBCL primarily exhibited an intermediate/rich immune TME GEP signature (p≤<0.005), based on published gene sets. Further unsupervised clustering identified two distinct groups, establishing a notable ‘immune-rich’ cluster dominated by bone-DLBCL (754%, p=0.0062). This immune-rich cluster demonstrated superior survival (p=≤0.0263) compared to the ‘immune-low’ cluster, which consisted mostly of nodal-DLBCL-GCB cases (61%). Gene-set enrichment analysis illustrated variations in cell proliferation and immune systemreceptor pathways for the immune-rich cluster (p<0.001), indicating a crucial role for the tumor microenvironment (TME) in disease behavior and outcome. Further supported by deconvolution applications (CIBERSORTx and single-sample gene-set enrichment analysis), The immune-rich cluster highlighted highlighting an abundantmainly regulatory T cells in immune-rich and cell proliferation in immune-low. infiltrate of NK/T, Treg, TFH and follicular dendritic cells (p<0.001). Conclusively, PB-DLBCL and polyostotic-DLBCL shared similar TME features and immune-molecular profiles. This study delineates tThe distinct immune-rich TME profile of bone-DLBCL, which is associated with a superior survival. These findings suggest that bone-DLBCL patients with immune-rich GEP might benefit from less intensive polychemotherapies and this could further shape targeted immunomodulatory strategies. The nanoString probeset (BLYM-777) consists out of 797 probes with 13 housekeeping genes. The probes were selected based on several published signatures important for B-cell lymphomas, indicative for survival, or marks different tumor microenvironment. The inclusion of selected signatures is discussed in the following review by de Groot et al. (PMID: 35454765) In total, 17 polyostotic-DLBCL (multiple osseous localizations), 42 primary bone DLBCL (one osseous localization with or without locoregional lymphodenopathy), and 34 nodal DLBCL with GCB-phenotype were collected for RNA isolation and consecutively analysis with the nanoString nCounter system and the BLYM-777 custom probeset.