ALBERT

Description: The mutational landscape of grey zone lymphoma (GZL) has not yet been established and differences to related entities are largely unknown. Here, we studied coding sequence mutations of 50 EBV-negative GZL and 20 polymorphic EBV-positive DLBCL NOS (poly-EBV-L) in comparison to classical Hodgkin lymphoma (cHL), primary mediastinal large B cell lymphoma (PMBCL), and diffuse large B cell lymphoma (DLBCL). Exomes of 21 GZL and 7 poly-EBV-L cases along with paired normals were analyzed as a discovery cohort followed by targeted sequencing of 217 genes in an extension cohort of 29 GZL and 13 poly-EBV-L cases. GZL cases with thymic niche involvement (anterior mediastinal mass) displayed a mutation profile closely resembling cHL and PMBCL, with SOCS1 (45%), B2M (45%), TNFAIP3 (35%), GNA13 (35%), LRRN3 (32%) and NFKBIA (29%) being the most recurrently mutated genes. In contrast, GZL cases without thymic niche involvement (N=18) had a significantly distinct pattern, enriched in mutations related to apoptosis defects (TP53 (39%), BCL2 (28%), BIRC6 (22%)) and depleted in GNA13, XPO1or NFKB signaling pathway mutations (TNFAIP3, NFKBIE, IKBKB, NFKBIA). They also presented more BCL2/BCL6 rearrangements as opposed to thymic GZL. Poly-EBV-L cases presented a distinct mutational profile including STAT3 mutations and a significantly lower coding-mutation load in comparison to EBV-negative GZL. Our study highlights characteristic mutational patterns in GZL associated with presentation in the thymic niche suggesting a common cell of origin with disease evolution overlapping with related anterior mediastinal lymphomas.

Description: When the WHO defined high-grade B-cell lymphoma with MYC and BCL2 and/or BCL6 rearrangements (HGBL-DH/TH) as a clinical category, rearrangements were the only structural variant (SV) incorporated. An "atypical double-hit" entity has been proposed, encompassing tumors with concurrent MYC and BCL2 SVs other than co-occurring translocations - i.e. copy number variations (CNVs). While the identification of a gene expression signature (DHITsig) shared among tumors harboring MYC and BCL2 rearrangements (HGBL-DH/TH-BCL2) has confirmed a shared underlying biology, the biological implication of MYC and BCL2 CNVs requires further elucidation. We performed a comprehensive analysis of MYC and BCL2 SVs, as determined by fluorescent in situ hybridization (FISH), in a cohort of 802 de novo tumors with diffuse large B-cell lymphoma (DLBCL) morphology. While BCL2 CNVs were associated with increased expression, MYC CNVs were not. Furthermore, MYC and BCL2 CNVs, in the context of atypical double-hit, did not confer a similar gene expression profile as HGBL-DH/TH-BCL2. Finally, while MYC IHC has been proposed as a screening tool for FISH testing, two mechanisms were observed that uncoupled MYC rearrangement from IHC positivity. 1) low MYC mRNA expression and 2) false-negative immunohistochemistry (IHC) staining mediated by a single nucleotide polymorphism resulting in an asparagine to serine substitution at the 11th amino acid residue of MYC (MYC-N11S). Taken together, these results support the current exclusion of MYC and BCL2 CNVs from HGBL-DH/TH and highlight the ability of a molecular based classification system to identify tumors with shared biology that FISH and IHC fail to fully capture.

Description: Background: LAG3 is one of the immune check point receptors that are expressed on activated cytotoxic T-cells and regulatory T cells. Physiologically, T-cell proliferation and memory T-cell differentiation is negatively regulated by LAG3-MHC interaction. In cancer tissues, T-cells that are chronically exposed to tumor antigens might upregulate LAG3 and receive inhibitory stimuli to enter an exhaustion state limiting anti-tumor immune responses. Currently, clinical trials using double blockade of LAG3/PD1 are active in several solid tumours, but there are only a small number of clinical trials using LAG3 monoclonal antibodies in lymphoma. Recently, we published a characteristic LAG3+ T-cell population as a mediator of immune suppression in classical Hodgkin lymphoma (Aoki & Chong et al. Cancer Discovery 2020). However, the abundance and variability of LAG3 positive T-cell populations across a spectrum of B-cell lymphoma has not been well studied and it remains an open question if LAG3 expression is associated with treatment outcome under standard-of-care conditions. Methods: We performed a LAG3 immunohistochemical (IHC) screen in a large cohort of B-cell Non-Hodgkin lymphoma (diffuse large B-cell lymphoma (DLBCL); N=341, follicular lymphoma (FL); N=198 (grade 1-3A), transformed FL to aggressive lymphoma (tFL); N=120, mantle cell lymphoma (MCL); N=179, primary mediastinal large B-cell lymphoma (PMBCL); N=61) and classical Hodgkin lymphoma (HL; N=459) to assess LAG3 expression in the tumor microenvironment (TME). Moreover, we characterized LAG3+ T-cell populations using multi-color immmunohistochemistry (IHC) (LAG3, PD1, CD4, CD8, FOXP3, CD20) in various lymphoma subtypes. Clinical parameters including treatment outcome were correlated with the abundance of LAG3+ T-cell populations in the TME. Results: On average, HL (7%) and PMBCL (6%) showed higher LAG3+ cellular frequency than the other B-cell lymphoma subtypes studied (DLBCL and FL: 2%, MCL: 0.8%). Comparing the frequency of LAG3+ cells according to MHC class I/II status, DLBCL showed a significant correlation with MHC class I status, and LAG3 expression correlated with MHC class II status in HL. Next, we performed multi-color IHC to describe subtype-specific expression patterns of LAG3 in T cell subsets. LAG3+PD1- T-cells were predominantly found in HL and PMBCL with only rare LAG3+PD1+ cells in HL. The majority of LAG3+ T-cells co-expressed CD4 in HL, in contrast to CD8 in PMBCL. DLBCL showed a mixed population pattern with a 1:1 ratio of LAG3+PD1- and LAG3+PD1+ T-cells. In FL, the majority of LAG3+ T-cells were CD4+PD1+, suggesting a more exhausted TME phenotype in FL than in other lymphoma subtypes. Cellular distance analysis showed that LAG3+CD4+ T-cells were in close vicinity to CD20+ lymphoma cells in FL, while in DLBCL and PMBCL, the nearest neighbors of malignant cells were LAG3+CD8+. Triple-positive LAG3+PD1+CD8+ T-cells significantly correlated with high infiltrating M2 macrophage (Pearson's correlation test, P 〈 0.001) content and the ABC cell-of-origin subtype (Pearson's correlation test, P = 0.002) in DLBCL. The abundance of LAG3+CD8+PD1- cells correlated with a high FLIPI score (Pearson's correlation test, P = 0.033), disease specific survival (HR = 2.8, 95% CI = 1.3-5.9, P = 0.006), time to progression (HR = 2.8, 95% CI = 1.6-5.0, P = 0.001) and transformation (HR = 4.0, 95%CI = 1.7-9.6, P = 0.002) in FL treated with R-CVP (N = 135). Assessing LAG3 expression by single color IHC in FL (cut-off at 5%), patients with LAG3-positive samples showed significantly higher FL transformation rates (P = 0.023) and tFL samples showed higher abundance of LAG3+ cells than the corresponding primary pretreatment FL samples (primary FL: 1.5±1.7% vs. tFL: 4.2±3.8%, t-test, P = 0.01). The increased transformation risk was validated in an independent FL cohort treated with R-CHOP/CVP (N=97, HR = 6.2, 95% CI = 2.8-13.9, P 〈 0.001). Conclusion: The highest abundance of LAG3+ T-cells in the TME was found in HL and its related entity PMBCL. The differential outcome correlations and co-expression patterns in LAG3+ T cells across B-cell lymphoma subtypes indicate heterogeneity in TME composition and related pathogenic mechanisms. Our results suggest that LAG3 expression patterns will be important in the interpretation of ongoing studies and highlight populations that may benefit from LAG3 checkpoint inhibition. Disclosures Sehn: AstraZeneca: Consultancy, Honoraria; Genentech, Inc.: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria; Chugai: Consultancy, Honoraria; TG therapeutics: Consultancy, Honoraria; Verastem Oncology: Consultancy, Honoraria; Teva: Consultancy, Honoraria, Research Funding; Servier: Consultancy, Honoraria; F. Hoffmann-La Roche Ltd: Consultancy, Honoraria, Research Funding; MorphoSys: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Apobiologix: Consultancy, Honoraria; Seattle Genetics: Consultancy, Honoraria; Gilead: Consultancy, Honoraria; Kite: Consultancy, Honoraria; Merck: Consultancy, Honoraria; Lundbeck: Consultancy, Honoraria; Karyopharm: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; Acerta: Consultancy, Honoraria. Savage:Merck, BMS, Seattle Genetics, Gilead, AstraZeneca, AbbVie, Servier: Consultancy; BeiGene: Other: Steering Committee; Roche (institutional): Research Funding; Merck, BMS, Seattle Genetics, Gilead, AstraZeneca, AbbVie: Honoraria. Scott:Celgene: Consultancy; Abbvie: Consultancy; AstraZeneca: Consultancy; NIH: Consultancy, Other: Co-inventor on a patent related to the MCL35 assay filed at the National Institutes of Health, United States of America.; Roche/Genentech: Research Funding; NanoString: Patents & Royalties: Named inventor on a patent licensed to NanoString, Research Funding; Janssen: Consultancy, Research Funding. Steidl:Bayer: Consultancy; Juno Therapeutics: Consultancy; Roche: Consultancy; Seattle Genetics: Consultancy; Bristol-Myers Squibb: Research Funding; AbbVie: Consultancy; Curis Inc: Consultancy.

Description: Introduction: Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) is a transcription factor family that regulates gene expression programs contributing to inflammation and cell survival. NF-κB signaling occurs via two branches: classical and alternative, and is often enriched in somatic mutations of key pathway members in several lymphoid malignancies. Here, we reveal deregulation and constitutive activation of the alternative NF-κB pathway in a subset of DLBCL patients with recurrent genomic loss of the gene encoding tumor necrosis factor receptor-associated factor 3 (TRAF3), a regulator of the NF-κB signaling pathway. Methods and Results: To uncover novel driver mutations of DLBCL pathogenesis and tumor maintenance, we performed Affymetrix SNP6.0 copy number analysis on 347 de novo DLBCL samples from patients uniformly treated with rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone (R-CHOP). We observed frequent, focal genomic loss of chr:14q32.31-32 which included TRAF3 and RCOR1 (7%, 22/313) in the minimally deleted region and an enrichment of activated B-cell-like (ABC) subtype cases over germinal center B-cell-like (GCB) subtype cases, confirming previously published data (Chan et al, Blood 2014). RNAseq of these DLBCL samples revealed a significant reduction of TRAF3 mRNA in chr:14q32.31-32 deleted cases compared to copy number neutral cases (p=0.002). Next, we focused on characterizing the phenotypic consequences of TRAF3 loss in DLBCL. We used CRISPR/Cas9 gene editing to knock out TRAF3 in 2 GCB-DLBCL (DOHH2, OCI-LY1) and 2 ABC-DLBCL (HBL1, OCI-LY3) cell lines. We performed immunoblotting analysis of NF-κB pathway members on cell fractionated samples of TRAF3 knockout cells and found increased levels of the NF-κB inducing kinase NIK (a direct target of TRAF3-mediated ubiquitin-proteasome degradation) and a concomitant increased nuclear translocation of NF-κB transcription factor complex subunits RelB and p52. Proteasome blockade restored RelB cytoplasmic localization and reduced processed p52 protein in TRAF3 knockout GCB-DLBCL lines only, indicating other factors may contribute to alternative NF-κB activation in ABC-DLBCL. Moreover, classical NF-κB activation remained unaffected, highlighting the specific role of TRAF3 regulation on the alternative NF-κB pathway in DLBCL. Consistent with these findings, TRAF3 knockout cells exhibited NF-κB-dependent transcriptional upregulation by luciferase reporter activity and elevated pro-inflammatory cytokine production (IL-6, TNF-β) by Luminex and ELISA. To study transcriptome changes as a result of TRAF3 loss-of-function, we performed RNAseq and differential gene expression analysis on wildtype and TRAF3 knockout DLBCL cell lines as well as primary DLBCL samples (N=347). We found enrichment of NIK and NF-κB associated pathways in TRAF3 deficient DLBCL and uncovered additional enriched gene sets including those involved in cell cycle regulation, cell division and metabolism, suggesting a potential proliferative and survival advantage. Conclusion: Our findings link TRAF3 loss-of-function to clinical and gene expression phenotypes in DLBCL and highlight alternative NF-κB activation as a pathogenically important pathway in both GCB and ABC subtypes. Future studies will be directed towards comprehensive evaluation of NF-κB inhibitors for effective blockade of constitutive alternative NF-κB activation in DLBCL. Disclosures Scott: NIH: Consultancy, Other: Co-inventor on a patent related to the MCL35 assay filed at the National Institutes of Health, United States of America.; Roche/Genentech: Research Funding; Janssen: Consultancy, Research Funding; Abbvie: Consultancy; AstraZeneca: Consultancy; Celgene: Consultancy; NanoString: Patents & Royalties: Named inventor on a patent licensed to NanoString, Research Funding. Steidl:Roche: Consultancy; Bristol-Myers Squibb: Research Funding; Seattle Genetics: Consultancy; Curis Inc: Consultancy; Juno Therapeutics: Consultancy; Bayer: Consultancy; AbbVie: Consultancy.

Description: Background: With the goal of translating biological discovery into clinical actionability, deciphering crosstalk in the cellular ecosystem of the tumor microenvironment (TME) has emerged as a research focus. Although comparatively little is known about the immune biology of diffuse large B-cell lymphoma (DLBCL), as reflected in clonal selection of specific somatic gene mutations in response to immune system pressure and the specific composition of the TME, PRAME has emerged as a prominent member of the cancer germline antigen/ tumor associated antigen (TAA) family of proteins. It is expressed in various types of cancers, but generally not in normal tissues, apart from male germinal cells, and triggers autologous T-cell mediated immune responses. PRAME is highlighted as a new cancer therapeutic target of T-cell or antibody-based immunotherapies with promising anti-tumor responses in early phase clinical trials and pre-clinical models for several types of cancers. In the context of developing new immunotherapies, targeting TAAs that are presented by major histocompatibility complexes on tumor cells is a promising therapeutic strategy for patients that experience treatment failure. Material and methods: We performed integrative genomic analysis of whole-transcriptome RNAseq, targeted genomic sequencing, and high-resolution copy number analysis in 347 de novo DLBCL tumors from patients uniformly treated with R-CHOP. Findings were correlated with pathological and clinical parameters, as well as TME composition. Using DLBCL-derived cell lines (7 EZH2 mutated and 5 wt) and CRISPR-Cas9 genome editing, we performed in vitro functional studies to characterize cell-intrinsic effects of PRAME knockout. Moreover, we studied EZH2 inhibition in a murine model of Ezh2 mutant lymphoma with a focus on mechanistic links between EZH2 activity and PRAME expression, as well as TME composition (cell-extrinsic effects). Results: We discovered recurrent, and highly focal deletions of 22q11.22 including the PRAME gene, which were associated with poor treatment outcome, independent of pathological and clinical risk factors. To explore PRAME-deletion-associated phenotypes and interaction with the tumor microenvironment (TME), we analyzed corresponding RNAseq, immunohistochemistry (IHC), and flow-cytometry data from our DLBCL cohort and utilized enzyme-linked immunospot (ELISPOT) assays using patient-derived peripheral blood mononuclear cells. PRAME deletions contributed to an immunologically "cold" TME, representing a somatically acquired mechanism to evade anti-tumor T-cell response (cell-extrinsic effect). Using PRAME knock out by CRISPR-Cas9 in vitro, TRAIL-mediated apoptotic signaling was impaired. In addition, PRAME down-modulation was strongly associated with somatic EZH2 Y641 mutations in DLBCL. Using proximity ligation assays and co-IP, we demonstrated that PRAME directly interacted with EZH2 as a negative regulator, establishing a link between PRAME deletions and EZH2 mutations with anti-apoptotic signaling in DLBCL (cell-intrinsic effect). An in vivo murine model of Ezh2 mutant lymphoma showed decreased T-cell infiltration in the TME and Ezh2 inhibition induced PRAME restoration as compared to vehicle controls. IHC for CD3, CD4, FOXP3, and GZMB revealed significant increases in various T-cell populations of the TME, including Tregs and cytotoxic T cells. EZH2 inhibition with EPZ-6438 abrogated these dualistic effects leading to increased immune cell infiltration in the tumor microenvironment and acceleration of apoptosis via PRAME restoration. Moreover, restoration of PRAME antigen presentation by EZH2 inhibition resulted in enhancement of PRAME binding using a T-cell receptor mimic PRAME antibody (Pr20), suggesting immunotherapeutic potential. Conclusion: Our findings highlight multiple functions of PRAME during lymphomagenesis. PRAME restoration by EZH2 inhibition provides a preclinical rationale for synergistic therapies combining epigenetic re-programming with PRAME-targeted therapies. Disclosures Dao: Eureka Therapeutics: Consultancy. Melnick:Jubilant: Consultancy; Epizyme: Consultancy; Constellation: Consultancy; Janssen: Research Funding; Daiichi Sankyo: Research Funding. Scheinberg:Lantheus: Current equity holder in private company; Eureka Therapeutics: Consultancy, Current equity holder in private company, Patents & Royalties: Eureka Therapuetics and MSKCC have filed patent on this ScFV and TCRm; Actinium: Consultancy, Current equity holder in private company; Contrafect: Current equity holder in private company; Sapience: Consultancy, Current equity holder in private company; Iovance: Current equity holder in private company; Enscyse: Current equity holder in private company; Arvenas: Current equity holder in private company; Pfizer: Consultancy, Current equity holder in private company; Sellas: Consultancy, Current equity holder in private company; Oncopep: Consultancy. Scott:Janssen: Consultancy, Research Funding; Abbvie: Consultancy; AstraZeneca: Consultancy; NIH: Consultancy, Other: Co-inventor on a patent related to the MCL35 assay filed at the National Institutes of Health, United States of America.; NanoString: Patents & Royalties: Named inventor on a patent licensed to NanoString, Research Funding; Celgene: Consultancy; Roche/Genentech: Research Funding. Steidl:Curis Inc: Consultancy; Roche: Consultancy; AbbVie: Consultancy; Seattle Genetics: Consultancy; Bayer: Consultancy; Bristol-Myers Squibb: Research Funding; Juno Therapeutics: Consultancy.

Description: Introduction: Classic Hodgkin lymphoma (CHL) features a unique crosstalk between malignant cells and different types of normal immune cells in the tumor-microenvironment (TME). On the basis of histomorphologic and immunophenotypic features of the malignant Hodgkin and Reed-Sternberg (HRS) cells and infiltrating immune cells, four histological subtypes of CHL are recognized: Nodular sclerosing (NS), Mixed cellularity, Lymphocyte-rich (LR) and Lymphocyte-depleted CHL. Recently, our group described the high abundance of various types of immunosuppressive CD4+ T cells including LAG3+ and/or CTLA4+ cells in the TME of CHL using single cell RNA sequencing (scRNAseq). However, the TME of LR-CHL has not been well characterized due to the rarity of the disease. In this study, we aimed at characterizing the immune cell profile of LR-CHL at single cell resolution. METHODS: We performed scRNAseq on cell suspensions collected from lymph nodes of 28 primary CHL patients, including 11 NS, 9 MC and 8 LR samples, with 5 reactive lymph nodes (RLN) serving as normal controls. We merged the expression data from all cells (CHL and RLN) and performed batch correction and normalization. We also performed single- and multi-color immunohistochemistry (IHC) on tissue microarray (TMA) slides from the same patients. In addition, an independent validation cohort of 31 pre-treatment LR-CHL samples assembled on a TMA, were also evaluated by IHC. Results: A total of 23 phenotypic cell clusters were identified using unsupervised clustering (PhenoGraph). We assigned each cluster to a cell type based on the expression of genes described in published transcriptome data of sorted immune cells and known canonical markers. While most immune cell phenotypes were present in all pathological subtypes, we observed a lower abundance of regulatory T cells (Tregs) in LR-CHL in comparison to the other CHL subtypes. Conversely, we found that B cells were enriched in LR-CHL when compared to the other subtypes and specifically, all four naïve B-cell clusters were quantitatively dominated by cells derived from the LR-CHL samples. T follicular helper (TFH) cells support antibody response and differentiation of B cells. Our data show the preferential enrichment of TFH in LR-CHL as compared to other CHL subtypes, but TFH cells were still less frequent compared to RLN. Of note, Chemokine C-X-C motif ligand 13 (CXCL13) was identified as the most up-regulated gene in LR compared to RLN. CXCL13, which is a ligand of C-X-C motif receptor 5 (CXCR5) is well known as a B-cell attractant via the CXCR5-CXCL13 axis. Analyzing co-expression patterns on the single cell level revealed that the majority of CXCL13+ T cells co-expressed PD-1 and ICOS, which is known as a universal TFH marker, but co-expression of CXCR5, another common TFH marker, was variable. Notably, classical TFH cells co-expressing CXCR5 and PD-1 were significantly enriched in RLN, whereas PD-1+ CXCL13+ CXCR5- CD4+ T cells were significantly enriched in LR-CHL. These co-expression patterns were validated using flow cytometry. Moreover, the expression of CXCR5 on naïve B cells in the TME was increased in LR-CHL compared to the other CHL subtypes We next sought to understand the spatial relationship between CXCL13+ T cells and malignant HRS cells. IHC of all cases revealed that CXCL13+ T cells were significantly enriched in the LR-CHL TME compared to other subtypes of CHL, and 46% of the LR-CHL cases showed CXCL13+ T cell rosettes closely surrounding HRS cells. Since PD-1+ T cell rosettes are known as a specific feature of LR-CHL, we confirmed co-expression of PD-1 in the rosetting cells by IHC in these cases. Conclusions: Our results reveal a unique TME composition in LR-CHL. LR-CHL seems to be distinctly characterized among the CHL subtypes by enrichment of CXCR5+ naïve B cells and CD4+ CXCL13+ PD-1+ T cells, indicating the importance of the CXCR5-CXCL13 axis in the pathogenesis of LR-CHL. Figure Disclosures Savage: BeiGene: Other: Steering Committee; Merck, BMS, Seattle Genetics, Gilead, AstraZeneca, AbbVie: Honoraria; Roche (institutional): Research Funding; Merck, BMS, Seattle Genetics, Gilead, AstraZeneca, AbbVie, Servier: Consultancy. Scott:Janssen: Consultancy, Research Funding; Celgene: Consultancy; NanoString: Patents & Royalties: Named inventor on a patent licensed to NanoString, Research Funding; NIH: Consultancy, Other: Co-inventor on a patent related to the MCL35 assay filed at the National Institutes of Health, United States of America.; Roche/Genentech: Research Funding; Abbvie: Consultancy; AstraZeneca: Consultancy. Steidl:AbbVie: Consultancy; Roche: Consultancy; Curis Inc: Consultancy; Juno Therapeutics: Consultancy; Bayer: Consultancy; Seattle Genetics: Consultancy; Bristol-Myers Squibb: Research Funding.

Description: Lymphocyte-rich classic Hodgkin lymphoma (LR-CHL) is a rare subtype of Hodgkin lymphoma. Recent technical advances have allowed for the characterization of specific cross-talk mechanisms between malignant Hodgkin Reed-Sternberg (HRS) cells and different normal immune cells in the tumor microenvironment (TME) of CHL. However, the TME of LR-CHL has not yet been characterized at single-cell resolution. Here, using single-cell RNA sequencing (scRNA-seq), we examined the immune cell profile of 8 cell suspension samples of LR-CHL in comparison to 20 samples of the mixed cellularity (MC, 9 cases) and nodular sclerosis (NS, 11 cases) subtypes of CHL, as well as 5 reactive lymph node controls. We also performed multicolor immunofluorescence (MC-IF) on tissue microarrays from the same patients and an independent validation cohort of 31 pretreatment LR-CHL samples. ScRNA-seq analysis identified a unique CD4+ helper T cell subset in LR-CHL characterized by high expression of Chemokine C-X-C motif ligand 13 (CXCL13) and PD-1. PD-1+CXCL13+ T cells were significantly enriched in LR-CHL compared to other CHL subtypes, and spatial analyses revealed that in 46% of the LR-CHL cases these cells formed rosettes surrounding HRS cells. MC-IF analysis revealed CXCR5+ normal B cells in close proximity to CXCL13+ T cells at significantly higher levels in LR-CHL. Moreover, the abundance of PD-1+CXCL13+ T cells in the TME was significantly associated with shorter progression-free survival in LR-CHL (P = 0.032). Taken together, our findings strongly suggest the pathogenic importance of the CXCL13/CXCR5 axis and PD-1+CXCL13+ T cells as a treatment target in LR-CHL.