Scott, David W.

Abstract Objective We hypothesized that a set of immunohistochemistry (IHC) stains could be used to distinguish Burkitt lymphoma (BL), the quintessential B-cell lymphoma with a germinal center B-cell (GCB) dark zone (DZ) expression signature, from diffuse large B-cell lymphoma, not otherwise specified (DLBCL, NOS). This might also be applicable to high-grade B-cell lymphomas (HGBCLs) with MYC and BCL2 rearrangements (double-hit lymphomas [DHLs]) and triple-hit lymphomas (THLs). Methods A 5-marker IHC algorithm was designed from gene lists that distinguish physiologic DZ from light zone GCBs. Results In training and validation cohorts, we distinguished BL from DLBCL, NOS with high sensitivity and specificity. Because DHLs/THLs are enriched for the gene expression DZ signature (DZsig), we evaluated 19 DHLs/THLs and 4 HGBCLs, NOS. Most (83%) cases were IHC DZ. The NanoString DLBCL90 assay was performed on 34 cases to correlate IHC DZ results with the molecular DZsig. The IHC DZ call was significantly associated with the DZsig (P = .0011). The sensitivity and specificity of IHC to recognize DZsig+ cases among DLBCL, NOS and DHLs with BCL2 rearrangements/THLs were 91% and 100%, respectively. Conclusions The IHC DZ algorithm can support a diagnosis of BL and identifies MYC-BCL2 DHLs/THLs with a molecular DZsig.

Introduction Plasmablastic lymphoma (PBL) is a rare aggressive subtype of lymphoma. It is more common in HIV positive patients, and is often associated with Epstein-Barr virus (EBV) and MYC rearrangements. PBL is characterized by markers of plasmacytic differentiation including CD138 and MUM1/IRF4, and loss of B-cell markers such as CD20, which suggests a cell of origin similar to that of multiple myeloma (MM) or activated B-cell-like (ABC) diffuse large B-cell lymphoma (DLBCL). The standard of care for PBL is CHOP-based chemotherapy but this is frequently not curative. Other than EBV-negative status, which defines a high-risk group, no other biological features have been discovered that are associated with outcomes. Methods Here, we provide a comprehensive analysis of the genomic and transcriptomic landscape of PBL using a collection of 176 exomes and genomes (n=55 new, contributed by Lymphoma/Leukemia Molecular Profiling Project [LLMPP] sites and centrally reviewed by the LLMPP pathology panel [WHO 2016]; n=121 previously published [PMID: 33225311, 33951889, 34465776, 34714908]), 65 transcriptomes (n=44 new; n=21 published) and 37 in situ single cell transcriptomic profiles (CosMx Spatial Molecular Imager) from archival diagnostic tissue biopsies. Somatic mutations (SNVs/Indels) were identified using an ensemble of four variant callers (Strelka2, Lofreq, Mutect2, SAGE). Salmon and DESeq2 were used to identify differentially expressed genes. This multi-omics dataset was compared to other known B-cell malignancies including 92 MM, 238 Burkitt lymphomas (BL), and 208 DLBCLs. Cell segmentation of the CosMx data was performed using Baysor and downstream analyses were conducted using the Seurat workflow. For functional validation, cell viability assays (CellTiter-Glo Luminescent Assay) were conducted in the PBL cell line, PBL-1, and 4 control DLBCL cell lines. Results Within the cohort, 63% (106/169) of primary PBL cases were EBV-positive (EBV+) and 57% (82/144) harbored MYC rearrangements (MYC+). When stratifying patients by EBV and MYC rearrangement status, mutations in different genes were enriched in each group: STAT3 occurred in 55% (29/53) of EBV+/MYC+ PBLs; NOTCH1 in 19% (7/36) of EBV+/MYC-; MYC in 24% (6/25) and TP53 in 40% (10/25) of EBV-/MYC+ tumors; TET2 was mutated in 38% (9/24) and KRAS in 25% (6/24) of EBV-/MYC- PBLs. EBV-/MYC+ tumors represented a subgroup of patients with dismal outcomes. The 2-year overall survival (OS) of these patients was 22% compared to 61%, 78%, and 54% of EBV+/MYC+, EBV+/MYC-, and EBV-/MYC- PBL patients, respectively (log-rank test p-adj. < 0.05). Consistent with previous studies, we observed recurrent mutations affecting JAK-STAT (STAT3, SOCS1, SOCS3, DUSP2) in 41% of cases and RAS-RAF (NRAS, KRAS, BRAF) signaling in 38% of all PBLs. In contrast to ABC-DLBCL, very few mutations occurred in the NF-κB signalling pathway. Accordingly, PBL showed marked downregulation of genes involved in B-cell receptor and NF-κB signaling. Consistent with the lack of reliance on these pathways, functional analyses in PBL-1 showed resistance to treatment to ibrutinib as well as PI3K- and MALT1-inhibitors. Moreover, constitutive expression of the IκBα super-repressor did not affect viability of PBL-1 cells. In situ single cell transcriptomic data analyses showed a sparse tumor microenvironment (TME) in PBL, with the primary non-malignant cell types being, on average, 10% macrophages, 7% NK/T cells, and 4% stromal cells of all represented cell types. EBV+/MYC+ tumors displayed a more abundant immune cell population with higher levels of macrophages (median 12%) and NK/T cells (median 9%), whereas EBV-/MYC- tumors were composed of the lowest levels of immune cells (median 4% macrophages and 1% NK/T cells). With respect to malignant cell phenotypes, we noted a novel population of SPP1-expressing cells that were enriched in EBV+/MYC+ tumors and a population of CD44-expressing cells that were enriched in EBV+/MYC- tumors. Conclusion Here we present novel subgroups of PBL with unique biology and clinical outcomes. We show that PBL does not rely on B-cell receptor signaling, instead relying on potentially targetable vulnerabilities in JAK-STAT, NOTCH, and RAS-RAF signaling according to EBV positivity and MYC rearrangement status. Lastly, we provide insight into the TME of PBL and demonstrate a novel population of SPP1 and CD44 expressing malignant cells in EBV+ tumors.

Background: The Phase 1/2 ECOG-ACRIN sponsored intergroup trial E4412 (NCT01896999) investigated brentuximab vedotin (BV) combined with the checkpoint inhibitors nivolumab (N) and ipilimumab (I) in patients with relapsed or refractory classic Hodgkin lymphoma (R/R HL). Here we present the safety and efficacy results for the cohort of pediatric patients aged 12-17 years. Methods: Patients were randomly assigned to treatment with the doublet of BV/N or triplet of BV/N/I, with the following dosing: BV 1.8mg/kg every 21 days for up to 16 cycles; Nivolumab 3mg/mg every 21 days for up to 34 cycles; Ipilimumab 1mg/kg every 9 weeks for up to 9 doses. Response evaluation by PET/CT was performed after 4 cycles. Transplant-eligible patients with CR could discontinue protocol therapy to receive a consolidative autologous stem cell transplant (ASCT). Results: Sixteen pediatric patients with a median age of 16 (range 12-17) were randomized. 75% of patients had received only 1 prior line of treatment with none having previously received BV and only 1 patient with prior ASCT. All patients were treated (8 in each arm) and included in the pediatric safety analysis cohort receiving at least one cycle of therapy. There were four reported grade (gr) 3 or greater toxicities: lymphopenia (gr 3) and neutropenia (gr 3) on the BV/N arm; and neutropenia (gr 4) and rash (gr 3) on the BV/N/I arm. Rash of any grade was more common in patients treated with BV/N/I (n=6) compared to BV/N (n=1). Peripheral sensory neuropathy was reported in 2 patients (BV/N, gr 2, n=2) There were no grade 5 toxicities. Fourteen patients (7 in each arm) were evaluable for response. The CR rate on both the BV/N and BV/N/I arms was 100%. The median survival follow up was 23.7 months (15.7 - 31.7). The 24-month PFS was 57% for BV/N and 100% for BV/N/I. Six patients (2 BV/N; 4 BV/N/I) discontinued protocol therapy to receive a consolidative ASCT. The 24-month PFS for patients consolidated with an ASCT was 100%, with all events occurring in patients randomized to BV/N, but not receiving an ASCT. Conclusion: Pediatric patients receiving both BV/N and BV/N/I had 100% CR rate with limited toxicity. Although this is a small cohort, there have been no progression events observed in patients treated with BV/N/I, including 3 patients treated without a consolidative ASCT.