Classic Hodgkin lymphoma (cHL) is the cancer type most susceptible to anti-programmed-death-receptor-1 (PD1) treatment and characterized by scarce Hodgkin and Reed-Sternberg cells (HRSC) perpetuating a unique tumor microenvironment (TME). Whilst in solid tumors anti-PD1 effects appear largely mediated by cytotoxic CD8+ T-cells, HRSC frequently lack major histocompatibility complex expression and the mechanism of anti-PD1 efficacy in cHL is unclear. Rapid clinical response and high interim complete response rate to anti-PD1 based 1st-line treatment was recently reported for patients with early-stage unfavorable cHL treated in the GHSG phase II NIVAHL trial. To investigate the mechanisms underlying this very early response to anti-PD1 treatment, we analyzed paired biopsies and blood samples obtained in NIVAHL patients before and during the first days of nivolumab 1st-line cHL therapy. Mirroring the rapid clinical response, HRSC had disappeared from the tissue within days after the first nivolumab application. The TME shows a reduction of Tr1 T-cells and PD-L1+ tumor associated macrophages (TAM) already at this early timepoint of treatment. Interestingly, neither a cytotoxic immune-response nor a clonal T-cell expansion was observed in the tumors or peripheral blood. These early changes of the TMA were distinct from alterations found in a separate set of cHL biopsies at relapse during anti-PD1 therapy. We identify a unique very early histologic response pattern to anti-PD1 therapy in cHL suggestive for withdrawal of pro-survival factors rather than induction of an adaptive anti-tumor immune response as main mechanism of action.

Background: Individualization of treatment in Hodgkin's lymphoma is necessary to improve cure rates and reduce treatment side effects. Currently, it is hindered by a lack of genomic characterization and sensitive molecular response assessment. Sequencing of cell-free DNA is a powerful strategy to understand the cancer genome and can be used for extremely sensitive disease monitoring. In Hodgkin's lymphoma, a high proportion of cell-free DNA is tumor-derived, whereas traditional tumor biopsies only contain a little tumor-derived DNA. Methods: We comprehensively genotype and assess minimal residual disease in 121 patients with baseline plasma as well as 77 follow-up samples from a subset of patients with our targeted cell-free DNA sequencing platform. Findings: We present an integrated landscape of mutations and copy number variations in Hodgkin's lymphoma. In addition, we perform a deep analysis of mutational processes driving Hodgkin's lymphoma, investigate the clonal structure of Hodgkin's lymphoma, and link several genotypes to Hodgkin's lymphoma phenotypes and outcome. Finally, we show that minimal residual disease assessment by repeat cell-free DNA sequencing, as early as a week after treatment initiation, predicts treatment response and progression-free survival, allowing highly improved treatment guidance and relapse prediction. Conclusions: Our targeted cell-free DNA sequencing platform reveals the genomic landscape of Hodgkin's lymphoma and facilitates ultrasensitive detection of minimal residual disease.

Individualizing treatment is key to improve outcome and reduce long-term side-effects in any cancer. In Hodgkin lymphoma (HL), individualization of treatment is hindered by a lack of genomic characterization and technology for sensitive, molecular response assessment. Sequencing of cell-free (cf)DNA is a powerful strategy to understand an individual cancer genome and can be used to develop assays for extremely sensitive disease monitoring. In HL, a high proportion of cfDNA is tumor-derived making it a highly relevant disease model to study the role of cfDNA sequencing in cancer. Here, we introduce our targeted cfDNA sequencing platform and present the largest genomic landscape of HL to date, which was entirely derived by cfDNA sequencing. We comprehensively genotype and assess minimal residual disease in 324 samples from 121 patients, presenting an integrated landscape of mutations and copy number variations in HL. In addition, we perform a deep analysis of mutational processes driving HL, investigate the clonal structure of HL and link several genotypes to HL phenotypes and outcome. Finally, we show that minimal residual disease assessment by repeat cfDNA sequencing as early as a week after treatment initiation is feasible and predicts overall treatment response allowing highly improved treatment guidance and relapse prediction. Our study also serves as a blueprint showcasing the utility of our platform for other cancers with similar therapeutic challenges.

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While classical Hodgkin lymphoma (HL) is highly susceptible to anti-programmed death protein 1 (PD1) antibodies, the exact modes of action remain controversial. To elucidate the circulating lymphocyte phenotype and systemic effects during anti-PD1 1st-line HL treatment we applied multicolor flow cytometry, FluoroSpot and NanoString to sequential samples of 81 HL patients from the NIVAHL trial (NCT03004833) compared to healthy controls. HL patients showed a decreased CD4 T-cell fraction, a higher percentage of effector-memory T cells and higher expression of activation markers at baseline. Strikingly, and in contrast to solid cancers, expression for 10 out of 16 analyzed co-inhibitory molecules on T cells (e.g., PD1, LAG3, Tim3) was higher in HL. Overall, we observed a sustained decrease of the exhausted T-cell phenotype during anti-PD1 treatment. FluoroSpot of 42.3% of patients revealed T-cell responses against ≥1 of five analyzed tumor-associated antigens. Importantly, these responses were more frequently observed in samples from patients with early excellent response to anti-PD1 therapy. In summary, an initially exhausted lymphocyte phenotype rapidly reverted during anti-PD1 1st-line treatment. The frequently observed IFN-y responses against shared tumor-associated antigens indicate T-cell-mediated cytotoxicity and could represent an important resource for immune monitoring and cellular therapy of HL.

Macrophages (Mφ) are abundantly present in the tumor microenvironment and may predict outcome in solid tumors and defined lymphoma subtypes. Mφ heterogeneity, the mechanisms of their recruitment, and their differentiation into lymphoma‐promoting, alternatively activated M2‐like phenotypes are still not fully understood. Therefore, further functional studies are required to understand biological mechanisms associated with human tumor‐associated Mφ (TAM). Here, we show that the global mRNA expression and protein abundance of human Mφ differentiated in Hodgkin lymphoma (HL)‐conditioned medium (CM) differ from those of Mφ educated by conditioned media from diffuse large B‐cell lymphoma (DLBCL) cells or, classically, by macrophage colony‐stimulating factor (M‐CSF). Conditioned media from HL cells support TAM differentiation through upregulation of surface antigens such as CD40, CD163, CD206, and PD‐L1. In particular, RNA and cell surface protein expression of mannose receptor 1 (MRC1)/CD206 significantly exceed the levels induced by classical M‐CSF stimulation in M2‐like Mφ; this is regulated by interleukin 13 to a large extent. Functionally, high CD206 enhances mannose‐dependent endocytosis and uptake of type I collagen. Together with high matrix metalloprotease9 secretion, HL‐TAMs appear to be active modulators of the tumor matrix. Preclinical in ovo models show that co‐cultures of HL cells with monocytes or Mφ support dissemination of lymphoma cells via lymphatic vessels, while tumor size and vessel destruction are decreased in comparison with lymphoma‐only tumors. Immunohistology of human HL tissues reveals a fraction of cases feature large numbers of CD206‐positive cells, with high MRC1 expression being characteristic of HL‐stage IV. In summary, the lymphoma‐TAM interaction contributes to matrix‐remodeling and lymphoma cell dissemination.

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Summary Hodgkin Lymphoma (HL) is an unusual B‐cell lymphoma because the malignant cells exist as a minority population in a densely cellular microenvironment. The microenvironment is comprised predominately of inflammatory and immune cells with fibrosis in some cases. There are multiple dysregulated signalling pathways that sustain HL within this microenvironment, such as the Nuclear factor‐κB and Janus kinase/signal transducers and activators of transcription pathways. Advances in genomic medicine have enabled a better characterisation of the rare tumour cells and improved our understanding of the signalling mechanisms that exist between the malignant cell and its microenvironment. Current therapy for HL produces excellent clinical outcomes in most younger patients. However, problems with current treatment approaches include poorer outcomes in the elderly, toxicity of highly‐effective combination chemotherapy regimens and relapse in high‐risk patients. Better understanding of disease biology aids in upfront prognostication of patients, defines new methods for treatment monitoring and assists in the recognition of novel targets for therapy. Biology‐driven therapies, including anti‐CD30 antibody conjugates, cellular immunotherapies and immune modulation, particularly with checkpoint inhibitors, have changed treatment algorithms for relapsed/refractory patients. Future challenges exist in incorporating immune‐based therapies earlier in treatment algorithms to reduce toxicity and prevent relapse for patients with HL.