Molecular analysis of a CD19-negative diffuse large B-cell lymphoma

How to integrate CD19 specific chimeric antigen receptor T cells with other CD19 targeting agents in diffuse large B-cell lymphoma?

About one third of patients with diffuse large B-cell lymphoma (DLBCL) have a relapsing/refractory (R/R) disease after first line chemo-immunotherapy, with particularly poor outcomes observed in patients with primary refractory disease and early relapse. CD19 specific chimeric antigen receptor (CAR) T cell therapy is a game changer that results in durable and complete response rates in almost half of the patients with R/R DLBCL. Other emerging CD19-targeting therapies include monoclonal antibodies, bispecific antibodies and targeting antibody-drug conjugates, which also show encouraging results. However, the timing and sequencing of different anti-CD19-targeting agents and how they might interfere with subsequent CAR T cell treatment is still unclear. In this review, we summarize the results of the pivotal clinical trials as well as evidence from real-world series of the use of different CD19-targeting approved agents. We discuss the effect of various therapies on CD19 expression and its implications for treatment sequencing.

How I treat refractory/relapsed diffuse large B-cell lymphomas with CD19-directed chimeric antigen receptor T cells

Chimeric antigen receptor (CAR) T cells targeting CD19 represent a promising salvage immunotherapy for relapsed/refractory diffuse large B-cell lymphoma (R/R DLBCL), offering ~40% of long-term responses. In everyday clinical practice, haematologists involved in CAR T cell treatment of patients with R/R DLBCL have to deal with diagnostically complex cases and difficult therapeutic choices. The availability of novel immunotherapeutic agents for R/R DLBCL and recent advances in understanding CAR T-cell failure mechanisms demand a rational approach to identify the best choice for bridging therapy and managing post-CAR T-cell therapy relapses. Moreover, positron emission tomography/computerised tomography may result in false-positive interpretation, highlighting the importance of post-treatment biopsy. In this review, we discuss all above issues, presenting four instructive cases, with the aim to provide criteria and new perspectives for CAR T-cell treatment of DLBCL.

Single-cell RNA sequencing profiling in a patient with discordant primary cutaneous B-cell and T-cell lymphoma reveals micromilieu-driven immune skewing

BACKGROUND

Primary cutaneous lymphomas comprise a heterogeneous group of B-cell and T-cell malignancies which often show an indolent course, but can progress to aggressive disease in a subset of patients. Diagnosis is often delayed owing to clinical and histopathological similarities with benign inflammatory conditions. Especially during early disease, cancer cells are present at relatively low percentages compared with the inflammatory infiltrate, an interplay that is currently only insufficiently understood.

OBJECTIVES

To improve diagnostics and perform molecular characterization of a complex type of primary cutaneous lymphoma.

METHODS

Single-cell RNA sequencing (scRNA-seq) was performed and combined with T-cell and B-cell receptor sequencing.

RESULTS

We were able to diagnose a patient with concurrent mycosis fungoides (MF) and primary cutaneous follicle centre lymphoma (PCFCL), appearing in mutually exclusive skin lesions. Profiling of tumour cells and the tissue microenvironment revealed a type-2 immune skewing in MF, most likely guided by the expanded clone that also harboured upregulation of numerous pro-oncogenic genes. By contrast, PCFCL lesions exhibited a more type-1 immune phenotype, consistent with its indolent behaviour.

CONCLUSIONS

These data not only illustrate the diagnostic potential of scRNA-seq, but also allow the characterization of specific clonal populations that shape the unique tissue microenvironment in clinically distinct types of lymphoma skin lesions.

Escape From ALL-CARTaz: Leukemia Immunoediting in the Age of Chimeric Antigen Receptors

Chimeric antigen receptor (CAR) T-cell therapy has been transformative for the treatment of B-cell malignancies, with CD19- and CD22-directed CARs being prime examples. However, immunoediting and ensuing antigen loss remain the major obstacles to curative therapy in up to 25% of patients. For example, to achieve the CD19-negative phenotype, malignant cells can pick from a broad array of mechanisms, including focal loss-of-function mutations, dysregulated trafficking to the cell surface, alternative splicing, and lineage switching. In other cases, where resistance is mediated by insufficient antigen density, trogocytosis has been proposed as a possible underlying mechanism. To overcome these barriers, compensatory strategies will be needed, which could include using combinatorial CARs, harnessing epitope spreading, and targeting tumor neoantigens.