Viktoria Kohlhas

Summary: Targeting the colony‐stimulating factor 1 receptor (CSF1R) to remove tumour‐associated macrophages is being explored as cancer therapy. This strategy may be relevant for chronic lymphocytic leukaemia (CLL), which strongly depends on support from myeloid cells. However, it is unclear how CSF1R expression affects the CLL microenvironment and leukaemic progression. To examine this question, we created Eμ‐TCL1 transgenic mice for CLL with Csf1r haploinsufficiency to investigate changes in myeloid cells, Csf1r expression and leukaemia progression. Csf1r haploinsufficiency reduced Csf1r expression on circulating monocytes, but did not significantly impair its expression in tissue macrophages or change the overall numbers of monocytes or macrophages in blood and lymphoid tissues. Eμ‐TCL1 transgenic mice with lower Csf1r levels had less leukaemia during early disease, but this effect faded with disease progression, and their overall survival was similar to controls. Furthermore, in vitro co‐culture demonstrates that depletion of CSF1R expression on cell lines did not affect the survival or migration of patient‐derived CLL cells. In summary, our results show that while the CSF1R pathway is important for maintaining the myeloid cells that support CLL, simply reducing CSF1R expression has only a limited effect on disease progression. Attempts to target the CSF1R for leukaemic therapy might benefit from a stronger depletion of macrophages or the combination with other agents.

Table S4 contains the individual mutations of PPMBC and MBC lymphomas.

Table S6 contains clinical parameters and sequencing results of human DLBCL samples.

Table S3 contains B cell receptor repertoire sequencing data and lists the individual sublcones of the dominant clones of MBC, SMBC and PPMBC lymphomas.

Table S1 contains the p values of comparisons of the V gene usage in non-malignant GC B cells between the individual genotypes. These comparisons were done on the family, gene and allele level. V usage was compared for all BCR sequences as well as for isotype subsets.

This file contains the Supplementary Figures S1 to S12.

Table S2 contains a summary of the B cell receptor sequencing data of lymphoma samples. It includes 1) an overview of the investigated samples, 2) a list of characteristics of the dominant clone of each lymphoma sample, 3) a list comparing the frequencies of V family usage in WT samples to the lymphoma frequency, 4) the frequencies of FR and CDR mutations in samples analyzed by full-length BCR sequencing.

Table S5 contains statistical values of gene set enrichment analyses of the KEGG, BIOCARTA and HALLMARK gene set collections.

Genomic profiling revealed the identity of at least 5 subtypes of diffuse large B-cell lymphoma (DLBCL), including the MCD/C5 cluster characterized by aberrations in MYD88, BCL2, PRDM1, and/or SPIB. We generated mouse models harboring B cell–specific Prdm1 or Spib aberrations on the background of oncogenic Myd88 and Bcl2 lesions. We deployed whole-exome sequencing, transcriptome, flow-cytometry, and mass cytometry analyses to demonstrate that Prdm1- or Spib-altered lymphomas display molecular features consistent with prememory B cells and light-zone B cells, whereas lymphomas lacking these alterations were enriched for late light-zone and plasmablast-associated gene sets. Consistent with the phenotypic evidence for increased B cell receptor signaling activity in Prdm1-altered lymphomas, we demonstrate that combined BTK/BCL2 inhibition displays therapeutic activity in mice and in five of six relapsed/refractory DLBCL patients. Moreover, Prdm1-altered lymphomas were immunogenic upon transplantation into immuno-competent hosts, displayed an actionable PD-L1 surface expression, and were sensitive to antimurine-CD19-CAR-T cell therapy, in vivo.Significance:Relapsed/refractory DLBCL remains a major medical challenge, and most of these patients succumb to their disease. Here, we generated mouse models, faithfully recapitulating the biology of MYD88-driven human DLBCL. These models revealed robust preclinical activity of combined BTK/BCL2 inhibition. We confirmed activity of this regimen in pretreated non–GCB-DLBCL patients.See related commentary by Leveille et al., p. 8.This article is highlighted in the In This Issue feature, p. 1