No Discernable Dysfunction of Peripheral T-Cells and NK-Cells Despite Distinct Phenotypes in MYC Rearranged Versus Non Rearranged B-Cell Lymphoma Patients

Background:

Patients with diffuse large B-cell lymphoma/high-grade B-cell lymphoma with MYC and BCL2 rearrangements (DLBCL/HGBL-MYC/BCL2, hereafter HGBL-MYC/BCL2) respond poorly to standard immunochemotherapy treatment compared with DLBCL not otherwise specified (LBCL-NOS) patients without a MYC rearrangement. This suggests a negative interaction between MYC and the immune system. As novel T-cell and NK-cell based immunotherapeutic approaches emerge as potential treatment options for aggressive lymphomas, we conducted comprehensive immune profiling to compare peripheral blood T-cells and NK-cells of HGBL-MYC/BCL2 with LBCL NOS patients.

Methods:

Peripheral blood mononuclear cells (PBMCs) were prospectively collected from HGBL-MYC/BCL2 patients (registered in the HOVON-152 trial, NCT03620578), LBCL-NOS (registered in the HOVON-902 cohort, NCT04139252) and age-matched healthy donors (HDs). Flow-cytometry-based immune profiling of T-cells and NK-cells was performed on baseline samples available from n=66 HGBL-MYC/BCL2 patients (median age 62 years), n=67 LBCL NOS patients (median age 69 years) and n=17 HDs (median age 64 years). The flow cytometry data were computationally analyzed using FlowSOM and UMAP. T-cells were also functionally assessed for intracellular cytokine secretion (ICS) after stimulation with PMA/ionomycin (4h) and proliferation after stimulation with CD3/CD28 beads (5 days) using CellTrace Violet. NK-cells were assessed for cytotoxicity against K562 and degranulation (CD107a/b upregulation) after 4h.

Mann-Whitney’s U tests were used to compare HGBL-MYC/BCL2 patients with LBCL-NOS patients (primary comparison), and for pairwise comparisons of the lymphoma groups with HDs. To correct for baseline characteristics (age), linear regression analysis was performed.

Results:

CD4⁺ helper T-cells did not significantly between the lymphoma subgroups, but were decreased in LBCL-NOS patients as compared to HDs. Frequencies of cytotoxic CD8⁺ and CD4⁺CD8⁺ T-cells did not significantly between the lymphoma subgroups and were similar as in HDs.

Regulatory T-cell (Treg) frequencies of HGBL-MYC/BCL2 patients were similar to that of HDs, but were decreased in LBCL NOS patients. The frequency of CD4^-CD8^- T-cells was increased in LBCL NOS patients.

Previously activated (HLA-DR⁺) CD4⁺ and CD8⁺ T-cells, as well as recently activated CD25⁺, CD38⁺ or CD127⁺ CD4⁺ T-cells (Figure 1A) or activated/exhausted (PD-1⁺) CD4⁺ T-cells and PD1⁺ Tregs were increased in both lymphoma subtypes (Figure 1B), but only HGBL-MYC/BCL2 displayed an increase in PD1⁺ CD8⁺ T-cells (Figure 1B). Conversely, recently activated CD8⁺ T-cells were decreased exclusively in LBCL NOS.

HGBL-MYC/BCL2 patients and HDs had similar percentages of T-cells with a senescent phenotype (CD28^-CD57⁺KLRG1⁺), but the frequency of T-cells with this senescent phenotype was increased in LBCL NOS patients (Figure 1A), also after adjustment for age.

Despite all these phenotypic differences, functional in vitro assays detected no differences in proliferation or cytokine secretion of peripheral T-cells from HGBL-MYC/BCL2 patients, LBCL NOS patients and HDs.

In the NK-cell compartment, both lymphoma subtypes contained lower frequencies of CD56^brightTim3⁺, CD56^bright/dimDNAM-1⁺ NK-cells, but LBCL NOS patients expressed a higher amount of NK-cells expressing inhibitory receptor NKG2A compared with HDs. NK-cells of HGBL-MYC/BCL2 patients, LBCL NOS patients and HDs displayed similar cytotoxic activity, suggesting no apparent functional impairment.

Conclusions:

HGBL-MYC/BCL2 patients have a distinct peripheral T-cell and NK-cell phenotype from LBCL NOS patients without a MYC rearrangement, but show no apparent functional deficiencies in terms of proliferation, cytokine secretion or cytotoxic activity. These results are not contradicting the application of T-cell and NK-cell based immunotherapeutic approaches for patients with aggressive B-cell lymphoma. Simultaneously, it emphasize the need to investigate the potential immunomodulatory impact of lymphoma intrinsic MYC in the tumor microenvironment.