Highlight
This study establishes a novel gradient of CD79B expression in diffuse large B-cell lymphoma (DLBCL) corresponding to cell-of-origin (COO) subtypes and germinal center (GC) B-cell maturation stages. It shows that CD79B expression is lowest in activated B-cell-like (ABC) DLBCL, higher in germinal center B-cell-like (GCB) DLBCL, and highest in dark-zone signature-positive (DZsigpos) cases. Single-cell proteomic and transcriptomic analyses reveal that CD79B expression progressively decreases as GC B-cells differentiate, elucidating the biological underpinning of these clinical observations and bearing implications for CD79B-targeted therapies such as polatuzumab-vedotin.
Study Background
Diffuse large B-cell lymphoma (DLBCL) is a biologically heterogeneous and aggressive B-cell lymphoma comprising distinct subtypes characterized by their cell-of-origin (COO). COO classification divides DLBCL into activated B-cell-like (ABC), germinal center B-cell-like (GCB), and less well-defined intermediate groups. This subclassification is clinically relevant as it reflects unique molecular pathways, prognoses, and responses to therapy. CD79B, an essential component of the B-cell receptor (BCR) complex, is a therapeutic target in DLBCL; notably, the antibody-drug conjugate polatuzumab-vedotin, which targets CD79B, improves outcomes predominantly in ABC-DLBCL despite this subtype not exhibiting the highest CD79B protein levels. This paradox prompted the investigation into the expression patterns of CD79B within DLBCL subtypes and their biological context in normal B-cell maturation.
Study Design
The study analyzed CD79B protein expression in formalin-fixed paraffin-embedded tissue samples from 590 treatment-naïve de novo DLBCL cases using immunohistochemistry (IHC). The cases were classified into COO subtypes using genomic signatures. To validate findings, an independent population-based cohort of 272 DLBCL cases from the BC Cancer registry was examined. Further, to explore CD79B dynamics in normal B-cell maturation, single-cell proteomic and transcriptomic analyses were conducted on 2,447 germinal center B-cells isolated from normal lymphoid tissues, focusing on the progressive changes in CD79B expression throughout stages of B-cell differentiation within the GC.
Key Findings
The analysis revealed a significant gradient of CD79B protein expression across COO subtypes: the ABC subtype exhibited the lowest median expression, followed by GCB, with the highest levels seen in DZsigpos DLBCL cases (P < 0.0001). This gradient was corroborated in the independent registry cohort, underscoring the robustness of the observation. Importantly, this study demonstrated for the first time that CD79B expression decrement parallels B-cell maturation in the germinal center, as evidenced by single-cell proteomic and transcriptomic profiling. CD79B levels decreased progressively as GC B-cells advanced toward terminal differentiation stages, reflecting that ABC-DLBCL cells, which resemble later differentiation stages, exhibit lower CD79B expression naturally. From a therapeutic perspective, this pattern informs understanding why polatuzumab-vedotin, targeting CD79B, works effectively in ABC-DLBCL despite their relatively lower CD79B levels, possibly due to functional receptor engagement or trafficking characteristics inherent to these cells. These findings challenge the notion that higher antigen expression always correlates with better therapeutic targeting and emphasize the biological context’s importance.
Expert Commentary
This comprehensive analysis adds valuable mechanistic insight into CD79B expression heterogeneity among DLBCL COO subtypes, integrated with normal B-cell differentiation trajectories. It refines our understanding of DLBCL biology, potentially explaining variable clinical responses to CD79B-directed therapies. The study’s strengths include large cohorts, validation in independent populations, and multidisciplinary single-cell approaches providing a multi-level perspective. However, clinical correlations linking precise CD79B expression thresholds with polatuzumab-vedotin efficacy remain to be elucidated prospectively. Furthermore, the intracellular signaling alterations accompanying CD79B expression changes and their influence on lymphoma pathogenesis warrant investigation. These results advocate for COO and differentiation-stage-informed biomarker stratification in DLBCL clinical trials and suggest that targeting strategies may benefit from considering functional receptor state rather than solely expression intensity.
Conclusion
In summary, this study identifies a novel gradational pattern of CD79B expression in DLBCL correlating with COO subclasses and germinal center B-cell differentiation stages. The finding that ABC-DLBCL exhibits the lowest CD79B expression yet remains a responsive target for polatuzumab-vedotin highlights the complexity of therapeutic antigen targeting and the need for deeper biological context in precision oncology. Future research should focus on integrating CD79B expression data with functional assessments and clinical outcomes to optimize patient stratification and treatment in DLBCL.
Funding and ClinicalTrials.gov
Details on specific funding sources or ClinicalTrials.gov identifiers were not provided in the original source article.
References
Naoi Y, Chijimatsu R, Urata T, et al. Gradient of CD79B expression in diffuse large B-cell lymphoma corresponds to stages of germinal center B-cell differentiation. Haematologica. 2026 Jun 25. PMID: 42345068. Available from: https://pubmed.ncbi.nlm.nih.gov/42345068/