Biological and clinical relevance of CD79 protein and gene expression in diffuse large B‐cell lymphoma

Introduction: CD79B is a target of polatuzumab vedotin, an antibody–drug conjugate, which may improve the prognosis of both previously untreated and relapsed/refractory patients with diffuse large B-cell lymphoma (DLBCL). However, the biological and clinical significance of CD79B protein and gene expression in DLBCL is largely unknown. Methods: We retrospectively analyzed de novo DLBCL patients, who were diagnosed and received rituximab-based immunochemotherapy from 2008 through 2018 in the Okayama Hematology Study Group from Japan. Immunohistochemistry (IHC) staining was performed using a CD79B antibody (AT107-2), and protein expression was assessed based on H-score according to a previous study (Sehn L et al. JCO 2020). We also performed gene expression profile-based cell-of-origin (COO) classification, including double-hit signature (DHITsig) which has been renamed to dark zone signature (DZsig) (Waleed A et al. Blood 2022), using the NanoString DLBCL90 assay. Results: CD79B IHC expression was evaluable in 602 cases. We idefined two groups according to median H-score of CD79B expression: CD79Bhigh and CD79Blow. The COO subtypes were assigned as follows: 308 patients (51%) with activated B-cell-like (ABC)-DLBCL, 196 (33%) with germinal center B-cell-like (GCB)-DLBCL, 32 (5%) with DZsig-pos DLBCL and 66 (11%) with unclassified (UNC). H-score of CD79B was the lowest in patients with ABC-DLBCL followed by GCB-DLBCL and DZsig-pos DLBCL in ascending order (Kruskal–Wallis test P < .00001; Figure A). Indeed, CD79Blow tumors were significantly enriched in ABC-DLBCL (57%) compared to GCB-DLBCL (40%) and DZsig-pos DLBCL (22%), respectively (both, P < .001). Consistently, using publicly available DLBCL datasets (Schmitz et al. NEJM 2018 and Ennishi et al. JCO 2019), we revealed that CD79B gene expression was the lowest in ABC-DLBCL compared to GCB- and DHITsig-DLBCL (Kruskal–Wallis test P = .01; Figure B and C). The association of CD79B expression with COO prompted us to evaluate CD79B expression in normal germinal center B cells. Notably single-cell transcriptomic analyses of six reactive lymphoid tissues from publicly available datasets revealed that the lowest expression of CD79B was found in plasmablasts followed by light zone B cells and dark zone B cells in ascending order (Kruskal–Wallis test P < .0001), supporting the differential expression of CD79Baccording to COO subtype. CD79Blow group had significantly shorter overall survival (OS) in the total DLBCL cohort (log-rank, P < .001) and within ABC-DLBCL (P = .001, Figure D and E). Moreover, CD79B protein expression was significantly associated with OS after adjusting for International Prognostic Index in the total cohort (Cox regression model; P< .001). Keywords: Aggressive B-cell non-Hodgkin lymphoma, Diagnostic and Prognostic Biomarkers Conflicts of interests pertinent to the abstract. K. Sunami Honoraria: Celgene, Sanofi, BMS, Ono, Janssen Research funding: Takeda, AbbVie, GSK, Chugai, Otsuka, MSD, Novartis, Astellas Amgen, Pfizer, Parexel, Kyowa Kirin, Symbio, Agios Y. Hiramatsu Honoraria: Chugai Pharmaceutical Co, Nippon Shinyaku Co, Bristol Myers Squibb, Sanofi K.K. I. Yoshida Honoraria: Kyowa Kirin, Chugai, Eisai, Jannsen, Nippon-shinyaku, Otsuka, Symbio, Takeda, Sumitomo Pharma, Meiji Research funding: Kyowa Kirin, Chugai Y. Maeda Research funding: Chugai, Nippon-shinyaku Other remuneration: Chugai, Eisai, Otsuka, Kyowa Kirin, Takeda D. W. Scott Consultant or advisory role: Abbvie, AstraZeneca, Janssen, Incyte Honoraria: AstraZeneca Research funding: Janssen, Roche/Genentech D. Ennishi Honoraria: Chugai, Eisai, Kyowa Kirin Research funding: Nipponshinyaku, Chugai