CD37 and CD20 expression show correlations but the prognostic significance of CD37 is independent of CD20 expression in DLBCL. (A) In both GCB- and ABC-DLBCL, the CD37⁻ group had significantly lower mean levels of CD37 and CD20 mRNA expression compared with the CD37⁺ group. (B) Geometric mean fluorescence intensities (gMFIs) of CD37 and CD20 protein expression in 3 different CD37⁻ and 3 different CD37⁺ DLBCL cell lines measured by flow cytometry. CD20 expression on the plasma membrane of DLBCL cells was detected by a nontherapeutic CD20 antibody (2H7; BioLegend) (upper) and by therapeutic Rituxan (Roche) (lower). Results are representative for 2 independent experiments. Coefficient for linear regression: R² = 0.9737 (left) and R² = 0.8043 (right). Dotted lines show 95% CI. (C) Low CD20 mRNA expression (less than mean) correlated with significantly worse OS and PFS, especially in ABC-DLBCL. (D) However, CD37⁺ patients with lower CD20 mRNA levels had significantly better OS and PFS than CD37⁻ patients with higher CD20 mRNA levels. (E) In GCB-DLBCL, CD37 antigen status but not CD20 mRNA levels predicted survival. In ABC-DLBCL, CD37 status and CD20 mRNA levels showed prognostic impact independent of each other, but CD37 status showed stronger prognostic impact. (F) In an independent CHOP-treated DLBCL cohort, overall CD37⁺ patients had significantly better PFS than CD37⁻ patients. However, the favorable impact was limited in patients with low (≤50%) CD37 levels and patients with high (>50%) CD37 expression showed similar PFS with CD37⁻ patients.