CD20 expression regulates CD37 levels in B-cell lymphoma – implications for immunotherapies

Abstract

Rituximab (RTX) plus chemotherapy (R-CHOP) applied as a first-line therapy for lymphoma leads to a relapse in approximately 40% of patients. Therefore, novel approaches to treat aggressive lymphomas are being intensively investigated. Several RTX-resistant (RR) cell lines have been established as surrogate models to study resistance to R-CHOP. Our study reveals that RR cells are characterized with a major downregulation of CD37, a molecule currently explored as a target for immunotherapy. Using CD20 knockout (KO) cell lines, we demonstrate for the first time that CD20 and CD37 form a complex and the presence of CD20 stabilizes CD37 in the cell membrane. Consequently, we observe a diminished cytotoxicity of anti-CD37 monoclonal antibody (mAb) in complement-dependent cytotoxicity in both RR and CD20 KO cells that can be partially restored upon lysosome inhibition. On the other hand, the internalization rate of anti-CD37 mAb in CD20 KO cells is increased when compared to controls, suggesting unhampered efficacy of antibody drug conjugates. Importantly, even a major downregulation in CD37 levels does not hamper the efficacy of CD37-directed chimeric antigen receptor (CAR) T cells. In summary, we present here a novel mechanism of CD37 regulation with further implications for the use of anti-CD37 immunotherapies.

Using adjusted local assortativity with Molecular Pixelation unveils colocalization of membrane proteins with immunological significance

“…The same laboratory employed later another technique, flow cytometric energy transfer, to find three tetraspan molecules (CD53, CD81, and CD82) complexed with MHC class I, MHC class II, and CD20 on the surface of a human B-cell line ( 37 ). Recently, CD20 and CD37 have been confirmed to form a complex by a proximity ligation assay ( 68 ). In this preprint, it is hypothesized that the presence of CD20 stabilizes CD37 in the cell membrane as increased internalization of anti-CD37 is measured on deficient CD20 lymphoma B-cell lines ( 68 ).…”

“…Recently, CD20 and CD37 have been confirmed to form a complex by a proximity ligation assay ( 68 ). In this preprint, it is hypothesized that the presence of CD20 stabilizes CD37 in the cell membrane as increased internalization of anti-CD37 is measured on deficient CD20 lymphoma B-cell lines ( 68 ).…”

“…Bobrowicz and colleagues recently tested that upon diminished levels of CD37 in different cell lines, even with downregulation of CD20, cytotoxicity of CAR-T cells was not significantly impaired. Therefore, in their opinion, CD37 remains an attractive therapeutic target ( 68 ).…”

Novel and multiple targets for chimeric antigen receptor-based therapies in lymphoma

“…CD37 is highly expressed on universally all B-NHL and some cutaneous T-cell lymphoma (CTCL) and peripheral T-cell lymphoma (PTCL), while absent on hematopoietic stem cells, making it a potentially feasible CAR target ( 172 ). Clinical trials utilizing anti-CD37 monoclonal or bispecific antibodies and ADC in R/R B-NHL have been disappointing in general, likely due to the close association between CD20 and CD37 ( 220 ). In CD20-down regulated B-NHL, CD37 expression is also decreased, impairing the function of antibody-based therapy.…”

“…In CD20-down regulated B-NHL, CD37 expression is also decreased, impairing the function of antibody-based therapy. Although CAR T typically requires high antigen expression, CD37 down-regulation do not seem to affect the function of CD37-CAR T ( 220 ). Preclinical study demonstrated potent cytotoxicity of CD37-CAR T against various CD37-expressing B- and T-NHL, without T-cell fratricide or detectable toxicity to other immune cells such as NK-cells and monocytes ( 29 , 172 ).…”