Session: 605. Molecular Pharmacology and Drug Resistance: Lymphoid Neoplasms: Poster II
Hematology Disease Topics & Pathways:
Fundamental Science, Research, Biological therapies, Antibody Therapy, Lymphomas, Translational Research, non-Hodgkin lymphoma, B Cell lymphoma, Diseases, immune mechanism, aggressive lymphoma, Therapies, Lymphoid Malignancies, Biological Processes
Methods: We employed combined drug-sensitization and CD79B-sorted CRISPR-Cas9 screening to identify molecular determinants of sensitivity to CD79B-directed, tumor killing by Pola-V in 9 cell lines representing different molecular subtypes of DLBCL.
Results: Our results reveal the striking impact of epitope glycosylation, specifically a2,6 sialylation, on the binding of Pola-V to CD79B and thereby its ability to kill tumor cells. Specifically, we identify the exact glycosylated residues on CD79A and CD79B which create a glycan shield around the Pola-V binding site, precluding binding to its target. We show how genetic, pharmacological and enzymatic approaches that remove terminal sialic acid residues from these N-linked glycans lead to enhanced tumor killing by Pola-V. We hypothesize and test multiple methods of targeting this pathway in order to enhance Pola-V killing both in vitro and in vivo. Finally, we reveal a previously unappreciated role for the ubiquitin ligase KLHL6 in regulating CD79B protein abundance and surface expression of the B cell antigen receptor (BCR), including how this pathway is used by physiological germinal center B cells and how it is corrupted to enhance BCR expression in GCB DLBCL.
Conclusions: These findings unravel the molecular basis of response heterogeneity to Pola-V and identify approaches that might be deployed therapeutically to enhance the efficacy of CD79B-specific tumor killing. In addition, we identify how KLHL6 determines expression of the BCR in both physiological and malignant germinal center B cells, and how KLHL6 mutation may modulate sensitivity of GCB DLBCL tumors to Pola-V.
Disclosures: Oellerich: Merck KGaA: Honoraria; Roche: Honoraria; Merck KGaA: Research Funding; Gilead: Research Funding.
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