Follicular lymphoma evolves with a surmountable dependency on acquired glycosylation motifs in the B cell receptor.

An early event in the genesis of follicular lymphoma (FL) is the acquisition of new glycosylation motifs in the B cell receptor (BCR) due to gene rearrangement and/or somatic hypermutation. These N-linked glycosylation motifs (N-motifs) contain mannose-terminated glycans and can interact with lectins in the tumor microenvironment, activating the tumor BCR pathway. N-motifs are stable during FL evolution suggesting that FL tumor cells are dependent on them for their survival. Here, we investigated the dynamics and potential impact of N-motif prevalence in FL at the single cell level across distinct tumor sites and over time in 17 patients. While most patients had acquired at least one N-motif as an early event, we also found (i) cases without N-motifs in the heavy or light chains at any tumor site or timepoint and (ii) cases with discordant N-motif patterns across different tumor sites. Inferring phylogenetic trees for the patients with discordant patterns, we observed that both N-motif-positive and N-motif-negative tumor subclones could be selected and expanded during tumor evolution. Comparing N-motif-positive to N-motif-negative tumor cells within a patient revealed higher expression of genes involved in the BCR pathway and inflammatory response, while tumor cells without N-motifs had higher activity of pathways involved in energy metabolism. In conclusion, while acquired N-motifs likely support FL pathogenesis through antigen-independent BCR signaling in most FL patients, N-motif-negative tumor cells can also be selected and expanded and may depend more heavily on altered metabolism for competitive survival.