Mantle cell lymphoma (MCL) accounts for 7% of non-Hodgkin lymphomas and represents a particularly challenging disease with patient outcomes inferior to most other lymphoma subtypes. We recently reported frequent mutations (18%) in UBR5, a gene encoding an E3 ubiquitin-protein ligase that has not been previously implicated in lymphomagenesis. All mutations were clustered within 100bp in or around exon 58 of UBR5 and are predicted to result in the loss of the conserved cysteine residue, which is responsible for binding the ubiquitin molecule. The recurrence and clustering of UBR5 mutations suggest their critical pathogenic nature in MCL that might be therapeutically targetable. The aim of this study is to determine the specific role of UBR5 mutations in the pathogenesis of MCL.
Mutations clustering in exon 58 of UBR5, as seen in MCL patients, were generated in three MCL cell lines (Granta-519, Jeko-1, and Mino) using the CRISPR-Cas9 genome engineering tool. First, global proteomes of UBR5 mutants and WT were analyzed by Tandem Mass Tag (TMT)-based mass spectrometry to identify proteins with differential expression due to the UBR5 mutations. Next, mass spectrometry-based immunoprecipitation proteomics (IP-MS) was employed to identify UBR5 interacting partners. Candidate UBR5 interacting proteins were functionally validated by flow cytometry, western blotting, co-immunoprecipitation, and immunofluorescence.
The global proteome and IP-MS analyses identified a number of DNA damage response, chromosome organization, and cell cycle response proteins as the predominant proteins affected (p
The proteome and functional analyses are consistent with UBR5 functioning as a key regulator of cell signalling and point to the critical role of UBR5 as a novel regulator of DNA damage response. Next, our goal is to develop mouse xeno-transplantation MCL models and identify therapeutic agents that render sensitivity in xeno-transplantation models with UBR5 mutations.
Clinical trial identification
Legal entity responsible for the study
Centre for Lymphoid Cancer, Vancouver, British Columbia, Canada
The Terry Fox Foundation
All authors have declared no conflicts of interest.