Investigating the role of TRIM33 in the DNA damage response in multiple Myeloma

Abstract

Multiple myeloma (MM) is a haematological malignancy of aberrant plasma cells in the bone marrow. Genomic instability is a hallmark of MM with most patients displaying chromosomal abnormalities. Deletions of chromosome 1p (del(1p)) are a recurrent genetic event associated with high-risk disease. Located at 1p13.2 is TRIM33, an E3 ligase and transcription co-repressor. There is increasing evidence that TRIM33 is involved in the regulation of the DNA damage response (DDR) and mitotic checkpoints, both of which are important for genome stability. In this thesis, the role of TRIM33 in MM pathogenesis was investigated, focusing on its role in the DDR, and ultimately if this role could be therapeutically exploited. Analysis of data from the publicly available CoMMpass dataset revealed around 12.3% of newly diagnosed MM patients to have a copy number loss of TRIM33, and these patients have a significantly increased frequency of chromosomal structural variants and poorer overall survival. TRIM33 shRNA knockdown was performed in two MM cell lines to investigate this loss in vitro. shTRIM33 cells exhibited increased endogenous DNA damage as shown by increased formation of 53BP1 foci and increased γH2AX expression indicating a potential DNA repair defect. Furthermore shTRIM33 cells displayed increased phosphorylation of CHK1 and KAP1 indicative of activation of ATR and ATM kinases respectively. Importantly, shTRIM33 cells were sensitized to PARP inhibitor Olaparib and ATR inhibitor VE-821, and these compounds were synergistic with standard-of-care bortezomib. RNA-seq analysis revealed massive differential expression of genes associated with immunity/inflammation in shTRIM33 cells suggesting this may contribute to, or be a consequence of, the observed DNA repair defect. To conclude, this study has identified a subgroup of MM patients with TRIM33 loss who display poor outcome and chromosomal instability, likely due to a defective DDR. In the future, PARP and ATR inhibitors may be potential therapy candidates for this high-risk subgroup.

Thesis embargoed until 31 July 2025

Date of Award	Jul 2022
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	Northern Ireland Department for the Economy & Leukaemia & Lymphoma NI
Supervisor	Lisa Crawford (Supervisor) & Ken Mills (Supervisor)