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Title: Investigating the roles of HMGB1 and its receptor, RAGE, in chronic lymphocytic leukaemia
Author: Norster, F. A.
ISNI:       0000 0004 7971 8030
Awarding Body: Queen Mary, University of London
Current Institution: Queen Mary, University of London
Date of Award: 2018
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High plasma levels of inflammatory mediator, high mobility group box protein 1 (HMGB1), and its main receptor, receptor for advanced glycation end products (RAGE), is associated with poor prognosis for a variety of cancers, but little is known about this signalling axis in chronic lymphocytic leukaemia (CLL). We have previously determined significantly increased HMGB1 levels in the plasma of CLL patients compared to healthy controls, associated with poor clinical outcome. It is unknown whether the HMGB1-RAGE signalling axis contributes to disease progression and can directly promote CLL B-cell survival by converging with toll-like receptor 9 (TLR9) signalling. Moreover, the role of soluble RAGE (sRAGE), a free extracellular receptor fragment that functions as a decoy receptor in blood plasma, is poorly documented for CLL. The overall aim of my PhD is to (1) determine expression of HMGB1 receptors, RAGE and TLR9, in CLL B-cells and their prognostic significance in patients with CLL; (2) assess global cell-signalling network activation following exogenous HMGB1 treatment and blockade with neutralising anti-RAGE antibody; (3) study the impact of sRAGE in CLL. Lymph node RAGE expression positively correlated with TLR9, Ki67 and ZAP70 - markers of proliferating and aggressive disease. Patients with high lymph node RAGE expression confer inferior overall survival in comparison to patients with low RAGE expression. Further risk stratification of RAGE with Ki67 and ZAP70 lymph node expression increased the prognostic power of RAGE, highlighting a significant interaction between these variables. HMGB1 induced activation and colocalization of RAGE and TLR9 in CLL B-cells. Phosphoproteomic analysis highlights activation of MAPK signalling in primary CLL cells following HMGB1 treatment in vitro for patients with ZAP70 expression. We confirmed increased plasma levels of HMGB1 and surprisingly of sRAGE in CLL patients compared to healthy controls, but not of other RAGE ligand, S100B. Plasma sRAGE levels did not reach a high enough concentration to inflict full HMGB1 inhibition, but RAGE shedding could be induced in vitro by stimulating metalloprotease termed a disintegrin and metalloproteinase domain-containing protein 10 (ADAM10) with ionomycin in RAGE-transfected HEK293 cell line and primary CLL cells, and blocked when ADAM10 was specifically inhibited with GI254023X. In summary, this study demonstrates that overexpression of HMGB1 receptor, RAGE, in CLL lymph nodes is associated with a worse clinical outcome in patients with CLL. HMGB1 activates both RAGE and TLR9 in primary CLL B-cells. sRAGE has a protective effect in CLL by prolonging time to first treatment and sRAGE originates from ectodomain shedding, dependent on ADAM10. We therefore propose that HMGB1 and surface RAGE may play an important role in promoting CLL cell proliferation and cell survival, and plasma sRAGE combined with HMGB1 could be markers of disease monitoring.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: chronic lymphocytic leukaemia ; high mobility group box protein 1 ; disease monitoring.