Investigating the impact of inflammasomes in bladder cancer

Abstract

Bladder cancer (BC) is the 10th most commonly diagnosed cancer worldwide and can be divided into two subtypes. Non-muscle invasive bladder cancer (NMIBC) is defined as BC that is confined to the urothelium and lamina propria, and accounts for 70% of BC diagnoses. Muscle-invasive bladder cancer (MIBC) has invaded beyond the lamina propria and into the detrusor smooth muscle Although the mortality rate associated with NMIBC is 30%, approximately 60-70% of NMIBC cancers recur within 5 years, and 20-30% will progress to MIBC, which is associated with poorer survival outcomes.

Chronic inflammation is a well-established risk factor for the development of BC and is associated with the progression of tumours. Inflammasomes are protein complexes that oligomerise in response to infection or tissue damage and mediate the immune response by the secretion of cytokines. Nucleotide-Binding Domain-Like Receptor (NLR) inflammasomes play a role in a number of bladder pathologies, and expression of NLRs has been detected in the urine of patients with high-grade BC. The aims of this study were to characterise the expression and impact of NLR inflammasome expression in BC tumour samples, and to investigate NLR activity in BC cell models and tumour/immune interactions.

Higher expression of NLR-related genes in BC tumours (TCGA) were associated with higher grade and later stage disease, increased immune infiltration and poorer patient outcomes than NLR-low tumours. NLR-high cell lines modelled a more invasive phenotype than NLR-low cell lines. NLRP3 activators, lipopolysaccharide (LPS) and nigericin (NGN), did not elicit NLRP3 inflammasome activation in BC cells; however, significant cell death occurred in BC cells treated with LPS/NGN. The impact of NLRP3 on tumour/immune cell interactions was further investigated by conditioned medium transfer. LPS/NGN evoked secretion of a number of cytokines from monocytes into the surrounding medium. Transfer of this conditioned medium to BC cells reduced their migration, increased cell death, and eradicated colony-formation. Interestingly, cell death was not evoked in normal urothelial cells by the conditioned media exposing a potential immunotherapeutic target in BC treatment. Interestingly, this phenomenon was NLRP3-independent as its inhibition did not rescue the functional changes in BC the media transfer from monocytes. In conclusion, NLR expression in BC is associated with increased immune infiltration and poorer patient outcomes. Release of signalling molecules from LPS/NGN-treated monocytes, modelling the tumour microenvironment, negatively impacts BC cells in an NLRP3-independent manner. This immune-tumour cell signalling has the potential to be exploited therapeutically to combat BC.

Thesis is embargoed until 31 July 2026.

Date of Award	Jul 2024
Original language	English
Awarding Institution	Queen's University Belfast
Supervisor	Jaine Blayney (Supervisor) & Karen McCloskey (Supervisor)