Delivering p53 mRNA and HSP90 siRNA via lipid nanoparticles for dual anti-cancer and stroma remodelling activities for Pancreatic ductal adenocarcinoma

Abstract

Pancreatic ductal adenocarcinoma (PDAC) remains one of the most lethal malignancies. Its poor prognosis stems from three interconnected resistance mechanisms: genetic heterogeneity, a dense desmoplastic stroma impairing drug delivery, and a profoundly immunosuppressive tumour microenvironment. TP53 mutation, present in ~70% of patients, is particularly consequential as it simultaneously amplifies all three barriers through dominant negative and gain-of-function activities. Restoring wild-type p53 functions therefore offers a unique opportunity to dismantle multiple resistance layers from a single molecular origin. This thesis systematically evaluated p53 restoration as a dual anti-cancer and anti-stromal approach across PDAC models with different p53 status using small molecule and gene-based strategies. Targeting the p53–MDM2 axis with nutlin-3a, alongside gene-based delivery of p53 via plasmid DNA or mRNA, induced apoptosis and cell cycle arrest in wild-type contexts. These approaches also reduced stellate cell activation, evidenced by decreased α-SMA and collagen expression and re-accumulation of lipid droplets indicative of a quiescent phenotype. However, in mutant p53 cells, restoration alone was insufficient, demonstrating the need for concurrent mutant p53 depletion. To address this, HSP90, a chaperone that stabilises mutant p53 and supports TGF-β-driven stellate cell activation, was investigated as a co-target. Disruption of the HSP90–mutant p53 axis using SAHA or siRNA degraded mutant p53 and restored p53 transcriptional function only when combined with p53 restoration strategies. In parallel, siRNAmediated HSP90 inhibition effectively suppressed stellate cell activation. Building on this, ionisable lipid nanoparticles were optimised for the delivery of p53 mRNA and HSP90 siRNA. Combined delivery efficiently restored p53 functions in vitro, resulting in synergistic activation of apoptosis in the mutant cells. In stellate cells, the combined regimen induced a massive reprogramming towards quiescence. Further, therapeutic relevance was confirmed in a syngeneic PDAC allograft model recapitulating mutant p53, desmoplasia, and immune suppression. Combination treatment significantly reduced tumour growth and fibrosis, whereas monotherapies were ineffective, underscoring the necessity of dual targeting.

Thesis is embargoed until 31st December 2031.

Date of Award	Dec 2026
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	Northern Ireland Department for the Economy
Supervisor	Wafa Al-Jamal (Supervisor) & Yi Ge (Supervisor)