Theses (MSc. Medical and Health Sciences)

Pancreatic adenocarcinoma (PDAC) ranks high among the causes of cancer-related mortality. The prognosis of this disease has not improved significantly over the past 50 years despite advancements in imaging techniques, cancer genetics and treatment modalities. Likewise, emerging developments in immunotherapy have yet to bring significant clinical advantage among PDAC patients. Tumour-intrinsic immune evasion mechanisms of PDAC remained poorly understood. By leveraging on the large-scale genomic datasets reported by the Australia Pancreatic Cancer Project (PACA-AU) and The Cancer Genomic Atlas Project (TCGA-PAAD), we investigated the immunophenotype of PDAC and identified that tumour with low cytotoxic T cell (CTL) killing activity exhibited poorer clinical outcomes as compared to tumour with high CTL killing activity. Integrative transcriptomic analysis identified TWIST1, IL6R, MMP3, and HDAC5 as putative immune modulators, responsible for the tumour-cell intrinsic immune evasion in pancreatic cancers. Connectivity Map (CMap) analysis identified histone deacetylase (HDAC) inhibitors as potential candidate drugs that could target CTL resistant PDAC. Indeed, in vitro study demonstrated that entinostat and quisinostat enhanced CTL killing of CTL-resistant BxPC3 and SW1990 cells. Overall, these findings suggest the immunomodulatory effects of HDAC inhibitors in pancreatic cancer and warrant further investigation.

With less than 10% of the 5-year survival rate, pancreatic ductal adenocarcinoma (PDAC) is known to be one of the most lethal types of cancer. Current literature supports that gemcitabine is the first-line treatment of PDAC. However, its poor cellular penetration, acquired and intrinsic chemoresistance is common despite the broad usage of gemcitabine. Photodynamic therapy (PDT), a more selective and minimally invasive treatment, may be used synergistically with gemcitabine to reduce the doses utilised and dose-related side effects. The anti-pancreatic cancer evaluation of gemcitabine and rhenium(I), Re(I) pyta complex as a single agent does not show much difference between with/without PDT treatment. In contrast, Re(I) bisquinolinyl complex was to the PDAC (SW1990 and BxPC3) at light irradiation regimen of 365 nm for 2.5 minutes and 1.3 J/cm2 (IC50 without PDT: > 100 μM; IC50 with PDT for BxPC3: 42.06 μM; IC50 with PDT for SW1990: 61.75 μM). Combinatorial therapy with gemcitabine and either Re(I) pyta complex or Re(I) bisquinolinyl complex was then performed. All the tested combinations indicated synergism at most ratios and no significant difference in synergism was observed between with/without PDT. To improve the cytotoxicity of Re(I) pyta complex, it was conjugated with gemcitabine and successfully killed PDAC. With the aim to enhance cellular uptake and therapeutic efficiency, potent Re(I) bisquinolinyl complex and gemcitabine were encapsulated into liquid crystalline nanoparticles (LCNPs) system. All LCNPs formulations were found to be homogeneous, with both drugs encapsulated efficiently, in nano-sized (159 to 173 nm) and stable within the acceptable range of zeta potential (+1.06 to -10 mV). Around 70% of gemcitabine and 90% of Re(I) bisquinolinyl complex were found to be entrapped efficiently in the synthesised LCNPs. The release rate of gemcitabine or/and Re(I) bisquinolinyl complex loaded into LCNPs were evaluated in vitro and the much hydrophilic gemcitabine was released at a faster rate than the much lipophilic Re(I) complex. LCNPs loaded with gemcitabine and Re(I) bisquinolinyl complex in 1:1 ratio illustrated the best anti-pancreatic cancer activity among the synthesised LCNPs formulations (IC50 of BxPC3: 0.15 μM; IC50 of SW1990: 0.76 μM) through apoptosis. This work highlights the relevance of drug combinations, drug conjugation and formulations with LCNPs strategies to improve therapeutic potency. Future in vivo validations will be helpful to further bridge this work from bench to bedside.