Protein disulfide isomerase inhibition: a novel therapeutic strategy against pancreatic cancer

Powell, Lauren (2025). Protein disulfide isomerase inhibition: a novel therapeutic strategy against pancreatic cancer. University of Birmingham. Ph.D.

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Abstract

As a lethal condition with poor prognosis, pancreatic cancer treatment needs to move away from conventional cytotoxic therapies and towards the development of novel therapies through the discovery of precise molecular targets. A potential target is protein disulfide isomerase (PDI). PDI acts to refold misfolded proteins and alleviate endoplasmic reticulum (ER) stress, a characteristic commonly recognised in cancer, as part of the unfolded protein response (UPR). This demonstrates the protective roles of PDI and highlights PDI as a potential therapeutic target for cancer treatment. The study aimed to develop novel therapeutic strategies through the investigation of the roles of PDI and the UPR pathway in pancreatic cancer progression.

Of the 21 proteins in the PDI gene family, PDIA1 and AGR2 were identified as potential influential members in pancreatic cancer progression. PDIA1 and AGR2 were significantly knocked down via small interfering RNA (siRNA) transfection. Knockdown was confirmed by Western blot, real-time quantitative polymerase chain reaction (RT-qPCR) and a PDI enzyme activity assay in pancreatic cancer cell lines: Panc-1, Mia-PaCa-2, and AsPC-1. PDI activity was also significantly inhibited after treatment with PDI inhibitors: propionic acid carbamoyl methyl amide (PACMA)-31 and CCF642. PDI inhibitor treatment and PDIA1 and AGR2 siRNA knockdown demonstrated significant inhibition of cell proliferation, cell viability and cell migration across the pancreatic cancer cell lines.

Investigations into ER stress marker mRNA and protein expression provided an insight into the effects of PDI inhibition on UPR pathway activations, particularly through the dysregulation of spliced X-box binding protein 1 (XBP-1s). PDIA1 knockdown significantly decreased XBP-1s mRNA and protein expression in AsPC-1. AGR2 knockdown significantly increased caspase-3 activity in Panc-1. These data suggest that AGR2 inhibition could trigger a pro-apoptotic response through chronic UPR signalling and caspase-3 activation and that PDIA1 inhibition may act to repress pro-survival gene XBP-1s.

Investigations of PDI inhibitor and gemcitabine combination therapy demonstrated a potential synergistic effect in driving significant inhibition of cell proliferation with 1µM PACMA-31 and 0.05µM gemcitabine combination treatment in Mia-PaCa-2. XBP-1s mRNA expression was also significantly increased with PACMA-31 and gemcitabine combination treatment, suggesting a potential role of XBP-1s in gemcitabine resistance and highlighting it as further therapeutic target.

Collectively, the data in the current study suggest that inhibition of PDI disrupts pancreatic cancer cell proliferation and migration and further contributes to UPR pathway dysregulation, driving ER stress-induced apoptosis.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):