Electronic Theses and Dissertations (PhDs)

Permanent URI for this collectionhttps://hdl.handle.net/10539/37932

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    Identification of (Novel) Immune Targets with Potential Roles in the Progression of Pancreatic Ductal Adenocarcinoma (PDAC)
    (University of the Witwatersrand, Johannesburg, 2024) Nsingwane, Zanele; Nweke, Ekene
    Background: Pancreatic ductal adenocarcinoma (PDAC) is a lethal cancer with a growing incidence and mortality despite novel therapeutic strategies. Its aggressiveness and difficulty to treat suggest the need for a better understanding of associated molecular mechanisms which could be targeted for treatment. The complement signalling pathway may play diverse roles in PDAC by eliciting an immune response, inducing inflammatory responses, and may elevate pathways linked to chemoresistance. However, their role in the progression of PDAC is not fully understood. This study aimed to identify potential immune response-related targets in a group of patients. Methods: In this study, 30 tissue samples (tumours and corresponding normal tissues) were obtained from 15 PDAC patients, 34 plasma samples were obtained from 25 PDAC patients, 6 patients with chronic pancreatitis, and 3 healthy control participants. Targeted pathway-specific PCR analysis was conducted to determine the gene expression profiles of immune-response-related genes. The circulating levels of complement proteins C3 and C5 were further investigated. Pharmacological inhibition of the complement pathway in MIA PaCa-2 pancreatic cancer cell lines was performed and the effect on cells was assessed by cell proliferation, cell migration, and cell cycle assays. Finally, SWATH-mass spectrometry was performed to identify potential molecular mechanisms during inhibition. Results: The results identified C3 to be overly expressed in early PDAC compared to later stages in plasma (p=0.047). Pharmacological inhibition of the complement pathway led to increased cell growth (p<0.0001), proliferation (p=0.001) and migration (p=0.002) in vitro. Proteomic analysis implicated several proteins such as the mitochondrial and histone proteins, that could play a role in inducing this phenotype. Conclusion: Both Complement C3 and C5 are elevated in PDAC samples compared to healthy ones. Furthermore, the inhibition of the complement pathway was shown in vitro to result in a more aggressive phenotype by stimulating cellular growth, proliferation, and migration, indicating the involvement of complement C3 and C5 in tumour progression. This study helps to further delineate the role of the complement pathway in PDAC progression.
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    Gene expression patterns of signalling pathways in PDAC: towards inhibiting metastases
    (University of the Witwatersrand, Johannesburg, 2024) Xelwa, Ntombikayise Hendrietta Marcia
    PDAC has a poor prognosis, with its prevalence varying by geographical location. In South Africa, PDAC ranked seventh among all cancer-related deaths in 2020 for both sexes. Specifically, it was the seventh leading cause of cancer death among males and the sixth among females. In 2020, an estimated 1,982 cancer deaths in South Africa were attributed to pancreatic cancer, with 1,006 occurring in males and 976 in females. However, the annual reported number of PDAC deaths in South Africa varies. This study aimed to identify potential novel therapeutic targets for PDAC in patients from the African population. Following ethical approval, tissue from fifteen patients (15 tumour and 15 corresponding normal tissues) were obtained during Whipple procedures from PDAC patients who consented to the study. Despite the development of new treatment strategies, patient outcomes have not significantly improved underscoring the necessity for extensive research to identify novel treatment options. A discovery study was conducted to determine the gene expression profile of signalling pathway-related genes using PDAC tissue samples. Top upregulated pathways included those involved in cytokine signalling, receptor kinase signalling, and PI3/Akt signalling. SPP1 was one of the most highly expressed genes identified in PDAC patients compared to normal corresponding tissues suggesting its potential role in the progression of the disease. To investigate SPP1's role in PDAC, RNA interference was employed to knockdown SPP1 in a PDAC cell line, MIA PaCa-2. Knockdown was confirmed by a significant reduction in SPP1 expression at the mRNA level. Combining SPP1 knockdown with conventional chemotherapy used for PDAC, gemcitabine, resulted in a synergistic effect, leading to an enhanced early apoptotic response. The study also examined the migratory and invasive capabilities of MIA PaCa-2 cells, revealing a noticeable decline in these abilities upon reduction in SPP1 expression with gemcitabine treatment. Furthermore, proteomic analyses uncovered the complex network of cellular processes influenced by the downregulation of SPP1 and the synergistic effects of combination therapy. Altogether, the findings from this study demonstrate the role of SPP1 in PDAC indicating that it could serve as a promising therapeutic target. The synergistic effects observed when SPP1 knockdown was combined with gemcitabine treatment suggest a potential avenue for developing more effective treatments for PDAC while exploring tumour cell adaptation for survival.