Periostin splice variants in pancreatic cancer

Rahim, Musamma Jamila (2019) Periostin splice variants in pancreatic cancer. (PhD thesis), Kingston University, .


Introduction: Pancreatic ductal adenocarcinoma (PDAC) is typically characterised with fibrotic stroma. It is a lethal disease due to its incidence rate being almost equal to its mortality rate. The poor prognosis of PDAC has not changed for the past forty years is due to lack of early detection, late diagnosis of the cancer and ineffectiveness of conventional treatments due to chemoresistance. Recent studies show a critical role of the tumour microenvironment in cancer progression. Periostin (POSTN) is a matricellular protein involved in development and tissue injury. POSTN is overexpressed in multiple types of cancer including PDAC. Alternative splicing has been shown to generate multiple POSTN transcript variants in other tissues but has not been examined in PDAC. The aim of this project was to investigate the POSTN isoforms in PDAC and carry out functional studies to characterise these isoforms. Methods: Bioinformatics analysis of POSTN was carried out to investigate the potential POSTN isoforms and an RT-PCR approach was used to detect the expression of POSTN isoforms in multiple cell lines. Western Blot analysis was carried out on PS-1 cell lysates to detect POSTN protein expression. Traditional cloning was utilized to clone all POSTN isoforms to produce recombinant proteins to carry out functional studies. Results: Bioinformatics analysis reveal ten POSTN transcript variants across three databases (Ensembl, Genbank and AceView). Predictions made from domain databases show two potential intracellular POSTN proteins. RT PCR analysis showed expression of seven POSTN transcript variants namely POSTN-001, 002,003,004, 201a, 201 band novel POSTN isoform in pancreatic stellate (PS-1) cells. POSTN was not expressed in any cancer cell lines tested. Similarly, Western blot analysis showed the presence of potential POSTN protein isoforms. Substantial progress was made with cloning POSTN isoforms. Conclusion: This study revealed the presence of several POSTN isoforms in pancreatic stellate cells which has the potential to be used as clinical biomarkers or therapeutic targets of PDAC. Further studies are warranted to fully characterise these isoforms.

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