Investigating the expression of plasma membrane calcium ATPase (PMCA) in patient-derived glioblastoma cultures

Glioblastoma is the most prevalent and aggressive form of primary brain tumour in adults, characterised by extensive heterogeneity, rapid progression, and resistance to conventional therapies such as surgery, radiotherapy, and chemotherapy. Despite decades of research, the median survival for glioblastoma patients remains approximately 15 months, and recurrence is almost universal. In light of these challenges, this thesis explores the role of Plasma Membrane Calcium ATPases (PMCAs) in the pathology of glioblastoma, with a specific focus on isoforms PMCA1, PMCA2, and PMCA4. Patient-derived glioblastoma cultures and biopsy samples were employed to investigate PMCA expression patterns at both the transcript and protein levels. Quantitative RT-PCR and western blotting revealed that PMCA1 and PMCA4 were significantly overexpressed in several patient-derived cell cultures compared to normal human astrocytes and control cell lines. PMCA2, in contrast, exhibited more variable expression, often low or undetectable in most glioblastoma cultures. Immunofluorescence and flow cytometry analysis supported these findings, demonstrating heterogeneous distribution of PMCA isoforms among samples. A key focus of the study was the effect of tumour hypoxia, a hallmark of glioblastoma, on PMCA expression. Cells cultured under hypoxic conditions (1% O₂) showed altered PMCA isoform expression, particularly a consistent downregulation of PMCA1 and PMCA2, suggesting a role in adaptation to hypoxic stress. This may have implications for calcium- mediated survival mechanisms in the hypoxic tumour core, contributing to treatment resistance and tumour progression. The study also evaluated how clinically relevant drugs modulate PMCA expression. Treatment with the anti-angiogenic agent sunitinib resulted in a dose-dependent upregulation of PMCA1 and downregulation of PMCA2 and PMCA4 at mRNA levels in multiple glioblastoma cell cultures, indicating that PMCA expression may be responsive to targeted therapy. Correlating PMCA expression with patient survival data revealed that elevated PMCA1 expression levels were associated with better overall survival, suggesting their potential as prognostic biomarkers. Furthermore, the characterisation of glioblastoma cultures using markers such as CD44 and Olig2 confirmed the coexistence of mesenchymal and proneural features within individual patient-derived cultures, reinforcing the intratumoral heterogeneity observed in clinical glioblastoma. The results of this study provide evidence that PMCA isoforms, particularly PMCA1 and PMCA4, play a functional role in glioblastoma pathophysiology, potentially contributing to hypoxia tolerance, drug response, and tumour aggressiveness. These findings not only deepen our understanding of calcium signalling in glioblastoma but also propose PMCAs as potential therapeutic targets or biomarkers for stratifying patients and guiding treatment strategies.

Citation

Najafi, S. (2026) Investigating the expression of plasma membrane calcium ATPase (PMCA) in patient-derived glioblastoma cultures. University of Wolverhampton. https://wlv.openrepository.com/handle/2436/626398

Publisher

University of Wolverhampton

URI

https://wlv.openrepository.com/handle/2436/626398

Type

Thesis or dissertation

Language

en

Description

A thesis submitted in fulfilment of the requirement of the University of Wolverhampton for the degree of Doctor of Philosophy.

Collections

Theses and Dissertations