Investigating WNK-SPAK/OSR1 signalling in breast cancer

Fdel, Azeza 2025. Investigating WNK-SPAK/OSR1 signalling in breast cancer. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

The WNK, SPAK, and OSR1 kinases regulate the function of cation chloride co-transporters (CCC), which influence electrolyte balance and blood pressure. Mutations in WNK kinases have been linked to Gordon's syndrome, a hereditary form of hypertension. Under osmotic stress, WNK kinases become activated and phosphorylate SPAK and OSR1 kinases, which in turn phosphorylate CCCs to control electrolyte transport. OSR1 has emerged as a potential therapeutic target and biomarker for poor prognosis in breast cancer, particularly triple-negative breast cancer (TNBC). This study investigated OSR1 expression, phosphorylation status, and kinase activity across various breast cancer cell lines. OSR1 was expressed in both luminal and TNBC subtypes but displayed constitutive kinase activity specifically in the highly migratory MDA-MB-231 TNBC cell line, independent of p53 mutation status. Functional studies revealed that while OSR1 inhibition did not significantly affect cell viability, it markedly reduced migration and invasion, suggesting its role in cancer cell motility. Overexpression of active OSR1 in the non-migratory MCF7 line enhanced its mobility, further supporting OSR1’s role in promoting metastatic potential. Using immunoprecipitation and mass spectrometry we identified new proteins that bind OSR1, which was confirmed by Western lotting. Notably, pulldown assays demonstrated the interaction between OSR1 and these new proteins was independent of OSR1’s CCT domain. Moreover, novel compounds AF-01, AF-02, and AF-03 potently inhibited OSR1 kinase activity in vitro. These results establish OSR1 as a key mediator of TNBC progression through its role in cell migration, regulated by WNK signalling, and support its therapeutic targeting for aggressive breast cancer subtypes.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Schools > Pharmacy
Subjects:	Q Science > Q Science (General)
Date of First Compliant Deposit:	3 November 2025
Last Modified:	03 Nov 2025 14:32
URI:	https://orca.cardiff.ac.uk/id/eprint/182061

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