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Title: Identifying novel substrates of salt-inducible kinase 2
Author: Mannion, David Leslie
ISNI:       0000 0004 6495 4321
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2016
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Salt-inducible kinase 2 (SIK2) has previously been identified as a potential therapeutic target in high-grade serous ovarian cancer. Depletion of SIK2 sensitises ovarian cancers to paclitaxel treatment both in vitro and in xenograft models. In patients, increased tumour SIK2 expression is associated with paclitaxel resistance and correlates with increased risk of cancer progression following paclitaxel treatment. Although high-grade serous tumours are highly chemosensitive, 80-90% of patients with advanced stage disease eventually relapse due to recurrent chemotherapy-resistant disease, so there is a pressing need for novel therapeutic targets. Inhibition of SIK2 is a plausible strategy to augment existing chemotherapy in ovarian cancer, but signalling downstream of SIK2 has not been well studied. Here, I present the optimisation and results of a chemical genetic screen to identify novel SIK2 substrates to facilitate its development as a therapeutic target. The screen used a SIK2 gatekeeper mutant engineered to utilise a 'bulky' A*TP?S analogue to specifically label its substrates in lysates from an ovarian cancer cell line. A covalent capture approach was then used to isolate labelled peptides for identification by tandem mass spectrometry. Between four independent screen experiments, 73 putative substrate proteins were identified, 18 of which were present in multiple replicates. SIK2 was found to phosphorylate the p85a regulatory subunit of PI3 kinase at S154, resulting in activation of the PI3K/AKT signalling pathway. Furthermore, PI3K/AKT signalling was stimulated in ovarian cancer cells upon incubation with primary adipocytes extracted from the omentum, a key site of ovarian cancer metastasis, in a SIK2 dependent manner. Finally, overexpression of wild-type SIK2, but not a kinase-inactive mutant, in ovarian cancer cell lines promoted tumour growth and metastasis in a xenograft model. Together, this evidence suggests that in addition to its role in chemotherapy resistance, SIK2 also promotes the establishment of omental metastases in ovarian cancer.
Supervisor: Ahmed, Ahmed Ashour ; McMichael, Andrew J. Sponsor: Medical Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available