Opioid binding Protein/Cell adhesion Molecule-Like (OPCML) is a tumour suppressor gene (TSG)
in epithelial ovarian cancer (EOC). EOC is one of the most common cancers affecting women
and has a very poor prognosis due to the asymptomatic nature of the disease, with the added issue of extremely high recurrence. OPCML functions as a tumour suppressor but the tumour
suppressor function is epigenetically inactivated in EOC. Previous studies have demonstrated
OPCML could be a viable therapeutic to treat EOC patients. Studies have shown re-introduction
of functional OPCML to cancer cell lines causes a reduction in growth and proliferation.
Therefore, a novel biotherapeutic of synthetic OPCML could have potential as a treatment postsurgery to prevent further spreading of the cancer and recurrence.
The focus of this thesis has been to create a novel biotherapeutic with a semi-synthetic OPCML targeted to the membrane of cancer cells using a GPI anchor mimetic, and to validate this
protein anchor complex as a potential drug in EOC.
The design and synthesis of a highly engineered OPCML construct, which has the functionality
required to introduce complex chemical prosthetic groups to mimic the GPI anchor, was
successfully expressed and purified. The construct included an HA tag for visualisation, an LPETG recognition site for sortase mediated transpeptidation (sortagging), an Fc protein sequence for purification, and a thrombin cleavage site so the Fc sequence could be removed postpurification.
The GPI anchor mimetic was synthesised by solid phase peptide synthesis (SPPS) on a biotin
resin and included myristoyl groups, a side chain with a photo cross-linkable moiety, and three
glycines suitable for acting as a sortagging nucleophile. The protein was consequently modified by attachment of a GPI anchor mimetic via sortagging successfully. However, purification postsortagging was challenging.