| Summary: | <p>Pancreatic ductal adenocarcinoma (PDAC) is a notoriously ferocious malignancy arising from the head of the pancreas, with aggressive biology and early-onset metastases. PDAC develop and progress asymptomatically with over 80% of the patients presenting for diagnosis with inoperable metastatic tumours that are resistant to standard therapies. Late diagnosis has resulted a grim increase of the five-year survival statistics from less than 5% to 8% over the past four decades.</p>
<p>The TP53 gene is mutated in approximately 75% of invasive pancreatic intraepithelial neoplasia lesions (PanIN-3) and PDAC. Mutations of p53 plays an important role in PDAC tumorigenesis, and several mutants have been shown to be overexpressed in both PanIN-3 lesions and PDAC patients. Mutant p53 overexpression is associated with chemoresistance and poor prognosis among PDAC patients. Thus, imaging of p53 overexpression could pave a new path for early diagnosis of enriched high risk PDAC population, and stratifying patients in treatment groups. In this study, I envisioned to interrogate aberrant p53 expression in PDAC models using monoclonal antibody- and peptide-based radioimmunoconjugates (RICs). I aimed to develop radiolabelled imaging agents for early diagnosis and prognosis evaluation of PDAC.</p>
<p>I produced, purified, and validated a novel anti-total p53 monoclonal antibody (49A1/H10) with nanomolar affinity and high specificity and selectivity. 49A1/H10 was employed to quantify mutant p53 levels in a panel of pancreatic cancer cell lines. I then employed the strain-promoted alkyne-azide cycloaddition (SPAAC) click chemistry radioconjugation method (DBCO-N3 method) to conjugate TAT cell penetrating peptide (CPP) and DTPA on 49A1/H10 mAb. DTPA-49A1/H10-TAT was further radiolabelled with indium-111 radionuclide [111In] to yield [111In]-DTPA-49A1/H10-TAT.</p>
<p>The cellular uptake and retention of [111In]-DTPA-49A1/H10-TAT were investigated in three PDAC cell lines with varying p53 expression. Having completed the in vitro validation of the anti-total p53 RICs, I established subcutaneous p53 PDAC xenograft models and employed SPECT/CT to image and quantify the tumour uptake and biodistribution of [111In]-DTPA-49A1/H10-TAT.</p>
<p>In the second part of my project, I attempted to validate p53-targeting peptides using in vitro techniques.</p>
<p>In this thesis, I establish preliminary evidence of SPECT imaging mutant p53 overexpression in PDAC models. This study opens new avenues for further exploring the suitability of imaging mutant p53 as a biomarker early diagnosis and prognosis evaluation of PDAC patients.</p>
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