Ovarian cancer is the eighth most common female cancer worldwide and the most lethal of all gynaecological malignancies. Mortality rates of this malignancy have remained largely unchanged for decades. This is mainly due to the majority of women presenting with advance disease. The aim of this study was to identify the spectrum of TP53 mutations in a cohort of ~80 primary high grade serous cancers (HGSCs) and small panel of previously untested HGSC cell lines using a Fluidigm p53 Access Array followed by deep sequencing (Illumina). The depth of coverage for the Illumina Sequencing was between 1000 to 3000 reads per individual base. Identified mutations were visualised using Integrative Genomics Viewer (IGV) software and confirmed by Sanger sequencing. p53 immunohistochemical staining was undertaken in matched FFPE sections and results compared with the type of mutation identified. Our results demonstrated that >85% of HGSC samples contained a TP53 mutation. Increased p53 staining was seen in 45 of 45 HGSCs that contained a missense TP53 mutation. Seventeen HGSCs that had mutations identified presumed to correlate with loss of function (i.e. frameshift, splice site, deletions, insertions and stop mutations) could not be distinguished from wild-type p53 by immunohistochemical staining. The Next Generation Sequencing (NGS) platform was determined to be better equipped to identify TP53 mutations occurring at low frequency due to tumour heterogeneity or presence of normal tissue compared with Sanger sequencing.
In conclusion, this study demonstrated a correlation between TP53 mutation type and p53 immunohistochemical staining profiles. Furthermore, we demonstrated the advantages of NGS as a powerful tool for detecting TP53 mutations compared with Sanger sequencing and immunohistochemistry.