Abstract 4328: New perspectives on the use of polo-like kinase 1 as a prognostic biomarker in non-small cell lung cancer

Introduction: Polo-like kinase 1 (Plk1) overexpression is observed in various tumors, including non-small cell lung cancer (NSCLC), and is correlated with poor patient prognosis and metastasis, suggesting a role in aggressive tumors. Previous studies reported Plk1 downregulation by P53 upon DNA damage, suggesting that TP53 mutations might have an influence on Plk1 expression. In this study, we determined the Plk1 protein level in NSCLC patients and correlated these results with the TP53 status, presence of hypoxia (carbonic anhydrase 9, CA-9) and apoptosis induction (cleaved caspase 3). Material & methods: Tumor tissues of 84 NSCLC patients and 16 control samples were obtained from the Antwerp University Hospital. Immunohistochemistry was performed using antibodies to Plk1 (208G4, 1/50), CA-9 (EPR4151(2), 1/350) and cleaved caspase 3 (9579S, 1/250). Based on the% positive cells and staining intensity, an overall score of negative, weak, moderate or strong expression was assigned for both the Plk1 and CA-9 protein. For the TP53 mutation analysis, DNA was isolated using the QIAamp® DNA FFPE tissue kit. For each sample, DNA concentration and purity were assessed using NanoDrop measurement. The relation between DNA input and FFPE derived DNA quality was determined using the QC-plex assay from Multiplicom. Samples were considered to be usable when the DNA quality coefficient was higher than 0.2. Determination of the TP53 mutation status was performed using Multiplicom's TP53 MASTRTM Plus test with MID for Illumina Miseq®. Results & discussion: Plk1 and CA-9 positivity was detected in 95% and 83% of all tumor samples, respectively. Of the 16 control samples, all samples stained negative, except for 4/16 and 1/16 samples that showed a low expression for Plk1 and CA-9, respectively. In a next phase, cleaved caspase 3 staining will be scored and both CA-9 and cleaved caspase 3 expression patterns will be correlated to Plk1 expression. Furthermore, results will be correlated with clinicopathological parameters, including incidence age, smoking behavior, tumor differentiation and stage, metastasis and survival. For the TP53 mutation analysis, sufficient DNA with acceptable purity was isolated from 82 patients. A QC plex reaction has already been performed for 20 samples, 12 of them showed an acceptable DQC value and 8 sampled were marked as low DNA quality samples. Nonetheless, the latter could be used for further analysis by increasing the DNA input. At present, 15