PO-199 Lysyl oxidase in head and neck cancer: metastasis and therapy response

Abstract

Introduction Hypoxia occurs when tumours out-grow the vasculature. It can induce therapy resistance, contribute to metastasis and is a potential biomarker of radioresistance (RR) in Head and Neck Squamous Cell Carcinoma (HNSCC). However, neither identification of patients who might benefit from hypoxia-modification, nor a full understanding of the molecular changes that contribute to metastasis/RR, has been achieved. A recent study by our lab was able to link hypoxic volume in patients with a genetic signature correlating to poor progression-free survival. Lysyl oxidase (LOX) was chosen for further investigation as it has been previously implicated in poor prognosis and hypoxia-induced metastasis. LOX has not however been extensively studied in the context of RR. Additionally, factors other than hypoxia have been shown to contribute to LOX's regulation, but, their relative contributions to metastasis and RR have not been defined. Material and methods LOX was found to be differentially expressed in a metastatic pair of HNSCC cell lines: HSC3 (primary tumour, low expression) and HSC3-M3 (metastatic daughter line, high expression). Using this model, the role of LOX in hypoxia-induced metastasis was studied using invasion, migration and anoikis-resistance assays. LOX was also overexpressed and inhibited (using active site inhibitor BAPN) to determine LOX-specificity. Currently, we are investigating LOX as an inducer of RR by clonogenic assays, comet assay and gH2AX staining. Pathways including epithelial-to-mesenchymal transition (EMT) have so far been investigated as mechanisms. Next we will use bioinformatics to correlate follow up data from our original study and existing datasets, to LOX's involvement in treatment failure and survival. Results and discussions Our results have shown that high expression of LOX, endogenously in metastatic HSC3-M3 cells or by overexpression, can induce a metastatic phenotype resulting in increased invasion, migration and anoikis resistance. Inhibition of LOX reverses these effects, exaggerated in hypoxia where LOX is upregulated. LOX upregulation has also been linked to a change in expression/localisation of EMT regulators such as E-Cadherin and Vimentin. Early results show a potential link to RR. Ongoing studies aim to determine if this effect is a result of LOX's enzymatic activity, or potential transcription factor functioning. Conclusion This work will be the first to highlight LOX as an important biomarker not only in hypoxia-induced metastasis of HNSCC, but also in therapy resistance.