The impact of Survivin, WRAP53β, and Hypoxia on treatment response in Head and Neck Cancer

Abstract: Squamous cell carcinoma (SCC) is the most common histological type of cancer in the head and neck region and arises in the epithelial mucosa of the upper aerodigestive tract. Approximately one and a half million people are living with the diagnosis. Despite efforts in prevention and advances in treatment, the 5-year survival rate still lies around 60%, and recurrences and second primary tumors remain a problem. Moreover, treatment responses vary from patient to patient, highlighting the need for individually tailored treatments. To make this possible, biomarkers predicting treatment outcome are needed to better guide treatment decisions.The aim of this thesis was to evaluate the expression of certain proteins and the frequency of certain SNPs (Single nucleotide polymorphisms) in tumor biopsies and cell cultures of head and neck squamous cell carcinomas (HNSCC), and to explore their potential as biomarkers for treatment outcome. Furthermore, we aimed to study the impact of hypoxia on treatment response, epithelial-tomesenchymal transition (EMT), and induction of cancer stem cells (CSC).In papers I and II, we investigated two proteins, survivin and WRAP53β, using immunohistochemistry (IHC) in tumor biopsies from 40 patients categorized as Non-responders or Responders to radiotherapy. High expression of survivin and nuclear expression of WRAP53β were significantly more prevalent in the Responder group. The combination of these two factors correlated strongest to overall survival, but not to a significantly higher extent compared to survivin alone. Moreover, when examined separately, a high percentage of p53-stained cells and the presence of the SNP FGFR4 Gln388Arg correlated to improved overall survival, whereas the SNP XPD Lys751Gln was associated with worse overall survival. The latter three showed no significant correlations to radiotherapy response. In paper III, the two most promising proteins identified in papers I and II were analyzed in a study cohort of 149 tumor biopsies of glottic laryngeal SCC, categorized as T2N0-T3N0. In this patient group, no significant associations between survivin expression and survival could be found. However, expression of cytoplasmic WRAP53β was significantly linked to worse disease-free-survival (DSF) compared to nuclear WRAP53β or negative staining for WRAP53β. Positive expression of p16INK4a was found in 7% of the tumors. The prevalence of p16 INK4a was higher in younger patients (<60) and associated with absence of recurrence and longer DSF.In paper IV, five HNSCC cell lines were cultured in normoxic (20% O2) and hypoxic (1% O2) conditions and changes in treatment response, EMT profile, and expression of CSC markers were examined. As expected, hypoxia induced EMT and to a certain extent expression of CSC markers. Silencing of the hypoxia-inducible-factor-1α (HIF-1α) only partly reversed these effects, suggesting that other mechanisms are involved. Whereas most cell lines became more resistant to treatment in hypoxia, one cell line (LK0412) became more sensitive to cetuximab-treatment in hypoxia, an effect that was revoked by depletion of HIF-1α, suggesting a possible sensitizing effect of HIF-1α to cetuximab-treatment.Taken together, WRAP53β appears to be a promising biomarker candidate for treatment outcome in HNSCC, but further evaluation especially on the subcellular localization of WRAP53β is required. Even though the role of survivin in radiotherapy response in glottic SCC seems to be insignificant, it might have a more important role in other HNSCC subsites. As far as the effects of hypoxia, it appears that hypoxia might have a sensitizing effect on cetuximab-treatment in certain cases, which seems to be HIF1-α –dependent. Further studies are required to clarify the importance of this observation.