Head and neck squamous cell carcinoma (HNSCC) is worldwide the 6th most frequent cancer and affects more than 550,000 individuals per year. Standard treatments include surgery, chemotherapy, radiotherapy, and molecular target regimes addressing the EGF receptor. Despite current developments, the radioresistance of tumours remains a main issue that causes therapy failure. Therefore, the identification of molecular markers that predict the radiation response of HNSCC could improve therapy by the enforcement of personalized therapy approaches. DNA gains on chromosome 16q23-24 have been shown to correlate with reduced progression-free survival after radiotherapy in HNSCC (Bauer et al., 2008). Located on chromosome 16q24.3, FancA has been proposed as a potential biomarker for the radiation response. To clarify the effect of FancA overexpression in vitro, FancA overexpressing keratinocytes were generated and characterized for their radiation response. FancA overexpressing cells demonstrated an enhanced clonogenic survival compared to the vector control (OKF6/vec) and the parental cell line (OKF6/TERT1) in response to gamma-irradiation, proving a radioprotective mechanism of FancA. To identify key players and pathways involved in FancA mediated radioresistance, microarray based global transcriptome analysis was performed on OKF6/FancA and OKF6/vec cells at 15 min, 2 h and 4 h after treatment with 4 Gy of gamma-irradiation or sham-irradiation (0 Gy). To analyse the effects of the FancA overexpression alone, OKF6/TERT1 cells were also subjected to transcriptome analyses. Differentially expressed genes were mapped to the global human interaction network from the Reactome database to reconstruct interaction networks and perform pathway enrichment analyses. FancA overexpression alone induced altered expression of 1129 genes (FDR<0.05). Interestingly, 37 of the top 50 genes are known to belong to the IFN signature. Pathway enrichment analysis identified 32 significantly overrepresented pathways including IFN signalling, mTOR, EGF receptor, ERBB1 and FGF signalling pathways. Gamma-irradiation led to the differential expression of 205 and 371 genes in OKF6/FancA and OKF6/vec cells, respectively. Pathway enrichment analysis showed the involvement of DNA damage response pathways in both cell lines. However, FOXM1 TF network, ECM, WNT, ERBB4, Aurora, c-Myc signalling pathways and the senescence-associated secretory phenotype (SASP) were involved exclusively in the radiation response of FancA overexpressing cells. Therefore, these pathways will be subjected to further in-depth analyses, in order to identify candidate targets for an improved personalized radiotherapy. Moreover, correlation of the 16q24.3 marker with overall survival was validated in the TCGA HNSCC cohort (n=113) supporting our findings. This collaborative project is funded by the BMBF (ZISS 02NUK024)
