Metastases of squamous cell carcinoma of the head and neck show increased levels of nucleotide excision repair protein XPF in vivo that correlate with increased chemoresistance ex vivo

Nucleotide excision repair (NER) is a key node of resistance of tumour cells to the anticancer drug cisplatin. Testicular germ cell tumours (TGCT) show exquisite sensitivity towards cisplatin, and this has been connected to low levels of the NER proteins ERCC1 and XPF. Tumours of some patients with advanced head and neck squamous cell carcinoma (HNSCC) regress well under cisplatin chemo- therapy but prediction of responsiveness is poor. Little is known about the levels of ERCC1-XPF in HNSCC tissues and cell lines. We investigated mRNA and protein levels of ERCC1 and XPF in 13 HNSCC cell lines and seven testis tumour cell lines and examined the correlation between levels of ERCC1 and XPF and cellular resistance towards cisplatin. No significant difference in mRNA expression of either ERCC1 or XPF in the HNSCC cell lines compared to the testis tumour cell lines was observed. Significantly higher XPF protein levels were found in HNSCC cell lines compared to testis tumour cell lines resulting in cellular cisplatin resistance. The data indicate a contribution of XPF protein for the cisplatin resistance observed in HNSCC cell lines. Subsequently, XPF and ERCC1 protein expression was investigated in cancer tissue of 34 patients. XPF levels were significantly higher in metastases of HNSCC patients than in primary cancer tissue. These findings indicate a contribution of XPF protein for the observed chemoresistance in some HNSCC tissue. XPF protein may be a predictive marker for cisplatin responsiveness of metastases in HNSCC patients.