Abstract A124: ERCC1 expression correlates with EGFR expression and is regulated by cisplatin, cetuximab, and dasatinib in head and neck cancer cells

Abstract

Abstract Background: ERCC1 has been linked to resistance against platin-based chemotherapy. Cetuximab sensitizes colorectal cancer cells to oxaliplatin. This sensitization coincides with ERCC1 downregulation, but the link between EGFR and ERCC1 is not fully understood. It is known that treatment with cetuximab inhibits nuclear transport of EGFR and DNA repair in response to irradiation. Moreover, cisplatin treatment results in phosphorylation at Y845 and nuclear transport of EGFR. We intended to investigate the regulation of ERCC1 by cisplatin, cetuximab and dasatinib, a src inhibitor stabilizing EGFR in the membrane, its relevance for chemosensitivity and its correlation with EGFR and its phosphorylation at Y845 in head and neck cancer cells. Material and Methods: In UM-SCC 14c head and neck cancer cell line, ERCC1, EGFR and EGFR (pY845) expression was determined by western blot and FACS analysis. Cell viability, cell cycle and apoptosis induction was assessed by cell titer blue assay, propidium iodide and caspase 3 staining, respectively. Results: In cell viability assay, combination of cisplatin with cetuximab led to a significant (p<0.05) and dose dependent sensitization to cisplatin. Cisplatin increased ERCC1 expression dose dependently. In contrast to previous reports, combination of cisplatin with cetuximab increased ERCC1 expression even stronger than the respective monotherapies. Mirroring the ERCC1 increase, we found a dose dependent increase of EGFR (pY845) after cisplatin and cetuximab treatment and the combination treatment led to an increased phosphorylation compared to monotherapy. Dasatinib decreased EGFR (pY845) but clearly increased EGFR and ERCC1 in parallel. To establish whether the findings after cisplatin and cetuximab treatment were EGF-receptor dependent we treated peripheral blood leukocytes, lacking the EGFR. No dose dependent regulation was observed by any monotherapy or combination of cetuximab and cisplatin. Conclusion: 14c cells are sensitized to cisplatin treatment by adding cetuximab. ERCC1 expression correlated with phosphorylation status of EGFR (pY845) following treatment with cisplatin and cetuximab. However, treatment with the src inhibitor dasatinib before adding cisplatin and cetuximab reduced phosphorylation of EGFR (Y845), but increased ERCC1 and EGFR expression. Whether the increase of ERCC1 is a late effect due to transcriptional upregulation of EGFR after dasatinib treatment remains to be determined. However, the dose-effect relationship and the lack of regulation of ERCC1 expression in peripheral blood leukocytes after treatment with cisplatin and cetuximab support the notion that ERCC1 expression is regulated by EGFR in 14c cells. Further studies elucidating the subcellular transport of EGFR and its transcriptional regulation after dasatinib treatment are ongoing and will be presented. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A124.