Despite aggressive chemoradiation (CRT) protocols in
the treatment of patients with head and neck squamous cell carcinomas
(HNSCC), the outcome is still unfavorable. To improve therapy efficacy
we had already successfully tested the multikinase inhibitor sorafenib
in combination with irradiation (IR) in previous studies on HNSCC cell
lines. In this study we investigated its effect on combined CRT
treatment using cisplatin.Radio- and chemosensitivity with and without
sorafenib was measured in four HNSCC cell lines and normal fibroblasts
(NF) by colony formation assay. Apoptosis and cell cycle analysis were
performed by flow cytometry.

In HNSCC cells,
sorafenib enhanced the antiproliferative effect of cisplatin without
affecting apoptosis induction and with only minor effects on cell
inactivation. Sorafenib added prior to irradiation enhanced cellular
radiosensitivity in three of the tested HNSCC cell lines and caused
massive overall cell inactivation when combined with CRT. In contrast,
sorafenib did not radiosensitize NF and reduced cisplatin-induced cell
inactivation. Cell inactivation by IR and cisplatin is further increased
by the addition of sorafenib in HNSCC, but not in NF cells. Therefore,
sorafenib is a promising candidate to improve therapy efficacy for
HNSCC.