Figure 5. Effects of VPA/HU on the growth factor receptors EGFR and ERB-B2, and suppression of HNSCC tumor growth in vivo.

A/B) FaDu cells were treated with V, HU, VPA/HU (1.5 mM each) or PBS (C). Expression of the indicated proteins was analyzed by immunoblotting. Actin served to control equal loading. VPA/HU treatment effectively reduced the levels of total and phosphorylated EGFR, whereas ERB-B2 levels were not affected. C) FaDu cells treated with VPA/HU (1.5 mM each) were FFPE and used for IHC analysis employing EGFR- or BIM-specific Ab. Treatment resulted in reduced expression and cell surface localization of the EGFR as well as increased BIM levels. D) VPA/HU suppressed the growth of FaDu HNSCC xenograft tumors. Growth curve of tumors subjected to VPA/HU (i.p., 350 mg/kg and 750 mg/kg body weight) or PBS control. Nude mice were inoculated with FaDu tumor cells. When tumors had reached the target size of 0.1 cm³, mice were treated once every second day for 14 days. *p<0.001, n=4 animals per treatment group, data are mean±SD. E) Enhanced BIM and reduced EGFR levels in xenograft tumors at the end of VPA/HU treatment. BIM and EGFR expression was visualized by IHC.