We determined whether blockade of the
epidermal growth factor-receptor (
EGF-R) signaling pathway by
oral administration of the
EGF-R
tyrosine kinase inhibitor PKI166 can inhibit angiogenesis and growth of SN12PM6 human
renal cell carcinoma (HRCC) in the kidney of nude mice and whether
gemcitabine can potentiate these effects. In vitro treatment of HRCC cells with
PKI166 inhibited
EGF-R autophosphorylation, which correlated with a decrease in expression of
Bcl-xl protein and phosphorylation of signal transducers and activators of transcription, particularly signal transducers and activators of transcription 3.
PKI166 also decreased expression of
vascular endothelial growth factor and
basic fibroblast growth factor in a dose-dependent manner.
Oral administration of
PKI166 or
PKI166 and injected
gemcitabine or
gemcitabine alone beginning 7 days after implantation of SN12PM6 cells into the kidney of athymic nude mice reduced the volume of
tumors by 26, 61, and 23%, respectively. In another experiment 28 days after the orthotopic implantation of SN12PM6 cells,
nephrectomy was performed followed by 4 weeks of treatment. Treatment with
PKI166 and, more so,
PKI166 plus
gemcitabine significantly inhibited lung
metastasis, corresponding to a significant increase in overall length of survival.
EGF-R activation was significantly blocked by
therapy with
PKI166 and was associated with a significant reduction in expression of
vascular endothelial growth factor and
interleukin-8, decreased microvessel density, decreased staining of
proliferating cell nuclear antigen, and increased
tumor cell apoptosis. Collectively, the data indicate that targeting activation of
EGF-R on HRCC produces significant therapeutic benefits.