Growth factor signals are propagated from the cell surface to intracellular 
processes that control critical functions such as growth, differentiation, 
angiogenesis, and inhibition of apoptosis via sequential kinase signaling. These 
kinases are receptor kinases, which are transmembrane proteins such as epidermal 
growth factor receptor or cytoplasmic kinases such as Src kinase. In 
malignancies, these signaling pathways are often exploited to optimize tumor 
growth and metastasis. Thus, they represent attractive targets for cancer 
therapy. This review will summarize current knowledge of the small-molecule 
multiple-kinase inhibitors in lung cancer therapy. These inhibitors generally 
hinder the phosphorylation of several protein kinases of membrane receptors, 
such as vascular endothelial growth factor receptors, platelet-derived growth 
factor receptors, the human epidermal growth factor receptor family, and 
cytoplasmic receptors such as c-Kit, Raf kinase, and FLT3. These inhibitors 
include ZD6474, SU11248, AEE 788, sorafenib, vatalanib, and AG-013736.