Among 26 cell lines, KYSE220 was the only FGF3/FGF4-amplified cell line (data not shown), and HSC-43, HSC-39, and KATOIII were the only FGFR2-amplified cell lines.14 Sorafenib potently inhibited cellular growth in these four cell lines at a sub-μM 50% inhibitory concentration (IC50) (Fig. 5A). The IC50 values were as follows: HSC43, 0.8 μM; HSC39, 0.6 μM; KATOIII, 0.4 μM; and KYSE220, 0.18 μM. These results suggest that activated FGFR signaling may be involved ACP-196 ic50 in the response to sorafenib.
Finally, we established cancer cell lines stably overexpressing EGFP, FGF3, or FGF4 to examine the relationship between the gene function of FGF3 or FGF4 and drug sensitivity to sorafenib in vivo. Western blotting confirmed that exogenously expressed FGF3 and FGF4 were secreted into the culture medium (Fig. 5B). Sorafenib inhibited the FGF4-conditioned, medium-mediated expression levels of phosphorylated FGFR
(Figure 5C). A similar result was obtained using recombinant FGF4 (data not shown). Mice inoculated with these cell lines were treated with a low dose of oral sorafenib (15 mg/kg/day) or without sorafenib (vehicle control). FGF3 overexpression did not increase the tumor volume compared with EGFP tumors; however, FGF4 overexpression aggressively increased tumor volume and clearly enhanced selleck the malignant phenotype (Fig. 5D). Notably, the low-dose sorafenib treatment significantly inhibited the growth of the A549/FGF4 tumors, whereas it was not effective against A549/EGFP and A549/FGF3 tumors (Fig. 5D). These results suggest that overexpression of FGF4 is partially involved in the response to sorafenib. The FGF3 gene was first identified and characterized based on its similarity to the mouse fgf3/int-2 gene, which is a proto-oncogene activated in virally induced mammary tumors in mice.15 Meanwhile, the FGF4 gene was first identified in gastric cancer as an oncogene HST,
which has the ability to induce the neoplastic transformation of NIH-3T3 cells Sulfite dehydrogenase upon transfection.16 These genes were initially regarded as proto-oncogenes. FGF3 and FGF4 genes are located side-by-side and are also closely located to the FGF19 and CCND1 genes (within 0.2 Mb of the 11q13 region).13 The 11q13 region is known as a gene-dense region, and gene amplification of this region is frequently observed in various solid cancers (including breast cancer, squamous cell carcinoma of the head and neck, esophageal cancer, and melanoma) at frequencies of 13%-60%.13 On the other hand, the frequency of FGF3/FGF4 amplification in HCC remains largely unclear.