However, at lower doses of vandetanib, growth of OZ (refractory to the anti-proliferative effects of selleck chem inhibitor EGFR inhibition) xenograft was not significantly inhibited despite the proliferation and angiogenesis being reduced. These in vivo experiments suggest that anti-EGFR treatment is effective in cholangiocarcinoma with activated EGFR signalling (e.g., EGFR amplification), and that inhibiting stromal angiogenesis through VEGFR inhibition also contributes to abrogate tumour environment and suppress tumour growth, although the synergistic effect between EGFR and VEGFR-2 inhibition was not clear in this study. As cholangiocarcinoma cases expressing VEGFR-2 was reported (Wiedmann et al, 2006), VEGFR-2 inhibition may also be directly effective in a part of cholangiocarcinoma.

Collectively, targeting both angiogenesis and the active growth signal pathway, for example, inhibiting EGFR, might exert an auxiliary effect, leading to robust tumour regression in cholangiocarcinoma. Anti-metastatic effects of vandetanib in vivo Metastasis is a main cause of cancer death, and intrahepatic or lymph node metastases are independent prognostic factors in cholangiocarcinoma (Yoshikawa et al, 2008). An in vivo imaging system was used in the intravenous tumour cell-seeding study to elucidate whether vandetanib has an anti-metastatic effect. As in vivo tumour imaging can observe chronological changes in tumour growth in the individual animals with a high degree of sensitivity, which has been difficult to estimate by other current methods (Jenkins et al, 2003), time to metastasis was assessed as an index of anti-metastatic effects in our model.

The time to metastasis in the vandetanib-treated group was significantly longer than that in the vehicle-treated group, although the final incidence of metastasis was not statistically different between the two groups at the end of study. Decreasing activity of MAPK, which is a downstream molecule of the EGFR pathway, reduces tumour proliferation in vivo (Aguirre Ghiso et al, 2003). In animal models, an EGFR inhibitor, gefitinib, prevents carcinogenesis of gallbladder and lung cancer (Kiguchi et al, 2005; Yan et al, 2006), and reduces the incidence of metastasis of prostate carcinoma cells (Angelucci et al, 2006). In our model, EGFR inhibition contributed to the anti-metastatic effect of vandetanib.

Moreover, angiogenesis is essential for the growth of tumours more than 1�C2mm in diameter (Fidler and Ellis, 1994; Ellis and Fidler, 1996; Yano et al, 2005), and VEGF is necessary for the formation of metastatic tissues at the primary site (K��sters et al, 2007). It is Entinostat possible that VEGFR inhibition at the primary site may reduce the hematogenic metastasis in cholangiocarcinoma. Indeed, VEGF expression is associated with intrahepatic metastasis in IHCC (Yoshikawa et al, 2008).