Anti-tumoral drug effect in combination with gemcitabine, 5-fluorouracil (5-FU) and Polo-like kinase 1 inhibitor BI2536 was also studied. RESULTS: In vitro treatment with NVP-AEW541 suppressed growth in all human BTC cell lines, however response was lower in gallbladder cancer. Treatment with NVP-AEW541 likewise was associated with dephosphorylation of IGF-1R and AKT. In contrast, phosphorylation of p42/p44 and Stat3 and expression of Bcl-xL were inconsistently downregulated. In addition, treated cells showed cell cycle arrest at the G1/S-checkpoint and an increase in sub-G1 peak. Moreover, IGF-1R and its ligands IGF-1 and IGF-2 were co-expressed in RT-PCR, suggesting an autocrine loop of tumor cell activation. Combined with gemcitabine, NVP-AEW541 exerted synergistic effects, particularly at low concentrations, while effects of combination with 5-FU or BI 2536 were only additive.

CONCLUSION: Our findings suggest that NVP-AEW541 is active against BTC in vitro and potentiates the efficacy of gemcitabine. Keywords: Tyrosine kinase inhibitor, Cholangiocarcinoma, Gemcitabine, NVP-AEW541 INTRODUCTION Insulin-like growth factor-1 receptor (IGF-1R) is a tyrosine kinase receptor with a 70% homology to the insulin receptor[1]. When activated by its ligands IGF-1, IGF-2 or insulin at supraphysiological concentrations, the IGF-1R transmits a signal to its two major substrates, insulin receptor substrate-1 (IRS-1) and Shc. The signal is subsequently transduced via the common signal transduction pathway, through ras, raf and p42/44 downstream of Shc and AKT downstream of IRS-1, all the way to the nucleus[2,3].

The IGF-1R system has emerged as an interesting target for cancer therapy, as it represents an important promoter of tumor transformation and survival of malignant cells, but is only partially involved in normal cell growth[4-6]. This is in part attributed to interactions with oncogenes. Moreover, activation of IGF-1R may contribute to tumor angiogenesis by up-regulation of vascular endothelial growth factor (VEGF) expression in certain cancer entities[7-9]. In the past, different strategies were used to inhibit IGF-1R function, among them monoclonal antibodies and anti-sense RNA directed against the receptor or recombinant IGF binding proteins, and IGF-specific antibodies reducing Brefeldin_A levels of ligands[5]. Thus, targeting the IGF-1R system with small molecule tyrosine kinase inhibitors, such as NVP-AEW541, a novel compound which is 27-fold more selective for IGF-1R than the insulin receptor at the cellular level, may be a new strategy of cancer growth inhibition[10,11].