Sorafenib enhances the in vitro anti-endothelial effects of low dose (metronomic) chemotherapy

Angiogenesis inhibitors may enhance the effects of low dose (metronomic) chemotherapy. However, there is a wide range of novel angiogenesis inhibitors which must be tested in combinations with oral chemotherapy agents to assess the anti-endothelial and anti-cancer effects. This preliminary testing is most suited to high throughput in vitro models, rather than clinical trials. We aimed to establish an in vitro model and test the anti-endothelial and anti-cancer effects of the multi-kinase inhibitor sorafenib when used as a single agent and in combination with oral chemotherapy agents used at low concentrations. Micro-vascular endothelial cells and 3 cancer cell lines were utilised and an extended treatment strategy (96 h) was employed in order to mimic a continuous low dose anti-angiogenic chemotherapy regimen. Sorafenib significantly enhanced the anti-endothelial effect of low dose etoposide, paclitaxel and temozolomide. Sorafenib also significantly enhanced the anti-cancer effect of low dose etoposide, paclitaxel and temozolomide in SK-MEL-2 melanoma cells, producing an additive effect on inhibition of cell growth in all cases. These combinations appear to be the most promising for in vivo pre-clinical studies, with a view to testing in melanoma patients as a continuous dosing strategy, due to the in vitro additive inhibitory effect on growth seen in both endothelial and cancer cells.