PTK787/ZK 222584 inhibits tumor growth promoting mesenchymal stem cells Kinase activity profiling as powerful tool in functional studies

Bone marrow (BM)-derived mesenchymal stem cells (MSCs) have been shown to favor tumor growth, suggesting the relevance of pharmaceutical inhibition of MSCs for the treatment of malignancies. We tested the effect of PTK787/ZK 222584 (PTK) on the outgrowth of MSCs from human bone marrow-derived mononuclear cells (MNCs) and the migration and tube formation capacity of MSCs in vitro. PTK dose-dependently inhibited the outgrowth of BM-MSCs from BM-MNCs (LC50 1.12 mu M PTK), while hematopoietic colony formation (HCF) was only slightly hampered (13 +/- 19% at 1 mu M PTK, and stable at similar to 50% at higher concentrations of PTK). Addition of 10 mu M PTK inhibited proliferation of MSCs by 74 +/- 6.6% compared to control (p <0.0001) and increased apoptosis of MSCs by 63 +/- 7.7% (p <0.01). In addition, upon addition of PTK, BM-MSCs showed impaired tube formation as well as reduced migration (52 +/- 19%, p = 0.006) compared to control. Pepchip array analysis revealed that PTK effectively inhibits activity of kinases involved in cell cycling (WEE1 and several cyclin dependent kinases), and migratory processes (including Rho kinase). In conclusion, we show that PTK impairs outgrowth, proliferation, migration and tube formation of human BM-MSCs. In addition, we show the usability of Pepchip array analysis as a powerful tool for kinase activity profiling in functional studies since the effect of PTK on the kinome profile of MSCs corresponds with the observed functional effects of PTK on proliferation and migration. Inhibition of BM-MSCs and their contribution to tumor growth may be an additional strategy for treatment of cancer in the future.