Actions of Midostaurin as Tyrosine Kinase and Cation Channel Inhibitor in Diffuse Intrinsic Pontine Glioma Cell Lines

Tyrosine kinases (TK) are dysregulated in Diffuse Intrinsic Pontine Glioma (DIPG). Here, the effects of TKI targeting different kinases, such as everolimus, crizotinib, dasatinib, erlotinib, lapatinib, perifosine, and midostaurin, in SU-DIPG-36 and SU-DIPG-50 cells (0.001-100 μM) were investigated. Methods: Cell viability assays in parallel with patch-clamp study investigating the effects of the most interesting drug were performed together with a western blot of target proteins. Results: Midostaurin is the most active drug with IC50 values of 10-7 M in different assays in either cell type. Patch-clamp investigations show that the acute application of 2.14 μM midostaurin reduced the whole-cell inward and outward cation currents vs controls in the presence of low internal ATP. These currents were reduced by KATP channel inhibitors, such as glibenclamide and repaglinide, as well as the unselective blockers TEA-BaCl2. Midostaurin also reduced currents that are sensitive to TRPV1 channel blockers, the capsazepine and ruthenium-red. On SU-DIPG-50 cells, midostaurin reduced the currents also after 20 minutes of incubation, it inhibited currents compared to controls. At positive potentials, at t= 0, midostaurin reduces currents with an increasing in-hibitory effect after 20 min of incubation time. In SU-DIPG-36 cells midostaurin causes a concentration-dependent up-regulation of the autophagy markers. In SU-DIPG-50 cells, midostaurin downregulates the VEGFR2, causes mTOR dephosphorylation, enhances the acetyl histone H3 content, and the cleaves caspase-3 with apoptosis. Conclusions: The inhibition of cation channel currents by midostaurin in SU-DIPG-36 and 50 cells and the autophagy potentiation in SU-DIPG-36 variant can be additional mechanisms in DIPG.