Glioblastoma (GBM) is the most aggressive type of brain cancer. Median survival time for GBM patients is about 12.1 to 14.6 month [1], and there are still extremely limited opportunities of conventional therapy. Tyrosine kinase inhibitors currently are considered as a perspective targeted therapy for GBM. There are numerous studies linking changes in kinase activity to carcinogenesis and tumor progression. Tyrosine kinase inhibitors generally target the active site of the kinase and thereby prevent the phosphorylation resulting in inhibition of migration and apoptosis of cancer cells [2]. One of them is sunitinib, a multi-targeted agent, approved for the treatment of kidney cancer and gastrointestinal stromal tumours [3]. Moreover, the new chemical compounds are suggested as more effective sunitinib analogues [4]. The aim of our study was to evaluate the effect of new sunitinib analogues on human brain cancer cell viability and migration.
The two human GBM cell lines, U87-MG and A172, and non-malignant human fibroblasts were used to investigate anticancer activity of 17 sunitinib analogues in vitro. The effect of kinase inhibitors on cell viability was evaluated by MTT assay after 72 hours of incubation. Then the most active kinase inhibitors that reduced cell viability up to 5% or less have been selected for further studies. The EC50 values of the most active compounds were established and compared to the sunitinib cytotoxicity. Single cell migration assay was performed to examine the effect of selected compounds on U87-MG cell migration. Cells were seeded in the dishes with numbered grids in such way that about 50-70 cells would be on the gridded area. Images of cells were taken every hour for 8 hours by inverted microscope. Coordinates of the cells were established and the travelled distance has been calculated. The single cell distance travelled per hour was defined as the cell velocity. The data were presented as average cell velocity + standard deviation.
The results of MTT assay experiment have shown that compounds 1, 6 and 7 were the most active ones. All three tested compounds had more potent reducing effect on the brain cancer cell viability of A172 cell line compared to U87-MG cell line and non-malignant cells. It should be noted, that compound 6 was the only one that showed a stronger cytotoxic effect on tested cancer cell lines in comparison with non-malignant cells. However, data analysis revealed that compound 1 had the greatest effect on reducing cell viability (EC50 values after 72 h on U87-MG, A172 and HF were 82 ± 6 nM, 72 ± 6 nM and 82 ± 6 nM, respectively). All tested sunitinib analogues were more cytotoxic than sunitinib. In migration assay, compound 6 reduced U-87-MG cell migration by 13% more efficiently than sunitinib, and decreased the average cell velocity by 2 times compared to the control. Unexpectedly, compounds 1 and 7 showed an opposite effect on cell migration as cell velocity was increased by 33% and 73%, respectively, compared to the control.
To conclude, compound 6 may be worthy of further studies as it had U87-MG and A172 cancer cell specific cytotoxicity as well as was the most effective kinase inhibitor in U87-MG cell line.