GTx-186 inhibits growth of ROS1-dependent cell lines.
A. GTx-186 inhibits the growth of HCC78 lung carcinoma cells. HCC78 lung carcinoma cells were plated in growth medium and treated with indicated concentrations of GTx-186 or crizotinib on days 1 and 6. Cells were fixed after 6 days and stained with sulforhodamine B (SRB) and OD measured at 535 nm. B. GTx-186 inhibits phosphorylation of ROS1. HCC78 cells were plated in growth medium and treated with 100 nM GTx-186 or crizotinib for 3 or 6 days. Protein was extracted and immunoblotted with phospho-ROS1 and total ROS1 antibodies. C. GTx-186 arrests cells in G1 phase of the cell cycle. HCC78 or A549 cells were treated for 3 or 6 days with 1 µM GTx-186 or crizotinib and flow cytometry was performed to determine the cell cycle distribution. A549 cells were used as ROS1 negative lung cancer control cells as they do not express ROS1. D and E. GTx-186 inhibits phosphorylation of ROS1 and growth of NIH3T3 cells over-expressing FIG-ROS1. NIH3T3 cells stably transfected with FIG-ROS1 were treated with GTx-186 or crizotinib for 3 days and the growth of cells (D) and phosphorylation (100 nM GTx-186 or crizotinib) of ROS1 (E) were measured by SRB assay and Western blotting, respectively. Cells in panel E were treated with indicated concentrations of GTx-186 and crizotinib. F and G. Over-expression of FIG-ROS1 increases proliferation of Ba/F3 cells. Ba/F3 cells stably transfected with vector or FIG-ROS1 were plated in equal numbers and growth of the cells after 3 days was measured by SRB assay (F). Ba/F3 cells stably expressing FIG-ROS1 were treated with indicated concentrations of GTx-186 for 3 days and growth of cells were measured by sulforhodamine B (SRB) assay. Values are expressed as Avg ± S.E. of n = 3.