Mivobulin Isethionate

The rapid increase in the volume of high-throughput anticancer chemical screening data requires a better interpretation of the relationships between diverse chemical structures and their varied effects in distinct cancer subtypes. Unexpected compound efficacy or resistance in cancer cells has been difficult to explain, in part because there has been no systematic analysis of compound response profiles in cancer cells with different genotypic backgrounds. In this study, we compared 2D chemical- and 3D shape-based similarity search methods to study the structure-activity relationships of anticancer compounds in a collection of heterogeneous cancer cell lines. The 3D shape-based metric provided better resolution than the 2D chemical topology-based method for identifying compound pairs with similar cellular response profiles. We confirmed that the 3D method exclusively identified compound pairs with different chemical scaffolds that stimulated highly similar cellular responses. The present analyses provide useful guidelines for investigating the lineage- and genotype-specific activities of diverse compounds and their mechanisms of action.

Tubulin is able to switch between a straight microtubule-like structure and a curved structure in complex with the stathmin-like domain of the RB3 protein (T(2)RB3). GTP hydrolysis following microtubule assembly induces protofilament curvature and disassembly. The conformation of the labile tubulin heterodimers is unknown. One important question is whether free GDP-tubulin dimers are straightened by GTP binding or if GTP-tubulin is also curved and switches into a straight conformation upon assembly. We have obtained insight into the bending flexibility of tubulin by analyzing the interplay of tubulin-stathmin association with the binding of several small molecule inhibitors to the colchicine domain at the tubulin intradimer interface, combining structural and biochemical approaches. The crystal structures of T(2)RB3 complexes with the chiral R and S isomers of ethyl-5-amino-2-methyl-1,2-dihydro-3-phenylpyrido[3,4-b]pyrazin-7-yl-carbamate, show that their binding site overlaps with colchicine ring A and that both complexes have the same curvature as unliganded T(2)RB3. The binding of these ligands is incompatible with a straight tubulin structure in microtubules. Analytical ultracentrifugation and binding measurements show that tubulin-stathmin associations (T(2)RB3, T(2)Stath) and binding of ligands (R, S, TN-16, or the colchicine analogue MTC) are thermodynamically independent from one another, irrespective of tubulin being bound to GTP or GDP. The fact that the interfacial ligands bind equally well to tubulin dimers or stathmin complexes supports a bent conformation of the free tubulin dimers. It is tempting to speculate that stathmin evolved to recognize curved structures in unassembled and disassembling tubulin, thus regulating microtubule assembly.