No abstract

STOP DIVIDING: In the quest for antitumorigenic compounds, aurora A kinase has recently emerged as a potential drug target. In this paper three novel aurora inhibitors (shown in the illustration) have been tested for their biological activity in cultured cells. One of them (TC-28) appears to be a promising specific aurora A inhibitor in vivo. The aurora kinase family groups several serine/threonine kinases with key regulatory functions during cell division. The three mammalian members, aurora A, B and C, are frequently over-expressed in human tumors and the aurora A gene is located in a genomic region frequently amplified in breast and colon cancer. All these data have fuelled the idea that aurora kinases are promising targets for anticancer therapy. Indeed some inhibitory compounds are currently being evaluated in clinical trials. However, it was recently shown that mutations in the targeted kinase can confer resistance to a broad range of inhibitors and render patients resistant to treatments. Moreover, aurora A over-expression results in increased resistance to antimitotic agents. The development of new compounds targeting aurora A is therefore highly relevant. We describe here the synthesis of three novel aurora kinase inhibitors, TC-28, TC-34 and TC-107. We report their properties as aurora inhibitors in vitro and their effect on human tissue culture cell lines. Interestingly, our results show that TC-28 has properties compatible with the specific inhibition of aurora A, in vivo.

Background and purpose: Angiopoietins (Ang) are crucial for new blood vessel formation and exert their effects by acting on the Tie2 receptor. We have recently described a sulindac analogue 2-((1E,Z)-1-benzylidene-5-bromo-2-methyl-1H-inden-3-yl)acetic acid; termed C-18 from now onwards) that inhibits Tie2 receptor activity in kinase assays in vitro. Here, we have assessed the ability of C-18 to inhibit angiogenesis-related properties of endothelial cells and tested its selectivity for the Tie2 receptor. Experimental approach: For in vitro experiments human umbilical vein endothelial cells (HUVEC) were used. Proliferation was measured using the MTT assay; migration assays were performed in a modified Boyden chamber and tube-like structure formation was determined on matrigel. The effects of C-18 in vivo were evaluated in the chicken chorioallantoic membrane (CAM). Key results: Pre-treatment of HUVEC with C-18 blocked Ang-1-stimulated migration, but also abolished vascular endothelial cell growth factor (VEGF)-and fibroblast growth factor 2-induced responses. Incubation with C-18 inhibited serum-induced proliferation in a concentration-dependent manner; C-18 was, however, without effect on Ang-1-induced survival. In addition, we observed that C-18 did not inhibit ligand-induced receptor phosphorylation of Tie2 or VEGFR2. On the other hand, C-18 blocked activation of members of the mitogen-activated protein kinase family and of the Ser/Thr kinase Akt induced by both VEGF and Ang-1. Furthermore, incubation of CAMs with C-18 led to a dose-dependent inhibition of vascular length. Conclusions and implications: C-18 did not act as a Tie2 inhibitor, as originally thought, but rather inhibited growth factorstimulated signalling pathways that regulate endothelial cell migration and potently reduces neovascularization in vivo.

Receptor tyrosine kinases (RTKs) are important mediators of signal transduction and play critical roles in cell growth, differentiation, metabolism, and apoptosis, and are deeply involved in oncogenesis. Binding of growth factors to the extracellular domains of RTKs leads to their dimerization, resulting in activation of the intracellular kinase domain, which eventually enables autophosphorylation at specific tyrosine residues. This family is also represented in oncogenic fusion proteins such as the Bcr-Abl protein of the Philadelphia chromosome.RTKs are organized into different families based on sequence homology and structural characteristics. There are more than 90 known protein kinase genes; 58 encode transmembrane receptor TKs distributed in 20 subfamilies, and 32 encode cytoplasmic non-receptor TKs distributed in 10 subfamilies. [1,2] Tyrosine kinases have been validated as suitable pharmacological targets for anticancer drugs, and several TK inhibitors have shown promising results in preclinical in vitro and in vivo models; others have been approved for the treatment in patients with cancer. This is best exemplified by the tyrosine kinase inhibitor imatinib (Gleevec), which has shown impressive activity against chronic myelogenous leukemia (CML) and has also been successful in the treatment of gastrointestinal stromal tumors, other leukemias, and solid tumors. [3]

The bacterial ribosome represents the confirmed biological target for many known antibiotics that interfere with bacterial protein synthesis. Aminoglycosides represent a lead paradigm in RNA molecular recognition and constitute ideal starting points for the design and synthesis of novel RNA binders. Previous rational design approaches of RNA-targeting small molecules have been mainly concentrated on direct functionalization of aminoglycosidic substructures. Herein, we successfully designed and synthesized rigid spirocyclic scaffolds locked in a predicted ribosome-bound "bioactive" conformation. These analogues are able to mimic many of the interactions of the natural products for the A-site, as proven by their obtained binding affinities. The development of an optimized approach for their synthesis and their potential to inhibit protein production in vitro are presented. Our results could be further utilized for the development of analogues with improved antibiotic profiles.