Congxin Liang

The Met kinase inhibitor SU11274 exhibits a selective inhibition pattern toward different receptor mutated variants

Point mutations constitute a major mode of oncogenic activation of the Met receptor tyrosine kinase. Met is aberrantly activated in many types of human malignancies and its deregulated activity is correlated with aggressive tumor traits such as abnormal proliferation and survival, leading to tumor growth, local invasion and metastasis. Here we report that the Met kinase inhibitor SU11274 differentially affects the kinase activity and subsequent signaling of various mutant forms of Met. Two Met variants tested, M1268T and H1112Y, were potently inhibited by 2 μM SU11274, while two other variants, L1213V and Y1248H, remained resistant under similar experimental conditions. Inhibition of the kinase altered cell proliferation, morphology and motility, while cells containing resistant mutants appeared unaffected by the compound. The basis for the sensitivity or resistance to SU11274 is discussed in terms of the position of the mutations predicted from a homology model.

PND-1186 FAK inhibitor selectively promotes tumor cell apoptosis in three-dimensional environments.

Tumor cells can grow in an anchorage-independent manner. This is mediated in part through survival signals that bypass normal growth restraints controlled by integrin cell surface receptors. Focal adhesion kinase (FAK) is a cytoplasmic protein-tyrosine kinase that associates with integrins and modulates various cellular processes including growth, survival, and migration. As increased FAK expression and tyrosine phosphorylation are associated with tumor progression, inhibitors of FAK are being tested for anti-tumor effects. Here, we analyze PND-1186, a substituted pyridine reversible inhibitor of FAK activity with a 50% inhibitory concentration (IC50) of 1.5 nM in vitro. PND-1186 has an IC50 of ~100 nM in breast carcinoma cells as determined by anti-phospho-specific immunoblotting to FAK Tyr-397. PND-1186 did not alter c‑Src or p130Cas tyrosine phosphorylation in adherent cells, yet functioned to restrain cell movement. Notably, 1.0 µM PND-1186 (>5-fold above IC50) had limited effects on cell proliferation. However, under non-adherent conditions as spheroids and as colonies in soft agar, 0.1 µM PND-1186 blocked FAK and p130Cas tyrosine phosphorylation, promoted caspase-3 activation, and triggered cell apoptosis. PND-1186 inhibited 4T1 breast carcinoma subcutaneous tumor growth correlated with elevated tumor cell apoptosis and caspase 3 activation. Addition of PND-1186 to the drinking water of mice was well tolerated and inhibited ascites- and peritoneal membrane-associated ovarian carcinoma tumor growth associated with the inhibition of FAK Tyr-397 phosphorylation. Our results with low-level PND-1186 treatment support the conclusion that FAK activity selectively promotes tumor cell survival in three-dimensional environments.

Structure-Based design and discovery of novel inhibitors of protein tyrosine phosphatases

Protein tyrosine phosphatases (PTPs) are important in the regulation of signal transduction processes. Certain enzymes of this class are considered as potential therapeutic targets in the treatment of a variety of diseases such as diabetes, inflammation, and cancer. However, many PTP inhibitors identified to date are peptide-based and contain a highly charged phosphate-mimicking component. These compounds usually lack membrane permeability and this limits their utility in the inhibition of intracellular phosphatases. In the present study, we have used structure-based design and modeling techniques to explore catalytic-site directed, reversible inhibitors of PTPs. Employing a non-charged phosphate mimic and non-peptidyl structural components, we have successfully designed and synthesized a novel series of trifluoromethyl sulfonyl and trifluoromethyl sulfonamido compounds as PTP inhibitors. This is the first time that an uncharged phosphate mimic is reported in the literature for general, reversible, and substrate-competitive inhibition of PTPs. It is an important discovery because the finding may provide a paradigm for the development of phosphatase inhibitors that enter cells and modify signal transduction.

Rational design of 4,5-disubstituted-5,7-dihydro-pyrrolo[2,3-d]pyrimidin-6-ones as a novel class of inhibitors of epidermal growth factor receptor (EGF-R) and Her2(p185erbB) tyrosine kinases

A novel class of 4,5-disubstituted-5,7-dihydro-pyrrolo[2,3-d]pyrimidin-6-ones has been discovered as potent and selective inhibitors of the EGF-R tyrosine kinase family. These compounds selectively inhibit EGF-R kinase activity at low nanomolar concentration and tyrosine autophosphorylation in cells expressing EGF-R or Her2 (p185(erbB)). Structure-activity relationships (SARs) for this class of compounds are presented.