The binding of hepatocyte growth factor (HGF) to its receptor MET activates a signaling cascade that promotes cell survival, proliferation, cell scattering, migration and invasion of malignant cells. HGF is secreted by cancer cells or by tumor-associated fibroblasts as pro-HGF, an inactive precursor. A key step in the regulation of HGF/MET signaling is proteolytic processing of pro-HGF to its active form by one of the three serine proteases, matriptase, hepsin or HGF activator (HGFA).We developed SRI 31215, a small molecule that acts as a triplex inhibitor of matriptase, hepsin and HGFA and mimics the activity of HAI-1/2, endogenous inhibitors of HGF activation. We demonstrated that SRI 31215 inhibits fibroblast-induced MET activation, epithelial-mesenchymal transition and migration of cancer cells. SRI 31215 overcomes primary resistance to cetuximab and gefitinib in HGF-producing colon cancer cells and prevents fibroblast-mediated resistance to EGFR inhibitors. Thus, SRI 31215 blocks signaling between cancer cells and fibroblasts and inhibits the tumor-promoting activity of cancer-associated fibroblasts.Aberrant HGF/MET signaling supports cell survival, proliferation, angiogenesis, invasion and metastatic spread of cancer cells, establishing HGF and MET as valid therapeutic targets. Our data demonstrate that inhibitors of HGF activation, such as SRI 31215, merit investigation as potential therapeutics in tumors that are addicted to HGF/MET signaling. The findings reported here also indicate that inhibitors of HGF activation overcome primary and acquired resistance to anti-EGFR therapy, providing a rationale for concurrent inhibition of EGFR and HGF to prevent therapeutic resistance and to improve the outcome of cancer patients.

Targeted therapeutic agents, such as inhibitors of epithelial growth factor receptor (EGFR), have transformed the management of non-small cell lung cancer (NSCLC) patients. MET-amplified NSCLC cells display resistance to EGFR-targeting agents, but are addicted to MET signaling for survival and proliferation and are sensitive to MET inhibition. However, responsive cancer cells invariably develop resistance to MET-targeted treatment.The tumor microenvironment plays a major role in resistance to anticancer therapy. We demonstrated that fibroblasts block the response of MET-amplified NSCLC cells to the MET kinase inhibitor, JNJ38877605 in an HGF-dependent manner. Thus, MET-amplified NSCLC cells become addicted to HGF upon pharmacological inhibition of MET. HGF restored phosphorylation of MET, EGFR and RON, and maintained pro-survival AKT and ERK signaling in MET-inhibited cells.We developed a small molecule inhibitor of pro-HGF activation, SRI31215, which acts as a triplex inhibitor of the pro-HGF activating proteases matriptase, hepsin and HGF activator (HGFA). SRI31215 blocked crosstalk between tumor cells and fibroblasts and overcame fibroblast-mediated resistance to MET inhibition by preventing fibroblast-mediated reactivation of AKT and ERK signaling. Structurally unrelated triplex inhibitors of matriptase, hepsin and HGFA that we developed in parallel showed similar biological activity.Our data suggest that simultaneous inhibition of HGF and MET is required to overcome resistance to MET inhibitors in MET-amplified NSCLC cells. This provides a rationale for the development of novel combination therapeutic strategies for the treatment of NSCLC patients with MET amplification.

An efficient synthesis of (−)-tetrahydrolipstatin (THL) is reported. This method takes advantage of a phosphate tether-mediated, one-pot, sequential RCM/CM/hydrogenation protocol to deliver THL in 8 total steps from a readily prepared (S,S)-triene. The strategy incorporates selective cross metathesis, regio-selective hydrogenation, regio-and diastereoselective cuprate addition and Mitsunobu inversion for installation of the C5 formamide ester subunit.(−)-Tetrahydrolipstatin (THL, 1) is an anti-obesity drug marketed under generic name Orlistat ® and is a stable saturated form of the naturally occuring lipstatin (2) (Figure 1). Lipstatin is a protein-reactive natural product and an irreversible pancreatic lipase inhibitor which was first isolated in 1987 from Streptomyces toxytricini. 1 The biological activity inherent to this family of molecules is based on the reactivity of the β-lactone moiety which is readily acylated by the pancreatic lipase enzyme. This process ultimately inhibits the enzyme reactivity aimed at hydrolyzing triglycerides to produce free fatty acids which are then readily absorbed into the dietary system. 1b,2 Recently, the discovery of selective inhibition of thioesterase activity of fatty acid synthase (FAS) in cancer cells has elevated the potential of Orlistat ® as an anticancer drug. 3,4 The inhibition of FAS stops both endothelial cell proliferation and angiogenesis and ultimately delays tumor progression in a variety of cancer cells. This promising activity highlights the broad and interesting biological profile of Orlistat ® and has prompted renewed synthetic efforts and corresponding biology of THL, lipstatin and analogs thereof.4 ,5 Herein we report a concise total synthesis of (−)-tetrahydrolipstatin via a strategy utilizing a phosphate-tether-mediated, one-pot, sequential RCM/CM/hydrogenation pathway of triene (S,S)-7. 6 Overall, the reported phanson@ku.edu. Supporting Information Available Experimental details and spectroscopic data of new compounds. This material is available free of charge via the Internet at http://pubs.acs.org. NIH Public Access Author ManuscriptOrg Lett. Author manuscript; available in PMC 2011 April 2. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript synthetic route comprises 9 total steps from the readily prepared diene diol-(S,S)-8 and highlights the utility of phosphate tethered processes and one-pot, multi-step operations.The first total synthesis of THL was achieved in 1987 by Schneider and coworkers utilizing Wittig olefination and an aldol condensation as key steps in a non-stereoselective process.7 Numerous total syntheses,8 formal syntheses 9 and synthetic analogues have followed this initial report, with the majority of synthetic pathways comprised of 14-25 steps. The shortest routes to THL reported to-date range from 10-12 steps using an array of synthetic strategies, including, (i) a 12-step anti-aldol approach,8i (ii) a 12-step diastereoselective allylation and crotylation sequence utilizing allyl/crotyltri...

In this letter we report first nonpeptide inhibitors of hepatocyte growth factor (HGF) activation. These compounds inhibit the three proteases (matriptase, hepsin, and HGF activator) required for HGF maturation. We show that 6, 8a, 8b, and 8d block activation of fibroblast-derived pro-HGF, thus preventing fibroblast-induced scattering of DU145 prostate cancer cells. Compound 6 (SRI 31215) is very soluble (91 μM) and has excellent microsome stability (human t 1/2 = 162 min; mouse t 1/2 = 296 min). In mouse 6 has an in vivo t 1/2 = 5.8 h following IV administration. The high solubility of 6 and IV t 1/2 make this compound a suitable prototype "triplex inhibitor" for the study of the inhibition of HGF activation in vivo.

A versatile three-step, one-pot, sequential reaction protocol involving RCM, CM, and chemoselective hydrogenation is reported. This phosphate tether-mediated process occurs without intermediate isolation, is chemoselective and is governed by stereoelectronic properties innate to phosphate tethers, which ultimately act to preserve the integrity of the bisallylic, bicyclic phosphate for subsequent nucleophilic additions. Overall, this process can be used to efficiently generate advanced polyol synthons.