Selective cytotoxicity of a bicyclic Ras inhibitor in cancer cells expressing K-RasG13D

Abstract

Mutation of RAS genes is a critical event in the pathogenesis of different human tumors and in some developmental disorders. Here we present an arabinose-derived bicyclic compound displaying selective cytotoxicity in human colorectal cancer cells expressing K-Ras(G13D), that shows high intrinsic nucleotide exchange rate. We characterize binding of bicyclic compounds by docking and NMR experiments and their inhibitory activity on GEF-mediated nucleotide exchange on wild-type and mutant Ras proteins. We demonstrate that the in vitro inhibition of Ras nucleotide exchange depends on the molar ratio between Ras and its GEF activator, suggesting that the observed in vivo selective effect may depend on biochemical parameters and actual intracellular concentration of the Ras protein and its regulators.

Direct Modulation of Small GTPase Activity and Function

“…[76] To improve their water solubility and potency, derivatives were designed which can inhibit RasGRF-1-catalyzed nucleotide exchange in vitro (half-maximum inhibitory concentration (IC 50 ) = 35-80 mm). [77] Reduced cell growth in Ras-dependent cell lines as well as decreased downstream signaling were observed at high micromolar concentrations,but the exact mode of action still remains elusive and off-target effects have to be considered in certain cases.F or another compound of the SCH compound family (SCH51344 (9), Figure 5a)which was reported to modulate the Ras signaling pathway through an ovel mechanism, [78] the human mutT homologue hMTH1 was recently identified as the actual target. [79] Based on the Ras-binding epitopes of its GEFs,rationally designed orthosteric peptidic inhibitors were developed to impair Ras nucleotide exchange.…”

Sugar-Based Inhibitors of Ras Activation

“…5.5) [25]. Other generations of type 1 and 2 compounds were synthesized with a 3,4 dihydroxyphenyl (3,4 catechol) group replacing phenylhydroxylamine and STD experiments consistently indicated the involvement of benzyl ether and catechol groups in the interaction with Ras ( Fig.…”

“…5.5) showed that in high-scoring poses, all compounds bind Ras in a cleft near the Switch 2 region [25]. 5.5) showed that in high-scoring poses, all compounds bind Ras in a cleft near the Switch 2 region [25].…”

Graded inhibition of oncogenic Ras-signaling by multivalent Ras-binding domains

“…Later, Ras neutralizing antibodies were employed as oncogenic Ras blockers in cell culture experimentation [24-26] and mutant Ras epitopes were exploited for their suitability as antigens in the development of cancer vaccines [27]. Further approaches to target oncogenic Ras rested on antisense oligonucleotides directed to the Ras mRNA [28], and more recently on exploiting structural information and improved in silico approaches to identify and target druggable pockets or moieties that affect Ras nucleotide exchange [29,30], Ras activation [31,32], effector interaction [33,34] or binding to escort proteins critical for subcellular trafficking [35]. Moreover, numerous studies have targeted Ras downstream effector pathways such as Raf kinases, MEK or PI3Ks [36,37].…”