Nontoxic Chemical Interdiction of the Epithelial-to-Mesenchymal Transition by Targeting Cap-Dependent Translation

Abstract

Normal growth and development depends upon high fidelity regulation of cap-dependent translation initiation; a process that is usurped and redirected in cancer to mediate acquisition of malignant properties. The epithelial-to-mesenchymal transition (EMT) is a key translationally-regulated step in the development of epithelial cancers as well as pathological tissue fibrosis (1-5). To date, no compounds targeting EMT have been developed. Here we report the synthesis of a novel class of Histidine Triad Nucleotide Binding Protein (HINT)-dependent pronucleotides that interdict EMT by negatively regulating the association of eIF4E with the mRNA cap. Compound eIF4E inhibitor-1 (4Ei-1) potently inhibited cap-dependent translation in a dose-dependent manner in zebrafish embryos without causing developmental abnormalities; and prevented eIF4E from triggering EMT in zebrafish ectoderm explants without toxicity. Metabolism studies with whole cell lysates demonstrated that the prodrug was rapidly converted into 7-Bn-GMP. Thus we have successfully developed the first non-toxic small molecule able to inhibit EMT, a key process in the development of epithelial cancer and tissue fibrosis by targeting the interaction of eIF4E with the mRNA cap; and demonstrate the tractability of zebrafish as a model organism for studying agents that modulate EMT. Our work provides strong motivation for the continued development of compounds designed to normalize cap-dependent translation as novel chemo-preventive agents and therapeutics for cancer and fibrosis.

Structural Insights into Parasite eIF4E Binding Specificity for m7G and m2,2,7G mRNA Caps

“…Increased expression of eIF4E is associated with a variety of cancers and cancer progression (4). Efforts in a number of laboratories are directed toward therapies against eIF4E in cancer, including the development of cap analogs (5)(6)(7)(8)(9).…”

Stabilizing the eIF4G1 α-Helix Increases Its Binding Affinity with eIF4E: Implications for Peptidomimetic Design Strategies

“…11 Ghosh et al have used nontoxic cap analogues to inhibit EMT (epithelial-to-mesenchymal transition), a key process in the development of epithelial cancer and tissue fibrosis, by targeting the interaction of eIF4E with the mRNA cap and by demonstrating the utility of zebra fish as a model organism. 12 Another approach that has also entered clinical trials is the use of antisense oligonucleotides to reduce the expression of eIF4E. 13 Small-molecule inhibitors that mimic the eIF4E-binding peptides, derived from either 4EBP1 or eIF4GI/II, have also been reported to displace eIF4G and the translational machinery from eIF4E.…”

Estimation of stacking interaction of 7-methyl-guanosine

“…At low molar ratios (2, 4, 8) of indole:caffeine (lower curve in Figure 2), the heat of interaction (Qreact) clearly depends almost linearly on the concentration of indole. At high molar ratios (20,40,80) of indole:caffeine (upper curve), Qreact tends to increase with increasing concentration of indole. This indicates that the mechanism of the interaction differs at low and high molar ratios.…”

“…The presence and effects of such interactions have been presumed in the interpretation of many biological functions of the 7-methylguanosine, other alkylated nucleic acid bases and their nucleotide derivatives. One example is the eukaryotic mRNA with a special CAP structure (see [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55] and the references therein) (the 5'cap is found on the end of mRNA molecule and consists of a guanine nucleotide connected to the mRNA via an unusual 5' to 5' triphosphate linkage). This guanosine is methylated on the 7 position directly after capping in vitro by a methyl transferase.…”