Conformationally Constrained Peptidomimetic Inhibitors of Signal Transducer and Activator of Transcription 3: Evaluation and Molecular Modeling

Abstract

Signal transducer and activator of transcription 3 (Stat3) is involved in aberrant growth and survival signals in malignant tumor cells and is a validated target for anti-cancer drug design. We are targeting its SH2 domain to prevent docking to cytokine and growth factor receptors and subsequent signaling. The amino acids of our lead phosphopeptide, Ac-pTyr-Leu-Pro-Gln-Thr-Val-NH 2 , were replaced with conformationally constrained mimics. Structure-affinity studies led to the peptidomimetic, pCinn-Haic-Gln-NHBn (21) which had an IC 50 of 162 nM (fluorescence polarization), as compared to 290 nM for the lead phosphopeptide (pCinn = 4-phosphoryloxycinnamate, Haic = (2S,5S)-5-amino-1,2,4,5,6,7-hexahydro-4-oxo-azepino[3,2,1-hi]indole-2-carboxylic acid). pCinn-Haic-Gln-OH was docked to the SH2 domain (AUTODOCK) and the two highest populated clusters were subjected to molecular dynamics simulations. Both converged to a common peptide conformation. The complex exhibits unique hydrogen bonding between Haic and Gln and Stat3 as well as hydrophobic interactions between the protein and pCinn and Haic.

Stat3 signaling in acute myeloid leukemia: ligand-dependent and -independent activation and induction of apoptosis by a novel small-molecule Stat3 inhibitor

“…on April 8, 2019. by guest www.bloodjournal.org From inhibitors is the peptidomimetics, which are relatively potent in vitro 28,29 but historically have carried the challenge of adequate cell permeability. CPA-7, a platinum compound, has been shown to inhibit Stat3 and Stat1 activity and to reduce tumor cell growth.…”

Characterization of molecular recognition of STAT3 SH2 domain inhibitors through molecular simulation

“…Although compound 5's hexyl group was not stable enough to maintain the intended conformation, this modification to the inhibitor's structure indicated the potential importance of the pY þ 1 pocket. In this regard, Mandal et al have very recently targeted an extended binding cleft including the pY þ 1 to pY þ 3 sites (occupied by D 706-710 of STAT3) with conformationally constrained peptidomimetic inhibitors (Mandal et al, 2009). Although our targeted binding site involves D 702-706 of STAT3, their findings on the pY þ 1 interaction could be helpful in optimizing the core region, which is revealed by our accumulated H-bond mapping results in Figure 10.…”

“…So far, there have been several systematic studies on phosphotyrosine peptide interactions with various SH2 domains ) including STAT3-SH2 (Mandal et al, 2009); but there have been no systematic computational study on small molecule interactions with any SH2 domain. To compare their binding potency, specificity, and dynamic nature, this work is to systematically evaluate eight representative STAT3-SH2 inhibitors ( Figure 3) computationally through combined molecular docking and molecular dynamics simulation.…”

Targeting Sh2 Domains in Breast Cancer

“…Extensive studies were carried out to probe the phosphopeptide binding site [64,96–101]. These studies revealed that phosphotyrosine could be replaced by the conformationally constrained 4-phosphocinnamate [99] (e.g., PM-66F, Figure 9) and inclusion of a methyl group on the β-carbon of the cinnamate increased affinity [97]. The central Leu–Pro dipeptide had a trans peptide bond [96] and could be replaced with the tricyclic lactam Haic [99].…”