Structure-activity relationships on cynnamoyl derivatives as inhibitors of p300 Histone acetyltransferase

Human p300 is a polyhedric transcriptional coactivator, playing a crucial role by acetylating histones on specific lysine residues. A great deal of evidences shows that p300 is involved in several diseases as leukemia, tumors and viral infection. Its involvement in pleiotropic biological roles and connections to diseases provide the rationale as to how its modulation could represent an amenable drug target. Several p300 inhibitors (HATi) have been described so far, but all suffer from low potency, lack of specificity or low cell-permeability, highlighting the need to find more effective inhibitors. Our cinnamoyl derivative, RC 56, was identified as active and selective p300 inhibitor, proving to be a good hit candidate to investigate the structure-activity relationship towards p300. Herein we describe the design, synthesis and biological evaluation of new HATi structurally related to our hit, investigating, moreover, the interactions between p300 and the best-emerged hits by means of induced fit docking and molecular dynamics simulations, gaining insight on the peculiar chemical features that influenced their activity toward the targeted enzyme

The contrasting chemical reactivity of potent isoelectronic iminopyridine and azopyridine osmium(ii) arene anticancer complexes

A wide variety of steric and electronic features can be incorporated into transition metal coordination complexes, offering the prospect of rationally-designed therapeutic agents with novel mechanisms of action. Here we compare the chemical reactivity and anticancer activity of organometallic OsII complexes [Os(η6-arene)(XY)Z]PF6 where arene = p-cymene or biphenyl, XY = N,N′-chelated phenyliminopyridine or phenylazopyridine derivatives, and Z = Cl or I. The X-ray crystal structure of [Os(η6-p-cym)(Impy-OH)I]PF6·0.5CH2Cl2·H2O (Impy-OH = 4-[(2-pyridinylmethylene)amino]-phenol) is reported. Like the azopyridine complexes we reported recently (Dalton Trans., 2011, 40, 10553–10562), some iminopyridine complexes are also potently active towards cancer cells (nanomolar IC50 values). However we show that, unlike the azopyridine complexes, the iminopyridine complexes can undergo aquation, bind to the nucleobase guanine, and oxidize coenzyme nicotine adenine dinucleotide (NADH). We report the first detection of an Os-hydride adduct in aqueous solution by 1H NMR (−4.2 ppm). Active iminopyridine complexes induced a dramatic increase in the levels of reactive oxygen species (ROS) in A549 lung cancer cells. The anticancer activity may therefore involve interference in the redox signalling pathways in cancer cells by a novel mechanism

p21-Activated Kinases Are Required for Transformation in a Cell-Based Model of Neurofibromatosis Type 2

NF2 is an autosomal dominant disease characterized by development of bilateral vestibular schwannomas and other benign tumors in central nervous system. Loss of the NF2 gene product, Merlin, leads to aberrant Schwann cell proliferation, motility, and survival, but the mechanisms by which this tumor suppressor functions remain unclear. One well-defined target of Merlin is the group I family of p21-activated kinases, which are allosterically inhibited by Merlin and which, when activated, stimulate cell cycle progression, motility, and increased survival. Here, we examine the effect of Pak inhibition on cells with diminished Merlin function.Using a specific peptide inhibitor of group I Paks, we show that loss of Pak activity restores normal cell movement in cells lacking Merlin function. In addition, xenografts of such cells form fewer and smaller tumors than do cells without Pak inhibition. However, in tumors, loss of Pak activity does not reduce Erk or Akt activity, two signaling proteins that are thought to mediate Pak function in growth factor pathways.These results suggest that Pak functions in novel signaling pathways in NF2, and may serve as a useful therapeutic target in this disease

Development of organometallic compounds as potent protein kinase inhibitors

Tightly controlled by the action of protein kinases, protein phosphorylation regulates most aspects of cellular life. Abnormalities in protein phosphorylation are either the cause or consequence of most diseases. Therefore, protein kinase inhibitors are becoming attractive agents to assess the physiological roles of individual kinases in cell signaling networks and potential tools for disease treatment. The most exploited avenue in protein kinase inhibition is the design of ATP competitive inhibitors, but this strategy brings the challenge of selectivity due to the high similarity of the ATP binding sites among different kinases. To address this challenge, our lab focuses on the development of organometallic compounds as protein kinase inhibitors. We aim to design organometallic compounds where the overall three-dimensional structure of the compounds, not reactivity of the metal, is responsible for their biological activity which can then easily be modified by shuffling the organic ligands around the metal center. In this work, first the concept of creating metal complexes with specific biological activities where the metal possesses a purely structural role is verified. It is demonstrated that exchanging ruthenium for its heavier homologue osmium in a bioactive half-sandwich scaffold does not alter its biological properties such as kinase binding, activation of a signaling pathway and anticancer activity. This is a unique example in which the replacement of a metal in an anticancer scaffold by its heavier homolog does not significantly alter the biological activity. Next, it was investigated if switching the selectivity between kinases could be achieved by varying the ligands around the metal center. By combining organoruthenium chemistry, small molecule screening and structure based inhibitor design, a highly potent and selective GSK-3 and PIM-1 half-sandwich complex NP309 was successfully converted into the octahedral PAK1 inhibitors Λ-FL172 and Λ-FL411. These compounds were shown to inhibit the PAK1 kinase with nanomolar potency and show significant selectivity when tested against a panel of kinases. In addition, these compounds were shown to be cell permeable and able to evoke cellular responses associated with PAK1 inhibition. Finally, the binding mode of an organoruthenium inhibitor to the kinase PAK4 was examined using X-ray crystallography. The main goal of this particular study was to demonstrate that PAK1 and PAK4 have significantly different inhibitor selectivity profiles and to lay the groundwork to develop potent and selective organometallic PAK4 inhibitors

Structure–activity relationships for organometallic osmium arene phenylazopyridine complexes with potent anticancer activity

We report the synthesis and characterisation of 32 half sandwich phenylazopyridine Os(II) arene complexes [Os(eta(6)-arene)(phenylazopyridine)X](+) in which X is chloride or iodide, the arene is p-cymene or biphenyl and the pyridine and phenyl rings contain a variety of substituents (F, Cl, Br, I, CF(3), OH or NO(2)). Ten X-ray crystal structures have been determined. Cytotoxicity towards A2780 human ovarian cancer cells ranges from high potency at nanomolar concentrations to inactivity. In general the introduction of an electron-withdrawing group (e.g. F, Cl, Br or I) at specific positions on the pyridine ring significantly increases cytotoxic activity and aqueous solubility. Changing the arene from p-cymene to biphenyl and the monodentate ligand X from chloride to iodide also increases the activity significantly. Activation by hydrolysis and DNA binding appears not to be the major mechanism of action since both the highly active complex [Os(eta(6)-bip)(2-F-azpy)I]PF(6) (9) and the moderately active complex [Os(eta(6)-bip)(3-Cl-azpy)I]PF(6) (23) are very stable and inert towards aquation. Studies of octanol-water partition coefficients (log P) and subcellular distributions of osmium in A2780 human ovarian cancer cells suggested that cell uptake and targeting to cellular organelles play important roles in determining activity. Although complex 9 induced the production of reactive oxygen species (ROS) in A2780 cells, the ROS level did not appear to play a role in the mechanism of anticancer activity. This class of organometallic osmium complexes has new and unusual features worthy of further exploration for the design of novel anticancer drugs