Cytotoxic effect of a non-peptidic small molecular inhibitor of the p53-HDM2 interaction on tumor cells

AIM: To investigate if non-peptidic small molecular inhibitors of the p53-HDM2 interaction could restore p53 function and kill tumor cells.METHODS: A series of non-peptidic small HDM2 inhibitors were designed by computer-aided model and synthesized by chemical method. Syl-155 was one of these inhibitors. Cytotoxic effect of syl-155 on three tumor cell lines with various states of p53, HT1080 (wild-type p53), KYSE510 (mutant p53), MG63 (p53 deficiency) was evaluated by MTT assay, Western blot and flow cytometry.RESULTS: Syl-155 stimulated the accumulation of p53 and p21 protein in HT1080 cells expressing wild-type p53, but not in KYSE510 and MG63 cells. Consequently, syl-155 induced cell cycle arrest and apoptosis in HT1080 cells.CONCLUSION: Non-peptidic small molecular inhibitors of the p53-HDM2 interaction show promise in treatment of tumors expressing wild-type p53.

Non-peptide ligands in the characterization of peptide receptors at the interface between neuroendocrine and mental diseases

Hypothalamic receptors for neuropeptide Y, melaninconcentrating hormone, melanocortins and orexins/ hypocretins as well as for the downstream signaling corticotrophic factor have been discussed broadly for their influence on food intake and reward but also on several psychiatric disorders. For the development of non-peptide ligands for the in vivo detection of alterations in density and affinity of such G-protein coupled (GPCRs) peptide receptors the requirements to affinity and pharmacokinetics have been shifted to thresholds markedly distict from classical GPCRs to dissociation constants ported originally as potential therapeutics in the treatment of obesity among which some are suitable candidates for labeling as PET or SPECT-tracers providing receptor affinities even below 0.1 nM. These could be unique tools not only for better understanding of the mechanism of obesity but also for investigations of extrahypothalamic role of “feeding receptors” at the interface between neuroendocrine and mental diseases.

Potential PET Ligands for Imaging of Cerebral VPAC and PAC Receptors: Are Non-Peptide Small Molecules Superior to Peptide Compounds?

Pituitary adenylate cyclase activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) have been known for decades to mediate neuroendocrine and vasodilative actions via G-protein-coupled receptors of Class B. These are targets of imaging probes for positron emission tomography (PET) or single photon emission tomography (SPECT) in tumor diagnostics and tumor grading. However, they play only a subordinate role in the development of tracers for brain imaging. Difficulties in development of non-peptide ligands typical for cerebral receptors of PACAP and VIP are shared by all members of Class B receptor family. Essential landmarks have been confirmed for understanding of structural details of Class B receptor molecular signalling during the last five years. High relevance in the explanation of problems in ligand development for these receptors is admitted to the large N-terminal?ectodomain markedly different from Class A receptor binding sites and poorly suitable as orthosteric binding sites for the most small-molecule compounds. The present study is focused on the recently available receptor ligands for PAC1, VPAC1 and VPAC2 receptors as well as potential small-molecule lead structures suitable for use in PET or SPECT. Recently, biaryl, cyanothiophene and pentanamide structures with affinities in nM-range have been proposed as non-peptide ligands at VPAC1 and VPAC2 receptors. However, most of these ligands have been classified as non-competitive related to the orthosteric binding site of endogenous peptide ligands of VPAC receptors. For PAC1 receptors have been identified hydrazide compounds for which an inhibitory and potentially competitive mechanism of receptor binding has been postulated based on molecular docking studies.