5 research outputs found

    Pseudopeptides and Peptidomimetics Modulating the Proteolytic Activity of Kallikrein-related Peptidase 3

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    The highly prostate specific serine protease kallikrein-related peptidase 3 (KLK3, also known as prostate specific antigen, PSA) is widely used as a biomarker for prostate cancer and it has also been postulated that it may play a part in tumour growth. Especially interestesting is the antiangiogenic effect exerted by proteolytically active KLK3 in cell line models. In order to stimulate the proteolytic activity of KLK3, a series of peptides have been developed by phage display methodology. Even though the peptides are quite potent KLK3 stimulators, they are not directly suitable for in vivo studies or use as drugs. Even though there are many natural and unnatural biologically active peptides, they suffer from rapid clearance via the liver and kidneys and proteolytic degradation of the compounds both in the gastrointestinal tract and other parts of the body. This gives peptides a poor oral bioavailability meaning that they are usually administered as intravenous or intramuscular injections. Several different strategies have been developed in order to access compounds with improved bioavailability including modifications of the peptide structure, development of pseudopeptides and development of small molecular weight peptidomimetics. This thesis concentrates on the further development of the two most potent peptides known to stimulate KLK3, i.e. B-2 and C-4. The main part of the work was concentrated on the replacement of disulphide bridges in the peptides in order to both gain more information on which residues are necessary for obtaining the biological activity and at the same time also gain information on how changes to the geometry of the disulphide bridge affects the activity. A series of different disulphide bridge mimicking building blocks were designed and synthesised with the intention of using them in a protocol for solid-phase synthesis of KLK3 stimulating peptides. Unfortunately, the use of these building blocks in the synthesis of pseudopeptides based on C-4 turned out to be an unsurmountable challenge and the synthesis had to be completed using a different strategy in which the key step was the use of ring-closing metathesis (RCM) for the cyclisation of the partly completed pseudopeptide. Pleasingly, the synthesis of pseudopeptide analogues of the B-2 peptide using the building blocks was more successful. In total three pseudopeptide analogues of C-4 and four of B-2 were synthesised and shown to retain the biological activity of the parent peptides. Based on the information from the synthesised pseudopeptides and a molecular modelling study, a 4-quinolone based peptidomimetic was designed to mimic the C-4 peptide and a synthetic protocol was devised to access this compound. Even though the synthesis of the desired target compound has so far not been successful, the synthetic protocol that was designed has given access to a number of 1,2,8-trisubstituted 4-quinolone derivatives.Prostatacancer Ă€r i nulĂ€get den vanligaste formen av cancer hos mĂ€n i vĂ€stvĂ€rlden, sĂ„ mycket som var sjĂ€tte man har uppskattats insjukna i den under sin livstid. Även om dödligheten berĂ€knas till endast nĂ„gra procent innebĂ€r den stora utbredningen att prostatacancer orsakar det nĂ€st högsta antalet dödsfall i cancer hos mĂ€n efter lungcancer. Pga detta Ă€r det viktigt att hitta nya metoder bĂ„de för att bota prostatacancer och för att sakta ner sjukdomsförloppet. Kallikrein 3 (human kallikrein-related peptidase 3, KLK3; Ă€ven kĂ€nd som prostataspecifik antigen, PSA) Ă€r ett prostataspecifikt enzym som klyver proteiner och peptider (en proteas). KLK3 utsöndras i sĂ€desvĂ€tskan och dess biologiska uppgift Ă€r att klyva de gelbildande proteiner som utsöndras vid ejakulation. Enzymatiskt aktivt KLK3 har visat sig inhibera tillvĂ€xten av blodkĂ€rl bĂ„de in vitro och in vivo vilket har antagits bidra till en lĂ„ngsammare tumörtillvĂ€xt. En elakartad tumör i prostatan sĂ€nker utsöndringen av KLK3 i epitelvĂ€vnaden jĂ€mfört med en frisk prostata. KLK3 inverkar pĂ„ tumörtillvĂ€xten i prostatacancer genom att pĂ„verka de proteolytiska kaskaderna som bryter ned den extracellulĂ€ra matrisen och dĂ€rmed inhibera tumörtillvĂ€xten. Substanser som gör det möjligt att modifiera den proteolytiska aktiviteten hos KLK3 Ă€r mycket intressanta för utvecklingen av nya lĂ€kemedel mot prostatacancer. En serie peptider som stimulerar den proteolytiska aktiviteten hos KLK3 har tidigare utvecklats vid Helsingfors universitet. Även om dessa peptider uppvisar en stark stimulerande effekt pĂ„ KLK3 sĂ„ sönderfaller de snabbt i plasma, de har ocksĂ„ en förhĂ„llandevis stor molekylmassa för att vara peptider vilket starkt begrĂ€nsar deras anvĂ€ndbarhet in vivo. Studier har pĂ„visat vilka delar av dessa peptider som Ă€r viktiga för den biologiska aktiviteten, utgĂ„ende frĂ„n denna information har vi syntetiserat serier med modifierade peptider för att vidare söka utreda vilka modifikationer som Ă€r möjliga att göra utan att den biologiska aktiviteten sjunker avsevĂ€rt. Förhoppningen Ă€r att dessa modifikationer ocksĂ„ förbĂ€ttrar peptidernas stabilitet in vitro och in vivo. De tvĂ„ mest aktiva av de kĂ€nda peptiderna valdes ut och de naturliga disulfidbryggorna i dessa ersattes med en kolvĂ€tekedja samtidigt som andra, mindre förĂ€ndringar, gjordes i övriga delar av peptiden. Vissa av peptiderna i dessa serier visade sig ha en klar biologisk aktivitet som dock var nĂ„got lĂ€gre Ă€n den hos ursprungspeptiderna. En viktig slutsats av studien var att inga omfattande förĂ€ndringar i peptidens struktur Ă€r möjliga. Det slutliga mĂ„let med projektet var att utveckla smĂ„molekyler med en biologisk effekt som motsvarar den hos de ursprungliga peptiderna. Information frĂ„n studierna av peptiderna och de modifierade peptiderna i kombination med datorbaserad molekylmodellering gjorde att vi valde att anvĂ€nda ett 1,2,8-trisubstituerat 4-kinolonskelett som grund för dessa peptidmimetika och ett syntesprotokoll för sĂ„dana substanser utvecklades. Detta syntesprotokoll visade sig vara generellt tillĂ€mpbart och anvĂ€ndes till att syntetisera en serie 1,2,8-trisubstituerade 4-kinoloner med variation i struktur och egenskaper. De syntetiserade substanserna studeras för tillfĂ€llet för sin KLK3-stimulerande effekt

    A scaffold replacement approach towards new sirtuin 2 inhibitors

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    Sirtuins (SIRT1-SIRT7) are an evolutionary conserved family of NAD(+)-dependent protein deacylases regulating the acylation state of epsilon-N-lysine residues of proteins thereby controlling key biological processes. Numerous studies have found association of the aberrant enzymatic activity of SIRTs with various diseases like diabetes, cancer and neurodegenerative disorders. Previously, we have shown that substituted 2-alkyl-chroman-4-one/chromone derivatives can serve as selective inhibitors of SIRT2 possessing an antiproliferative effect in two human cancer cell lines. In this study, we have explored the bioisosteric replacement of the chroman-4-one/chromone core structure with different less lipophilic bicyclic scaffolds to overcome problems associated to poor physiochemical properties due to a highly lipophilic substitution pattern required for achieve a good inhibitory effect. Various new derivatives based on the quinolin-4(1H)-one scaffold, bicyclic secondary sulfonamides or saccharins were synthesized and evaluated for their SIRT inhibitory effect. Among the evaluated scaffolds, the benzothiadiazine-1,1-dioxide-based compounds showed the highest SIRT2 inhibitory activity. Molecular modeling studies gave insight into the binding mode of the new scaffold-replacement analogues.Peer reviewe

    Replacement of the Disulfide Bridge in a KLK3-Stimulating Peptide Using Orthogonally Protected Building Blocks

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    Peptide “B-2”, which is one of the most potent kallikrein-related peptidase 3 (KLK3)-stimulating compounds, consists of 12 amino acids and is cyclized by a disulfide bridge between the N- and C-terminal cysteines. Orthogonally protected building blocks were used in the peptide synthesis to introduce a disulfide bridge mimetic consisting of four carbon atoms. The resulting pseudopeptides with alkane and <i>E</i>-alkene linkers doubled the proteolytic activity of KLK3 at a concentration of 14 ÎŒM. They were almost as potent as the parent “B-2” peptide, which gives a 3.6-fold increase in the proteolytic activity of KLK3 at the same concentration
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