La Leucémie Lymphoïde Chronique (LLC) est caractérisée par l’accumulation dans le sang de lymphocytes B/CD5+ qui sont déficients pour leur programme de mort apoptotique. Malgré les progrès thérapeutiques récents, la LLC est une maladie toujours incurable. La stratégie de rétablissement des processus apoptotiques semble pertinente pour améliorer les traitements des patients, et cette stratégie nécessite l’identification de cibles spécifiques. Dans ce but, nous avons développé une recherche du mécanisme d’action de l’hyperforine, un phloroglucinol purifié à partir de la plante Millepertuis, qui est un inducteur d’apoptose des cellules de LLC ex vivo par la voie mitochondriale dépendante des caspases. Les résultats montrent que le traitement des cellules primaires de LLC régule positivement Noxa, une protéine de la famille Bcl-2 du type « BH3-only » qui est un ligand antagoniste spécifique de Mcl-1, la protéine de survie majeure pour le défaut d’apoptose dans les LLC. Nous montrons que Noxa interagit effectivement avec Mcl-1, ce qui entraine la dissociation du complexe que Mcl-1 forme avec Bak, et l’activation de cette protéine responsable de la libération par la mitochondrie des facteurs d’activation des caspases. La régulation positive de Noxa ne résulte apparemment pas d’une activation transcriptionnelle mais plutôt d’une régulation au niveau protéique comme le suggère la capacité de l’hyperforine à inhiber l’activité protéolytique du protéasome dans les cellules de LLC. Par ailleurs, l’apoptose induite par l’hyperforine est réduite en partie par l’extinction de Noxa avec des ARN interférents. Nos résultats indiquent donc que la régulation positive de Noxa est un des mécanismes qui permet à l’hyperforine de déclencher l’apoptose des cellules de LLC. Ce mécanisme semble être commun à d’autres composés d’origine végétale, comme nous l’avons observé avec l’extrait M2Yn dans la seconde partie de notre travail qui a permis de mettre en évidence que cet extrait de plantes d’Asie centrale est capable lui aussi d’induire l’apoptose des cellules de LLC par la voie mitochondriale dépendante des caspases. Enfin, nous avons contribué à la mise en évidence des propriétés pro-apoptotiques de l’hyperforine dans un autre modèle de leucémie, la leucémie myéloïde aiguë, grâce en partie à la régulation positive de Noxa ainsi qu’à l’inhibition de l’activité kinasique de Akt-1.En conclusion, nos travaux de thèse décrivent des nouvelles étapes dans le mécanisme d’action de l’hyperforine et permettent d’établir que la protéine « BH3-only » Noxa est une cible majeure pour la stratégie thérapeutique du rétablissement d’apoptose dans les LLC, ce qui devrait susciter le développement de nouveaux agents capables d’imiter spécifiquement l’action de Noxa. / Chronic lymphocytic leukemia (CLL) is characterized by blood accumulation of CD5+/B lymphocytes which are deficient in their apoptotic program. Despite recent therapeutic advances, CLL remains an incurable disease. Treatment strategy based on the re-establishment of apoptotic processes has retained much attention, and such a strategy requires the identification of specific targets. To this aim, we have investigated the mechanism of action of hyperforin, a phloroglucinol purified from St John’s wort, capable of inducing apoptosis of CLL cells ex vivo via the caspase-dependent mitochondrial pathway. Our results show that treatment of CLL patients’ cells upregulates the BH3-only protein Noxa that is a specific antagonist ligand of Mcl-1, the crucial prosurvival protein for apoptosis deficiency in CLL. We find that hyperforin provokes both the interaction of Noxa with Mcl-1 and the dissociation of Mcl-1/Bak complex, leading to Bak activation responsible for the release of apoptogenic factors from mitochondria. Noxa upregulation does not seem to result from transcription activation but rather from a regulation at the protein level, as suggested by the ability of hyperforin to inhibit proteasome activity in CLL cells. Using siRNA, Noxa silencing partially reduces hyperforin-induced apoptosis. Our data indicate that Noxa upregulation is one of the mechanisms through which hyperforin triggers CLL cell apoptosis. This mechanism appears to be shared with other plant-derived compounds, as observed with M2Yn, an extract from central Asia plants, that we show here to be an inducer of apoptosis in CLL cells by activating the caspase-dependent mitochondrial pathway. Finally, we have participated in highlighting the proapoptotic properties of hyperforin in another leukemia model, acute myeloid leukemia, via in part Noxa upregulation and Akt1 kinase activity inhibition.In conclusion, our data describe new steps in the mechanism of action of hyperforin and favor that the BH3-only protein Noxa is a major target for the therapeutic strategy based on apoptosis induction in CLL. Thus, this thesis should prompt the development of new BH3 mimetics specific for Noxa.

An ideal drug delivery system should contain an appropriate therapeutic agent and biocompatible carrier. In this study, we investigated the ability of the all-complementary self-assembling peptide AC8 in stabilizing the anticancer compound and determined the in-vitro therapeutic efficacy of the peptide-mediated anticancer drug delivery. The all-complementary peptide AC8 was designed based on the amino acid pairing principle (AAP), which contains hydrogen bonding, electrostatic, and hydrophobic interaction amino acid pairs. AAP interactions make the peptide capable of self-assembling into β-sheet structure in solution in a concentration dependent manner. Peptide solution concentration is a key parameter in controlling the nanoscale assembling of the peptide. The critical assembly concentration (CAC) of the peptide was found ~ 0.01 mg/ml by several techniques. The all-complementary peptide AC8 was found to be able to stabilize neutral state of hydrophobic anticancer compound ellipticine in aqueous solution. The formation of peptide-ellipticine complex was monitored by fluorescence spectroscopy at different mass ratios of peptide-to-ellipticine. The anticancer activity of the complexes with neutral state of ellipticine was found to show great anticancer activity against two cancer cells lines, A-549 and MCF-7. This peptide-mediated anticancer delivery system showed the induction of apoptosis on cancer cells in vitro by flow Cytometry.

An ideal drug delivery system should contain an appropriate therapeutic agent and biocompatible carrier. In this study, we investigated the ability of the all-complementary self-assembling peptide AC8 in stabilizing the anticancer compound and determined the in-vitro therapeutic efficacy of the peptide-mediated anticancer drug delivery. The all-complementary peptide AC8 was designed based on the amino acid pairing principle (AAP), which contains hydrogen bonding, electrostatic, and hydrophobic interaction amino acid pairs. AAP interactions make the peptide capable of self-assembling into β-sheet structure in solution in a concentration dependent manner. Peptide solution concentration is a key parameter in controlling the nanoscale assembling of the peptide. The critical assembly concentration (CAC) of the peptide was found ~ 0.01 mg/ml by several techniques. The all-complementary peptide AC8 was found to be able to stabilize neutral state of hydrophobic anticancer compound ellipticine in aqueous solution. The formation of peptide-ellipticine complex was monitored by fluorescence spectroscopy at different mass ratios of peptide-to-ellipticine. The anticancer activity of the complexes with neutral state of ellipticine was found to show great anticancer activity against two cancer cells lines, A-549 and MCF-7. This peptide-mediated anticancer delivery system showed the induction of apoptosis on cancer cells in vitro by flow Cytometry.

<p>U radu je ispitan uticaj odabranih modifikovanih steroida na proliferaciju ćelija humanih malignih tumora i zdravih ćelija, a zatim njihov uticaj na modifikaciju ćelijskog ciklusa, indukovanje apoptoze i genetskih o&scaron;tećenja u tumorskim ćelijama najsenzitivnijim na ova jedinjenja (MDA-MB-231 ćelijska linija humanog adenokarcinoma dojke, ER-). Ispitana je<em> in vitro </em>citotoksičnost odabranih&nbsp; steroidnih derivata prema ćelijskim linijama MCF-7, MDA-MB-231, PC3, HeLa, HT-29, MRC-5, K562 i A549, i proučavan ćelijski mehanizam koji je u osnovi uočenog antiproliferativnog efekta svakog od ispitivanih derivata. Sva ispitivana jedinjenja indukuju apoptozu MDA-MB-231&nbsp; ćelija, na različite načine i sa različitim potencijalom. Genotoksikolo&scaron;ka studija upotpunjuje rezultate proučavanja efekta ispitivanih steroidnih jedinjenja na biolo&scaron;ke sisteme, ukazujući na izostanak genotoksičnosti ovih jedinjenja i njihov biomedicinski potencijal.</p> / <p>In this work the effect of selected modified steroids on proliferation of human&nbsp; malignant tumor and healthy cells, as well as their impact on the modification of cell cycle arrest, induction of apoptosis and genetic defects in tumor cells most sensitive&nbsp; to these compounds (MDA-MB-231 cell line of human breast adenocarcinoma, ER-) were examined. We examined the<em> in vitro </em>cytotoxicity of selected steroidal derivatives towards MCF-7, MDA-MB-231, PC-3, HeLa, HT-29, MRC-5, K562 and A549 cell lines, and studied the cellular mechanism that is underlying the antiproliferative activity expressed by these steroidal derivatives. All tested compounds induced apoptosis of&nbsp; MDA-MB-231 cells, in different ways and with different potential. Genotoxicological study complements the results of the study of the effect of tested steroidal compounds on biological systems, pointing out the lack of genotoxicity of these compounds and therefore their biomedical potential.</p>

Apoptosis represents one of the cell death mechanisms which is realized after the application of taxanes in breast cancer cell lines. Apoptosis induction can be principally triggered either by outer or inner pathway. The aim of the diploma thesis is to contribute to the elucidation of role and mechanisms of the inner mitochondrial pathway of apoptosis induction after taxane application (paclitaxel and SB-T-1216) employing a model of breast carcinoma cell lines SK- BR-3 (nonfunctional p53, functional capase-3) and MCF-7 (functional p53, nonfunctional caspase-3). Specifically, we tested the effect of both employed taxanes on mitochondrial membrane potential, ROS level and the expression and localization of proteins regulating inner mitochondrial pathway. Taxane application resulted in mitochondrial membrane dissipation in SK-BR-3 cell line. However, this was not shown in MCF-7 cell line. We found no changes in Bax and Smac/DIABLO expression after taxane application in both tested cell lines. There was a decrease of Bid expression after taxane application in SK-BR-3 line, but not in MCF-7 line. Taxane application did not lead to the translocation of Bax and Bid (tBid) proteins from cytosol to mitochondria in both tested cell lines. Similarly, there was no Smac/DIABLO release from mitochondria to...