TY - THES A1 - Pfann, Christina T1 - Untersuchungen zu neuen therapeutischen Ansätzen zur Beeinflussung der MYC-Expression im kolorektalen Karzinom T1 - Experiments on new therapeutic strategies to influence MYC expression in colorectal cancer N2 - Eine veränderte Expression des Transkriptionsfaktors MYC wird als entscheidender Faktor für Tumorentstehung und -progress im kolorektalen Karzinom gesehen. Somit ist die Hemmung dessen Expression und Funktion ein zentraler Ansatz bei der zielgerichteten Tumortherapie. Als geeignete Strategie, sowohl die Halbwertszeit als auch die Translation von MYC zu verringern, erschien eine duale PI3K-/mTOR-Hemmung durch den small molecule-Inhibitor BEZ235. Gegenteilig ist jedoch unter Behandlung mit BEZ235 eine verstärkte MYC-Expression in verschiedenen Kolonkarzinom-Zelllinien zu beobachten. Neben verstärkter Transkription, konnte eine verstärkte IRES-abhängige Translation von MYC nach Hemmung der mTOR-/5´Cap-abhängigen Translation durch BEZ235, als Ursache der MYC-Induktion nachgewiesen werden. Es konnte gezeigt werden, dass die Induktion von MYC nach PI3K-/mTOR-Hemmung durch eine kompensatorische Aktivierung des MAPK-Signalwegs in Folge einer FOXO-abhängigen Induktion von Rezeptortyrosinkinasen, stattfindet. Eine mögliche Strategie, diese Feedback-Mechanismen zu umgehen, ist die direkte Hemmung der Translationsinitiation. Hierfür wurden Rocaglamid und dessen Derivat Silvestrol als small molecule-Inhibitoren der eIF4A-Helikase verwendet. Im Gegensatz zur PI3K/mTOR-Hemmung, ist durch eIF4A-Inhibition eine Reduktion der MYC-Proteinexpression in verschiedenen Kolonkarzinom-Zelllinien zu erreichen – ohne einhergehende MAPK-Aktivierung. Anhand der Ergebnisse kann postuliert werden, dass Silvestrol das Potential besitzt, sowohl die Cap-/eIF4F-abhängie als auch die somit eIF4A-abhängige IRES-vermittelte Translation von MYC zu hemmen. Weiterhin kann eine proliferationshemmende Wirkung durch Silvestrol auf Kolonkarzinom-Zellen in vitro, via Zellzyklusarrest und Induktion von Apoptose, gezeigt werden. Dies stellt die Voraussetzung für eine potentielle Eignung als tumorhemmender Wirkstoff in der Therapie des kolorektalen Karzinoms dar. N2 - Deregulated expression of MYC is a driver of colorectal carcinogenesis. Thus inhibition of MYC function and expression may be a central aim in targeted therapy. Inhibiting the PI3K-and mTOR pathway seemed to be a proper strategy to increase MYC turnover and reduce its translation. Instead, we observe enhanced MYC expression in colon carcinoma cells upon treatment with the dual PI3K-/mTOR-inhibitor BEZ235. PI3K-/mTOR-Inhibition permits both enhanced transcription and induction of IRES-dependent translation of MYC through feedback activation of the MAPK pathway via FOXO-dependent induction of receptor tyrosine kinases. A strategy to bypass the signalling feedback mechanisms, is targeting the translation initiation. Using Silvestrol, a Rocaglamid derivate as small molecule inhibitor of the initiation factor eIF4A, MYC protein expression can be reduced in colorectal cancer cells – without observed MAPK-activation. So Silvestrol has he potential to inhibit Cap-/eIF4F-dependend as well as eIF4A-dependent IRES-mediated tranlation of MYC. Furthermore Silvestrol inhibits proliferation of colon carcinoma cells in vitro, shown by cell cycle arrest and induction of apoptosis. Our data argue that targeting translation initiation is a promising strategy to limit MYC expression in colorectal cancer. Thus, together with its antiproliferative effect, Silvestrol might be a potential anti-tumor agent. KW - Myc KW - colorectal cancer Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-216687 ER - TY - JOUR A1 - Baur, Florentin A1 - Nietzer, Sarah L. A1 - Kunz, Meik A1 - Saal, Fabian A1 - Jeromin, Julian A1 - Matschos, Stephanie A1 - Linnebacher, Michael A1 - Walles, Heike A1 - Dandekar, Thomas A1 - Dandekar, Gudrun T1 - Connecting cancer pathways to tumor engines: a stratification tool for colorectal cancer combining human in vitro tissue models with boolean in silico models JF - Cancers N2 - To improve and focus preclinical testing, we combine tumor models based on a decellularized tissue matrix with bioinformatics to stratify tumors according to stage-specific mutations that are linked to central cancer pathways. We generated tissue models with BRAF-mutant colorectal cancer (CRC) cells (HROC24 and HROC87) and compared treatment responses to two-dimensional (2D) cultures and xenografts. As the BRAF inhibitor vemurafenib is—in contrast to melanoma—not effective in CRC, we combined it with the EGFR inhibitor gefitinib. In general, our 3D models showed higher chemoresistance and in contrast to 2D a more active HGFR after gefitinib and combination-therapy. In xenograft models murine HGF could not activate the human HGFR, stressing the importance of the human microenvironment. In order to stratify patient groups for targeted treatment options in CRC, an in silico topology with different stages including mutations and changes in common signaling pathways was developed. We applied the established topology for in silico simulations to predict new therapeutic options for BRAF-mutated CRC patients in advanced stages. Our in silico tool connects genome information with a deeper understanding of tumor engines in clinically relevant signaling networks which goes beyond the consideration of single drivers to improve CRC patient stratification. KW - in silico simulation KW - 3D tissue models KW - colorectal cancer KW - BRAF mutation KW - targeted therapy KW - stratification Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-193798 SN - 2072-6694 VL - 12 IS - 1 ER - TY - JOUR A1 - Schmidt, Stefanie A1 - Denk, Sarah A1 - Wiegering, Armin T1 - Targeting protein synthesis in colorectal cancer JF - Cancers N2 - Under physiological conditions, protein synthesis controls cell growth and survival and is strictly regulated. Deregulation of protein synthesis is a frequent event in cancer. The majority of mutations found in colorectal cancer (CRC), including alterations in the WNT pathway as well as activation of RAS/MAPK and PI3K/AKT and, subsequently, mTOR signaling, lead to deregulation of the translational machinery. Besides mutations in upstream signaling pathways, deregulation of global protein synthesis occurs through additional mechanisms including altered expression or activity of initiation and elongation factors (e.g., eIF4F, eIF2α/eIF2B, eEF2) as well as upregulation of components involved in ribosome biogenesis and factors that control the adaptation of translation in response to stress (e.g., GCN2). Therefore, influencing mechanisms that control mRNA translation may open a therapeutic window for CRC. Over the last decade, several potential therapeutic strategies targeting these alterations have been investigated and have shown promising results in cell lines, intestinal organoids, and mouse models. Despite these encouraging in vitro results, patients have not clinically benefited from those advances so far. In this review, we outline the mechanisms that lead to deregulated mRNA translation in CRC and highlight recent progress that has been made in developing therapeutic strategies that target these mechanisms for tumor therapy. KW - colorectal cancer KW - protein synthesis KW - translation initiation Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-206014 SN - 2072-6694 VL - 12 IS - 5 ER -