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Projekt Druckansicht

Der Hedgehog Signalweg als therapeutisches Target in leukämischen Stammzellen bei der Akuten Myeloischen Leukämie

Fachliche Zuordnung Hämatologie, Onkologie
Förderung Förderung von 2011 bis 2018
Projektkennung Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 195237310
 
Erstellungsjahr 2018

Zusammenfassung der Projektergebnisse

During the five years of the funding period, we examined the role of hedgehog (HH) signaling in AML, myeloproliferative diseases and CLL in vitro and in vivo. We established various genetic mouse models with depletion of essential components of the HH signaling pathway within hematopoieses and different niche cells, and developed xenograft models for AML and CLL. Our results in CLL strongly altered our strategy, leading to a broader investigation of the HH-pathway, not only focused on the malignant cells, but also on the niche cells. Furthermore, we found, that the Ptch receptors not only regulate canonical, SMO-dependent HH signaling, but that they additionally activate non-canonical ERK signaling, resulting in a broader investigation of further HH driven pathways in AML. The results about HH signaling in CLL were published in "Blood" and show dependency of a certain subgroup of CLL cells on the HH signaling pathway. Biomarkers which discriminate in between HH responsive and resistant CLLs are elevated PTCH1 and GLI1 transcript levels and the presence of trisomy 12. Furthermore we found, that stroma secreted HH ligands not only activated the classical SMO-dependent canonical HH signaling pathway in CLL, but that they additionally stimulate ERK signaling directly downstream of the PTCH1 receptor, which implies the requirement of a dual inhibition of SMO and ERK in HH active CLLs. The results about the HH signaling component Ptch2 in normal and malignant hematopoiesis was published in the "Journal of Experimental Medicine". We show, that HH ligands are produced by MPN and AML cells, activating canonical and non-canonical HH signaling within the malignant cells, but also within the stem cell niche. Overactivation of canonical and noncanonical HH signaling by depletion of Ptch2 induces an MPN phenotype in mice, and accelerates JAK2 driven myeloproliferative diseases into AMLs. The complete phenotype requires the constitutive activation of canonical and non-canonical HH signaling within hematpoiesis and the niche. In fully developed AMLs we find similar mechanisms, and the more differentiated CD33+ AML cells are HH independent, while the immature KIT+ and CD34+ blasts have an acitve HH signaling pathway and respond to HH inhibitors. The effect of HH inhibitors on AML blasts is pronounced in the presence of stroma cells. Furthermore in AML xenografts we find reduction of the primary disease with loss of LSCs upon HH inhibition in vivo, and reduced retransplantability of the disease. In contrast, in murine hematopoiesis and murine AMLs major effects of SMO inhibition are mediated by the niche. Smo deletion or inhibition in niche cells alters normal and malignant hematopoiesis (AML), and causes an increase in differentiated cells in the PB, but reduced colony forming cells and reduced normal HSCs and/or leukemic stem cells within the bone marrow. Thus Smo deletion cannot block, but delayes AML development in mice, reduces LSC frequencies and therefore hampers the retransplantability of the disease into secondary recipients. By deleting Smo in different niche cell subsets (conditional Smo-/- mice are crossed into niche cell deleter strains) we currently aim to identify the essential niche cell for those effects. The final experiments for this project part shall be finished within the next 12 months. Besides these projects, which are focused on the hedgehog signaling pathway, we have finished two kinase projects (PIM and SYK) in AML/CLL. They were published in 2014 in "Molecular Cancer Therapeutics" and "Blood Cancer Journal".

Projektbezogene Publikationen (Auswahl)

 
 

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