Characterization of pro- and anti-apoptotic BCL-2 proteins regulating leukemogenesis in juvenile myelomonocytic leukemia (JMML)

Abstract: Juvenile myelomonocytic leukemia (JMML) is a highly aggressive myeloid malignancy of early childhood and driven by RAS pathway activation and epigenetic deregulation. Most patients require hematopoietic stem cell transplantation. Only recently, the DNA methyl transferase inhibitor azacitidine has been shown to have unprecedented activity against JMML, both in patients and the JMML xenograft mouse model. BH3-mimetics, small molecules inhibiting pro-survival BCL-2 proteins and thereby inducing apoptosis, were shown to be promising in many cancer entities but have not been used yet in JMML patients. It was the aim of my thesis to study the role of BCL-2 proteins and the activity of various BH3-mimetics in JMML and the RASopathy Noonan syndrome (NS) that can be associated with a JMML-like myeloproliferative disorder (MPD). Like JMML, NS- MPD is caused by oncogenic mutations in PTPN11 coding for the phosphatase SHP2. It was my first aim to establish clinically relevant models of NS, MPD and JMML. A model of PTPN11-driven leukemogenesis was generated by lentivirally introducing the oncogenic PTPN11E76A/K mutants into cord blood-derived CD34+ cells. In addition, naive JMML cells were subjected long-term to different culture conditions to allow spontaneous immortalization. However, I noted no leukemic transformation but rather senescence in CD34+ cells expressing oncogenic PTPN11 mutations. Also the generation of the JMML cells remained unsuccessful. In addition, I used a patient-derived xenograft model for JMML established in my group. Upon successful engraftment, mice were treated with ABT737, S63845 or azacitidine in vivo. These experiments were complemented by in vitro treatment of naive JMML cells with ABT737, S63845, A1155463 or ABT199, four BH3-mimetics inhibiting BCL-2/BCL-XL/BCL-W, MCL-1, BCL-XL or BCL-2, respectively. Finally, I analyzed whether low-dose azacitidine can sensitize JMML towards BH3-mimetics. While treatment with ABT737 resulted in a general reduction of all leukemic cell subsets, high-dose azacitidine showed efficient depletion of leukemic cells and, most importantly, leukemia-initiating cells (LICs). However, high-dose azacitidine was toxic in the JMML mouse model. Different doses of azacitidine could cause dose related decrease of the number of LICs. This was accompanied by a reduction of the BCL-2 expression in vivo. High dose azacitidine in addition caused the reduction of MCL-1 expression. Low-dose azacitidine and ABT737 had additive effects in vivo. In vitro, MCL-1 inhibition showed stronger cytotoxic activities on naive JMML cells than BCL- 2 and/or BCL-XL inhibition. Low-dose azacitidine sensitized JMML cells to the BCL- XL inhibitor A1155463 and the BCL-2/BCL-XL/BCL-W inhibitor ABT737. In sum, I propose to use BH3-mimetics to induce apoptosis in JMML cells, either alone or in combination with low-dose azacitidine

Angaben zum Objekt

• Standort: Deutsche Nationalbibliothek Frankfurt am Main
• Umfang: Online-Ressource
• Sprache: Englisch
• Anmerkungen: Universität Freiburg, Dissertation, 2020

Beteiligte, Orts- und Zeitangaben

• Ereignis: Veröffentlichung
• (wo): Freiburg
• (wer): Universität
• (wann): 2021
• Urheber: Wu, Ying
• Beteiligte Personen und Organisationen: Erlacher, Miriam ; Albert-Ludwigs-Universität Freiburg. Fakultät für Biologie

Weitere Informationen

• DOI: 10.6094/UNIFR/175831
• URN: urn:nbn:de:bsz:25-freidok-1758312
• Rechteinformation: Open Access; Der Zugriff auf das Objekt ist unbeschränkt möglich.
• Letzte Aktualisierung: 15.08.2025, 07:32 MESZ