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Role of autophagy in normal and malignant hematopoiesis

Chen, Xiaoyi
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1490354914070478

Abstract Details

2017, PhD, University of Cincinnati, Medicine: Cancer and Cell Biology.
In this thesis work, we investigate the role of autophagy in normal and malignant hematopoiesis. In normal hematopoiesis, we study the mechanism of autophagy regulation by mTOR in hematopoietic stem and progenitor cells (HSPCs) using genetic mTOR knockout and knock-in mouse models. We find that HSPCs have varied basal autophagy activity in different subpopulations, higher in more primitive hematopoietic stem cells (HSC) and lower in more differentiated progenitor cells, suggesting varied dependence on autophagy in these cells. We also observe that the autophagy activity responds differently to mTOR deletion in HSPCs subpopulations. HSC and GMP subpopulations show mTOR independent autophagy regulation, while CMP has increased autophagy activity upon mTOR deletion. We speculate that a compensatory kinase pathway in HSC and GMP exists to negatively regulate autophagy activity upon mTOR loss in HSC population based on our kinase inhibitor data. We also find that the autophagy response in mTOR knock-in cells is similar to mTOR knockout, suggesting that mTOR regulates autophagy through its kinase function, not a protein scaffolding effect. The autophagy response in Raptor knockout cells mimics that of the mTOR knockout, indicating that mTORC1 regulates autophagy in HSPCs. This project is progressing and more studies are needed to validate our current observations and conclusions. In malignant hematopoiesis, we investigate the therapeutic potential of inhibiting autophagy for AML treatment. We show that Kmt2a/Mll-Mllt3/Af9 AML (MA9-AML) cells have high autophagy flux compared to normal bone marrow cells, but autophagy-specific targeting, either through Rb1cc1-disruption to abolish autophagy initiation, or via Atg5-disruption to prevent autophagosome membrane elongation, does not affect the growth or survival of MA9-AML cells, either in vitro or in vivo. Mechanistically, neither Atg5 nor Rb1cc1 disruption impairs the endolysosome formation or survival signaling pathways. The autophagy inhibitor, chloroquine, shows autophagy-independent anti-leukemic effects in vitro but has no efficacy in vivo likely due to limited achievable drug efficacy in blood. Further, vesicular exocytosis appears to mediate chloroquine resistance in AML cells and exocytotic inhibition significantly enhances the anti-leukemic effect of chloroquine. Thus, the autophagy inhibitor chloroquine can induce leukemia cell death in vitro in an autophagy-independent manner but with inadequate efficacy in vivo, and vesicular exocytosis is a possible mechanism of chloroquine resistance in MA9-AML. This study also reveals that autophagy-specific targeting is unlikely to benefit MA9-AML therapy.
Yi Zheng, Ph.D. (Committee Chair)
Maria Czyzyk-Krzeska, M.D. Ph.D. (Committee Member)
Marie-Dominique Filippi, Ph.D. (Committee Member)
Gang Huang, Ph.D. (Committee Member)
Daniel Starczynowski, Ph.D. (Committee Member)
138 p.
Molecular Biology
autophagy; hematopoiesis; acute myeloid leukemia; chloroquine; mTOR; Atg5

Recommended Citations

Citations

  • Chen, X. (2017). Role of autophagy in normal and malignant hematopoiesis [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1490354914070478

    APA Style (7th edition)

  • Chen, Xiaoyi. Role of autophagy in normal and malignant hematopoiesis. 2017. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1490354914070478.

    MLA Style (8th edition)

  • Chen, Xiaoyi. "Role of autophagy in normal and malignant hematopoiesis." Doctoral dissertation, University of Cincinnati, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1490354914070478

    Chicago Manual of Style (17th edition)

ucin1490354914070478
282
© 2017, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.