Cell-Type Specific Requirement for Pyruvate Dehydrogenase in Hematopoiesis and Leukemia Development

Date

August 2021

Authors

Jun, Sojeong

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Abstract

When I joined the lab, it was already established that pyruvate dehydrogenase complex (PDC) was required for double positive (DP) T cells, and for the initiation of T- cell acute lymphoblastic leukemia (T-ALL). However, it was not known if lymphoid-specific deletion of PDHA1 using lymphoid-specific Cre line (CD2Cre, CD4Cre) would provide us with a similar phenotype as pan-hematopoietic deletion of PDHA1 using Mx1Cre, and we did not know the metabolic consequences of PDHA1 deletion in the thymus versus bone marrow. Our metabolomics analysis led us to investigate the contribution of glucose in the thymus versus bone marrow, leading us to develop low cell number isotope-tracing method in hematopoietic stem and progenitor cells (HSPCs) after U-13C glucose tracing. The conclusion that PDC is required in DP and T-ALL cells was previously established via flow and transplantation analysis. However, it was not known 1) the metabolic consequences of PDHA1 deletion after hematopoietic deletion, and 2) whether the thymus or bone marrow primarily uses glucose as an energy source using in vivo tracing method. U-13C glucose tracing followed by metabolomics analysis in the bone marrow also provided evidence that HSCs do not preferentially utilize glucose, at least evidenced from the metabolites we were able to examine, but this question needs to be further investigated with more extensive low-cell number metabolomics experiments that can detect more metabolites. My work in collaboration with S. Mahesula also arrived at a conceptually novel discovery that the role of PDC in the thymus is to prevent upstream metabolites from accumulating, rather than to generate acetyl-CoA to fuel the TCA cycle. Moreover, I showed that PDC is needed to maintain NAD+/NADH homeostasis in the thymus. Here, I present that PDC was not required to generate acetyl-CoA or maintain levels of TCA cycle metabolites but was required to prevent pyruvate accumulation and to maintain glutathione levels and redox homeostasis. Moreover, I present results highlighting the efforts to rescue metabolic defects seen in the PDHA1-deficient mice. My work shows the importance of employing in vivo approaches to characterize the metabolic requirement of DP thymocytes and T-ALL cells, and through this work we could draw a conclusive result that some metabolic characteristics of cancer cells may be inherited from the metabolism of the normal cell type of origin.

General Notes

Pages i-xii are misnumbered as pages ii-xiii, and page 142 is misnumbered as page 121.

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