Citrate Synthase is Required for the Initiation of PTEN-Deficient T-Cell Acute Lymphoblastic Leukemogenesis, but not PTEN-Deficient Myeloproliferative Neoplasms

Abstract

The “Warburg Effect” marks the metabolic tendencies of cancer cells to primarily utilize aerobic glycolysis over oxidative phosphorylation. However, a comprehensive understanding of the interplay between altered tricarboxylic acid (TCA) cycle activity and mitochondrial dysfunction in the initiation and progression of cancer remains elusive. Particularly in T- cell acute lymphoblastic leukemia (T-ALL), an aggressive hematologic malignancy derived from immature T-cell progenitors, the role of aerobic glycolysis in leukemogenesis warrants further investigation. The PTEN gene is one of the most frequently mutated/functionally-inactivated onco- suppressors in various cancers, and PTEN mutations account for 16% percent of all T-ALL cases. In this research, I wanted to investigate if changes to aerobic respiration would initiate the leukemogenesis of PTEN- deficient T-ALL and contradict the Warburg effect, through the removal of the citrate synthase gene, a catalytic metabolite of the TCA cycle. Mx1-Cre conditional knockout of citrate synthase (CS), a catalytic metabolite of the TCA cycle, and PTEN, an oncosuppressor often linked to T-ALL, were employed to evaluate T-ALL in wild-type, single knockout (PTEN -/-) and double knockout (CS -/-; PTEN -/-) mouse models. T-ALL-related lymphocyte concentrations were analyzed through flow cytometry of thymus, bone marrow, blood, and spleen cell samples bound to respective antibody cocktails, followed by tissue composition analysis and supplemental western blotting. Aberrant levels of T-ALL-associated lymphocytes amongst solely PTEN-deficient samples, yet a return to normalcy with CS deficiency, indicates the requirement of citrate synthase for PTEN-deficient T-ALL progression. Individual t-tests on CD3+CD4+CD8+ cells, amongst other T-ALL- associated lymphocytes, confirm significance in reduced leukemogenesis (p-value < 0.01). However, analysis of PTEN;CS-deficient myeloid cells indicates insufficient blockade of PTEN-deficient myeloproliferative neoplasms, presumably from impaired RBC maintenance post-CS deletion. This research demonstrates that the sequential context achieved via citrate synthase deletion undermines leukemogenesis and contrasts pre-existing ideals about the metabolic tendencies of cancer cells, therefore implying the dual reliance of cancer proliferation on both aerobic and anaerobic metabolic processes.