Biology subjects

Patel, S. B.

Publications and source records attributed to Patel, S. B..

5 recordsLinked to original sources

bioRxiv2026

Aberrant oxidative metabolism selects for TET2-deficient hematopoietic stem and progenitor cells

The mechanism(s) driving selective expansion of mutant hematopoietic stem and progenitor cells (HSPC) in clonal hematopoiesis (CH) are incompletely understood. Here, we address the role of metabolism in selection for HSPC with loss of function mutations in TET2. Loss of Tet2 in murine HSPC triggers overexpression of glycolysis and oxidative phosphorylation genes and increased oxidative metabolism via an enlarged mitochondrial network. However, Tet2-deficient HSPC maintain a normal redox state. Strikingly, compound loss of the rate-limiting pentose phosphate pathway (PPP) enzyme glucose-6-phosphate dehydrogenase (G6PD) triggers increased reactive oxygen species and impairs the fitness of Tet2-deficient HSPC. We find that aberrant oxidative metabolism is also a feature of HSPC in human CH and clonal cytopenia of unknown significance (CCUS). Overall, our data point to aberrant metabolism as a critical and conserved driver of selection in TET2-deficient CH and identify the PPP as a crucial compensatory pathway needed to maintain their selective advantage. Statement of SignificanceThis study identifies oxidative metabolism as a critical driver of selection for TET2-deficient HSPC in clonal hematopoiesis (CH). It also demonstrates that cellular redox state is a vulnerability that impairs their fitness. These insights establish targetable metabolic pathway(s) that could be exploited in the setting of TET2 mutant CH.

cancer biology↗

bioRxiv2025

The Nicotinamide Salvage Pathway is a Metabolic Vulnerability of High-Risk MDS Stem Cells

High-risk myelodysplastic syndrome (HR-MDS) is a malignant clonal disorder originating in hematopoietic stem and progenitor cells (HSPCs). The current standard of care for HR-MDS patients is hypomethylating agents; however, the response rate is poor. There is thus a need to explore vulnerabilities of HR-MDS HSPCs for better clinical outcomes. We demonstrate that HR-MDS HSPCs have significant upregulation of metabolic proteins required for glycolysis, citric acid cycle, and oxidative phosphorylation. Consistently, we see increased oxygen consumption rate in HR-MDS HSPCs compared to healthy, suggesting an increased metabolic rate. Corroboratively, compared to healthy HSPCs, HR-MDS HSPCs have increased abundance of mitochondrial complex I proteins, which are NADH dehydrogenases, and crucial for energy production. Therefore, we investigated whether HR-MDS HSPCs are functionally reliant on NAMPT, the rate-limiting enzyme in the nicotinamide salvage pathway of NAD anabolism. NAMPT inhibition significantly decreased NAD(H) in HR-MDS HSPCs. Consequently, NAMPT inhibition reduced the oxygen-consuming capacity of HR-MDS-HSPCs compared to healthy. Importantly, NAMPT inhibition significantly impaired the self-renewal and colony-forming potential, increased cell death and reduced disease burden specifically of HR-MDS HSPCs, compared to healthy controls. Collectively, our data suggest that NAMPT is selectively required for the function and survival of HR-MDS HSPCs representing a promising therapeutic target.

cancer biology↗

bioRxiv2025

Therapy resistance in AML is mediated by cytoplasmic sequestration of the transcriptional repressor IRF2BP2

While the development of venetoclax with azacitidine (ven/aza) has improved AML therapy, drug resistance remains a major challenge. Notably, primary ven/aza-resistant AML are frequently reliant on MCL1, however, the underlying mechanisms remain unclear. Co-immunoprecipitation of MCL1 from ven/aza-resistant AML samples coupled with mass spectrometry analysis identified the transcriptional repressor Interferon Regulatory Factor 2 Binding Protein 2 (IRF2BP2) as an MCL1 binding partner. This interaction results in cytoplasmic IRF2BP2 localization and loss of transcriptional repression within ven/aza-resistant leukemic stem cells (LSC). Consequently, ven/aza-resistant LSC have increased IRF2BP2 target gene expression, including acyl-CoA synthetase long-chain family member 1 (ACSL1), an essential rate-limiting enzyme for fatty acid oxidation (FAO). Inhibition of ACSL1 functionally impaired ven/aza-resistant LSC through a depletion of long-chain acyl-carnitine metabolites and FAO. Collectively, these data provide evidence for a previously undescribed mechanism by which MCL1 mediates IRF2BP2 cytoplasmic sequestration and consequent de-repression of ACSL1, thereby promoting ven/aza-resistance in AML.

cancer biology↗

bioRxiv2023

Targeting Acute Myeloid Leukemia Stem Cells Through Perturbation of Mitochondrial Calcium

We previously reported that acute myeloid leukemia stem cells (LSCs) are uniquely reliant on oxidative phosphorylation (OXPHOS) for survival. Moreover, maintenance of OXPHOS is dependent on BCL2, creating a therapeutic opportunity to target LSCs using the BCL2 inhibitor drug venetoclax. While venetoclax-based regimens have indeed shown promising clinical activity, the emergence of drug resistance is prevalent. Thus, in the present study, we investigated how mitochondrial properties may influence mechanisms that dictate venetoclax responsiveness. Our data show that utilization of mitochondrial calcium is fundamentally different between drug responsive and non-responsive LSCs. By comparison, venetoclax-resistant LSCs demonstrate a more active metabolic (i.e., OXPHOS) status with relatively high steady-state levels of calcium. Consequently, we tested genetic and pharmacological approaches to target the mitochondrial calcium uniporter, MCU. We demonstrate that inhibition of calcium uptake sharply reduces OXPHOS and leads to eradication of venetoclax-resistant LSCs. These findings demonstrate a central role for calcium signaling in the biology of LSCs and provide a therapeutic avenue for clinical management of venetoclax resistance. SignificanceWe identify increased utilization of mitochondrial calcium as distinct metabolic requirement of venetoclax-resistant LSCs and demonstrate the potential of targeting mitochondrial calcium uptake as a therapeutic strategy.

cancer biology↗

bioRxiv2022

A novel type of monocytic leukemia stem cell revealed by the clinical use of venetoclax-based therapy

The BCL-2 inhibitor venetoclax has recently emerged as an important component of acute myeloid leukemia (AML) therapy. Notably, use of this agent has revealed a previously unrecognized form of pathogenesis characterized by monocytic disease progression. We demonstrate that this form of disease arises from a fundamentally different type of leukemia stem cell (LSC), which we designate as monocytic LSC (m-LSC), that is developmentally and clinically distinct from the more well-described primitive LSC (p-LSC). The m-LSC is distinguished by a unique immunophenotype (CD34-, CD4+, CD11b-, CD14-, CD36-), unique transcriptional state, reliance on purine/pyrimidine metabolism, and selective sensitivity to cladribine. Critically, in some instances m-LSC and p-LSC subtypes can co-reside in the same AML patient and simultaneously contribute to overall tumor complexity. Thus, our findings demonstrate that LSC heterogeneity has direct clinical significance and highlights the need to distinguish and target m-LSCs as a means to improve clinical outcomes with venetoclax-based regimens. Statement of SignificanceThese studies identify and characterize a new type of human acute myeloid leukemia stem cell (LSC) that is responsible for monocytic disease progression in acute myeloid leukemia (AML) patients treated with venetoclax-based regimens. Our studies describe the phenotype, molecular properties, and drug sensitivities of this unique LSC subclass.

cancer biology↗