Biology subjects

Mbong, N.

Publications and source records attributed to Mbong, N..

5 recordsLinked to original sources

bioRxiv2026

Cell-state-dependent responses to PLK1 inhibition reveal a non-canonical microtubule-endolysosomal vulnerability in quiescent leukemia stem cells

Relapse in cancer is frequently driven by therapy-resistant quiescent cancer stem cells. Conventional chemotherapy has been designed to target proliferating tumor cells and is generally presumed to be ineffective against non-cycling cancer stem cells. Using acute myeloid leukemia (AML) as a model, we challenge this prevailing view by showing that inhibition of the mitotic master regulator Polo-like kinase 1 (PLK1), a kinase extensively pursued for antiproliferative cancer therapy, unexpectedly eradicates quiescent leukemia stem cells (LSC) through a mechanism distinct from its canonical mitotic function. In proliferating AML cells, PLK1 inhibition (PLK1i) induced G2/M arrest and mitotic catastrophe. In contrast, quiescent LSC underwent apoptosis independent of mitotic arrest, revealing a cell-state-dependent mode of drug action. Mechanistically, PLK1i initiated a multi-step process through disruption of a previously unrecognized, stem cell-specific interaction between PLK1 and MAP1A, resulting in perturbed vesicle trafficking and endolysosomal homeostasis characterized by altered receptor internalization, vesicle accumulation and lysosomal dysfunction, ultimately culminating in apoptotic cell death. Combinatorial pharmacologic perturbation studies established microtubule regulation as a critical determinant of quiescent LSC survival, while ex vivo and in vivo assays demonstrated depletion of functionally-defined LSC following PLK1i. These findings identify a previously unrecognized role for PLK1 in intracellular trafficking and establish MAP1A-dependent control of vesicle homeostasis as a mechanistic determinant of cancer stem cell survival. More broadly, this study demonstrates that classical antimitotic compounds, including microtubule-targeting agents and PLK1 inhibitors, can eradicate both cycling leukemic blasts and quiescent LSC through distinct, cell state-dependent mechanisms, challenging proliferation-centric models of chemotherapy action.

cancer biology↗

bioRxiv2024

Distinct gene regulatory networks govern hematopoietic and leukemia stem cells

The underlying gene regulatory networks (GRN) that govern leukemia stem cells (LSC) in acute myeloid leukemia (AML) and hematopoietic stem cells (HSC) are not well understood. Here, we identified GRNs by integrating gene expression (GE) and chromatin accessibility data derived from functionally defined cell populations enriched for HSC and LSC. We analyzed n=32 LSC+ and n=32 LSC-cell fractions from n=22 AML patients, along with n=7 stem and n=10 progenitor enriched cell populations sorted from human umbilical cord blood (hUCB), producing a database of n{approx}17,000 transcription factor (TF) regulatory interactions for hUCB-HSPC and AML. We developed an iterative algorithm that associates the degree of chromatin openness with TF binding preferences, and the GE of candidate TF and target genes within 100kb upstream of transcription start sites. A putative regulatory structure was found to be enriched in HSC-enriched cell populations, comprising TF-target gene interactions between ETS1, EGR1, RUNX2, and ZNF683 oriented in a self-reinforcing configuration. A regulatory loop comprising FOXK1 and MEIS1, rather than the 4-factor HSC subnetwork, was detected in the LSC-specific GRN. The core HSC and LSC TF networks were extended using protein-protein interaction (PPI) data to determine connectivity with interacting genes whose expression strongly associated with LSC/HSC frequency estimates, producing a database of n=103,516 PPI target pathways. The effect of perturbing genes along the identified pathways on functional HSC and LSC frequency was predicted based on statistical regression analyses. To validate GRN predictions, we used pharmacologic and CRISPR targeting, in addition to re-examining published functional data associated with several network nodes that were predicted to impact stemness. Notably, we found that inhibition of CDK6 in AML samples markedly reduced LSC numbers as assessed in de novo serial xenotransplantation studies (fold change {approx} 10), as predicted by the LSC GRN model. Additionally, in-house CRISPR-based knockdown of ETS1 resulted in a significant decrease in HSC quiescence-associated microRNA-126 expression, and increased HSC frequency. Taken together, our models provide a comprehensive view of the underlying regulatory structures governing functional human HSC and LSC. This approach has translational potential as it can be used as a high-throughput in-silico screening tool for the systematic identification of gene targets for LSC elimination and HSC expansion.

bioinformatics↗

bioRxiv2022

KDM6A loss sensitizes human acute myeloid leukemia to PARP and BCL2 inhibition

Acute myeloid leukemia (AML) is a heterogeneous, aggressive malignancy with dismal prognosis and with limited availability of targeted therapies. AML exhibits epigenetic deregulation and transcriptional plasticity that contributes to pathogenesis. KDM6 proteins are histone-3 lysine-27 demethylases that play major context dependent roles in AML evolution and therapy resistance. Here, we demonstrate that KDM6 demethylase function critically regulates DNA damage repair (DDR) gene expression programs in AML. Mechanistically, KDM6 family protein expression is regulated by genotoxic stress, with deficiency of KDM6A (UTX) and KDM6B (JMJD3) impairing DDR transcriptional activation and compromising repair potential. Acquired KDM6A loss-of-function mutations have been implicated in chemoresistance, although a significant percentage of relapsed AML have upregulated KDM6A. Based on these mechanistic findings, olaparib treatment significantly reduced engraftment of patient-derived xenografts. Thus KDM6A-mutant human primary AML samples have increased susceptibility to Poly-(ADP-ribose)-polymerase (PARP) inhibition in vivo. Crucially, a higher KDM6A expression is correlated with venetoclax tolerance. Loss of KDM6A increased mitochondrial activity, BCL2 expression, and sensitized AML cells to venetoclax. Additionally, KDM6A loss was accompanied with a downregulated BCL2A1, which is commonly associated with venetoclax resistance. Corroborating these results, dual targeting of PARP and BCL2 was superior to PARP or BCL2 inhibitor monotherapy in inducing AML apoptosis, and primary AML cells carrying acquired KDM6A-domain mutations were even more sensitive to the combination. Together, our study illustrates a mechanistic rationale in support for a novel combination targeted therapy for human AML based on subtype heterogeneity, and establishes KDM6A as an important molecular regulator for determining therapeutic efficacy.

cancer biology↗

bioRxiv2022

A primary patient-derived model for investigating functional heterogeneity within the human Leukemic Stem Cell Compartment

The ability of leukemic stem cells (LSC) to evade therapy and fuel leukemic progression causing relapse impedes therapeutic success in acute myeloid leukemia (AML). The LSC pool within a patient sample is not homogenous but comprises distinct LSC subsets that vary in self-renewal and propagation properties. The stemness programs that underlie LSC types are poorly understood since human LSC studies require primary patient samples where LSC numbers are low and isolation methods impure. To overcome these challenges, we developed a patient-derived AML model system (OCI-AML22) displaying a functionally, transcriptionally and epigenetically defined cellular hierarchy driven by functional LSCs that can be immunophenotypically identified and isolated. Through single cell and functional approaches, the OCI-AML22 LSC fraction was found to contain distinct LSCs that vary in proliferative and differentiation properties. OCI-AML22 represents a valuable resource to decipher mechanisms driving stemness and the multiple layers of heterogeneity within LSCs.

cancer biology↗

bioRxiv2021

Identification of the Global miR-130a Targetome Reveals a Novel Role for TBL1XR1 in Hematopoietic Stem Cell Self-Renewal and t(8;21) AML

Gene expression profiling and proteome analysis of normal and malignant hematopoietic stem cells (HSC) point to shared core stemness properties. However, discordance between mRNA and protein signatures underscores an important role for post-transcriptional regulation by miRNAs in governing this critical nexus. Here, we identified miR-130a as a regulator of HSC self-renewal and differentiation. Enforced expression of miR-130a impaired B lymphoid differentiation and expanded long-term HSC. Integration of protein mass spectrometry and chimeric AGO2 eCLIP-seq identified TBL1XR1 as a primary miR-130a target, whose loss of function phenocopied miR-130a overexpression. Moreover, we found that miR-130a is highly expressed in t(8;21) AML where it is critical for maintaining the oncogenic molecular program mediated by AML1-ETO. Our study establishes that identification of the comprehensive miRNA targetome within primary cells enables discovery of novel genes and molecular networks underpinning stemness properties of normal and leukemic cells. HIGHLIGHTSO_LImiR-130a is a regulator of HSC self-renewal and lineage commitment C_LIO_LITBL1XR1 is a principal target of miR-130a C_LIO_LITBL1XR1 loss of function in HSPC phenocopies enforced expression of miR-130a C_LIO_LIElevated miR-130a levels maintain the AML1-ETO repressive program in t(8;21) AML C_LI

cell biology↗