Biology subjects

Dhir, A.

Publications and source records attributed to Dhir, A..

5 recordsLinked to original sources

bioRxiv2025

PAMD-Ch17, a Polymeric Analog of Plerixafor, Induces Mitochondrial Dysfunction in T-ALL Cells Independent of CXCR4

PAMD-Ch17 is a polymer composed of the CXCR4 inhibitor AMD3100/Plerixafor with a cholesterol modification. In previous work, we showed that PAMD-Ch17, but not AMD3100, induces cell death and differentiation in mouse Acute Myeloid Leukemia cells. To investigate the mechanism of PAMD-Ch17s novel anti-leukemic effects, we tested PAMD-Ch17 against a panel of human leukemia cell lines and found that PAMD-Ch17 is effective against a variety of acute leukemias, with T-ALL cell lines being highly sensitive. Surprisingly, CXCR4 knock out T-ALL cells were equally sensitive to PAMD-Ch17. Using a fluorescently tagged PAMD-Ch17, we found that the drug colocalized to the mitochondria. We also found that PAMD-Ch17 induced changes in expression of genes related to mitochondrial function, increased levels of mitochondrial superoxide, and decreased mitochondrial membrane potential. Using seahorse assays, we found that PAMD-Ch17 decreased baseline oxygen consumption, ATP production, and proton leakage. PAMD-Ch17 also decreased baseline extracellular acidification rate, indicating a decrease in overall metabolism. In mouse primary T-ALL but not healthy bone marrow cells, PAMD-Ch17 induced both mitochondrial superoxide and cell death. Using human bone marrow organoids, we found that PAMD-Ch17 induced mitochondrial superoxide and cell death in human primary T-ALL cells, but not in healthy stromal and hematopoietic cells. Collectively, our results indicate that PAMD-Ch17 has anti-leukemic effects against T-ALL cells but not healthy cells, likely mediated through a CXCR4 independent, mitochondrial based mechanism. These findings support further development of PAMDs as potential therapeutics for patients with T-ALL. KEY POINTSO_LIPAMD-Ch17, a polymeric drug based on AMD3100/Plerixafor, has novel anti-leukemic activities against T-ALL that are independent of CXCR4 inhibition. C_LIO_LIPAMD-Ch17 induces increased mitochondrial superoxide and cell death in primary ALL cells, but not healthy bone marrow cells. C_LI

cancer biology↗

bioRxiv2025

The Splicing Factor PTBP1 interacts with RUNX1 and is Required for Leukemia Cell Survival

Runt-related Transcription Factor 1 (RUNX1) is essential for definitive hematopoiesis and is among the most frequently mutated genes in leukemia. Previous work from our lab demonstrated that Histone Deacetylase 1 (HDAC1), a known RUNX1 partner, is unexpectedly required for active transcription suggesting a non-histone role for HDAC1 regulating components of the RUNX1 complex. Here, we use proteomics, genomics, and long-read transcriptomics to identify novel RUNX1 interacting partners and decipher their role in gene regulation and RNA splicing in leukemia cells. We demonstrate that Polypyrimidine Tract Binding Protein 1 (PTBP1) interacts with RUNX1 in an HDAC1 dependent manner. Chromatin profiling revealed extensive genome-wide overlap in sites occupied by RUNX1 and PTBP1, with significant enrichment at promoters of actively transcribed genes. Loss of PTBP1 in AML cells led to widespread alterations in RNA splicing and decreased expression of genes whose promoters are bound by both factors, including metabolic genes. In agreement with these findings, we found that loss of PTBP1 reduced glycolysis and glucose uptake and ultimately caused cell death. Based on our data, we propose that the interaction between RUNX1 and PTBP1 facilitates expression of metabolic proteins essential for leukemia cell growth and survival. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=92 SRC="FIGDIR/small/654547v1_ufig1.gif" ALT="Figure 1"> View larger version (20K): org.highwire.dtl.DTLVardef@74e3b9org.highwire.dtl.DTLVardef@12a090org.highwire.dtl.DTLVardef@eb5a48org.highwire.dtl.DTLVardef@17465dc_HPS_FORMAT_FIGEXP M_FIG C_FIG KEY POINTSO_LIPTBP1 binds RUNX1 in a HDAC1-dependent manner and co-localizes to the promoters of target genes in leukemia cells. C_LIO_LILoss of PTBP1 decreases expression of key metabolic genes, resulting in decreased cell growth and glycolysis, increased sensitivity to chemotherapy, and cell death. C_LI

cancer biology↗

bioRxiv2025

Chronic lysosome damage boosts interferon responses to Palbociclib through a mitochondrial signalling axis

Acute lysosome damage triggers the endolysosome damage response (ELDR) in order to co-ordinate vesicle repair or removal by autophagy (lysophagy). However, it is unclear whether persistent damage, as occurs after chronic challenge to lysosome integrity, triggers wider cellular responses. Here, we show that longitudinal treatment with a lysosomotropic cancer therapeutic, the CDK4/6 inhibitor Palbociclib, invokes chronic lysosome damage in breast and lung cancer cells. Autophagy ameliorates but does not avert this phenotype, which persists over days. Damaged lysosomes form contacts with mitochondria, which correlates with mitochondrial stress and cytosolic efflux of immunostimulatory mitochondrial nucleic acids. Importantly, mitochondrial nucleic acid release is necessary for the anti-cancer interferon response to Palbociclib. In conclusion, chronic lysosome damage rewires cellular signalling responses in a mitochondrion-dependent manner and this effect should be considered when assessing the cellular actions of cancer therapeutics. Summary statementBozic et al suggest that lysosome damage can trigger interferon responses dependent upon mitochondrial release of immunogenic nucleic acid. This is associated with damaged lysosome-mitochondrion contacts and is prevented by autophagy.

cell biology↗

bioRxiv2024

Loss of the Inv(16) Oncogene CBFB::MYH11 Eliminates Leukemia from the Blood and Spleen, but not the Bone Marrow

Inversion of chromosome 16 [inv(16)] generates the fusion gene CBFB::MYH11 (CM) and is one of the most common chromosomal rearrangements in Acute Myeloid Leukemia (AML). Expression of CM is required for leukemia initiation. Patients with inv(16) at diagnosis invariably have the rearrangement at relapse, leading to the assumption that CM is also required after leukemic transformation. However, a role for CM in leukemia maintenance has yet to be shown experimentally. To address this, we used an inducible CM knockdown (KD) mouse model and found that decreased CM eliminated leukemia cells from the peripheral blood and spleen, but not the bone marrow, despite all populations exhibiting significantly decreased CM mRNA and protein. The surviving CM KD cells in the bone marrow showed decreased apoptosis and proliferation, and increased expression of autophagy related genes. Surprisingly, with prolonged KD of CM, [~]40% of mice re-established disease despite maintaining decreased CM. Our work indicates that CM is required for leukemia survival in the spleen and peripheral blood, but in the bone marrow CM KD leukemia cells can survive and re-establish disease independent of the fusion protein. These findings imply that targeting CM alone has potential to reduce leukemic burden but not cure the disease.

cancer biology↗

bioRxiv2021

Enhanced cGAS-STING-dependent interferon signaling associated with mutations in ATAD3A

Mitochondrial DNA (mtDNA) has been suggested to drive immune system activation, but the induction of interferon signaling by mtDNA has not been demonstrated in a Mendelian mitochondrial disease. We initially ascertained two patients, one with a purely neurological phenotype, and one with features suggestive of systemic sclerosis in a syndromic context, and found them both to demonstrate enhanced interferon-stimulated gene (ISG) expression in blood. We determined each to harbor a previously described de novo dominant-negative heterozygous mutation in ATAD3A, encoding ATPase family AAA domain-containing protein 3A (ATAD3A). We identified five further patients with mutations in ATAD3A, and recorded up-regulated ISG expression and interferon alpha protein in four of them. Knockdown of ATAD3A in THP-1 cells resulted in increased interferon signaling, mediated by cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING). Enhanced interferon signaling was abrogated in THP-1 cells and patient fibroblasts depleted of mtDNA. Thus, mutations in the mitochondrial membrane protein ATAD3A define a novel type I interferonopathy. SummaryDominant-negative mutations in ATAD3A, a ubiquitously expressed mitochondrial protein, cause mitochondrial DNA-dependent up-regulation of type I interferon signaling in the context of neurological disease and autoimmunity, thereby defining a novel type I interferonopathy.

immunology↗