Biology subjects

Bar-Sagi, D.

Publications and source records attributed to Bar-Sagi, D..

6 recordsLinked to original sources

bioRxiv2025

Exploiting macropinocytosis for therapeutic intervention in RAS mutant Multiple Myeloma

Roughly 50% of newly diagnosed multiple myeloma (MM) cases harbor KRAS (25%) or NRAS (24%) mutations with an even greater frequency of these mutations observed at relapse. By and large, mutant RAS-driven MM is more resistant to existing therapies including proteasome inhibitors, immunomodulator drugs (IMiDs), and monoclonal anti-CD38 antibodies. In the present study, we demonstrate that mutant RAS-dependent macropinocytosis (MP) can be leveraged for selective delivery of a monobody-drug conjugate (MDC) to mutant RAS MM cells. This MDC delivery platform consists of monobody, a fragment of human fibronectin (FN), used as the carrier to which monomethyl auristatin E (MMAE) is site-specifically conjugated (FN-MMAE). In comparison to standard of care (SoC) therapeutics, FN-MMAE displays a substantially improved anti-tumor effect in vitro and in vivo when administered alone or in combination with SoC treatments. Furthermore, the in vivo safety profile of FN-MMAE is tolerable affording increased drug dosing compared to clinically used ADCs. This MDC platform offers a way of selectively targeting mutant RAS MM and RRMM to potentially improve patient outcomes. Statement of SignificanceRas mutations are present in approximately 50% of MM patients and are associated with poor prognosis and drug resistance. Herein, we describe a novel protein-drug conjugate designed to target selectively mutant RAS harboring MM cells. Our findings uncover a new therapeutic modality for improving the outcomes for patients with mutant Ras MM.

cancer biology↗

bioRxiv2022

Cytoskeletal association of ATP citrate lyase controls the mechanodynamics of macropinocytosis

Macropinocytosis is an actin-dependent mode of non-selective endocytosis that mediates the uptake of extracellular fluid-phase cargoes. It is now well-recognized that tumor cells exploit macropinocytosis to internalize macromolecules that can be catabolized and used to support cell growth and proliferation under nutrient limiting conditions. Therefore, the identification of molecular mechanisms that control macropinocytosis is fundamental to the understanding of the metabolic adaptive landscape of tumor cells. Here we report that the acetyl-CoA producing enzyme, ATP citrate lyase (ACLY), is a key regulator of macropinocytosis and describe a heretofore unappreciated association of ACLY with the actin cytoskeleton. The cytoskeletal tethering of ACLY is required for the spatially-defined acetylation of heterodimeric actin capping protein, which we identify as an essential mediator of the actin remodeling events that drive membrane ruffling and macropinocytosis. Furthermore, we identify a requirement for mitochondrial-derived citrate, an ACLY substrate, for macropinocytosis, and show that mitochondria traffic to cell periphery regions juxtaposed to plasma membrane ruffles. Collectively these findings establish a new mode of metabolite compartmentalization that supports the spatiotemporal modulation of membrane-cytoskeletal interactions required for macropinocytosis by coupling regional acetyl-CoA availability with dynamic protein acetylation. SignificanceThe scavenging of extracellular macromolecules via macropinocytosis is a key adaptive mechanism that supports the metabolic fitness of cancer cells. Although the importance of macropinocytosis for sustaining tumor cell growth under nutrient limiting conditions is well documented, less is known about the molecular mechanisms by which macropinocytosis is regulated. This study describes a previously uncharacterized dependence of macropinocytosis on the compartmentalized generation of acetyl-CoA through the association of ACLY with the actin cytoskeleton. This metabolic channeling process establishes a new mechanistic framework for understanding actin remodeling events that drive macropinocytosis.

cell biology↗

bioRxiv2022

Chromosome 9p21.3 Coordinates Cell Intrinsic and Extrinsic Tumor Suppression

Somatic chromosomal deletions are prevalent in cancer, yet their functional contributions remain ill-defined. Among the most prominent of these events are deletions of chromosome 9p21.3, which disable a cell intrinsic barrier to tumorigenesis by eliminating the CDKN2A/B tumor suppressor genes. However, half of 9p21.3 deletions encompass a cluster of 16 type I interferons (IFNs) whose co-deletions have not been functionally characterized. To dissect how 9p21.3 and other genomic deletions impact cancer, we developed MACHETE (Molecular Alteration of Chromosomes with Engineered Tandem Elements), a genome engineering strategy that enables flexible modeling of megabase-sized deletions. Generation of 9p21.3-syntenic deletions in a mouse model of pancreatic cancer revealed that concomitant loss of Cdkn2a/b and the IFN cluster led to immune evasion and metastasis compared to Cdkn2a/b-only deletions. Mechanistically, IFN co-deletion disrupted type I IFN signaling, altered antigen-presenting cells, and facilitated escape from CD8+ T cell surveillance in a cell extrinsic manner requiring loss of interferon epsilon (Ifne). Our results establish co-deletions of the IFN cluster as a pervasive route to tumor immune evasion and metastasis, revealing how deletions can disable physically linked cell intrinsic and extrinsic tumor suppression. Our study establishes a framework to dissect the functions of genomic deletions in cancer and beyond.

cancer biology↗

bioRxiv2021

Pancreatic cancer ductal cell of origin drives CD73-dependent generation of immunosuppressive adenosine

The microenvironment that surrounds pancreatic ductal adenocarcinoma (PDAC) is profoundly desmoplastic and immunosuppressive. Understanding initial triggers of immunosuppression during the process of pancreatic tumorigenesis would aid in establishing novel targets for effective prevention and therapy. Here, we interrogate the differential molecular mechanisms dependent on cell of origin and pathology subtype that determine immunosuppression during PDAC initiation and in established tumors. Transcriptomic analysis of cell of origin dependent-epithelial gene signatures revealed that Nt5e/CD73, a cell surface enzyme that is the pacemaker for extracellular adenosine generation, is one of the top 10% of genes over-expressed in murine tumors arising from ductal pancreatic epithelium as opposed to those rising from acinar cells. These findings were confirmed by Imaging Mass Cytometry and High-Performance Liquid Chromatography. Our data indicate that ductal activation of oncogenic mutant Kras results in loss of PTEN and elevated AKT signaling which ultimately releases CD73 suppression. Delivery of CD73 small molecule inhibitors through various delivery routes reduced tumor development and growth in genetically engineered and syngeneic mouse models. Analysis in human PDAC subtypes indicates that high Nt5e in murine ductal PDAC models overlaps with high NT5E in human PDAC Squamous and Basal Subtypes, considered to have the highest immunosuppression and worst prognosis. These findings highlight a molecular trigger of the immunosuppressive PDAC microenvironment which is dependent on ductal cell of origin, linking biology with pathological subtype classification, critical components to personalized approaches for PDAC prevention and immunotherapeutic intervention. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=185 SRC="FIGDIR/small/470415v1_ufig1.gif" ALT="Figure 1"> View larger version (66K): org.highwire.dtl.DTLVardef@14625org.highwire.dtl.DTLVardef@1a43372org.highwire.dtl.DTLVardef@12dc0c8org.highwire.dtl.DTLVardef@cbb835_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2021

Integrated Systems-Analysis of the Human and Murine Pancreatic Cancer Glycomes Reveal a Tumor Promoting Role for ST6GAL1

Pancreatic ductal adenocarcinoma (PDA) is the 3rd leading cause of cancer-death in the U.S.. Glycans, such as CA-19-9, are biomarkers of PDA and are emerging as important modulators of cancer phenotypes. Herein, we utilized a systems-based approach integrating glycomic analysis of human PDA and the well-established KC mouse model, with transcriptomic data to identify and probe the functional significance of aberrant glycosylation in pancreatic cancer. We observed both common and distinct patterns of glycosylation in pancreatic cancer across species. Common alterations included increased levels of -2,3- and -2,6-sialic acids, bisecting GlcNAc and poly-LacNAc. However, core fucose, which was increased in human PDAC, was not seen in the mouse, indicating that not all human glycomic changes can be modeled in the KC mouse. In silico a nalysis of bulk and single cell sequencing data identified ST6GAL1, which underlies -2,6-sialic acid, as overexpressed in human PDA, concordant with histological data. Enzymes levels correlated with the stage of clinical disease. To test whether ST6GAL1 promotes pancreatic cancer we created a novel mouse in which a pancreas-specific genetic deletion of this enzyme overlays the KC mouse model. Analysis of our new model showed delayed cancer formation and a significant reduction in fibrosis. Our results highlight the importance of a strategic systems-approach to identifying glycans whose functions can be modeled in mouse, a crucial step in the development of therapeutics targeting glycosylation in pancreatic cancer. SIGNIFICANCEPancreatic ductal adenocarcinoma (PDA) is the 3rd leading cause of cancer-death in the U.S.. Glycosylation is emerging as an important modulator of cancer phenotype. Herein we use a systems-approach integrating glycomics of human PDA and a well-established PDA mouse model with transcriptomic data to identify ST6GAL1, the enzyme underlying -2,6-sialic acid, as a potential cancer promoter. A pancreatic specific ST6GAL1 knockout in the KC mouse showed delayed cancer formation and a reduction in fibrosis. Our results highlight the importance of a strategic systems-approach to identifying glycans whose functions can be modeled in mouse, a crucial step in the development of therapeutics targeting glycosylation in pancreatic cancer.

cancer biology↗

bioRxiv2021

Adaptive stimulation of macropinocytosis overcomes aspartate limitation in cancer cells under hypoxia

Stress-adaptive mechanisms enable tumor cells to overcome metabolic constraints in nutrient and oxygen poor tumors. Aspartate is an endogenous metabolic limitation under hypoxic conditions, but the nature of the adaptive mechanisms that contribute to aspartate availability and hypoxic tumor growth are poorly understood. Here, using a combination of metabolomics and CRISPR-based genetic screens, we identify GOT2-catalyzed mitochondrial aspartate synthesis as an essential metabolic dependency for the proliferation of pancreatic tumor cells under hypoxic culture conditions. In contrast, GOT2-catalyzed aspartate synthesis is dispensable for pancreatic tumor formation in vivo. The dependence of pancreatic tumor cells on aspartate synthesis is bypassed in part by a hypoxia-induced potentiation of extracellular protein scavenging via macropinocytosis. This effect is mutant KRas-dependent, and is mediated by hypoxia inducible factor 1 (HIF1A) and its canonical target carbonic anhydrase-9 (CA9) through the cooption of the bicarbonate-macropinocytosis signaling axis. Our findings reveal high plasticity of aspartate metabolism and define an adaptive regulatory role for macropinocytosis by which mutant KRas tumors can overcome nutrient deprivation under hypoxic conditions.

cancer biology↗