Biology subjects

Sarosiek, K.

Publications and source records attributed to Sarosiek, K..

10 recordsLinked to original sources

bioRxiv2026

Extracellular vesicles facilitate the horizontal transfer of drug resistance and stem-like properties between ovarian tumor cells

Ovarian cancer stem cells (CSCs) can seed recurrent drug-resistant disease. Likewise, non-CSCs can acquire CSC phenotypic properties. How this process is orchestrated is of interest to inform how it might be prevented. We tested the hypothesis that ovarian CSC and/or drug-resistant tumor cells confer stem-like properties via extracellular vesicles (EVs). We focused our investigation on how EVs might mediate EZH2 signaling to promote a phenotypic change in drug-sensitive, non-CSCs. To accomplish this, we utilized paired PARP inhibitor-sensitive and - resistant ovarian cancer (OvCa) cell lines, EZH2 knockdown lines, and patient-derived organoids (PDOs) originating from recurrent high-grade serous OvCa. Small EVs isolated from drug-sensitive, CSC and/or drug-resistant enriched cultures, PARP inhibitor (olaparib) resistant lines, or drug-treated (olaparib or carboplatin) lines were cultured with treatment naive or sensitive lines for defined time points. The impact of small EV exposure was determined by assessing cell number, metabolic activity, viability, sphere and colony-forming capacity, ALDH activity, DNA damage, and changes in associated signaling pathways. We found that EVs from CSC or drug-resistant enriched cell fractions communicate CSC-like phenotypes to the more sensitive tumor cells via EZH2 canonical and non-canonical signaling pathways, promoting stemness. We conclude that EV-mediated activation of EZH2 signaling represents a targetable mechanism contributing to stemness-associated drug resistance in OvCa. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=160 SRC="FIGDIR/small/699925v1_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@6b4ffborg.highwire.dtl.DTLVardef@1501931org.highwire.dtl.DTLVardef@1a5f31aorg.highwire.dtl.DTLVardef@1fb475f_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2025

BCL-XL Dependence is a Subtype Agnostic Actionable Feature of Difficult-to-Treat Kidney Cancers

The BCL-XL anti-apoptotic protein is a clear cell Renal Cell Carcinoma (ccRCC) dependency; however, the mechanism of this dependence and its relevance in other aggressive kidney cancer contexts, including metastatic and/or rare RCC subtypes [e.g., Fumarate Hydratase (FH)-deficient and sarcomatoid RCCs], is unknown. Computational predictions, using a machine learning model trained on the human RCC TCGA dataset, and cell-based validations, confirmed BCL-XL dependence in all RCC subtypes. Remarkably, cell state changes, anoikis programs, inflammatory state, and metabolic perturbations (e.g., fumarate production in FH-deficient RCCs) independently conferred increased BCL-XL dependence. Correlation studies revealed that increased AMPK isoform 2 (PRKAA2) expression is a kidney-specific biomarker of BCL-XL dependence. Indeed, pharmacological AMPK activation sensitized RCCs to BCL-XL blockade. Finally, using functional studies, we developed a multivariate model that accurately predicted BCL-XL dependence in RCC. Our studies offer biomarkers for patient stratification and credential BCL-XL as a subtype agnostic vulnerability in difficult-to-treat RCCs.

cancer biology↗

bioRxiv2025

Paclitaxel-induced mitotic arrest results in a convergence of apoptotic dependencies that can be safely exploited by BCL-XL degradation to overcome cancer chemoresistance

Paclitaxel and other microtubule-targeting agents are cornerstone therapies for diverse cancers, including lung, breast, cervical, pancreatic, and ovarian malignancies. Paclitaxel induces tumor cell apoptosis during mitosis by disrupting microtubule dynamics required for chromosome segregation. However, despite initial responsiveness, many tumors develop resistance, limiting therapeutic durability. Here, we used high-grade serous ovarian carcinoma (HGSOC), the most common and lethal subtype of ovarian cancer, as a model to dissect the mechanisms underlying this resistance. We find that paclitaxel-induced mitotic arrest triggers degradation of the pro-survival protein MCL-1 and upregulation of BCL-XL, followed by inactivating phosphorylation of BCL-XL at Ser62 to promote apoptosis. In resistant cells, this MCL-1 downregulation is insufficient to commit cells to apoptosis but instead results in a transient convergence of apoptotic dependencies by forcing BCL-XL to sequester the pro-apoptotic proteins BIM, BAX, and BAK. During this state, BCL-XL inhibition induces synergistic apoptosis, even in chemoresistant cells. Surprisingly, we also discover that loss of substrate attachment recapitulates this apoptotic convergence both in vitro and in vivo, with HGSOC cells growing in metastasis-promoting malignant ascites displaying heightened apoptotic priming and dependence on BCL-XL relative to solid tumors. In HGSOC xenografts, targeted degradation of BCL-XL using the platelet-sparing proteolysis-targeting chimera (PROTAC) DT2216 matches the efficacy of paclitaxel monotherapy while avoiding the chronic thrombocytopenia induced by BCL-XL inhibitors such as navitoclax (ABT-263). Strikingly, combination therapy leveraging the synergy between paclitaxel and DT2216 leads to complete eradication of HGSOC cell line and patient-derived xenografts. Moreover, DT2216 treatment blunts the rapid apoptotic adaptation caused by other BCL-XL inhibitors, indicating that targeted degradation of pro-survival proteins may yield more durable responses than inhibition alone. These findings uncover a mechanistic framework for safely exploiting the apoptotic dependency convergence caused by mitotic arrest and substrate detachment and support the clinical development of BCL-XL-targeting PROTACs to overcome chemoresistance in ovarian cancer and other solid tumors.

cancer biology↗

bioRxiv2025

A molecular circuit regulates fate plasticity in emerging and adult AT2 cells

Alveolar AT1 and AT2 cells are vital for lung gas exchange and become compromised in several diseases. While key differentiation signals are known, their emergence and fate plasticity are unclear. Here we show in the embryonic lung that single AT2s emerge at intermediate zones, extrude, and connect with nearby epithelium via interlumenal junctioning. We observe that AT2s retain fate plasticity until the bZIP transcription factor C/EBP suppresses Notch signaling at a novel Dlk1 enhancer. Both Dlk1 and Cebpa are regulated by the polycomb repressive complex (PRC2), which together form a "pulse generator" circuit that times Dlk1 expression and thus Notch activation, resulting in a "salt and pepper" pattern of AT1 and AT2 fate. In injured adult lungs, C/EBP downregulation is required to re-access AT2 fate plasticity and is mediated by the dominant negative C/EBP family member CHOP. Finally, Cebpa loss also activates a "defender" AT2 state, distinct from its reparative state, and we propose AT2s toggle between either state following infection to protect and repair alveoli.

developmental biology↗

bioRxiv2023

Pulsed ultrasound promotes secretion of anti-inflammatory extracellular vesicles from skeletal myotubes via elevation of intracellular calcium level

The regulation of inflammatory responses is an important intervention in biological function and macrophages play an essential role during inflammation. Skeletal muscle is the largest organ in the human body and releases various factors which mediate anti-inflammatory/immune modulatory effects. Recently, the roles of extracellular vesicles (EVs) from a large variety of cells are reported. In particular, EVs released from skeletal muscle are attracting attention due to their therapeutic effects on dysfunctional organs and tissues. Also, ultrasound (US) promotes release of EVs from skeletal muscle. In this study, we investigated the output parameters and mechanisms of US-induced EV release enhancement and the potential of US-treated skeletal muscle-derived EVs in the regulation of inflammatory responses in macrophages. High-intensity US (3.0 W/cm2) irradiation increased EV secretion via elevating intracellular Ca2+ level without negative effects. Moreover, US-induced EVs suppressed expression levels of pro-inflammatory factors in macrophages. miRNA sequencing analysis revealed that miR-206-3p and miR-378a-3p were especially abundant in skeletal myotube-derived EVs. In this study we demonstrated that high-intensity US promotes the release of anti-inflammatory EVs from skeletal myotubes and exert anti-inflammatory effects on macrophages.

immunology↗

bioRxiv2023

In situ architecture of Opa1-dependent mitochondrial cristae remodeling

Cristae membrane state plays a central role in regulating mitochondrial function and cellular metabolism. The protein Optic atrophy 1 (Opa1) is an important crista remodeler that exists as two forms in the mitochondrion, a membrane-anchored long form (l-Opa1) and a processed short form (s-Opa1). The mechanisms for how Opa1 influences cristae shape have remained unclear due to lack of native three-dimensional views of cristae. We perform in situ cryo-electron tomography of cryo-focused ion beam milled mouse embryonic fibroblasts with defined Opa1 states to understand how each form of Opa1 influences cristae architecture. In our tomograms, we observe a variety of cristae shapes with distinct trends dependent on s-Opa1:l-Opa1 balance. Increased l-Opa1 levels promote cristae stacking and elongated mitochondria while increased s-Opa1 levels correlated with irregular cristae packing and round mitochondria shape. Functional assays indicate a role for l-Opa1 in wild-type apoptotic and calcium handling responses, and compromised respiratory function under Opa1 imbalance. In summary, we provide three-dimensional visualization of cristae architecture to reveal relationships between mitochondrial ultrastructure and cellular function dependent on Opa1-mediated membrane remodeling. HighlightsO_LIIn situ ultrastructural characterization of mitochondrial cristae with different forms of Opa1. C_LIO_LIMitochondria with predominantly l-Opa1 show crista stacking, longer cristae, reduced globular cristae and an absence of tubular cristae. C_LIO_LIMitochondria with mostly s-Opa1 showed irregular cristae packing with wider cristae junctions and narrower cristae. C_LIO_LIl-Opa1 expressing cells with WT-like cristae junction properties, show wild-type apoptotic response and calcium handling. C_LIO_LIImbalance in Opa1 processing show compromised respiratory function and an increase in amorphous cristae. C_LI

biophysics↗

bioRxiv2022

LKB1 loss rewires JNK-induced apoptotic protein dynamics through NUAKs and sensitizes KRAS-mutant NSCLC to combined KRASG12C + MCL-1 blockade

The efficacy of molecularly targeted anti-cancer therapies may be limited by the presence of co-occurring mutations within a tumor1-3. Conversely, these alterations may confer collateral vulnerabilities that can be leveraged for the development of novel therapeutic approaches. KRAS-mutant lung cancers are distinguished by recurrent inactivating mutations in the tumor suppressor STK11/LKB14 that facilitate tumorigenesis by modulating energy balance5, 6, enhancing metastatic potential7,8 and enabling immune evasion9,10. However, whether LKB1 plays a role in modulating cellular responses to therapeutic stress is largely unknown. Here we show that LKB1 suppresses JNK-dependent stress signaling in KRAS-mutant lung cancer cells upon acute loss of oncogenic signaling. In LKB1-deficient KRAS-mutant cells, inhibition of KRAS or its downstream effector MEK leads to hyperactivation of JNK due to loss of NUAK-mediated PP1B phosphatase activity. JNK-mediated inhibitory phosphorylation of BCL-XL rewires apoptotic dependencies, rendering LKB1-deficient cells vulnerable to MCL-1 inhibition. These results uncover a previously unknown role for LKB1 in regulating stress signaling and the mitochondrial apoptotic response of cancer cells independent of its tumor suppressor activity mediated by AMPK11-13 and SIK14,15 kinases. Additionally, our study reveals a therapy-induced vulnerability in LKB1-deficient KRAS-mutant lung cancer cells that could be exploited as a genotype-informed strategy to improve the efficacy of KRAS-targeted therapies.

cancer biology↗

bioRxiv2022

Discovery of diverse human BH3-only and non-native peptide binders of pro-apoptotic BAK indicate that activators and inhibitors use asimilar binding mode and are not distinguished by binding affinity or kinetics

Apoptosis is a programmed form of cell death important for the development and maintenance of tissue homeostasis. The BCL-2 protein family controls key steps in apoptosis, dysregulation of which can lead to a wide range of human diseases. BCL-2 proteins comprise three groups: anti-apoptotic proteins, pro-apoptotic proteins, and BH3-only proteins. BAK is one of two pro-apoptotic proteins, and previous work has shown that binding of certain BH3-only proteins such as truncated BID (tBID), BIM, or PUMA to BAK leads to mitochondrial outer membrane permeabilization, the release of cytochrome c, and ultimately cell death. This process, referred to as activation, involves the BH3-stimulated conversion of BAK from monomer to dimer and then to oligomers that promote membrane disruption. Crystal structures of putative intermediates in this pathway, crosslinking data, and in vitro functional tests have provided insights into the activation event, yet the sequence-function relationships that make some but not all BH3-only proteins function as activators remain largely unexamined. In this work, we used computational protein design, yeast surface-display screening of candidate BH3-like peptides, and structure-based energy scoring to identify ten new binders of BAK that span a large sequence space. Among the new binders are two peptides from human proteins BNIP5 and PXT1 that promote BAK activation in liposome assays and induce cytochrome-c release from mitochondria, expanding current views of how BAK-mediated cell death may be triggered in cells. High-resolution crystal structures and binding experiments revealed a high degree of similarity in binding geometry, affinity, and association kinetics between peptide activators and inhibitors, including peptides described previously and those identified in this work. We propose a model for BAK activation that is based on differential engagement of BAK monomers vs. the BAK activation transition state that integrates our observations with previous reports of BAK binders, activators, and inhibitors.

biochemistry↗

bioRxiv2022

A Mesenchymal Tumor Cell State Confers Increased Dependency on the BCL-XL Anti-apoptotic Protein in Kidney Cancer

Genome-wide genetic screens have identified cellular dependencies in many cancers. Using the Broad Institutes Achilles shRNA screening dataset, we mined for targetable dependencies by cell lineage. Our studies identified a strong dependency on BCL2L1, which encodes the BCL-XL anti-apoptotic protein, in a subset of kidney cancer cells. Genetic and pharmacological inactivation of BCL-XL, but not the related anti-apoptotic proteins BCL-2, led to fitness defects in renal cancer cells, and also sensitized them to chemotherapeutics. Neither BCL-XL levels (absolute or normalized to BCL-2) nor the status of the VHL gene, which is frequently mutated in kidney cancer, predicted BCL-XL dependence. Transcriptional profiling, however, identified a BCL-XL dependency mRNA signature, which included elevated mesenchymal gene expression in BCL-XL dependent cells. Promoting mesenchymal transition increased BCL-XL dependence; whereas, conversion to a more differentiated state overcame BCL-XL dependence in kidney cancer cells. The BCL-XL dependency mRNA signature was observed in almost a third of human clear cell Renal Cell Carcinomas (ccRCCs), which were also associated with worse clinical outcomes. Finally, an orally bioavailable BCL-XL inhibitor, A-1331852, showed anti-tumor efficacy in vivo. Altogether, our studies uncovered an unexpected link between cancer cell state and dependence on the anti-apoptotic BCL-XL protein and justify further testing on BCL-XL blockade as a potential way to target a clinically aggressive subset of human kidney cancers. One Sentence SummaryCell state, but not pVHL and/or HIF status, defines the dependency of kidney cancer cells on the BCL-XL anti-apoptotic protein.

cancer biology↗

bioRxiv2019

Clonal plasma cells in AL amyloidosis are dependent on pro survival BCL-2 family proteins and sensitive to BH3 mimetics

Immunoglobulin light chain (AL) amyloidosis is a protein misfolding disorder characterized by the production of amyloidogenic immunoglobulin light chains by clonal populations of plasma cells. These abnormal light chains misfold and accumulate as amyloid fibrils in healthy tissues causing devastating multi-organ dysfunction that is rapidly fatal. Current treatment regimens, which include proteasome inhibitors, alkylating agents, and immunomodulatory agents, were developed for the treatment of the more common plasma cell disease, multiple myeloma, and have limited efficacy in AL amyloidosis as demonstrated by the median survival of 2-3 years. The recent development of novel small-molecule inhibitors of the major pro-survival proteins from the apoptosis-regulating BCL-2 family has created an opportunity to therapeutically target abnormal cell populations, yet identifying the extent of these dependencies and how to target them clinically has thus far been challenging. Using bone marrow-derived plasma cells from 45 patients with AL amyloidosis, we find that clonal plasma cells are highly primed to undergo apoptosis and exhibit strong dependencies on pro-survival BCL-2 family proteins. Specifically, we find that clonal plasma cells in a majority of patients are highly dependent on the pro-survival protein MCL-1 and undergo apoptosis when treated with an MCL-1 inhibitor as a single agent. In addition, BCL-2 inhibition sensitizes clonal plasma cells to several current standard of care therapies. Our results suggest that BH3 mimetics, when deployed rationally, may be highly effective therapies for AL amyloidosis.

cancer biology↗