Biology subjects

Pollok, K. E.

Publications and source records attributed to Pollok, K. E..

8 recordsLinked to original sources

bioRxiv2026

ZNF423 depletion induces the integrated stress response and represents a potential vulnerability in NF1-associated MPNST

Malignant peripheral nerve sheath tumors (MPNST) are aggressive sarcomas with limited systemic therapies and represent the leading cause of mortality for individuals with neurofibromatosis type 1 (NF1). Malignant progression can reactivate developmental precursor programs that are largely absent from normal nerve and benign tumors, creating tumor-selective vulnerabilities. Zinc finger protein 423 (ZNF423; also known as OAZ/ROAZ) is a developmentally regulated transcription factor that delays olfactory precursor differentiation and has been implicated in B-cell malignancy. Here, we asked whether ZNF423 is reactivated and functionally required in NF1-associated MPNST. In genetically defined models, Nf1 loss reduced Zfp423 in a benign tumor cell-of-origin context, whereas combined Nf1 and Cdkn2a loss induced marked Zfp423 upregulation during transformation. ZNF423 depletion impaired DNA synthesis and proliferation, induced DNA damage signaling, and activated the integrated stress response (ISR), increasing sensitivity to cytotoxic agents. In an orthotopic MPNST model, shRNA-mediated suppression of ZNF423 reduced tumor initiation in vivo; however, tumors that eventually emerged showed restoration of ZNF423 expression. ZNF423 is developmentally restricted in the peripheral nerve lineage yet elevated in MPNST, with single-cell analyses of patient nerve sheath tumors revealing localized expression restricted to malignant cells rather than SOX10-positive benign tumor cells. These data identify ZNF423 as a putative malignant biomarker, a potential dependency in NF1-MPNST, and nominate downstream stress and genome maintenance pathways as cooperative therapeutic vulnerabilities. STATEMENT OF SIGNIFICANCEZNF423 is a developmentally restricted transcription factor selectively reactivated in NF1-associated malignant peripheral nerve sheath tumors. Targeted ablation triggers the integrated stress response, impairs DNA synthesis, sensitizes cells to chemotherapy and PARP inhibition, and restricts in vivo growth. ZNF423 represents a candidate biomarker and therapeutic vulnerability in this aggressive sarcoma.

cancer biology↗

bioRxiv2025

Repurposing Romidepsin for Osteosarcoma: Screening FDA-Approved Oncology Drugs with Three-Dimensional Osteosarcoma Spheroids

Osteosarcoma is the most common primary malignant bone tumor and predominantly affects children, adolescents, and young adults. It is the third most common cause of cancer-related deaths among 9-24-year-olds. Despite aggressive chemotherapeutic and surgical therapies, the survival rate is only 25% for patients with detectable lung metastases at diagnosis and only 70% in patients that present without detectable lung metastases. The poor prognosis is due to growth of metastases irrespective of whether they are initially large enough to detect clinically. It is therefore necessary to develop new methods to target the growth of lung micrometastases. An NCI panel of FDA-approved oncology drugs was therefore screened using three highly metastatic human osteosarcoma cell lines. To more closely approximate in vivo micro-metastases, the screen used a 3D multicellular in vitro osteosarcoma spheroid (sarcosphere) model. Among 13 hits from the initial screen, we identified the histone deacetylase inhibitor (HDI) romidepsin as the most promising inhibitor in secondary screens based on sarcosphere viability. Romidepsin potency was evident with and without standard-of-care chemotherapeutics (MAP: Methotrexate, Adriamycin, Cisplatin) at drug concentrations that are clinically achievable and did not affect non-transformed cells. By those criteria, romidepsin also substantially outperformed the other three FDA-approved HDIs and eight HDIs in clinical trials. Importantly, sarcospheres derived from 30-50% of human and canine patient samples were also sensitive to romidepsin with ED50s 10- to 700-fold less than the Cmax in human patients. Based on these 3-D screening approaches, romidepsin is a promising drug to repurpose for osteosarcoma. Significance StatementOur unbiased sarcosphere-based drug screen identified romidepsin as a promising candidate to repurpose for canine and human patients with metastatic osteosarcoma. This screening strategy allowed us to identify romidepsin-sensitive and -resistant patients. Sarcosphere-based screening may therefore be useful to stratify patients most likely to respond clinically to romidepsin or other drugs.

cancer biology↗

bioRxiv2025

Chemical inhibition of RPA gap protection sensitizes BRCA1-deficient cancers to PARP inhibition

Poly (ADP-ribose) polymerase inhibitors (PARPi) are standard of care for many BRCA1 deficient cancers, though few cures are achieved. We sought to determine if targeting the protection of the single-strand DNA gaps induced by PARPi in BRCA-deficient cancers could increase efficacy. Replication protein A (RPA) participates in critical protein-protein and protein-DNA interactions to protect single-stranded DNA (ssDNA) and support DNA metabolism. We have reported the optimization of small molecule RPA inhibitors (RPAi) that target protein-ssDNA interactions to chemically exhaust RPA and elicit single-agent anticancer activity. RPAi sensitizes cells to PARPi in BRCA1-deficient non-cancerous cells, where ssDNA gap formation drives therapeutic efficacy. We show that RPAi treatment abolishes PARPi-induced replication gap protection, resulting in genomic instability via replication fork degradation and chromosomal integrity, and that, in vivo, the RPA and PARP targeted combination abrogates cancer growth in a BRCA1-mutant breast cancer model. We find that genetic predispositions to ssDNA gap accumulation correlate with RPAi sensitivity, and BRCA1-proficient cells remain sensitive to combination treatment but require more PARP inhibition to increase ssDNA gaps. RPAi-PARPi combination activity in patient-derived ovarian cancer models demonstrates the utility of targeting gap protection to increase PARPi sensitivity and circumvent resistance. Collectively, this work provides a unifying mechanism of chemical RPA exhaustion as a cancer therapeutic strategy. One Sentence SummaryInhibition of single-strand DNA gap protection potentiates PARP targeted treatment of BRCA1 deficient cancers.

cancer biology↗

bioRxiv2023

A novel triptolide analog downregulates NF-κB and induces mitochondrial apoptosis pathways in human pancreatic cancer

BackgroundPancreatic cancer is the seventh leading cause of cancer-related death worldwide, and despite advancements in disease management, the 5-year survival rates stands at only 9%. Triptolides have potent anti-tumor activity against different types of cancers, including pancreatic cancer, however poor solubility and toxicity limit their translation into clinical use. MethodsWe synthesized a novel pro-drug of triptolide, (E)-19-[(1-benzoyloxy-1-phenyl)-methylidene]-Triptolide (CK21), and formulated into an emulsion for in vitro and in vivo testing in rats and mice, and using human pancreatic cancer cell lines and patient-derived pancreatic tumor organoids. A time-course transcriptomic profiling of tumor organoids treated with CK21 in vitro was conducted to define its mechanism of action, as well as transcriptomic profiling at a single time point post-CK21 administration in vivo. FindingsIntravenous administration of emulsified CK21 resulted in the stable release of triptolide, and potent anti-proliferative effects on human pancreatic cancer cell lines and patient-derived pancreatic tumor organoids in vitro, and with minimal toxicity in vivo. Time course transcriptomic profiling of tumor organoids treated with CK21 in vitro revealed <10 differentially expressed genes (DEGs) at 3 h and [~]8,000 DEGs at 12 h. Overall inhibition of general RNA transcription was observed, and Ingenuity pathway analysis together with functional cellular assays confirmed inhibition of the NF-{kappa}B pathway, increased oxidative phosphorylation and mitochondrial dysfunction, leading ultimately to increased reactive oxygen species (ROS) production, reduced B-cell-lymphoma protein 2 (BCL2) expression, and mitochondrial-mediated tumor cell apoptosis. InterpretationCK21 is a novel pro-drug of triptolide that exerts potent anti-proliferative effects on human pancreatic tumors by inhibiting the NF-{kappa}B pathway, leading ultimately to mitochondrial-mediated tumor cell apoptosis. FundingThe study of the anti-tumor efficacy of CK21 supported in part by a research grant from Cinkate Pharmaceutical Corp; the funders had no role in the study design, interpretation or decision to publish. Patient-derived pancreatic tumor organoids were a generous gift from the Organoid and Primary Culture Research Core at University of Chicago.

pharmacology and toxicology↗

bioRxiv2022

Osteosarcoma-enriched transcripts paradoxically generate osteosarcoma-suppressing extracellular proteins

Osteosarcoma (OS) is the common primary bone cancer that affects mostly children and young adults. To augment the standard-of-care chemotherapy, we examined the possibility of protein-based therapy using mesenchymal stem cells (MSCs)-derived proteomes and osteosarcoma-elevated proteins. While a conditioned medium (CM), collected from MSCs, did not present tumor-suppressing ability, the activation of PKA converted MSCs into induced tumor-suppressing cells (iTSCs). In a mouse model, the direct and hydrogel-assisted administration of CM inhibited tumor-induced bone destruction, and its effect was additive with Cisplatin. CM was enriched with proteins such as Calreticulin, which acted as an extracellular tumor suppressor by interacting with CD47. Notably, the level of Calr transcripts was elevated in OS tissues, together with other tumor-suppressing proteins, including histone H4, and PCOLCE. PCOLCE acted as an extracellular tumor-suppressing protein by interacting with amyloid precursor protein (APP), a prognostic OS marker with poor survival. The results supported the possibility of employing a paradoxical strategy of utilizing OS transcriptomes for the treatment of OS.

cancer biology↗

bioRxiv2020

Chemical exhaustion of RPA in cancer treatment

Replication protein A (RPA) plays essential roles in DNA replication, repair, recombination and the DNA-damage response (DDR). We have developed second generation RPA inhibitors (RPAis) that block the RPA-DNA interaction. These DNA-binding inhibitors (DBis) can elicit a state of cellular RPA exhaustion resulting in single agent in vitro anticancer activity across a broad spectrum of cancers and in vivo activity in two non-small cell lung cancer models. The cellular response to RPAi treatment suggests a threshold exists before RPA inhibition induces cell death. Chemical RPA exhaustion potentiates the anticancer activity of other DDR inhibitors as well as traditional DNA damaging cancer therapeutics. Consistent with the chemical RPA exhaustion model, we demonstrate that the effects of RPAi on replication fork dynamics and DNA damage signaling are similar to other known DDR inhibitors. In accordance with the RPA threshold model, retrospective analysis of lung cancer patient data demonstrates high RPA expression as a negative prognostic biomarker for overall survival in smoking-related lung cancers. Similarly, relative expression of RPA is a predictive marker for response to chemotherapy. These observations are consistent with the increase in RPA expression serving as an adaptive mechanism that allows tolerance of the genotoxic stress resulting from carcinogen exposure. These data demonstrate a unique mechanism of action of RPAis eliciting a state of RPA exhaustion that impacts the DDR and may provide an effective therapeutic option for difficult to treat lung cancers. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=130 SRC="FIGDIR/small/404640v1_ufig1.gif" ALT="Figure 1"> View larger version (18K): org.highwire.dtl.DTLVardef@d662e4org.highwire.dtl.DTLVardef@f68b11org.highwire.dtl.DTLVardef@241c0corg.highwire.dtl.DTLVardef@ad7398_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2020

Development of Targetable Multi-Drug Nanoparticles for Glioblastoma Treatment and In Vitro Evaluation in Glioblastoma Stem Cells

Glioblastoma (GBM) is a malignant brain tumor with a poor long-term prognosis. The current median survival is approximately fifteen to twenty months with the standard of care therapy which includes surgery, radiation, and chemotherapy. An important factor contributing to recurrence of GBM is high resistance of GBM cancer stem cells (CSCs) to several anticancer drugs, for which a systemically delivered single drug approach will be unlikely to produce a viable cure. Therefore, multidrug therapies have the potential to improve the survival time. Currently, only temozolomide (TMZ), which is a DNA alkylator, affects overall survival in GBM patients. CSCs regenerate rapidly and over-express a methyl transferase which overrides the DNA-alkylating mechanism of TMZ, leading to drug resistance. Idasanutlin (RG7388, R05503781) is a potent, selective MDM2 antagonist that additively kills GBM CSCs when combined with TMZ. Nanotechnology is an emerging field that shows great promise in drug delivery and diagnostics. The ability to combine both therapy and imaging allows real time assessment of drug delivery in vivo for the field of theranostics. To develop a multi-drug therapy using multi-functional nanoparticles (NPs) that preferentially target the GBM CSC subpopulation and provide in vivo preclinical imaging capability. Polymer-micellar NPs composed of poly(styrene-b-ethylene oxide) (PS-b-PEO) and poly(lactic-co-glycolic) acid (PLGA) were developed investigating both single and double emulsion fabrication techniques as well as combinations of TMZ and RG7388. The NPs were covalently bound to a 15-base-pair CD133 aptamer in order to target the CD133 antigen expressed on the surface of GBM CSC subpopulation. For theranostic functionality, the NPs were also labelled with a radiotracer, Zirconium-89 (89Zr). The NPs maintained a small size of less than 100 nm, a low negative charge and exhibited the ability to effectively target and kill the CSC subpopulation. In addition, the conjugation of the CD133 aptamer was able to promote killing in CSCs leading to the justification of a targeted nanosystem to potentially improve localized therapy in future in vivo models. This work has provided a potentially therapeutic option for GBM specific for CSC targeting and theranostic imaging.

cell biology↗

bioRxiv2020

Tumor-responsive, multifunctional CAR-NK cells cooperate with impaired autophagy to infiltrate and target glioblastoma

Tumor antigen heterogeneity, a severely immunosuppressive tumor microenvironment (TME) and lymphopenia resulting in inadequate immune intratumoral trafficking have rendered glioblastoma (GBM) highly resistant to therapy. As a result, GBM immunotherapies have failed to demonstrate sustained clinical improvements in patient overall survival (OS). To overcome these obstacles, here we describe a novel, sophisticated combinatorial platform for GBM: the first multifunctional immunotherapy based on genetically-engineered, human NK cells bearing multiple anti-tumor functions, including local tumor responsiveness, that addresses key drivers of GBM resistance to therapy: antigen escape, poor immune cell homing, and immunometabolic reprogramming of immune responses. We engineered dual-specific CAR-NK cells to bear a third functional moiety that is activated in the GBM TME and addresses immunometabolic suppression of NK cell function: a tumor-specific, locally-released antibody fragment which can inhibit the activity of CD73 independently of CAR signaling and decrease the local concentration of adenosine. The multifunctional human NK cells targeted patient-derived GBM xenografts, demonstrated local tumor site specific activity in the tissue and potently suppressed adenosine production. We also unveil a complex reorganization of the immunological profile of GBM induced by inhibiting autophagy. Pharmacologic impairment of the autophagic process not only sensitized GBM to antigenic targeting by NK cells, but promoted a chemotactic profile favorable to NK infiltration. Taken together, our study demonstrates a promising new NK cell-based combinatorial strategy that can target multiple clinically-recognized mechanisms of GBM progression simultaneously.

immunology↗