Browsing by Subject "Polyethylene glycols"

Now showing 1 - 4 of 4
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    BCL-XL Protects ASS1-Deficient Cancers from Arginine Starvation-Induced Apoptosis
    (American Association for Cancer Research, 2025) Panda, Prashanta Kumar; Paschoalini Mafra, Ana Carolina; Bastos, Alliny C. S.; Cao, Li; Bonet, Maria Serra; Brashears, Caitlyn B.; Chen, Ethan Yang; Benedict-Hamilton, Heather M.; Ehrhardt, William; Bomalaski, John; Dehner, Carina; Rogers, Leonard C.; Oyama, Toshinao; Van Tine, Brian A.; Pathology and Laboratory Medicine, School of Medicine
    Purpose: Argininosuccinate synthetase 1 (ASS1) silencing in carcinomas and sarcomas leads to a dependence on extracellular arginine for survival. Arginine deprivation therapies, such as PEGylated arginine deiminase (ADI-PEG20), have shown limited effectiveness, which may be due to underlying mechanisms that inhibit apoptosis. Experimental design: The effects of ADI-PEG20 on cell-cycle regulation, apoptosis, and BCL-XL-mediated survival pathways in ASS1-deficient cancer cells were determined. The mechanism of cell death protection was determined by assessing caspase and PARP cleavage, CDK2 activity, MCL1 expression, and the interactions among BCL-XL, BAX, and BAK. In vitro synergy was determined, and in vivo efficacy was modeled. Results: Treatment with ADI-PEG20 led to reduced CDK2 activity and inhibited cell-cycle progression but did not induce significant cell death. BCL-XL was found to bind to BAX and BAK, preventing the initiation of apoptosis despite arginine starvation. Inhibition of BCL-XL allowed proapoptotic BAX and BAK to initiate the intrinsic apoptosis pathway, leading to increased cell death. This was found to be synergistic in vitro and efficacious in combination in vivo. Conclusions: The study identifies BCL-XL as a key factor limiting the efficacy of arginine starvation therapies. Combining BCL-XL inhibitors with arginine deprivation strategies may overcome this resistance and enhance therapeutic outcomes. These findings provide a strong preclinical rationale for testing this combination approach in phase 1 clinical trials for ASS1-deficient cancers.
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    Heparinized Gelatin-Based Hydrogels for Differentiation of Induced Pluripotent Stem Cells
    (American Chemical Society, 2022) Arkenberg, Matthew R.; Koehler, Karl; Lin, Chien-Chi; Biomedical Engineering, School of Engineering and Technology
    Chemically defined hydrogels are increasingly utilized to define the effects of extracellular matrix (ECM) components on cellular fate determination of human embryonic and induced pluripotent stem cell (hESC and hiPSCs). In particular, hydrogels cross-linked by orthogonal click chemistry, including thiol-norbornene photopolymerization and inverse electron demand Diels-Alder (iEDDA) reactions, are explored for 3D culture of hESC/hiPSCs owing to the specificity, efficiency, cytocompatibility, and modularity of the cross-linking reactions. In this work, we exploited the modularity of thiol-norbornene photopolymerization to create a biomimetic hydrogel platform for 3D culture and differentiation of hiPSCs. A cell-adhesive, protease-labile, and cross-linkable gelatin derivative, gelatin-norbornene (GelNB), was used as the backbone polymer for constructing hiPSC-laden biomimetic hydrogels. GelNB was further heparinized via the iEDDA click reaction using tetrazine-modified heparin (HepTz), creating GelNB-Hep. GelNB or GelNB-Hep was modularly cross-linked with either inert macromer poly(ethylene glycol)-tetra-thiol (PEG4SH) or another bioactive macromer-thiolated hyaluronic acid (THA). The formulations of these hydrogels were modularly tuned to afford biomimetic matrices with similar elastic moduli but varying bioactive components, enabling the understanding of each bioactive component on supporting hiPSC growth and ectodermal, mesodermal, and endodermal fate commitment under identical soluble differentiation cues.
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    Probing osteocyte function in gelatin hydrogels with tunable viscoelasticity
    (American Chemical Society, 2021) Nguyen, Han D.; Sun, Xun; Yokota, Hiroki; Lin, Chien-Chi; Biomedical Engineering, School of Engineering and Technology
    Bone is an attractive site for metastatic cancer cells and has been considered as "soil" for promoting tumor growth. However, accumulating evidence suggests that some bone cells (e.g., osteocytes) can actually suppress cancer cell migration and invasion via direct cell-cell contact and/or through cytokine secretion. Toward designing a biomimetic niche for supporting 3D osteocyte culture, we present here a gelatin-based hydrogel system with independently tunable matrix stiffness and viscoelasticity. In particular, we synthesized a bifunctional macromer, gelatin-norbornene-boronic acid (i.e., GelNB-BA), for covalent cross-linking with multifunctional thiol linkers [e.g., four-arm poly(ethylene glycol)-thiol or PEG4SH] to form thiol-NB hydrogels. The immobilized BA moieties in the hydrogel readily formed reversible boronate ester bonds with 1,3-diols on physically entrapped poly(vinyl alcohol) (PVA). Adjusting the compositions of GelNB-BA, PEG4SH, and PVA afforded hydrogels with independently tunable elasticity and viscoelasticity. With this new dynamic hydrogel platform, we investigated matrix mechanics-induced growth and cytokine secretion of encapsulated MLO-A5 pre-osteocytes. We discovered that more compliant or viscoelastic gels promoted A5 cell growth. On the other hand, cells encapsulated in stiffer gels secreted higher amounts of pro-inflammatory cytokines and chemokines. Finally, conditioned media (CM) collected from the encapsulated MLO-A5 cells (i.e., A5-CM) strongly inhibited breast cancer cell proliferation, invasion, and expression of tumor-activating genes. This new biomimetic hydrogel platform not only serves as a versatile matrix for investigating mechano-sensing in osteocytes but also provides a means to produce powerful anti-tumor CM.
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    Recruitment and retention strategies in a clinical trial for children with chronic hepatitis C infection
    (Elsevier, 2013) Aparna, Roy; Whitney, Lieb; Beth, Garrett; Marcia, Hodik; Ann, Klipsch; Melissa, Young; Bruce, Barton; Kathleen, Schwarz; Pediatrics, School of Medicine
    Successful strategies for recruitment and retention (R & R) in pediatric trials are needed. The purpose of our study was to analyze the effectiveness of R&R in a trial for children with hepatitis C. Recruitment strategies were (1) Initial (months 0-12) and (2) extra effort (months 13-18). Initial strategies enrolled 70/114 (61%) of patients. Extra effort strategies included: (1) radio broadcasts, (2) contact with adult hepatologists, (3) dissemination of study material and (4) modification of the exclusion criteria. The overall retention rate was 84% at 2 years. Lessons learned will be valuable in designing future pediatric trials.