Biology subjects

Holcomb, K.

Publications and source records attributed to Holcomb, K..

4 recordsLinked to original sources

bioRxiv2026

Laminin-511 protects pancreatic β-cells from cytokine-induced death through integrin-mediated pro-survival signaling and modulation of protein kinase C δ

During the progression of type 1 diabetes (T1D), the extracellular matrix (ECM) surrounding pancreatic islets is degraded concurrent with infiltration of autoreactive immune cells and {beta}-cell death. Among the lost ECM proteins, laminin-511 is known to be essential for islet survival under healthy and T1D associated conditions, including high levels of pro-inflammatory cytokines. However, the key {beta}-cell signaling pathways regulated by laminin and the contributions to T1D pathogenesis when these cues are lost are poorly understood. This study utilizes a biomimetic reverse thermal gel (RTG) with laminin-511 to determine if laminin protects {beta}-cells against cytokine-induced death and elucidate the signaling pathways involved. MIN6 cells, C57Bl/6 mouse islets and human islets were encapsulated in RTG scaffolds with laminin-511 and treated with a cytokine cocktail for 24 hours. Islet viability and the activities of several pro- and anti-apoptotic proteins were studied. Laminin-511 was shown to protect islets against cytokine-induced death by interacting with {beta}1 integrins and activating pro-survival Akt signaling. Pro-survival signaling was mediated by reduced activity of protein kinase C{delta} (PKC{delta}), a key mediator of cytokine-induced {beta}-cell death, at the cell membrane in the presence of laminin via reduced levels of diacylglycerol (DAG), a canonical activator of PKC{delta}. Taken together, these results demonstrate that laminin-511 is an essential factor in protecting {beta}-cells against cytokine-induced death by downregulation of membrane DAG, inhibiting activation of pro-apoptotic PKC{delta}. Our results suggest that loss of ECM in T1D may make {beta}-cells more susceptible to cytokine-induced death by increasing activation of PKC{delta}. HighlightsO_LILaminin-511 improves islet survival under cytokine treatment C_LIO_LIPro-survival Akt is upregulated by laminin-511 C_LIO_LIPro-apoptotic PKC{delta} activity is downregulated at the cell membrane by laminin-511 C_LIO_LILaminin-511 decreases membrane DAG levels leading to reduced PKC{delta} activation C_LIO_LILaminin-511 is an essential ECM component for islet survival during type 1 diabetes C_LI

cell biology↗

bioRxiv2025

Pan-Cancer PDOs Preserve Tumor Heterogeneity and Uncover Therapeutic Vulnerabilities

We developed a tumor-matched, pan-cancer patient-derived organoid (PDO) platform comprising 220 PDOs from 190 patients across 15 cancer types to advance functional precision oncology. Our comprehensively characterized PDOs showed 93% histopathology concordance, 80% median genomic concordance for driver mutations, and a 0.85 median gene expression correlation with parent tumors. Gene expression in PDOs remained stable across [≥] 10 passages, supporting reproducibility for long-term drug screening. Even PDOs with low genomic concordance retained oncogenic drivers, supporting their use as disease models. Clonality analysis revealed that 85% of PDOs preserved dominant tumor clones. Higher genomic concordance was associated with greater clonal similarity, while lower genomic concordance was associated with clonal divergence. Functional assays showed that 58% of PDOs from a subset of patients ineligible for FDA-approved PARP inhibitors responded to Talazoparib, with sensitivity linked to alterations in DNA damage repair. Combination screens revealed drugs that effectively overcame resistance, especially in TP53-mutant PDOs. In summary, our platform supports investigation of targeted therapies, identification of molecular features linked to drug sensitivity, and translational discovery, offering insights into personalized cancer treatment beyond current biomarker guidelines.

cancer biology↗

bioRxiv2024

Peptide Coated Polycaprolactone-Benzalkonium Chloride Nanocapsules for Targeted Drug Delivery to the Pancreatic β-Cell

Targeting of current therapies to treat or prevent loss of pancreatic islet {beta}-cells in Type 1 Diabetes (T1D) may provide improved efficacy and reduce off target effects. Current efforts to target the {beta}-cell are limited by a lack of {beta}-cell specific targets and the inability to test multiple targeting moieties with the same delivery vehicle. Here we fabricate a novel tailorable polycaprolactone nanocapsule (NC) where multiple different targeting peptides can be interchangeably attached for {beta}-cell specific delivery. Incorporation of a cationic surfactant in the NC shell allows for the attachment of Exendin-4 and an antibody for ectonucleoside triphosphate diphosphohydrolase 3 (ENTPD3) for {beta}-cell specific targeting. The average NC size ranges from 250-300nm with a polydispersity index under 0.2. The NCs are non-toxic, stable in media culture, and can be lyophilized and reconstituted. NCs coated with targeting peptide were taken up by human cadaveric islet {beta}-cells and human stem cell-derived {beta}-like cells (sBC) in vitro with a high level of specificity. Furthermore, NCs successfully delivered both hydrophobic and hydrophilic cargo to human {beta}-cells. Finally, Exendin-4 coated NCs were stable and targeted the mouse pancreatic islet {beta}-cell in vivo. Our unique NC design allows for the interchangeable coating of targeting peptides for future screening of targets with improved cell specificity. The ability to target and deliver thera-peutics to human pancreatic {beta}-cells opens avenues for improved therapies and treatments to help the delay onset, prevent, or reverse T1D.

bioengineering↗

bioRxiv2020

Respiratory tract explant infection dynamics of influenza A virus in California sea lions, northern elephant seals, and rhesus macaques and severe acute respiratory syndrome virus-2 in rhesus macaques

To understand susceptibility of wild California sea lions and Northern elephant seals to influenza A virus (IAV), we developed an ex vivo respiratory explant model and used it to compare infection kinetics for multiple IAV subtypes. We first established the approach using explants from colonized rhesus macaques, a model for human IAV. Trachea, bronchi, and lungs from 11 California sea lions, 2 Northern elephant seals and 10 rhesus macaques were inoculated within 24 hours post-mortem with 6 strains representing 4 IAV subtypes. Explants from the 3 species showed similar IAV infection kinetics with peak viral titers 48-72 hours post-inoculation that increased by 2-4 log10 plaque forming units (PFU)/explant relative to the inoculum. Immunohistochemistry localized IAV infection to apical epithelial cells. These results demonstrate that respiratory tissue explants from wild marine mammals support IAV infection. In the absence of the ability to perform experimental infections of marine mammals, this ex vivo culture of respiratory tissues mirrors the in vivo environment and serves as a tool to study IAV susceptibility, host-range, and tissue tropism. ImportanceAlthough influenza A virus can infect marine mammals, a dearth of marine mammal cell lines and ethical and logistical challenges prohibiting experimental infections of living marine mammals means that little is known about IAV infection kinetics in these species. We circumvented these limitations by adapting a respiratory tract explant model first to establish the approach with rhesus macaques and then for use with explants from wild marine mammals euthanized for non-respiratory medical conditions. We observed that multiple strains representing 4 IAV subtypes infected trachea, bronchi, and lungs of macaques and marine mammals with variable peak titers and kinetics. This ex vivo model can define infection dynamics for IAV in marine mammals. Further, use of explants from animals euthanized for other reasons reduces use of animals in research.

microbiology↗