Biology subjects

Adams-Tzivelekidis, S.

Publications and source records attributed to Adams-Tzivelekidis, S..

6 recordsLinked to original sources

bioRxiv2025

APC loss promotes intestinal transformation through induction of bistable stem cell states

Colorectal cancer (CRC) is a leading cause of cancer deaths, predominantly initiated by genetic inactivation of the APC tumor suppressor. Current dogma holds that APC inactivation promotes tumorigenesis via hyperactivation of the WNT pathway transcriptional effector, {beta}-CATENIN. Although {beta}-CATENIN activation is required for tumor initiation, activating mutations in {beta}-CATENIN are infrequent. Here, we ask what underlies the selective pressure for APC inactivation by comparing the oncogenic effects of APC loss to {beta}-CATENIN hyperactivation. We find that APC loss activates a {beta}-CATENIN-independent fetal intestinal transcriptional program driven by dysregulation of GSK-3 activity upon the LIM-domain protein AJUBA, a positive regulator of YAP. This results in AJUBA stabilization and downstream transcriptional activation of the YAP-driven fetal intestinal gene expression program. We find that {beta}-CATENIN- and YAP-driven transcriptional states are mutually exclusive, existing in an interchangeable bistable balance among APC-null cells. This results in more robust tumor initiation and metastatic progression downstream of APC loss relative to {beta}-CATENIN activation. Taken together, our findings explain the preferential selection for APC inactivation in CRC development and illuminate how {beta}-CATENIN- and YAP-driven gene expression programs coexist to promote tumorigenesis.

cancer biology↗

bioRxiv2023

Vascular Endothelial-derived SPARCL1 Exacerbates Viral Pneumonia Through Pro-Inflammatory Macrophage Activation

Inflammation upon infectious lung injury is a double-edged sword: while tissue-infiltrating immune cells and cytokines are necessary to control infection, these same factors often aggravate injury. Full appreciation of both the sources and targets of inflammatory mediators is required to facilitate strategies to maintain antimicrobial effects while minimizing off-target epithelial and endothelial damage. Recognizing that the vasculature is centrally involved in tissue responses to injury and infection, we observed that pulmonary capillary endothelial cells (ECs) exhibit dramatic transcriptomic changes upon influenza injury punctuated by profound upregulation of Sparcl1. Endothelial deletion and overexpression of SPARCL1 implicated this secreted matricellular protein in driving key pathophysiologic symptoms of pneumonia, which we demonstrate result from its effects on macrophage polarization. SPARCL1 induces a shift to a pro-inflammatory "M1-like" phenotype (CD86+CD206-), thereby increasing associated cytokine levels. Mechanistically, SPARCL1 acts directly on macrophages in vitro to induce the pro-inflammatory phenotype via activation of TLR4, and TLR4 inhibition in vivo ameliorates inflammatory exacerbations caused by endothelial Sparcl1 overexpression. Finally, we confirmed significant elevation of SPARCL1 in COVID-19 lung ECs in comparison with those from healthy donors. Survival analysis demonstrated that patients with fatal COVID-19 had higher levels of circulating SPARCL1 protein compared to those who recovered, indicating the potential of SPARCL1 as a biomarker for prognosis of pneumonia and suggesting that personalized medicine approaches might be harnessed to block SPARCL1 and improve outcomes in high-expressing patients.

immunology↗

bioRxiv2022

Mapping and modeling human colorectal carcinoma interactions with the tumor microenvironment

The initiation and progression of cancer are inextricably linked to the tumor microenvironment (TME). Understanding the function of specific cancer-TME interactions poses a major challenge due in part to the complexity of the in vivo microenvironment. Here we predict cancer-TME interactions from single cell transcriptomic maps of both human colorectal cancers (CRCs) and mouse CRC models, ask how these interactions are altered in established, long-term human tumor organoid (tumoroid) cultures, and functionally recapitulate human myeloid-carcinoma interactions in vitro. Tumoroid cultures suppress gene expression programs involved in promoting inflammation and immune cell migration through receptor-ligand interactions, providing a reductive platform for re-establishing carcinoma-immune cell interactions in vitro. Introduction of human monocyte-derived macrophages into tumoroid cultures instructs macrophages to acquire pro-tumorigenic gene expression programs similar to those observed in vivo. This includes hallmark induction of SPP1, encoding Osteopontin, an extracellular CD44 ligand with established oncogenic effects. Taken together, these findings offer a framework for understanding CRC-TME interactions and provide a reductionist tool for modeling specific aspects of these interactions.

cancer biology↗

bioRxiv2022

Autophagic state prospectively identifies facultative stem cells in the intestinal epithelium

The intestinal epithelium exhibits a rapid and efficient regenerative response to injury. Emerging evidence supports a model where plasticity of differentiated cells, particularly those in the secretory lineages, contributes to epithelial regeneration upon ablation of injury-sensitive stem cells. However, such facultative stem cell activity is rare within secretory populations. Here we ask whether specific functional properties predict facultative stem cell activity. We utilize in vivo labeling combined with ex vivo organoid formation assays to evaluate how cell age and autophagic state contribute to facultative stem cell activity within secretory lineages. Strikingly, we find that cell age (time elapsed since cell cycle exit) does not correlate with secretory cell plasticity. Instead, high autophagic activity predicts plasticity and resistance to DNA damaging injury independently of cell lineage. Our findings indicate that autophagic status prior to injury serves as a lineageagnostic marker for the prospective identification of facultative stem cells.

cell biology↗

bioRxiv2022

ΔNp63 drives dysplastic alveolar remodeling and restricts epithelial plasticity upon severe lung injury

Unlike many mammalian vital organs, the lung exhibits a robust, multifaceted regenerative response to severe injuries such as influenza infection, which primarily targets epithelial cells in the airways and alveoli. Quiescent lung-resident epithelial progenitors proliferate, migrate, and differentiate following lung injury, participating in two distinct reparative pathways: functionally beneficial regeneration and dysplastic tissue remodeling. Intrapulmonary airway-resident basal-like p63+ progenitors are one such progenitor cell type that migrates from the airways to form ectopic bronchiolar tissue in the alveoli, generating honeycomb-like cysts that fail to resolve after injury. Though this phenomenon is now well described, the cell-autonomous signals that drive dysplastic alveolar remodeling remain uncertain, a question made especially salient by observations that p63+ progenitors also expand dramatically upon diffuse alveolar damage in humans resulting from a variety of insults including SARS-CoV-2-induced ARDS. Here we show that the master basal cell transcription factor {Delta}Np63 is required for the immense migratory capacity of intrapulmonary p63+ progenitors and consequently for the dysplastic repair pathway manifest by these cells. We further demonstrate that {Delta}Np63 restricts the fate plasticity of intrapulmonary p63+ progenitors by regulating their epigenetic landscape, and that loss of {Delta}Np63 alters the deposition of active and repressive histone modifications at key differentiation gene loci, allowing {Delta}Np63KO progenitors to proceed towards airway or alveolar differentiation depending on their surrounding environment. These insights into the regulatory mechanisms of dysplastic repair and intrapulmonary p63+ progenitor fate choice highlight potential therapeutic targets to promote more effective alveolar regeneration following severe lung injuries.

molecular biology↗

bioRxiv2021

Patient induced pluripotent stem cell-derived hepatostellate organoids establish a basis for liver pathologies in telomeropathies

Patients with dyskeratosis congenita (DC) and related telomeropathies resulting from premature telomere dysfunction suffer from multi-organ failure. In the liver, DC patients present with nodular hyperplasia, steatosis, inflammation, and cirrhosis. We model DC liver pathologies using isogenic human induced pluripotent stem (iPS) cells harboring a causal DC mutation in DKC1, or a clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9-corrected control allele. Differentiation of these iPS cells into hepatocytes or hepatic stellate cells followed by generation of genotype-admixed hepatostellate organoids revealed a dominant phenotype in the parenchyma, with DC hepatocytes eliciting a pathogenic hyperplastic response in stellate cells independent of stellate cell genotype. Pathogenic phenotypes could be rescued via suppression of AKT activity, a central regulator of MYC-driven hyperplasia downstream of DKC1 mutation. Thus, isogenic iPS-derived admixed hepatostellate organoids offer insight into the liver pathologies in telomeropathies and provide a framework for evaluating emerging therapies.

cell biology↗