modeling-oral-esophageal-squamous-cell-carcinoma-in-3d-organoids

Modeling Oral-Esophageal Squamous Cell Carcinoma in 3D Organoids

Esophageal squamous cell carcinoma (ESCC) is prevalent worldwide, accounting for 90% of all esophageal cancer cases each year, and is the deadliest of all ...

Columbia University

Columbia College

The canonical Wnt/β-catenin signalling pathway governs diverse developmental, homeostatic and pathological processes. Palmitoylated Wnt ligands engage cell-surface frizzled (FZD) receptors and LRP5 and LRP6 co-receptors, enabling β-catenin nuclear translocation and TCF/LEF-dependent gene transactivation. Mutations in Wnt downstream signalling components have revealed diverse functions thought to be carried out by Wnt ligands themselves. However, redundancy between the 19 mammalian Wnt proteins and 10 FZD receptors and Wnt hydrophobicity have made it difficult to attribute these functions directly to Wnt ligands. For example, individual mutations in Wnt ligands have not revealed homeostatic phenotypes in the intestinal epithelium-an archetypal canonical, Wnt pathway-dependent, rapidly self-renewing tissue, the regeneration of which is fueled by proliferative crypt Lgr5(+) intestinal stem cells (ISCs). R-spondin ligands (RSPO1-RSPO4) engage distinct LGR4-LGR6, RNF43 and ZNRF3 receptor classes, markedly potentiate canonical Wnt/β-catenin signalling, and induce intestinal organoid growth in vitro and Lgr5(+) ISCs in vivo. However, the interchangeability, functional cooperation and relative contributions of Wnt versus RSPO ligands to in vivo canonical Wnt signalling and ISC biology remain unknown. Here we identify the functional roles of Wnt and RSPO ligands in the intestinal crypt stem-cell niche. We show that the default fate of Lgr5(+) ISCs is to differentiate, unless both RSPO and Wnt ligands are present. However, gain-of-function studies using RSPO ligands and a new non-lipidated Wnt analogue reveal that these ligands have qualitatively distinct, non-interchangeable roles in ISCs. Wnt proteins are unable to induce Lgr5(+) ISC self-renewal, but instead confer a basal competency by maintaining RSPO receptor expression that enables RSPO ligands to actively drive and specify the extent of stem-cell expansion. This functionally non-equivalent yet cooperative interaction between Wnt and RSPO ligands establishes a molecular precedent for regulation of mammalian stem cells by distinct priming and self-renewal factors, with broad implications for precise control of tissue regeneration.

Non-equivalence of Wnt and R-spondin ligands during Lgr5(+) intestinal stem-cell self-renewal.

-expressing tuft cells constitute a unique intestinal epithelial lineage that is distinct from enterocytes, Paneth cells, goblet cells, and enteroendocrine cells. Tuft cells express taste-related receptors and distinct transcription factors and interact closely with the enteric nervous system, suggesting a chemosensory cell lineage. In addition, recent work has shown that tuft cells interact closely with cells of the immune system, with a critical role in the cellular regulatory network governing responses to luminal parasites. Importantly, ablation of tuft cells severely impairs epithelial proliferation and tissue regeneration after injury, implicating tuft cells in the modulation of epithelial stem/progenitor function. Finally, tuft cells expand during chronic inflammation and in preneoplastic tissues, suggesting a possible early role in inflammation-associated tumorigenesis. Hence, we outline and discuss emerging evidence that strongly supports tuft cells as key regulatory cells in the complex network of the intestinal microenvironment.

Dclk1-expressing tuft cells: critical modulators of the intestinal niche?

Several cell populations have been reported to possess intestinal stem cell (ISC) activity during homeostasis and injury-induced regeneration. Here, we explored inter-relationships between putative mouse ISC populations by comparative RNA-sequencing (RNA-seq). The transcriptomes of multiple cycling ISC populations closely resembled Lgr5(+) ISCs, the most well-defined ISC pool, but Bmi1-GFP(+) cells were distinct and enriched for enteroendocrine (EE) markers, including Prox1. Prox1-GFP(+) cells exhibited sustained clonogenic growth in vitro, and lineage-tracing of Prox1(+) cells revealed long-lived clones during homeostasis and after radiation-induced injury in vivo. Single-cell mRNA-seq revealed two subsets of Prox1-GFP(+) cells, one of which resembled mature EE cells while the other displayed low-level EE gene expression but co-expressed tuft cell markers, Lgr5 and Ascl2, reminiscent of label-retaining secretory progenitors. Our data suggest that the EE lineage, including mature EE cells, comprises a reservoir of homeostatic and injury-inducible ISCs, extending our understanding of cellular plasticity and stemness.

Intestinal Enteroendocrine Lineage Cells Possess Homeostatic and Injury-Inducible Stem Cell Activity.

Distinct stem/progenitor cells generate intestinal epithelium during fetal and postnatal life. In a recent issue of Nature, Nusse and Savage et al. use helminth infection to show that Lgr5 intestinal stem cells are replaced by fetal-like progenitors following injury, suggesting that some fetal developmental pathways are repurposed during injury-induced tissue regeneration.

Intestinal Crypts Assume the Fetal Position in Response to Injury.

The intestinal epithelium is maintained by long-lived intestinal stem cells (ISCs) that reside near the crypt base. Above the ISC zone, there are short-lived progenitors that normally give rise to lineage-specific differentiated cell types but can dedifferentiate into ISCs in certain circumstances. However, the role of epithelial dedifferentiation in cancer development has not been fully elucidated.

BHLHA15-Positive Secretory Precursor Cells Can Give Rise to Tumors in Intestine and Colon in Mice.

The enteric neurotransmitter acetylcholine governs important intestinal epithelial secretory and immune functions through its actions on epithelial muscarinic Gq-coupled receptors such as M3R. Its role in the regulation of intestinal stem cell function and differentiation, however, has not been clarified. Here, we find that nonselective muscarinic receptor antagonism in mice as well as epithelial-specific ablation of M3R induces a selective expansion of DCLK1-positive tuft cells, suggesting a model of feedback inhibition. Cholinergic blockade reduces Lgr5-positive intestinal stem cell tracing and cell number. In contrast, Prox1-positive endocrine cells appear as primary sensors of cholinergic blockade inducing the expansion of tuft cells, which adopt an enteroendocrine phenotype and contribute to increased mucosal levels of acetylcholine. This compensatory mechanism is lost with acute irradiation injury, resulting in a paucity of tuft cells and acetylcholine production. Thus, enteroendocrine tuft cells appear essential to maintain epithelial homeostasis following modifications of the cholinergic intestinal niche.

Prox1-positive cells monitor and sustain the murine intestinal epithelial cholinergic niche.

Intestinal crypts have a remarkable capacity to regenerate after injury from loss of crypt base columnar (CBC) stem cells. After injury, facultative stem cells (FSCs) are activated to replenish the epithelium and replace lost CBCs. Our aim was to assess the role of insulin-like growth factor-1 (IGF-1) to activate FSCs for crypt repair.

Insulin-like Growth Factor-1 and mTORC1 Signaling Promote the Intestinal Regenerative Response After Irradiation Injury.

Emerging single-cell technologies, like single-cell RNA sequencing (scRNA-seq), enable the study of heterogeneous biological systems at cellular resolution. By profiling the set of expressed transcripts in each cell, single-cell transcriptomics has allowed for the cataloging of the cellular constituents of multiple organs and tissues, both in health and disease. In addition, these technologies have provided mechanistic insights into cellular function, cell state transitions, developmental trajectories and lineage relationships, as well as helped to dissect complex, population-level responses to environmental perturbations. scRNA-seq is particularly useful for characterizing the intestinal epithelium because it is a dynamic, rapidly self-renewing tissue comprised of more than a dozen specialized cell types. Here we discuss the fundamentals of single-cell transcriptomics of the murine small intestinal epithelium. We review the principles of proper experimental design and provide methods for the dissociation of the small intestinal epithelium into single cells followed by fluorescence-activated cell sorting (FACS) and for scRNA-seq using the 10× Genomics Chromium platform.

Single-Cell Transcriptional Profiling of the Intestinal Epithelium.

Single-cell RNA-sequencing (scRNA-seq) provides a unique opportunity to study heterogeneous cell populations within tissues, including the intestinal epithelium, to gain detailed molecular insights into their biology. Many new putative markers of intestinal stem cells and their progeny have been described using single-cell transcriptomics, which has contributed to the identification of novel subpopulations of mature cell types and insight into their developmental trajectories. This approach has revealed tremendous cellular heterogeneity within the intestinal epithelium that is concordant with its diverse and multifaceted functions. We discuss the function of these subpopulations during tissue homeostasis, as well as putative subpopulations with inducible regenerative potential following tissue injury.

Single-Cell Studies of Intestinal Stem Cell Heterogeneity During Homeostasis and Regeneration.

COVID-19 Gastrointestinal Symptoms and Attenuation of the Immune Response to SARS-CoV-2.

Knowledge of the development and hierarchical organization of tissues is key to understanding how they are perturbed in injury and disease, as well as how they may be therapeutically manipulated to restore homeostasis. The rapidly regenerating intestinal epithelium harbors diverse cell types and their lineage relationships have been studied using numerous approaches, from classical label-retaining and genetic lineage tracing methods to novel transcriptome-based annotations. Here, we describe the developmental trajectories that dictate differentiation and lineage specification in the intestinal epithelium. We focus on the most recent single-cell RNA-sequencing (scRNA-seq)-based strategies for understanding intestinal epithelial cell lineage relationships, underscoring how they have refined our view of the development of this tissue and highlighting their advantages and limitations. We emphasize how these technologies have been applied to understand the dynamics of intestinal epithelial cells in homeostatic and injury-induced regeneration models.

Cellular origins and lineage relationships of the intestinal epithelium.

Hand injuries often result in significant functional impairments and are rarely completely restored. The spontaneous regeneration of injured appendages, which occurs in salamanders and newts, for example, has been reported in human fingertips after distal amputation, but this type of regeneration is rare in mammals and is incompletely understood. Here, we study fingertip regeneration by amputating murine digit tips, either distally to initiate regeneration, or proximally, causing fibrosis. Using an unbiased microarray analysis, we found that digit tip regeneration is significantly associated with hair follicle differentiation, Wnt, and sonic hedgehog (SHH) signaling pathways. Viral over-expression and genetic knockouts showed the functional significance of these pathways during regeneration. Using transgenic reporter mice, we demonstrated that, while both canonical Wnt and HH signaling were limited to epidermal tissues, downstream hedgehog signaling (through Gli) occurred in mesenchymal tissues. These findings reveal a mechanism for epidermal/mesenchyme interactions, governed by canonical hedgehog signaling, during digit regeneration. Further research into these pathways could lead to improved therapeutic outcomes after hand injuries in humans.

Epidermal-Derived Hedgehog Signaling Drives Mesenchymal Proliferation during Digit Tip Regeneration.

The microbiome is an emerging key co-factor in the development of esophageal cancer, the sixth leading cause of cancer death worldwide. However, there is a paucity of data delineating how the microbiome contributes to the pathobiology of the two histological subtypes of esophageal cancer: esophageal squamous cell carcinoma and esophageal adenocarcinoma. This critical knowledge gap is partially due to inadequate modeling of host-microbiome interactions in the etiology of esophageal cancers. Recent advances have enabled progress in this field. Three dimensional (3D) organoids faithfully recapitulate the structure and function of the normal, preneoplastic, and neoplastic epithelia of the esophagus ex vivo and serve as a platform translatable for applications in precision medicine. Elsewhere in the gastrointestinal (GI) tract, the co-culture of 3D organoids with the bacterial microbiome has fostered insight into the pathogenic role of the microbiome in other GI cancers. Herein, we will summarize our current understanding of the relationship between the microbiome and esophageal cancer, discuss 3D organoid models of esophageal homeostasis, review analogous models of host-microbiome interactions in other GI cancers, and advocate for the application of these models to esophageal cancers. Together, we present a promising, novel approach with the potential to ameliorate the burden of esophageal cancer-related morbidity and mortality via improved prevention and therapeutic interventions.

3D Organoids: An Untapped Platform for Studying Host-Microbiome Interactions in Esophageal Cancers.

Clinical outcomes in colorectal cancer (CRC) correlate with T cell infiltrates, but the specific contributions of heterogenous T cell types remain unclear. To investigate the diverse function of T cells in CRC, we profiled 37,931 T cells from tumors and adjacent normal colon of 16 patients with CRC with respect to transcriptome, TCR sequence, and cell surface markers. Our analysis identified phenotypically and functionally distinguishable effector T cell types. We employed single-cell gene signatures from these T cell subsets to query the TCGA database to assess their prognostic significance. We found 2 distinct cytotoxic T cell types. GZMK+KLRG1+ cytotoxic T cells were enriched in CRC patients with good outcomes. GNLY+CD103+ cytotoxic T cells with a dysfunctional phenotype were not associated with good outcomes, despite coexpression of CD39 and CD103, markers that denote tumor reactivity. We found 2 distinct Treg subtypes associated with opposite outcomes. While total Tregs were associated with good outcomes, CD38+ Tregs were associated with bad outcomes independently of stage and possessed a highly suppressive phenotype, suggesting that they inhibit antitumor immunity in CRC. These findings highlight the potential utility of these subpopulations in predicting outcomes and support the potential for novel therapies directed at CD38+ Tregs or CD8+CD103+ T cells.

Multiplexed single-cell analysis reveals prognostic and nonprognostic T cell types in human colorectal cancer.

Presentation of the Julius M. Friedenwald Medal to Timothy C. Wang, MD, AGAF.

The human respiratory epithelium is derived from a progenitor cell in the distal buds of the developing lung. These "bud tip progenitors" are regulated by reciprocal signaling with surrounding mesenchyme; however, mesenchymal heterogeneity and function in the developing human lung are poorly understood. We interrogated single-cell RNA sequencing data from multiple human lung specimens and identified a mesenchymal cell population present during development that is highly enriched for expression of the WNT agonist RSPO2, and we found that the adjacent bud tip progenitors are enriched for the RSPO2 receptor LGR5. Functional experiments using organoid models, explant cultures, and FACS-isolated RSPO2 mesenchyme show that RSPO2 is a critical niche cue that potentiates WNT signaling in bud tip progenitors to support their maintenance and multipotency.

Article	Year
Non-equivalence of Wnt and R-spondin ligands during Lgr5(+) intestinal stem-cell self-renewal. Nature\| PubMed ID: 28467820	2017
Dclk1-expressing tuft cells: critical modulators of the intestinal niche? American journal of physiology. Gastrointestinal and liver physiology\| PubMed ID: 28684459	2017
Intestinal Enteroendocrine Lineage Cells Possess Homeostatic and Injury-Inducible Stem Cell Activity. Cell stem cell\| PubMed ID: 28686870	2017
Intestinal Crypts Assume the Fetal Position in Response to Injury. Cell stem cell\| PubMed ID: 30075126	2018
BHLHA15-Positive Secretory Precursor Cells Can Give Rise to Tumors in Intestine and Colon in Mice. Gastroenterology\| PubMed ID: 30448068	2019
Prox1-positive cells monitor and sustain the murine intestinal epithelial cholinergic niche. Nature communications\| PubMed ID: 31913277	2020
Insulin-like Growth Factor-1 and mTORC1 Signaling Promote the Intestinal Regenerative Response After Irradiation Injury. Cellular and molecular gastroenterology and hepatology\| PubMed ID: 32502530	2020
Single-Cell Transcriptional Profiling of the Intestinal Epithelium. Methods in molecular biology (Clifton, N.J.)\| PubMed ID: 32705639	2020
Single-Cell Studies of Intestinal Stem Cell Heterogeneity During Homeostasis and Regeneration. Methods in molecular biology (Clifton, N.J.)\| PubMed ID: 32705640	2020
COVID-19 Gastrointestinal Symptoms and Attenuation of the Immune Response to SARS-CoV-2. Gastroenterology\| PubMed ID: 33753106	2021
Cellular origins and lineage relationships of the intestinal epithelium. American journal of physiology. Gastrointestinal and liver physiology\| PubMed ID: 34431400	2021
Epidermal-Derived Hedgehog Signaling Drives Mesenchymal Proliferation during Digit Tip Regeneration. Journal of clinical medicine\| PubMed ID: 34575372	2021
3D Organoids: An Untapped Platform for Studying Host-Microbiome Interactions in Esophageal Cancers. Microorganisms\| PubMed ID: 34835308	2021
Multiplexed single-cell analysis reveals prognostic and nonprognostic T cell types in human colorectal cancer. JCI insight\| PubMed ID: 35192548	2022
Presentation of the Julius M. Friedenwald Medal to Timothy C. Wang, MD, AGAF. Gastroenterology\| PubMed ID: 35443933	2022
R-SPONDIN2 mesenchymal cells form the bud tip progenitor niche during human lung development. Developmental cell\| PubMed ID: 35679862	2022

Kelley Yan

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