Early clonal extinction in glioblastoma progression revealed by genetic barcoding

Cell competition as an emerging mechanism and therapeutic target in cancer

Cell competition, as an internal quality control mechanism that constantly monitor cell fitness and eliminate unfit cells, maintains proper embryogenesis and tissue integrity during early development and adult homeostasis. Recent studies have revealed that cell competition functions as a tumor-suppressive mechanism to defend against cancer by removing neoplastic cell, which however, is hijacked by tumor cells and drive cell competition in favor of mutant cells, thereby promoting cancer initiation and progression. In this review, with a special focus on mammalian systems, we discuss the latest insights into the mechanisms regulating cell competition and its dual role in tumor development. We also provide current strategies to modulate the direction of cell competition for the prevention and treatment of cancers.

Neural cell competition sculpting brain from cradle to grave

Darwinian selection, operating within the cellular ecosystem of multicellular organisms, drives a pervasive surveillance mechanism of cell-cell competition that shapes tissue architecture and function. While cell competition eliminates suboptimal cells to ensure tissue integrity across various tissues, neuronal competition specifically sculpts neural networks to establish precise circuits for sensory, motor and cognitive functions. However, our understanding of cell competition across diverse neural cell types in both developmental and pathological contexts remains limited. Here, we review recent advances on the phenomenon, and mechanisms and potential functions of neural cell competition (NCC), ranging from neural progenitors, neurons, astrocytes and oligodendrocytes to microglia. Physiological NCC governs cellular survival, proliferation, arborization, organization, function and territorial colonization, whereas dysregulated NCC may cause neurodevelopmental disorders, accelerate aging, exacerbate neurodegenerative diseases and drive brain tumor progression. Future work that leverages cell competition mechanisms may help to improve cognition and curb diseases.

Combining the RCAS/tv-a retrovirus and CRISPR/Cas9 gene editing systems to generate primary mouse models of diffuse midline glioma

Diffuse midline gliomas (DMGs) are lethal brain tumors that arise in children and young adults, resulting in a median survival of less than two years. Genetically engineered mouse models (GEMMs) are critical to studying tumorigenesis and tumor-immune interactions, which may inform new treatment approaches. However, current midline glioma GEMM approaches are limited in their ability to multiplex perturbations and/or target specific cell lineages in the brain for genetic manipulation. Here, we combined the RCAS/tv-a avian retrovirus system and CRISPR/Cas9 genetic engineering to drive midline glioma formation in mice. CRISPR/Cas9-based disruption of Trp53, a tumor suppressor that is frequently disrupted in midline gliomas, along with the oncogene PDGF-B resulted in high grade tumor formation with moderate latency (median time to tumor formation of 12 weeks). We confirmed CRISPR-mediated Trp53 disruption using next-generation sequencing (NGS) and immunohistochemistry (IHC). Next, we disrupted multiple midline glioma tumor suppressor genes (Trp53, Pten, Atm, Cdkn2a) in individual mouse brains. These mini-pooled in vivo experiments generated primary midline gliomas with decreased tumor latency (median time to tumor formation of 3.6 weeks, P < 0.0001, log-rank test compared to single-plex gRNA). Quantification of gRNA barcodes and CRISPR editing events revealed that all tumors contained cells with various disruptions of all target genes and suggested a multiclonal origin for the tumors as well as stronger selection for Trp53 disruption compared to disruption of the other genes. This mouse modeling approach will streamline midline glioma research and enable complex experiments to understand tumor evolution and therapeutics.

The lives of cells, recorded

A paradigm for biology is emerging in which cells can be genetically programmed to write their histories into their own genomes. These records can subsequently be read, and the cellular histories reconstructed, which for each cell could include a record of its lineage relationships, extrinsic influences, internal states and physical locations, over time. DNA recording has the potential to transform the way that we study developmental and disease processes. Recent advances in genome engineering are driving the development of systems for DNA recording, and meanwhile single-cell and spatial omics technologies increasingly enable the recovery of the recorded information. Combined with advances in computational and phylogenetic inference algorithms, the DNA recording paradigm is beginning to bear fruit. In this Perspective, we explore the rationale and technical basis of DNA recording, what aspects of cellular biology might be recorded and how, and the types of discovery that we anticipate this paradigm will enable.

Deciphering Precursor Cell Dynamics in Esophageal Preneoplasia via Genetic Barcoding and Single-Cell Transcriptomics

Cancer cells exhibit high heterogeneity and lineage plasticity, complicating studies of tumorigenesis and development of therapies. Recently, preneoplastic cells, although histologically normal, have been shown to possess high plasticity and early genetic alterations, yet their origins and lineage trajectories remain unclear. Herein, we introduce a lineage-tracing tool integrating genetic barcoding with single-cell RNA sequencing to map preneoplastic esophageal cell lineages. We identified preneoplastic precursor cells (PNPCs) as a distinct progenitor-like population with unique transcriptional profiles and high plasticity, contributing to proliferative and basal cell populations. To enhance lineage mapping, we developed the eXamined Ridge (XR) score, accurately identifying high-plasticity cells. Nfib and Qk emerged as conserved PNPC markers, peaking in early preneoplasia and declining after malignant transformation. These findings reveal PNPCs as key players in early tumorigenesis and highlight their potential as biomarkers for early cancer detection and therapeutic intervention, offering new strategies for preventing esophageal cancer progression.

Emerging strategies to investigate the biology of early cancer

Early detection and intervention of cancer or precancerous lesions hold great promise to improve patient survival. However, the processes of cancer initiation and the normal-precancer-cancer progression within a non-cancerous tissue context remain poorly understood. This is, in part, due to the scarcity of early-stage clinical samples or suitable models to study early cancer. In this Review, we introduce clinical samples and model systems, such as autochthonous mice and organoid-derived or stem cell-derived models that allow longitudinal analysis of early cancer development. We also present the emerging techniques and computational tools that enhance our understanding of cancer initiation and early progression, including direct imaging, lineage tracing, single-cell and spatial multi-omics, and artificial intelligence models. Together, these models and techniques facilitate a more comprehensive understanding of the poorly characterized early malignant transformation cascade, holding great potential to unveil key drivers and early biomarkers for cancer development. Finally, we discuss how these new insights can potentially be translated into mechanism-based strategies for early cancer detection and prevention.

A microdeletion event at 19q13.43 in IDH-mutant astrocytomas is strongly correlated with MYC overexpression

MYC dysregulation is pivotal in the onset and progression of IDH-mutant gliomas, mostly driven by copy-number alterations, regulatory element alterations, or epigenetic changes. Our pilot analysis uncovered instances of relative MYC overexpression without alterations in the proximal MYC network (PMN), prompting a deeper investigation into potential novel oncogenic mechanisms. Analysing comprehensive genomics profiles of 236 "IDH-mutant 1p/19q non-co-deleted" lower-grade gliomas from The Cancer Genome Atlas, we identified somatic genomic alterations within the PMN. In tumours without PMN-alterations but with MYC-overexpression, genes correlated with MYC-overexpression were identified. Our analyses yielded that 86/236 of astrocytomas exhibited no PMN-alterations, a subset of 21/86 displaying relative MYC overexpression. Within this subset, we discovered 42 genes inversely correlated with relative MYC expression, all on 19q. Further analysis pinpointed a minimal common region at 19q13.43, encompassing 15 genes. The inverse correlations of these 15 genes with relative MYC overexpression were re-confirmed using independent scRNAseq data. Further, the micro-deleted astrocytoma subset displayed significantly higher genomic instability compared to WT cases, but lower instability compared to PMN-hit cases. This newly identified 19q micro-deletion represents a potential novel mechanism underlying MYC dysregulation in astrocytomas. Given the prominence of 19q loss in IDH-mutant gliomas, our findings bear significant implications for understanding gliomagenesis.

Cellular spartans at the pass: Emerging intricacies of cell competition in early and late tumorigenesis

Cell competition is a mechanism for cellular quality control based on cell-cell comparisons of fitness. Recent studies have unveiled a central and complex role for cell competition in cancer. Early tumors exploit cell competition to replace neighboring normal epithelial cells. Intestinal adenomas, for example, use cell competition to outcompete wild-type epithelial cells. However, oncogenic mutations do not always confer an advantage: wild-type cells can identify mutant cells and enforce their extrusion through cell competition, a process termed "epithelial defense against cancer". A particularly interesting situation emerges in metastasis: supercompetitive tumor cells encounter heterotypic partners and engage in reciprocal competition with diverging outcomes. This article sheds light on the emerging complexity of cell competition by highlighting recent studies that unveil its context dependency. Finally, we propose that tissue histomorphology implies a crucial role for cell competition at tumor invasion fronts particularly in metastases, warranting increased attention in future studies.

Interdependence of Molecular Lesions That Drive Uveal Melanoma Metastasis

The metastatic risk of uveal melanoma (UM) is defined by a limited number of molecular lesions, somatic mutations (SF3B1 and BAP1), and copy number alterations (CNA): monosomy of chromosome 3 (M3), chr8q gain (8q), chr6p gain (6p), yet the sequence of events is not clear. We analyzed data from three datasets (TCGA-UVM, GSE27831, GSE51880) with information regarding M3, 8q, 6p, SF3B1, and BAP1 status. We confirm that BAP1 mutations are always associated with M3 in high-risk patients. All other features (6p, 8q, M3, SF3B1 mutation) were present independently from each other. Chr8q gain was frequently associated with chr3 disomy. Hierarchical clustering of gene expression data of samples with different binary combinations of aggressivity factors shows that patients with 8q|M3, BAP1|M3 form one cluster enriched in samples that developed metastases. Patients with 6p combined with either 8q or SF3B1 are mainly represented in the other, low-risk cluster. Several gene expression events that show a non-significant association with outcome when considering single features become significant when analyzing combinations of risk features indicating additive action. The independence of risk factors is consistent with a random risk model of UM metastasis without an obligatory sequence.

Clonal Extinction Drives Tumorigenesis

Before a tumor is diagnosed and surgically removed, it has been growing for many months or even years [...].