Biology subjects

Leon, D.

Publications and source records attributed to Leon, D..

6 recordsLinked to original sources

bioRxiv2026

Integrated analysis of stemness-associated immune modulatory circuits in squamous cell carcinomas

Emerging evidence indicates that a subset of cancer cells enriched for stemness-related gene signatures possess distinct immunomodulatory capacities, enabling these tumor-initiating stem cells (tSCs) to more effectively evade or resist anti-tumor immunity. Despite these advances, the tSC-specific molecular circuits orchestrating their specialized immune privilege program are not well defined. Here, in squamous cell carcinomas of the skin and oral cavity, we comprehensively delineate the unique immune-evasive properties of tSCs and dissect the transcriptional regulation shaping their immunomodulatory programs. By integrating transcriptome profiling, chromatin landscape mapping, genetic perturbation, and single-cell RNA sequencing, we found that the tSC-specific immune program is broadly governed by SOX2, a stemness-associated transcription factor. We demonstrate that SOX2 enables tSCs to sustain immature tumor-associated neutrophils (TANs) and subsequently trigger these myeloid cells to foster the development of tumor-associated macrophages (TAMs). This SOX2-directed tSC-TAN-TAM axis establishes a localized immunosuppressive niche for protecting tSC. SIGNIFICANCEHere, we uncover SOX2 as a master regulator that orchestrates conserved immune modulatory circuits in tSCs to sustain pro-tumor myeloid cell states. These findings place tSCs at the apex of immune landscape remodeling, asserting a central role of stemness-associated program in organizing the immunosuppressive tumor microenvironment.

cancer biology↗

bioRxiv2026

Comparative single cell analysis of wound and cancer identifies the metabolic dialogues between tumor initiating stem cells and macrophages

Macrophages are pivotal mediators of wound healing, yet the cellular programs they employ can be hijacked by cancers to drive tumorigenesis. Although similar macrophage programs support both physiological tissue regeneration and pathological cell growth, the molecular and functional difference between wound-associated macrophages (WAMs) and tumor-associated macrophages (TAMs) remain poorly defined. Here, we perform comparative single-cell RNA sequencing to delineate the dynamic cell states of macrophages during skin wound healing and the progression of cutaneous squamous cell carcinoma. Our analyses reveal that aberrantly regulated lipid metabolism is a distinct feature of TAMs. Critically, our genetic manipulations allow us to identify SOX2High tumor-initiating stem cells as key orchestrators that modulate the lipid metabolism of TAMs and shape their cell states. These findings suggest that disrupting the metabolic crosstalk between tumor-initiating stem cells and TAMs represents a promising strategy to normalize myeloid cell function and enhance cancer immunotherapy efficacy.

cancer biology↗

bioRxiv2025

SARS-CoV-2 Variant-Dependent Alterations in Nasopharyngeal Microbiota and Host Inflammatory Response

The SARS-CoV-2 pandemic saw multiple outbreaks occur over short periods. This was linked to the viruss high infectivity and rapid mutation rate, which hindered the development of effective treatments and a comprehensive understanding of COVID-19 pathophysiology. The nasopharyngeal tract, the main entry site of SARS-CoV-2, interacts with angiotensin-converting enzyme 2 (ACE2) receptors via the viral spike glycoprotein, triggering pro-inflammatory responses that affect both tissue integrity and the resident microbiota. Viral infection induces dysbiosis by modulating microbiome diversity. Although distinct variants produce independent symptoms and viral loads, their impact on the nasopharyngeal microbiota and host inflammatory profile remains poorly understood. To address this, we analyzed nasopharyngeal samples from Chilean individuals collected during different phases of the pandemic. The microbiota was characterized by 16S rRNA gene sequencing (V3-V4 region), and cytokine expression was quantified by RT-qPCR. Finally, applied rigorous data processing and machine-learning models Random Forest and K-Nearest Neighbors to identify associations between SARS-CoV-2 variants, inflammatory markers, and opportunistic bacterial genera. Our results reveal that SARS-CoV-2 infection promotes distinct immunomicrobial signatures marked by TNF--driven inflammation and the expansion of opportunistic taxa. These variant-dependent alterations indicate that host inflammatory responses and microbial dysbiosis are closely intertwined in the nasopharyngeal environment. This study provides a comprehensive framework integrating microbial and host factors to better understand the mechanisms underlying COVID-19 pathogenesis and highlights the potential of combining microbiome and cytokine profiling with machine-learning approaches to differentiate infection outcomes across viral variants. ImportanceUnderstanding how SARS-CoV-2 infection alters the upper respiratory microbiota and host immune responses is essential to uncover the mechanisms underlying COVID-19 severity. In this study, we integrate bacterial 16S rRNA sequencing, inflammatory markers, and machine learning to identify key descriptors of infection such as TNF-, Acinetobacter, Prevotella, and Staphylococcus. These markers define a conserved immunomicrobial signature across viral variants, linking inflammatory activation with microbial dysbiosis in the nasopharyngeal environment. Our findings highlight the value of the correct and robust application of machine learning models and nested cross-validation strategies in high-dimensional (wide) datasets to improve variant discrimination, reveal host-microbe interactions, and support the development of therapeutic strategies for respiratory viral infections.

microbiology↗

bioRxiv2025

Tumor-Initiating Cells Fine-tune the Plasticity of Neutrophils to Sculpt a Protective Niche

The abundant accumulation of neutrophils in various solid cancers has been well recognized, but the functions of tumor-associated neutrophils (TANs) remain controversial. TANs have long been believed to be immune suppressive and have thus been referred to as "myeloid-derived suppressor cells". However, effective tumor control induced by immunotherapy was recently found to be associated with strong neutrophil signatures. These seemingly contradictory findings highlight the unexpected degree of plasticity and heterogeneity unique to TANs. How the cellular plasticity and functional heterogeneity of TANs are regulated remains unknown. Here, we show that, while anti-PDL1/CD40 agonist immunotherapy can induce interferon responses to reprogram many TANs, allowing them to become plastic and regain anti-tumor activities in squamous cell carcinomas, a subset of TANs residing at the tumor-stroma interface can preserve their immune suppressive state. Importantly, by designing a reverse genetic screening, we identified a group of Sox2Hi tumor-initiating cells (TICs) at the tumor-stroma interface that could upregulate Fatty Acid Desaturase 1 (Fads1) to produce arachidonic acid. This TIC-specific pathway can disrupt the interferon responsive potentials of TANs, preventing the interferon-mediated reprogramming. Thus, by fine-tuning the plasticity of neutrophils, TICs shape neutrophil heterogeneity and sculpt a protective micro-niche to survive from immunotherapy and drive cancer relapse.

cancer biology↗

bioRxiv2018

Directed evolution of Escherichia coli with lower-than-natural plasmid mutation rates

Unwanted evolution of designed DNA sequences limits metabolic and genome engineering efforts. Engineered functions that are burdensome to host cells and slow their replication are rapidly inactivated by mutations, and unplanned mutations with unpredictable effects often accumulate alongside designed changes in large-scale genome editing projects. We developed a directed evolution strategy, Periodic Reselection for Evolutionarily Reliable Variants (PResERV), to discover mutations that prolong the function of a burdensome DNA sequence in an engineered organism. Here, we used PResERV to isolate E. coli cells that replicate ColE1 plasmids with higher fidelity. We found mutations in DNA polymerases I and IV and in RNase E that reduce plasmid mutation rates by 6-to 30-fold. The PResERV method implicitly selects to maintain the growth rate of host cells, and high plasmid copy numbers and gene expression levels are maintained in some of the evolved E. coli strains, indicating that it is possible to improve the genetic stability of cellular chassis without encountering trade-offs in other desirable performance characteristics. Utilizing these new antimutator E. coli and applying PResERV to other organisms in the future promises to prevent evolutionary failures and unpredictability to provide a more stable genetic foundation for synthetic biology.

evolutionary biology↗

bioRxiv2018

An evolutionary innovation is contingent on maintaining adaptive potential until competition subsides

After 15 years of the Lenski experiment one of twelve Escherichia coli populations evolved the ability to utilize an abundant but previously untapped carbon source, citrate. Mutations responsible for the appearance of rudimentary citrate utilization (Cit+ phenotype) and for refining this ability have been characterized. However, the complete nature of the genetic and/or ecological events that set the stage for this key innovation remain unknown. We found that there was a slight fitness benefit for introducing an activated citT cassette that mimics the mutation causing Cit+ into the ancestor of the evolution experiment and strains isolated from the population close to when it evolved. However, there was no benefit or even a large deleterious effect in intermediate strains. We conclude that achieving Cit+ was contingent on both an evolutionary trajectory that maintained a potentiated genetic state and the slowing rate of adaptation in this population late in the experiment.

evolutionary biology↗