Cellular Origin Research Articles

Intraluminal release of citrullinated histone 3 from various cellular origins coincides with microvascular thrombosis in burn wounds.

Loss of perfusion in the burn wound might cause wound deepening and impaired healing. We previously showed persistent microvascular thrombosis coinciding with intraluminal neutrophils extracellular traps in human burned skin. This study investigates the presence of intraluminal citrullinated histone 3 (H3cit) from different cellular origins (neutrophils, monocytes, and lymphocytes) in relation to microvascular thrombosis of burn wounds. Eschar was obtained from burn patients (n = 18) 6-40 days postburn with a mean total burned body surface area of 23%. Microvascular presence of tissue factor (TF), factor XII (FXII) and thrombi was assessed by immunohistochemistry. Intramicrovascular cell death was analyzed via immunofluorescent microscopy, combining antibodies for neutrophils (MPO), monocytes (CD14), and lymphocytes (CD45) with endothelial cell markers CD31 and H3cit. Significantly increased microvascular expression of TF, FXII, and thrombi (CD31+) was found in all eschar samples compared with control uninjured skin. Release of H3cit from different cellular origins was observed in the lumen of the dermal microvasculature in the eschar tissue 7-40 days postburn, with release from neutrophilic origin being 2.7 times more abundant. Intraluminal presence of extracellular H3cit colocalizing with either MPO, CD14, or CD45 is correlated to increased microvascular thrombosis in eschar of burn patients.

The intricate interplay between cancer stem cells and cell-of-origin of cancer: implications for therapeutic strategies

BackgroundCancer stem cells (CSCs) have emerged as pivotal players in tumorigenesis, disease progression, and resistance to therapies.ObjectiveThis comprehensive review delves into the intricate relationship between CSCs and the cell-of-origin in diverse cancer types.DesignComprehensive review of thematically-relevant literature.MethodsWe explore the underlying molecular mechanisms that drive the conversion of normal cells into CSCs and the impact of the cell-of-origin on CSC properties, tumor initiation, and therapeutic responses. Moreover, we discuss potential therapeutic interventions targeting CSCs based on their distinct cell-of-origin characteristics.ResultsAccruing evidence suggest that the cell-of-origin, the cell type from which the tumor originates, plays a crucial role in determining the properties of CSCs and their contribution to tumor heterogeneity.ConclusionBy providing critical insights into the complex interplay between CSCs and their cellular origins, this article aims to enhance our understanding of cancer biology and pave the way for more effective and personalized cancer treatments.

Could Cerebral Inflammatory Lesions be the Cellular Origin of Primary Central Nervous System Lymphoma?

Primary central nervous system lymphoma (PCNSL) presents a diagnostic enigma due to the inherent absence of lymphoid tissue in the central nervous system (CNS). The hypothesis posits that lymphocytes infiltrating the CNS during inflammatory responses could represent a cellular source for PCNSL, challenging traditional understandings of its etiology. In 2 illustrative cases, patients presented with neurological symptoms initially misdiagnosed as encephalitis and demyelinating disease, respectively. These diagnoses were established based on clinical assessments and initial biopsy findings. Subsequent biopsies, conducted months after the first signs of disease, confirmed the diagnosis of PCNSL in both patients. Identifying CD20-positive tumor cells was pivotal, indicating a B-cell lymphoma origin. Treatment strategies included high-dose methotrexate chemotherapy for both patients. In addition, the second patient underwent adjuvant whole-brain radiotherapy after the chemotherapy regimen. The therapeutic approach significantly reduced tumor size in both cases, with no evidence of recurrence observed during the follow-up period. This outcome underscores the potential efficacy of the chosen interventions. In response to inflammatory lesions, lymphocyte infiltration into the CNS may serve as a pivotal origin for tumor cells in PCNSL. These cases highlight the complexity of diagnosing CNS disorders and suggest that various forms of encephalitis in the early stages could influence the prognosis of lymphoma. This insight into the cellular origins and treatment responses of PCNSL contributes to a broader understanding of its pathophysiology and management.

Exosomes in Atherosclerosis: Role in the Pathogenesis and Targets for Therapy.

Atherosclerotic cardiovascular disease (ASCVD) is an advanced chronic inflammatory disease and the leading cause of death worldwide. The pathological development of ASCVD begins with atherosclerosis, characterised by a pathological remodelling of the arterial wall, lipid accumulation and build-up of atheromatous plaque. As the disease advances, it narrows the vascular lumen and limits the blood, leading to ischaemic necrosis in coronary arteries. Exosomes are nano-sized lipid vesicles of different origins that can carry many bioactive molecules from their parental cells, thus playing an important role in intercellular communication. The roles of exosomes in atherosclerosis have recently been intensively studied, advancing our understanding of the underlying molecular mechanisms. In this review, we briefly introduce exosome biology and then focus on the roles of exosomes of different cellular origins in atherosclerosis development and progression, functional significance of their cargoes and physiological impact on recipient cells. Studies have demonstrated that exosomes originating from endothelial cells, vascular smooth muscle cells, macrophages, dendritic cells, platelets, stem cells, adipose tissue and other sources play an important role in the atherosclerosis development and progression by affecting cholesterol transport, inflammatory, apoptotic and other aspects of the recipient cells' metabolism. MicroRNAs are considered the most significant type of bioactive molecules transported by exosomes and involved in ASCVD development. Finally, we review the current achievements and limitations associated with the use of exosomes for the diagnosis and treatment of ASCVD.

The oxidant-antioxidant imbalance was involved in the pathogenesis of chronic rhinosinusitis with nasal polyps

BackgroundAlthough oxidative stress is involved in the pathophysiological process of chronic rhinosinusitis with nasal polyps (CRSwNP), the specific underlying mechanism is still unclear. Whether antioxidant therapy can treat CRSwNP needs further investigation.MethodsImmunohistochemistry, immunofluorescence, western blotting and quantitative polymerase chain reaction (qPCR) analyses were performed to detect the distribution and expression of oxidants and antioxidants in nasal polyp tissues. qPCR revealed correlations between oxidase, antioxidant enzymes and inflammatory cytokine levels in CRSwNP patients. Human nasal epithelial cells (HNEpCs) and primary macrophages were cultured to track the cellular origin of oxidative stress in nasal polyps(NPs) and to determine whether crocin can reduce cellular inflammation by increasing the cellular antioxidant capacity.ResultsThe expression of NOS2, NOX1, HO-1 and SOD2 was increased in nasal epithelial cells and macrophages derived from nasal polyp tissue. Oxidase levels were positively correlated with those of inflammatory cytokines (IL-5 and IL-6). Conversely, the levels of antioxidant enzymes were negatively correlated with those of IL-13 and IFN-γ. Crocin inhibited M1 and M2 macrophage polarization as well as the expression of NOS2 and NOX1 and improved the antioxidant capacity of M2 macrophages. Moreover, crocin enhanced the ability of antioxidants to reduce inflammation via the KEAP1/NRF2/HO-1 pathway in HNEpCs treated with SEB or LPS. Additionally, we observed the antioxidant and anti-inflammatory effects of crocin in nasal explants.ConclusionOxidative stress plays an important role in the development of CRSwNP by promoting various types of inflammation. The oxidative stress of nasal polyps comes from epithelial cells and macrophages. Antioxidant therapy may be a promising strategy for treating CRSwNP.

A review of natural products and small-molecule therapeutics acting on central nervous system malignancies: Approaches for drug development, targeting pathways, clinical trials, and challenges.

In 2021, the World Health Organization released the fifth edition of the central nervous system (CNS) tumor classification. This classification uses histopathology and molecular pathogenesis to group tumors into more biologically and molecularly defined entities. The prognosis of brain cancer, particularly malignant tumors, has remained poor worldwide, approximately 308,102 new cases of brain and other CNS tumors were diagnosed in the year 2020, with an estimated 251,329 deaths. The cost and time-consuming nature of studies to find new anticancer agents makes it necessary to have well-designed studies. In the present study, the pathways that can be targeted for drug development are discussed in detail. Some of the important cellular origins, signaling, and pathways involved in the efficacy of bioactive molecules againstCNS tumorigenesis or progression, as well as prognosis and common approaches for treatment of different types of brain tumors, are reviewed. Moreover, different study tools, including cell lines, in vitro, in vivo, and clinical trial challenges, are discussed. In addition, in this article, natural products as one of the most important sources for finding new chemotherapeutics were reviewed and over 700 reported molecules with efficacy against CNS cancer cells are gathered and classified according to their structure. Based on the clinical trials that have been registered, very few of these natural or semi-synthetic derivatives have been studied in humans. The review can help researchers understand the involved mechanisms and design new goal-oriented studies for drug development against CNS malignancies.

Quantitative Assessment of Tumor Contact with Neurogenic Zones and Its Effects on Survival: Insights beyond Traditional Predictors.

So far, the cellular origin of glioblastoma (GBM) needs to be determined, with prevalent theories suggesting emergence from transformed endogenous stem cells. Adult neurogenesis primarily occurs in two brain regions: the subventricular zone (SVZ) and the subgranular zone (SGZ) of the hippocampal dentate gyrus. Whether the proximity of GBM to these neurogenic niches affects patient outcome remains uncertain. Previous studies often rely on subjective assessments, limiting the reliability of those results. In this study, we assessed the impact of GBM's relationship with the cortex, SVZ and SGZ on clinical variables using fully automated segmentation methods. In 177 glioblastoma patients, we calculated optimal cutpoints of minimal distances to the SVZ and SGZ to distinguish poor from favorable survival. The impact of tumor contact with neurogenic zones on clinical parameters, such as overall survival, multifocality, MGMT promotor methylation, Ki-67 and KPS score was also examined by multivariable regression analysis, chi-square test and Mann-Whitney-U. The analysis confirmed shorter survival in tumors contacting the SVZ with an optimal cutpoint of 14 mm distance to the SVZ, separating poor from more favorable survival. In contrast, tumor contact with the SGZ did not negatively affect survival. We did not find significant correlations with multifocality or MGMT promotor methylation in tumors contacting the SVZ, as previous studies discussed. These findings suggest that the spatial relationship between GBM and neurogenic niches needs to be assessed differently. Objective measurements disprove prior assumptions, warranting further research on this topic.

Cell-specific extracellular vesicle-encapsulated exogenous GABA controls seizures in epilepsy

BackgroundEpilepsy affects ∼60 million people worldwide. Most antiseizure medications in the market act on voltage-gated sodium or calcium channels, indirectly modulating neurotransmitter GABA or glutamate levels or multiple targets. Earlier studies made significant efforts to directly deliver GABA into the brain with varied success. Herein, we have hypothesized to directly deliver exogenous GABA to the brain with epilepsy through extracellular vesicles (EVs) from human GABA-producing cells and their progenitors as EVs largely mimic their parent cell composition.MethodsHuman neural stem cells (NSCs), medial ganglionic eminence (MGE) cells, and GABAergic interneurons (INs) were generated from induced pluripotent stem cells (iPSCs) and characterized. EVs were isolated from NSCs, MGE cells, and INs and characterized for size and distribution, morphological features, and molecular markers. Exogenous GABA was passively loaded to the isolated EVs as a zwitterion at physiological pH, and the encapsulated dose of GABA was quantified. Epilepsy was developed through status epilepticus induction in Fisher rats by administration of repeated low doses of kainic acid. The extent of the seizures was measured for 10 h/ day for 3–6 months by video recording and its evaluation for stage III, IV and V seizures as per Racine scale. EVs from INs, MGE cells, and NSCs encapsulated with exogenous GABA were sequentially tested in the 4th, 5th, and 6th months by intranasal administration in the rats with epilepsy for detailed seizure, behavioral and synapse analysis. In separate experiments, several controls including exogenic GABA alone and EVs from INs and MGE cells were evaluated for seizure-controlling ability.ResultsExogenic GABA could enter the brain through EVs. Treatment with EVs from INs and MGE cells encapsulated with GABA significantly reduced total seizures, stage V seizures, and total time spent in seizure activity. EVs from NSCs encapsulated with GABA demonstrated limited seizure control. Exogenic GABA alone and EVs from INs and MGE cells individually failed to control seizures. Further, exogenic GABA with EVs from MGE cells improved depressive behavior while partially improving memory functions. Co-localization studies confirmed exogenous GABA with presynaptic vesicles in the hippocampus, indicating the interaction of exogenous GABA in the brain with epilepsy.ConclusionFor the first time, the study demonstrated that exogenous GABA could be delivered to the brain through brain cell-derived EVs, which could regulate seizures in temporal lobe epilepsy. It is identified that the cellular origin of EVs plays a vital role in seizure control with exogenous GABA.

Capillary malformations.

Capillary malformation (CM), or port wine birthmark, is a cutaneous congenital vascular anomaly that occurs in 0.1%-2% of newborns. Patients with a CM localized on the forehead have an increased risk of developing a neurocutaneous disorder called encephalotrigeminal angiomatosis or Sturge-Weber syndrome (SWS), with complications including seizure, developmental delay, glaucoma, and vision loss. In 2013, a groundbreaking study revealed causative activating somatic mutations in the gene (GNAQ) encoding guanine nucleotide-binding protein Q subunit α (Gαq) in CM and SWS patient tissues. In this Review, we discuss the disease phenotype, the causative GNAQ mutations, and their cellular origin. We also present the endothelial Gαq-related signaling pathways, the current animal models to study CM and its complications, and future options for therapeutic treatment. Further work remains to fully elucidate the cellular and molecular mechanisms underlying the formation and maintenance of the abnormal vessels.

Annelid adult cell type diversity and their pluripotent cellular origins

Many annelids can regenerate missing body parts or reproduce asexually, generating all cell types in adult stages. However, the putative adult stem cell populations involved in these processes, and the diversity of cell types generated by them, are still unknown. To address this, we recover 75,218 single cell transcriptomes of the highly regenerative and asexually-reproducing annelid Pristina leidyi. Our results uncover a rich cell type diversity including annelid specific types as well as novel types. Moreover, we characterise transcription factors and gene networks that are expressed specifically in these populations. Finally, we uncover a broadly abundant cluster of putative stem cells with a pluripotent signature. This population expresses well-known stem cell markers such as vasa, piwi and nanos homologues, but also shows heterogeneous expression of differentiated cell markers and their transcription factors. We find conserved expression of pluripotency regulators, including multiple chromatin remodelling and epigenetic factors, in piwi+ cells. Finally, lineage reconstruction analyses reveal computational differentiation trajectories from piwi+ cells to diverse adult types. Our data reveal the cell type diversity of adult annelids by single cell transcriptomics and suggest that a piwi+ cell population with a pluripotent stem cell signature is associated with adult cell type differentiation.

Cell-type-resolved mosaicism reveals clonal dynamics of the human forebrain.

Debate remains around the anatomical origins of specific brain cell subtypes and lineage relationships within the human forebrain1-7. Thus, direct observation in the mature human brain is critical for a complete understanding of its structural organization and cellular origins. Here we utilize brain mosaic variation within specific cell types as distinct indicators for clonal dynamics, denoted as cell-type-specific mosaic variant barcode analysis. From four hemispheres and two different human neurotypical donors, we identified 287 and 780 mosaic variants, respectively, that were used to deconvolve clonal dynamics. Clonal spread and allele fractions within the brain reveal that local hippocampal excitatory neurons are more lineage-restricted than resident neocortical excitatory neurons or resident basal ganglia GABAergic inhibitory neurons. Furthermore, simultaneous genome transcriptome analysis at both a cell-type-specific and a single-cell level suggests a dorsal neocortical origin for a subgroup of DLX1+ inhibitory neurons that disperse radially from an origin shared with excitatory neurons. Finally, the distribution of mosaic variants across 17 locations within one parietal lobe reveals that restriction of clonal spread in the anterior-posterior axis precedes restriction in the dorsal-ventral axis for both excitatory and inhibitory neurons. Thus, cell-type-resolved somatic mosaicism can uncover lineage relationships governing the development of the human forebrain.

Tracing the origin of alveolar stem cells in lung repair and regeneration

Alveolar type 2 (AT2) cells are stem cells of the alveolar epithelia. Previous genetic lineage tracing studies reported multiple cellular origins for AT2 cells after injury. However, conventional lineage tracing based on Cre-loxP has the limitation of non-specific labeling. Here, we introduced a dual recombinase-mediated intersectional genetic lineage tracing approach, enabling precise investigation of AT2 cellular origins during lung homeostasis, injury, and repair. We found AT1 cells, being terminally differentiated, did not contribute to AT2 cells after lung injury and repair. Distinctive yet simultaneous labeling of club cells, bronchioalveolar stem cells (BASCs), and existing AT2 cells revealed the exact contribution of each to AT2 cells post-injury. Mechanistically, Notch signaling inhibition promotes BASCs but impairs club cells' ability to generate AT2 cells during lung repair. This intersectional genetic lineage tracing strategy with enhanced precision allowed us to elucidate the physiological role of various epithelial cell types in alveolar regeneration following injury.

Feline Facial Spindle Cell Tumors in 29 Cats: Histomorphological and Immunohistochemical Characterization.

Soft tissue tumors/sarcomas (STSs) in felines, encompassing a variety of mesenchymal tumors with similar histomorphological features, present diagnostic challenges due to their diverse cellular origins and the overlap with other tumor types such as feline sarcoid. This study aimed to delineate the clinical, histomorphological, and immunohistochemical characteristics of 34 feline facial spindle cell tumors affecting 29 cats, including testing for bovine papillomavirus type 14 (BPV14), the virus causing feline sarcoids. Only five out of 12 tumors previously diagnosed as feline sarcoids based on histomorphology were confirmed by PCR for BPV14, underscoring the importance of comprehensive diagnostic approaches to accurately distinguish between STSs and feline sarcoids. This study shows that most facial spindle cell tumors were compatible with peripheral nerve sheath tumors (PNSTs) based on positive immunohistochemical staining for Sox10 and other immunohistochemical markers such as GFAP, NSE, and S100. Some of these tumors displayed as multiple independent masses on the face or as erosive and ulcerative lesions without obvious mass formation, an atypical presentation and an important highlight for general practitioners, dermatologists, and oncologists. This study also describes periadnexal whorling of neoplastic cells as a novel histomorphologic finding in feline facial PNSTs and emphasizes Sox10 as a useful complementary immunohistochemical marker for the diagnosis of facial PNST in cats, providing valuable insights for veterinary pathologists.

CD4+ Regulatory T Cells in Human Cancer: Subsets, Origin, and Molecular Regulation.

CD4+CD25hiFOXP3+ regulatory T cells (Treg) play major roles in the maintenance of immune tolerance, prevention of inflammation, and tissue homeostasis and repair. In contrast with these beneficial roles, Tregs are abundant in virtually all tumors and have been mechanistically linked to disease progression, metastases development, and therapy resistance. Tregs are thus recognized as a major target for cancer immunotherapy. Compared with other sites in the body, tumors harbor hyperactivated Treg subsets whose molecular characteristics are only beginning to be elucidated. Here, we describe current knowledge of intratumoral Tregs and discuss their potential cellular and tissue origin. Furthermore, we describe currently recognized molecular regulators that drive differentiation and maintenance of Tregs in cancer, with a special focus on those signals regulating their chronic immune activation, with relevant implications for cancer progression and therapy.

Osteosarcoma through the Lens of Bone Development, Signaling, and Microenvironment.

In this work, we review the multifaceted connections between osteosarcoma (OS) biology and normal bone development. We summarize and critically analyze existing research, highlighting key areas that merit further exploration. The review addresses several topics in OS biology and their interplay with normal bone development processes, including OS cell of origin, genomics, tumor microenvironment, and metastasis. We examine the potential cellular origins of OS and how their roles in normal bone growth may contribute to OS pathogenesis. We survey the genomic landscape of OS, highlighting the developmental roles of genes frequently altered in OS. We then discuss the OS microenvironment, emphasizing the transformation of the bone niche in OS to facilitate tumor growth and metastasis. The role of stromal and immune cells is examined, including their impact on tumor progression and therapeutic response. We further provide insights into potential development-informed opportunities for novel therapeutic strategies.

Xenopus tropicalis osteoblast-specific open chromatin regions reveal promoters and enhancers involved in human skeletal phenotypes and shed light on early vertebrate evolution

While understanding the genetic underpinnings of osteogenesis has far-reaching implications for skeletal diseases and evolution, a comprehensive characterization of the osteoblastic regulatory landscape in non-mammalian vertebrates is still lacking. Here, we compared the ATAC-Seq profile of Xenopus tropicalis (Xt) osteoblasts to a variety of non mineralizing control tissues, and identified osteoblast-specific nucleosome free regions (NFRs) at 527 promoters and 6747 distal regions. Sequence analyses, Gene Ontology, RNA-Seq and ChIP-Seq against four key histone marks confirmed that the distal regions correspond to bona fide osteogenic transcriptional enhancers exhibiting a shared regulatory logic with mammals. We report 425 regulatory regions conserved with human and globally associated to skeletogenic genes. Of these, 35 regions have been shown to impact human skeletal phenotypes by GWAS, including one trps1 enhancer and the runx2 promoter, two genes which are respectively involved in trichorhinophalangeal syndrome type I and cleidocranial dysplasia. Intriguingly, 60 osteoblastic NFRs also align to the genome of the elephant shark, a species lacking osteoblasts and bone tissue. To tackle this paradox, we chose to focus on dlx5 because its conserved promoter, known to integrate regulatory inputs during mammalian osteogenesis, harbours an osteoblast-specific NFR in both frog and human. Hence, we show that dlx5 is expressed in Xt and elephant shark odontoblasts, supporting a common cellular and genetic origin of bone and dentine. Taken together, our work (i) unravels the Xt osteogenic regulatory landscape, (ii) illustrates how cross-species comparisons harvest data relevant to human biology and (iii) reveals that a set of genes including bnc2, dlx5, ebf3, mir199a, nfia, runx2 and zfhx4 drove the development of a primitive form of mineralized skeletal tissue deep in the vertebrate lineage.

Exhaled breath condensate contains extracellular vesicles (EVs) that carry miRNA cargos of lung tissue origin that can be selectively purified and analyzed.

Lung diseases, including lung cancer, are rising causes of global mortality. Despite novel imaging technologies and the development of biomarker assays, the detection of lung cancer remains a significant challenge. However, the lung communicates directly with the external environment and releases aerosolized droplets during normal tidal respiration, which can be collected, stored and analzsed as exhaled breath condensate (EBC). A few studies have suggested that EBC contains extracellular vesicles (EVs) whose microRNA (miRNA) cargos may be useful for evaluating different lung conditions, but the cellular origin of these EVs remains unknown. In this study, we used nanoparticle tracking, transmission electron microscopy, Western blot analyses and super resolution nanoimaging (ONi) to detect and validate the identity of exhaled EVs (exh-EVs). Using our customizable antibody-purification assay, EV-CATCHER, we initially determined that exh-EVs can be selectively enriched from EBC using antibodies against three tetraspanins (CD9, CD63 and CD81). Using ONi we also revealed that some exh-EVs harbour lung-specific proteins expressed in bronchiolar Clara cells (Clara Cell Secretory Protein [CCSP]) and Alveolar Type II cells (Surfactant protein C [SFTPC]). When conducting miRNA next generation sequencing (NGS) of airway samples collected at five different anatomic levels (i.e., mouth rinse, mouth wash, bronchial brush, bronchoalveolar lavage [BAL] and EBC) from 18 subjects, we determined that miRNA profiles of exh-EVs clustered closely to those of BAL EVs but not to those of other airway samples. When comparing the miRNA profiles of EVs purified from matched BAL and EBC samples with our three tetraspanins EV-CATCHER assay, we captured significant miRNA expression differences associated with smoking, asthma and lung tumor status of our subjects, which were also reproducibly detected in EVs selectively purified with our anti-CCSP/SFTPC EV-CATCHER assay from the same samples, but that confirmed their lung tissue origin. Our findings underscore that enriching exh-EV subpopulations from EBC allows non-invasive sampling of EVs produced by lung tissues.

Translocator Protein TSPO (Peripheral Benzodiazepine Receptor): The Modern Story of the Ancient Preserved Protein with Ambiguous Functions

In several tissues, including the brain, heart, blood, intestines, adrenal glands, and liver, the 18 kDa translocator protein (TSPO) was shown to be the peripheral benzodiazepine receptor. There is strong evidence that TSPO is expressed in microglial cells in the central nervous system. Five transmembrane regions are seen at the cellular level in TSPO at the contact points between the outer and inner layers of mitochondria. The cytosolic region of the complex of amino acids that binds cholesterol is where cholesterol is taken up. TSPO is found as a monomer of 18 kDa and homomultimers and homodimers. Different factors, such as cholesterol concentration and reactive oxygen species, change the multimeric structure. As a result, TSPO gains responsibility for transferring cholesterol to the mitochondrial intermembrane space, transforming it into a steroid. Additionally, TSPO appears to collaborate with other mitochondrial membrane proteins to play a part in regulating the activity of the MPTP (mitochondrial permeability transition pore) and, therefore, in the elements of apoptosis. In vivo imaging of TSPO addresses a significant test in examining brain pathology like neuroinflammatory, Alzheimer’s, and schizophrenia. Additionally, TSPO’s use as a biomarker may have important implications for developing more viable diagnostic and therapeutic approaches. The current work surveys the TSPO cellular origin and attempts to comprehend its role in various physiological and pathological conditions.

Abstract 7369: Passenger mutations link cellular origins and transcriptional identity in human lung adenocarcinoma

Abstract Lineage plasticity hinders identification of cellular origin of cancers, as malignant cells cease to resemble benign cells from which they presumably evolved. Lung adenocarcinoma (LUAD), the most common primary lung cancer in United States is thought to arise from alveolar type II (AT2) cells. However recent mouse models have shown that LUADs may also arise from other cell types such as basal and club. Although such mouse models are considered to be gold standard for identifying cell of origin for cancers, they are generally limited to a specific genetic context and lack all cell types that are present in human lung. Thus, to better understand the cellular origins of LUAD, we utilized a publicly available lung scRNA-seq atlas from Human Cell Atlas, spanning over 584,000 cells from 107 individuals to investigate cell type specific passenger mutational footprints of transcriptional coupled repair process (a sub-pathway of nucleotide excision repair that preferentially corrects mutations in highly expressed genes) across 295 lung cancer WGS profiles. As most mutations in self-renewing tissues are thought to occur prior to the onset of tumorigenesis, genes that are most highly transcribed in the cell of origin would have fewer somatic single nucleotide variants (SNV). To test this hypothesis, our study correlated somatic mutational density with gene expression profiles of cell types to identify Alveolar Type 0 (AT0, newly identified cell type) cells to be most strongly associated with LUAD mutation density, suggesting that the ancestor of LUAD cells in tumor spent most of their non-cancerous time in AT0 state. Interestingly studies have shown that following DNA damage in AT2 cells, transition to AT1 occurs to repair the damage. However, if the damage is detrimental, the transition of AT2 to AT1 is stalled and the cells remain in AT0 (i.e., a transitionary) state. We propose that such stalling for a long period of time can give rise to LUAD. Further our study identified a subset of LUAD patients with non-AT2 (i.e., proximal) origin. In particular, we observed significantly higher KRAS mutations in distal origin LUAD patients compared to those in proximal origin LUADs. Finally, a subset of LUAD patients with distal cell of origin adopted a more proximal transcriptional identity. Extending our analysis to lung squamous cell carcinoma (LUSC) patients, we observed basal resting cells to be the Cell of Origin (COO) for LUSC. Our study provides a novel approach for identifying cell of origin for cancers and points to a complex interplay between origin and identify in lung adenocarcinoma evolution. Citation Format: Sukanya Panja, Padmaja Mantri, Juan Andrade Martinez, Marcin Imielinski. Passenger mutations link cellular origins and transcriptional identity in human lung adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7369.

Abstract 6557: Longitudinal cell-free tumor load dynamics represent an early endpoint for immunotherapy response in non-small cell lung cancer

Abstract Background: Liquid biopsies can inform treatment strategies by rapidly and accurately assessing tumor burden; with emerging data supporting the clinical utility of circulating cell-free tumor DNA (ctDNA) as an early endpoint of immunotherapy response. Methods: We performed targeted error-correction sequencing of ctDNA (n=330) and matched white blood cell (WBC) DNA (n=109) from 109 patients with advanced non-small cell lung cancer (NSCLC) who received immune checkpoint inhibitor monotherapy (n=79) or immunotherapy-containing combination regimens (n=30). Variant cellular origin was determined using a tumor-independent WBC DNA-informed approach. The maximum mutant allele fraction (maxMAF) of tumor-derived mutations was tracked longitudinally to assess changes in total cell-free tumor load (cfTL). Results: Among 3,418 variants with resolved cellular origin, 2,452 (72%) were tumor-derived, 125 (4%) were germline, while 841 (25%) were related to clonal haematopoiesis (CH). Cell-free DNA fragments harbouring tumor-derived mutations were significantly shorter than fragments containing wild-type alleles; however, fragment length alone was insufficient to distinguish CH variants from wild-type. Overall, 97 (89%) patients with >1 detectable tumor mutation were considered for cfTL tracking and molecular response assessment. Clearance of cfTL indicated molecular response (mR) whereas persistence indicated molecular progression (mPD). Time-course analyses, aiming to establish the optimal timing for molecular response assessment, revealed that early cfTL clearance within 3-9 weeks was significantly linked to improved survival outcomes. Notably, blood tumor mutation burden above or below 16 mutations/megabase showed no association with overall survival (OS; log rank p=0.98) or progression-free survival (PFS; log rank p=0.95). Of 81 patients evaluated for early on-therapy molecular responses, 28 (35%) were classified as having an mR, while 53 (65%) patients were classified in the mPD category. The median time to mR was 5 weeks in patients receiving immune checkpoint monotherapy and 6 weeks in patients receiving chemo-immunotherapy combination regimens. Patients in the mR group achieved longer OS (log rank p=0.001) and PFS (log rank p=0.0003) compared to those with mPD. Assessment of landmark PFS at 6 months demonstrated a significant association between ctDNA molecular response and durable clinical benefit (DCB) in patients receiving immune checkpoint monotherapy (p < 0.001, Fisher’s exact test), and a numerical association with DCB in patients on chemo-immunotherapy (p=0.07, Fisher’s exact test). Conclusions: Longitudinal tracking of ctDNA provides a real-time and accurate approach for monitoring immunotherapy response. These findings underscore the clinical utility of employing ctDNA molecular response to inform clinical decision-making. Citation Format: Lavanya Sivapalan, Bahar Alipanahi, Archana Balan, Jamie E. Medina, Noushin Niknafs, Erica Peters, Jaime Wehr, Alissa Konicki, Mimi Najjar, Bryan Chesnick, Gavin Pereira, Sarah Rongione, Nisha Rao, Michael Rongione, Brittany Shavatt, Lorenzo Rinaldi, Benjamin Levy, Victor E. Velculescu, Patrick M. Forde, Valsamo Anagnostou. Longitudinal cell-free tumor load dynamics represent an early endpoint for immunotherapy response in non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6557.