ABSTRACT
Cancer driver events refer to key genetic aberrations that drive oncogenesis; however, their exact molecular mechanisms remain insufficiently understood. Here, our multi-omics pan-cancer analysis uncovers insights into the impacts of cancer drivers by identifying their significant cis-effects and distal trans-effects quantified at the RNA, protein, and phosphoprotein levels. Salient observations include the association of point mutations and copy-number alterations with the rewiring of protein interaction networks, and notably, most cancer genes converge toward similar molecular states denoted by sequence-based kinase activity profiles. A correlation between predicted neoantigen burden and measured T cell infiltration suggests potential vulnerabilities for immunotherapies. Patterns of cancer hallmarks vary by polygenic protein abundance ranging from uniform to heterogeneous. Overall, our work demonstrates the value of comprehensive proteogenomics in understanding the functional states of oncogenic drivers and their links to cancer development, surpassing the limitations of studying individual cancer types.
Subject(s)
Neoplasms , Proteogenomics , Humans , Neoplasms/genetics , Oncogenes , Cell Transformation, Neoplastic/genetics , DNA Copy Number VariationsABSTRACT
Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive cancer with poor patient survival. Toward understanding the underlying molecular alterations that drive PDAC oncogenesis, we conducted comprehensive proteogenomic analysis of 140 pancreatic cancers, 67 normal adjacent tissues, and 9 normal pancreatic ductal tissues. Proteomic, phosphoproteomic, and glycoproteomic analyses were used to characterize proteins and their modifications. In addition, whole-genome sequencing, whole-exome sequencing, methylation, RNA sequencing (RNA-seq), and microRNA sequencing (miRNA-seq) were performed on the same tissues to facilitate an integrated proteogenomic analysis and determine the impact of genomic alterations on protein expression, signaling pathways, and post-translational modifications. To ensure robust downstream analyses, tumor neoplastic cellularity was assessed via multiple orthogonal strategies using molecular features and verified via pathological estimation of tumor cellularity based on histological review. This integrated proteogenomic characterization of PDAC will serve as a valuable resource for the community, paving the way for early detection and identification of novel therapeutic targets.
Subject(s)
Adenocarcinoma/genetics , Carcinoma, Pancreatic Ductal/genetics , Pancreatic Neoplasms/genetics , Proteogenomics , Adenocarcinoma/diagnosis , Adult , Aged , Aged, 80 and over , Algorithms , Carcinoma, Pancreatic Ductal/diagnosis , Cohort Studies , Endothelial Cells/metabolism , Epigenesis, Genetic , Female , Gene Dosage , Genome, Human , Glycolysis , Glycoproteins/biosynthesis , Humans , Male , Middle Aged , Molecular Targeted Therapy , Pancreatic Neoplasms/diagnosis , Phenotype , Phosphoproteins/metabolism , Phosphorylation , Prognosis , Protein Kinases/metabolism , Proteome/metabolism , Substrate Specificity , Transcriptome/geneticsABSTRACT
Lung squamous cell carcinoma (LSCC) remains a leading cause of cancer death with few therapeutic options. We characterized the proteogenomic landscape of LSCC, providing a deeper exposition of LSCC biology with potential therapeutic implications. We identify NSD3 as an alternative driver in FGFR1-amplified tumors and low-p63 tumors overexpressing the therapeutic target survivin. SOX2 is considered undruggable, but our analyses provide rationale for exploring chromatin modifiers such as LSD1 and EZH2 to target SOX2-overexpressing tumors. Our data support complex regulation of metabolic pathways by crosstalk between post-translational modifications including ubiquitylation. Numerous immune-related proteogenomic observations suggest directions for further investigation. Proteogenomic dissection of CDKN2A mutations argue for more nuanced assessment of RB1 protein expression and phosphorylation before declaring CDK4/6 inhibition unsuccessful. Finally, triangulation between LSCC, LUAD, and HNSCC identified both unique and common therapeutic vulnerabilities. These observations and proteogenomics data resources may guide research into the biology and treatment of LSCC.
Subject(s)
Carcinoma, Squamous Cell/genetics , Lung Neoplasms/genetics , Proteogenomics , Acetylation , Adult , Aged , Aged, 80 and over , Cluster Analysis , Cyclin-Dependent Kinase 4/genetics , Cyclin-Dependent Kinase 6/genetics , Epithelial-Mesenchymal Transition/genetics , Female , Gene Expression Regulation, Neoplastic , Humans , Male , Middle Aged , Mutation/genetics , Neoplasm Proteins/metabolism , Phosphorylation , Protein Binding , Receptor Tyrosine Kinase-like Orphan Receptors/metabolism , Receptors, Platelet-Derived Growth Factor/metabolism , Signal Transduction , UbiquitinationABSTRACT
The integration of mass spectrometry-based proteomics with next-generation DNA and RNA sequencing profiles tumors more comprehensively. Here this "proteogenomics" approach was applied to 122 treatment-naive primary breast cancers accrued to preserve post-translational modifications, including protein phosphorylation and acetylation. Proteogenomics challenged standard breast cancer diagnoses, provided detailed analysis of the ERBB2 amplicon, defined tumor subsets that could benefit from immune checkpoint therapy, and allowed more accurate assessment of Rb status for prediction of CDK4/6 inhibitor responsiveness. Phosphoproteomics profiles uncovered novel associations between tumor suppressor loss and targetable kinases. Acetylproteome analysis highlighted acetylation on key nuclear proteins involved in the DNA damage response and revealed cross-talk between cytoplasmic and mitochondrial acetylation and metabolism. Our results underscore the potential of proteogenomics for clinical investigation of breast cancer through more accurate annotation of targetable pathways and biological features of this remarkably heterogeneous malignancy.
Subject(s)
Breast Neoplasms/genetics , Breast Neoplasms/pathology , Carcinogenesis/genetics , Carcinogenesis/pathology , Molecular Targeted Therapy , Proteogenomics , APOBEC Deaminases/metabolism , Adult , Aged , Aged, 80 and over , Breast Neoplasms/immunology , Breast Neoplasms/therapy , Cohort Studies , DNA Damage , DNA Repair , Female , Humans , Immunotherapy , Metabolomics , Middle Aged , Mutagenesis/genetics , Phosphorylation , Protein Kinase Inhibitors/pharmacology , Protein Kinases/metabolism , Receptor, ErbB-2/metabolism , Retinoblastoma Protein/metabolism , Tumor Microenvironment/immunologyABSTRACT
To explore the biology of lung adenocarcinoma (LUAD) and identify new therapeutic opportunities, we performed comprehensive proteogenomic characterization of 110 tumors and 101 matched normal adjacent tissues (NATs) incorporating genomics, epigenomics, deep-scale proteomics, phosphoproteomics, and acetylproteomics. Multi-omics clustering revealed four subgroups defined by key driver mutations, country, and gender. Proteomic and phosphoproteomic data illuminated biology downstream of copy number aberrations, somatic mutations, and fusions and identified therapeutic vulnerabilities associated with driver events involving KRAS, EGFR, and ALK. Immune subtyping revealed a complex landscape, reinforced the association of STK11 with immune-cold behavior, and underscored a potential immunosuppressive role of neutrophil degranulation. Smoking-associated LUADs showed correlation with other environmental exposure signatures and a field effect in NATs. Matched NATs allowed identification of differentially expressed proteins with potential diagnostic and therapeutic utility. This proteogenomics dataset represents a unique public resource for researchers and clinicians seeking to better understand and treat lung adenocarcinomas.
Subject(s)
Adenocarcinoma of Lung/drug therapy , Adenocarcinoma of Lung/genetics , Lung Neoplasms/drug therapy , Lung Neoplasms/genetics , Proteogenomics , Adenocarcinoma of Lung/immunology , Adult , Aged , Aged, 80 and over , Biomarkers, Tumor/metabolism , Carcinogenesis/genetics , Carcinogenesis/pathology , DNA Copy Number Variations/genetics , DNA Methylation/genetics , Female , Humans , Lung Neoplasms/immunology , Male , Middle Aged , Mutation/genetics , Oncogene Proteins, Fusion , Phenotype , Phosphoproteins/metabolism , Proteome/metabolismABSTRACT
We undertook a comprehensive proteogenomic characterization of 95 prospectively collected endometrial carcinomas, comprising 83 endometrioid and 12 serous tumors. This analysis revealed possible new consequences of perturbations to the p53 and Wnt/ß-catenin pathways, identified a potential role for circRNAs in the epithelial-mesenchymal transition, and provided new information about proteomic markers of clinical and genomic tumor subgroups, including relationships to known druggable pathways. An extensive genome-wide acetylation survey yielded insights into regulatory mechanisms linking Wnt signaling and histone acetylation. We also characterized aspects of the tumor immune landscape, including immunogenic alterations, neoantigens, common cancer/testis antigens, and the immune microenvironment, all of which can inform immunotherapy decisions. Collectively, our multi-omic analyses provide a valuable resource for researchers and clinicians, identify new molecular associations of potential mechanistic significance in the development of endometrial cancers, and suggest novel approaches for identifying potential therapeutic targets.
Subject(s)
Carcinoma/genetics , Endometrial Neoplasms/genetics , Gene Expression Regulation, Neoplastic , Proteome/genetics , Transcriptome , Acetylation , Animals , Antigens, Neoplasm/genetics , Carcinoma/immunology , Carcinoma/pathology , Endometrial Neoplasms/immunology , Endometrial Neoplasms/pathology , Epithelial-Mesenchymal Transition/genetics , Feedback, Physiological , Female , Genomic Instability , Humans , Mice , MicroRNAs/genetics , MicroRNAs/metabolism , Microsatellite Repeats , Phosphorylation , Protein Processing, Post-Translational , Proteome/metabolism , Signal TransductionABSTRACT
To elucidate the deregulated functional modules that drive clear cell renal cell carcinoma (ccRCC), we performed comprehensive genomic, epigenomic, transcriptomic, proteomic, and phosphoproteomic characterization of treatment-naive ccRCC and paired normal adjacent tissue samples. Genomic analyses identified a distinct molecular subgroup associated with genomic instability. Integration of proteogenomic measurements uniquely identified protein dysregulation of cellular mechanisms impacted by genomic alterations, including oxidative phosphorylation-related metabolism, protein translation processes, and phospho-signaling modules. To assess the degree of immune infiltration in individual tumors, we identified microenvironment cell signatures that delineated four immune-based ccRCC subtypes characterized by distinct cellular pathways. This study reports a large-scale proteogenomic analysis of ccRCC to discern the functional impact of genomic alterations and provides evidence for rational treatment selection stemming from ccRCC pathobiology.
Subject(s)
Carcinoma, Renal Cell/genetics , Neoplasm Proteins/genetics , Proteogenomics , Transcriptome/genetics , Adult , Aged , Aged, 80 and over , Biomarkers, Tumor/genetics , Biomarkers, Tumor/immunology , Carcinoma, Renal Cell/immunology , Carcinoma, Renal Cell/pathology , Disease-Free Survival , Exome/genetics , Female , Gene Expression Regulation, Neoplastic/genetics , Genome, Human/genetics , Humans , Male , Middle Aged , Neoplasm Proteins/immunology , Oxidative Phosphorylation , Phosphorylation/genetics , Signal Transduction/genetics , Transcriptome/immunology , Tumor Microenvironment/genetics , Tumor Microenvironment/immunology , Exome SequencingABSTRACT
Identifying molecular cancer drivers is critical for precision oncology. Multiple advanced algorithms to identify drivers now exist, but systematic attempts to combine and optimize them on large datasets are few. We report a PanCancer and PanSoftware analysis spanning 9,423 tumor exomes (comprising all 33 of The Cancer Genome Atlas projects) and using 26 computational tools to catalog driver genes and mutations. We identify 299 driver genes with implications regarding their anatomical sites and cancer/cell types. Sequence- and structure-based analyses identified >3,400 putative missense driver mutations supported by multiple lines of evidence. Experimental validation confirmed 60%-85% of predicted mutations as likely drivers. We found that >300 MSI tumors are associated with high PD-1/PD-L1, and 57% of tumors analyzed harbor putative clinically actionable events. Our study represents the most comprehensive discovery of cancer genes and mutations to date and will serve as a blueprint for future biological and clinical endeavors.
Subject(s)
Neoplasms/pathology , Algorithms , B7-H1 Antigen/genetics , Computational Biology , Databases, Genetic , Entropy , Humans , Microsatellite Instability , Mutation , Neoplasms/genetics , Neoplasms/immunology , Principal Component Analysis , Programmed Cell Death 1 Receptor/geneticsABSTRACT
We conducted the largest investigation of predisposition variants in cancer to date, discovering 853 pathogenic or likely pathogenic variants in 8% of 10,389 cases from 33 cancer types. Twenty-one genes showed single or cross-cancer associations, including novel associations of SDHA in melanoma and PALB2 in stomach adenocarcinoma. The 659 predisposition variants and 18 additional large deletions in tumor suppressors, including ATM, BRCA1, and NF1, showed low gene expression and frequent (43%) loss of heterozygosity or biallelic two-hit events. We also discovered 33 such variants in oncogenes, including missenses in MET, RET, and PTPN11 associated with high gene expression. We nominated 47 additional predisposition variants from prioritized VUSs supported by multiple evidences involving case-control frequency, loss of heterozygosity, expression effect, and co-localization with mutations and modified residues. Our integrative approach links rare predisposition variants to functional consequences, informing future guidelines of variant classification and germline genetic testing in cancer.
Subject(s)
Germ Cells/metabolism , Neoplasms/pathology , DNA Copy Number Variations , Databases, Genetic , Gene Deletion , Gene Frequency , Genetic Predisposition to Disease , Genotype , Germ Cells/cytology , Germ-Line Mutation , Humans , Loss of Heterozygosity/genetics , Mutation, Missense , Neoplasms/genetics , Polymorphism, Single Nucleotide , Proto-Oncogene Proteins c-met/genetics , Proto-Oncogene Proteins c-ret/genetics , Tumor Suppressor Proteins/geneticsABSTRACT
Chromatin accessibility is essential in regulating gene expression and cellular identity, and alterations in accessibility have been implicated in driving cancer initiation, progression and metastasis1-4. Although the genetic contributions to oncogenic transitions have been investigated, epigenetic drivers remain less understood. Here we constructed a pan-cancer epigenetic and transcriptomic atlas using single-nucleus chromatin accessibility data (using single-nucleus assay for transposase-accessible chromatin) from 225 samples and matched single-cell or single-nucleus RNA-sequencing expression data from 206 samples. With over 1 million cells from each platform analysed through the enrichment of accessible chromatin regions, transcription factor motifs and regulons, we identified epigenetic drivers associated with cancer transitions. Some epigenetic drivers appeared in multiple cancers (for example, regulatory regions of ABCC1 and VEGFA; GATA6 and FOX-family motifs), whereas others were cancer specific (for example, regulatory regions of FGF19, ASAP2 and EN1, and the PBX3 motif). Among epigenetically altered pathways, TP53, hypoxia and TNF signalling were linked to cancer initiation, whereas oestrogen response, epithelial-mesenchymal transition and apical junction were tied to metastatic transition. Furthermore, we revealed a marked correlation between enhancer accessibility and gene expression and uncovered cooperation between epigenetic and genetic drivers. This atlas provides a foundation for further investigation of epigenetic dynamics in cancer transitions.
Subject(s)
Epigenesis, Genetic , Gene Expression Regulation, Neoplastic , Neoplasms , Humans , Cell Hypoxia , Cell Nucleus , Chromatin/genetics , Chromatin/metabolism , Enhancer Elements, Genetic/genetics , Epigenesis, Genetic/genetics , Epithelial-Mesenchymal Transition , Estrogens/metabolism , Gene Expression Profiling , GTPase-Activating Proteins/metabolism , Neoplasm Metastasis , Neoplasms/classification , Neoplasms/genetics , Neoplasms/pathology , Regulatory Sequences, Nucleic Acid/genetics , Single-Cell Analysis , Transcription Factors/metabolismABSTRACT
Sex pheromones play crucial role in mating behavior of moths, involving intricate recognition mechanisms. While insect chemical biology has extensively studied type I pheromones, type II pheromones remain largely unexplored. This study focused on Helicoverpa armigera, a representative species of noctuid moth, aiming to reassess its sex pheromone composition. Our research unveiled two previously unidentified candidate type II sex pheromones-3Z,6Z,9Z-21:H and 3Z,6Z,9Z-23:H-in H. armigera. Furthermore, we identified HarmOR11 as an orphan pheromone receptor of 3Z,6Z,9Z-21:H. Through AlphaFold2 structural prediction, molecular docking, and molecular dynamics simulations, we elucidated the structural basis and key residues governing the sensory nuances of both type I and type II pheromone receptors, particularly HarmOR11 and HarmOR13. This study not only reveals the presence and recognition of candidate type II pheromones in a noctuid moth, but also establishes a comprehensive structural framework for PRs, contributing to the understanding of connections between evolutionary adaptations and the emergence of new pheromone types.
Subject(s)
Moths , Receptors, Pheromone , Sex Attractants , Animals , Sex Attractants/metabolism , Sex Attractants/chemistry , Moths/metabolism , Moths/physiology , Receptors, Pheromone/metabolism , Receptors, Pheromone/genetics , Male , Insect Proteins/metabolism , Insect Proteins/chemistry , Female , Molecular Docking Simulation , Amino Acid Sequence , Phylogeny , Molecular Dynamics Simulation , Sexual Behavior, Animal/physiologyABSTRACT
Retrotransposons are genomic DNA sequences that copy themselves to new genomic locations via RNA intermediates; LINE-1 is the only active and autonomous retrotransposon in the human genome. The mobility of LINE-1 is largely repressed in somatic tissues but is derepressed in many cancers, where LINE-1 retrotransposition is correlated with p53 mutation and copy number alteration (CNA). In cell lines, inducing LINE-1 expression can cause double-strand breaks (DSBs) and replication stress. Reanalyzing multiomic data from breast, ovarian, endometrial, and colon cancers, we confirmed correlations between LINE-1 expression, p53 mutation status, and CNA. We observed a consistent correlation between LINE-1 expression and the abundance of DNA replication complex components, indicating that LINE-1 may also induce replication stress in human tumors. In endometrial cancer, high-quality phosphoproteomic data allowed us to identify the DSB-induced ATM-MRN-SMC S phase checkpoint pathway as the primary DNA damage response (DDR) pathway associated with LINE-1 expression. Induction of LINE-1 expression in an in vitro model led to increased phosphorylation of MRN complex member RAD50, suggesting that LINE-1 directly activates this pathway.
Subject(s)
DNA Copy Number Variations/genetics , Long Interspersed Nucleotide Elements/genetics , Tumor Suppressor Protein p53/genetics , Cell Cycle/genetics , Cell Cycle Proteins/metabolism , DNA Breaks, Double-Stranded , DNA Repair/genetics , DNA-Binding Proteins/metabolism , Databases, Genetic , Gene Expression/genetics , Gene Expression Regulation, Neoplastic/genetics , Humans , Long Interspersed Nucleotide Elements/physiology , Neoplasms/genetics , Nuclear Proteins/metabolism , Proteins/genetics , Proteins/metabolism , Retroelements/genetics , S Phase Cell Cycle Checkpoints/genetics , Tumor Suppressor Protein p53/metabolismABSTRACT
BACKGROUND: Ecosystems are brimming with myriad compounds, including some at very low concentrations that are indispensable for insect survival and reproduction. Screening strategies for identifying active compounds are typically based on bioassay-guided approaches. RESULTS: Here, we selected two candidate odorant receptors from a major pest of cruciferous plants-the diamondback moth Plutella xylostella-as targets to screen for active semiochemicals. One of these ORs, PxylOR16, exhibited a specific, sensitive response to heptanal, with both larvae and adult P. xylostella displaying heptanal avoidance behavior. Gene knockout studies based on CRISPR/Cas9 experimentally confirmed that PxylOR16 mediates this avoidance. Intriguingly, rather than being involved in P. xylostella-host plant interaction, we discovered that P. xylostella recognizes heptanal from the cuticular volatiles of the parasitoid wasp Cotesia vestalis, possibly to avoid parasitization. CONCLUSIONS: Our study thus showcases how the deorphanization of odorant receptors can drive discoveries about their complex functions in mediating insect survival. We also demonstrate that the use of odorant receptors as a screening platform could be efficient in identifying new behavioral regulators for application in pest management.
Subject(s)
Aldehydes , Moths , Receptors, Odorant , Wasps , Animals , Ecosystem , LarvaABSTRACT
A novel two-step synthesis of ß-trifluoromethyl primary amines from readily available α-(trifluoromethyl)styrenes and phthalimide is developed. The first step involves a hydroamination between α-(trifluoromethyl)styrenes and phthalimide (PhthNH) with the assistance of a base. Next, the hydrazinolysis of the resulting N-(ß-trifluoromethyl-ß-arylethyl)phthalimides with hydrazine hydrate affords the desired N-(ß-trifluoromethyl-ß-arylethyl)amines.
ABSTRACT
Male moths utilize their pheromone communication systems to distinguish potential mates from other sympatric species, which contributes to maintaining reproductive isolation and even drives speciation. The molecular mechanisms underlying the evolution of pheromone communication systems are usually studied between closely-related moth species for their similar but divergent traits associated with pheromone production, detection, and/or processing. In this study, we first identified the functional differentiation in two orthologous pheromone receptors, OR14b, and OR16, in four Helicoverpa species, Helicoverpa armigera, H. assulta, H. zea, and H. gelotopoeon. To understand the substrate response specificity of these two PRs, we performed all-atom molecular dynamics simulations of OR14b and OR16 based on AlphaFold2 structural prediction, and molecular docking, allowing us to predict a few key amino acids involved in substrate binding. These candidate residues were further tested and validated by site-directed mutagenesis and functional analysis. These results together identified two hydrophobic amino acids at positions 164 and 232 are the determinants of the response specificity of HarmOR14b and HzeaOR14b to Z9-14:Ald and Z9-16:Ald by directly interacting with the substrates. Interestingly, in OR16 orthologs, we found that position 66 alone determines the specific binding of Z11-16:OH, likely via allosteric interactions. Overall, we have developed an effective integrated method to identify the critical residues for substrate selectivity of ORs and elucidated the molecular mechanism of the diversification of pheromone recognition systems.
Subject(s)
Moths , Receptors, Pheromone , Animals , Male , Receptors, Pheromone/genetics , Receptors, Pheromone/metabolism , Molecular Docking Simulation , Pheromones/genetics , Pheromones/metabolism , Moths/genetics , Moths/metabolismABSTRACT
BACKGROUND: The purpose of this study was to study the effect of STING-IFN-I pathway on incision induced postoperative pain in rats and its possible mechanisms. METHODS: The pain thresholds were evaluated by measuring the mechanical withdrawal threshold and the thermal withdrawal latency. The satellite glial cell and macrophage of DRG were analyzed. The expression of STING, IFN-a, P-P65, iNOS, TNF-α, IL-1ß and IL-6 in DRG was evaluated. RESULTS: The activation of STING-IFN-I pathway can reduce the mechanical hyperalgesia, thermal hyperalgesia, down-regulate the expression of P-P65, iNOS, TNF-α, IL-1ß and IL-6, and inhibit the activation of satellite glial cell and macrophage in DRG. CONCLUSIONS: The activation of STING-IFN-I pathway can alleviate incision induced acute postoperative pain by inhibiting the activation of satellite glial cell and macrophage, which reducing the corresponding neuroinflammation in DRG.
Subject(s)
Ganglia, Spinal , Tumor Necrosis Factor-alpha , Rats , Animals , Rats, Sprague-Dawley , Tumor Necrosis Factor-alpha/metabolism , Interleukin-6/metabolism , Neuroinflammatory Diseases , Hyperalgesia/metabolism , Pain, Postoperative/drug therapy , Pain, Postoperative/metabolismABSTRACT
A practical and efficient solvent-free synthesis of ß-trifluoromethyl-substituted phosphonates and phosphine oxides via hydrophosphonylation and hydrophosphinylation of α-(trifluoromethyl)styrenes with H-phosphonates and H-phosphine oxides, respectively, was developed. The reaction proceeded smoothly within 2 h at room temperature without the cleavage of the rather fragile C-F bond in α-(trifluoromethyl)styrenes and afforded a wide variety of structurally diverse and valuable ß-trifluoromethyl-containing phosphonates and phosphine oxides in moderate to good yields. This protocol features mild conditions, wide substrate scope, simple manipulation, and excellent functional group compatibility.
ABSTRACT
BACKGROUND: Fiberoptic bronchoscopy (FOB) and bronchoscopic biopsy are the established methods for diagnosing and treating sputum crust. However, sputum crust in concealed locations can sometimes be missed or undiagnosed, even with bronchoscopy. CASE PRESENTATION: We present the case of a 44-year-old female patient who experienced initial extubation failure and postoperative pulmonary complications (PPCs) due to the missed diagnosis of sputum crust by FOB and low-resolution bedside chest X-ray. The FOB examination showed no apparent abnormalities prior to the first extubation, and the patient underwent tracheal extubation 2 h after aortic valve replacement (AVR). However, she was reintubated 13 h after the first extubation due to a persistent irritating cough and severe hypoxemia, and a bedside chest radiograph revealed pneumonia and atelectasis. Upon performing a repeat FOB examination prior to the second extubation, we serendipitously discovered the presence of sputum crust at the end of the endotracheal tube. Subsequently, we found that the sputum crust was mainly located on the tracheal wall between the subglottis and the end of the endotracheal tube during the "Tracheobronchial Sputum Crust Removal" procedure, and most of the crust was obscured by the retained endotracheal tube. The patient was discharged on the 20th day following therapeutic FOB. CONCLUSION: FOB examination may miss specific areas in endotracheal intubation (ETI) patients, particularly the tracheal wall between the subglottis and distal end of the tracheal catheter, where sputum crust can be concealed. When diagnostic examinations with FOB are inconclusive, high-resolution chest CT can be helpful in identifying hidden sputum crust.