Evaluating nitrogen dynamic and utilization under controlled-release fertilizer application for sunflowers in an arid region: Experimental and modeling approach.

Traditional nitrogen fertilizers (TNF), such as urea, percolate easily in arid fields, posing low nitrogen use efficiency (NUE) and a high non-point pollution risk. Controlled-release fertilizers (CRF) exhibit significantly lower deep seepage, rendering it a favorable choice in arid fields due to its ability to enhance NUE through slow-release mechanisms. However, current models do not fully account for the soil nitrogen dynamics and crop interactions under controlled-release conditions, and lack quantification. This study improved the APSIM model by adjustment the urea hydrolysis rate to assess the impact of CRF and TNF applications on soil health, crop growth, and water quality. Calibration and validation were conducted through experiments in the Hetao Irrigation District of China from 2019 to 2020, with different nitrogen application rates (135, 225, and 315 kg/ha). The model accurately simulated soil NO3-N concentration (SNC), cumulative NO3-N leaching (CNL), nitrogen uptake (NU), and sunflower yield. During the validation process, R2 and Nash-Sutcliffe efficiency (NSE) values were both above 0.75. Results indicated that the average SNC, NU, and yield under CRF application were significantly higher than those under TNF application, with increases of 38.62%, 44.92%, and 18.38%, respectively. Notably, the proportion of soil nitrogen available (PSNA), a novel metric proposed in this study, was 159.50% higher in the 0-40 cm soil layer with CRF compared to TNF. Additionally, CNL and NO3-N leaching loss rate (NLLR) decreased by 25.76% and 25.77%, respectively. Scenario simulations indicated that the optimal fertilization strategy for this region is to use 180-193.5 kg/ha of CRF with a release period of 80-85.5 d to balance agricultural productivity and ecological protection. This study confirms the significant advantages of CRF in enhancing yield, improving nitrogen management, and promoting environmental sustainability, providing a scientific basis for CRF management strategies and supporting the shift towards more efficient and environmentally friendly agricultural practices.

Impact of fertilization depth on sunflower yield and nitrogen utilization: a perspective on soil nutrient and root system compatibility.

Introduction: The depth of fertilizer application significantly influences soil nitrate concentration (SNC), sunflower root length density (RLD), sunflower nitrogen uptake (SNU), and yield. However, current studies cannot precisely capture subtle nutrient variations between soil layers and their complex relationships with root growth. They also struggle to assess the impact of different fertilizer application depths on sunflower root development and distribution as well as their response to the spatial and temporal distribution of nutrients. Methods: The Agricultural Production Systems sIMulator (APSIM) model was employed to explore the spatial and temporal patterns of nitrogen distribution in the soil at three controlled-release fertilizer (CRF) placement depths: 5, 15, and 25 cm. This study investigated the characteristics of the root system regarding nitrogen absorption and utilization and analyzed their correlation with sunflower yield formation. Furthermore, this study introduced the modified Jaccard index (considering the compatibility between soil nitrate and root length density) to analyze soil-root interactions, providing a deeper insight into how changes in CRF placement depth affect crop growth and nitrogen uptake efficiency. Results: The results indicated that a fertilization depth of 15 cm improved the modified Jaccard index by 6.60% and 7.34% compared to 5 cm and 25 cm depths, respectively, maximizing sunflower yield (an increase of 9.44%) and nitrogen absorption rate (an increase of 5.40%). This depth promoted a greater Root Length Density (RLD), with an increases of 11.95% and 16.42% compared those at 5 cm and 25 cm, respectively, enhancing deeper root growth and improving nitrogen uptake. In contrast, shallow fertilization led to higher nitrate concentrations in the topsoil, whereas deeper fertilization increased the nitrate concentrations in the deeper soil layers. Discussion: These results provide valuable insights for precision agriculture and sustainable soil management, highlighting the importance of optimizing root nitrogen absorption through tailored fertilization strategies to enhance crop production efficiency and minimize environmental impact.

The clinicopathological significance and prognostic value of PD-L1 in oral squamous cell carcinoma.

OBJECTIVE: To investigate the relationship between the expression of PD-L1 in OSCC and the clinicopathological features and prognosis of patients. METHODS: We retrospectively analyzed the clinicopathological data and prognosis of 381 OSCC patients. Immunohistochemical staining was performed on OSCC tumor specimens, and the expression level of PD-L1 was evaluated according to the combined positive score (CPS). Kaplan-Meier analysis was used to identify the effect of PD-L1 expression and clinicopathological features on the prognosis of patients. Univariate and multivariate Cox regression analyses were conducted to determine the hazard factors affecting the prognosis of patients. RESULTS: PD-L1 overexpression was significantly associated with cervical lymph node metastasis (p = 0.018), worse clinical stage (p = 0.022), worse tumor differentiation (p = 0.046), and worse depth of invasion (DOI) (p = 0.003). Poorer clinical stage and degree of tumor differentiation were significantly associated with poorer OS and DSS in patients. PD-L1 expression was not associated with prognosis in patients with OSCC. CONCLUSIONS: High PD-L1 expression was significantly associated with higher tumor malignancy in OSCC patients. Poorer clinical stage and degree of tumor differentiation were associated with poor prognosis in OSCC patients. Our results may help clinicians develop more appropriate individualized treatment strategies for their patients, thus improving their outcomes.

Circ-CDK8 regulates SLC7A11-mediated ferroptosis by inhibiting miR-615-5p to promote progression in oral squamous cell carcinomas.

Introduction: Ferroptosis is a new mode of programmed cell death distinct from necrosis, apoptosis, and autophagy, induced by iron-ion-dependent lipid peroxide accumulation. Circular RNAs are a class of endogenous non-coding RNAs that regulate the biological behavior of tumors. However, the role of circ-CDK8 in regulating ferroptosis, migration, and invasion of oral squamous cell carcinoma (OSCC) remains unknown. Methods: The effect of circ-CDK8 on OSCC cell ferroptosis, migration, and invasion was evaluated using CCK-8, wound healing, transwell, reactive oxygen species (ROS), malondialdehyde (MDA), and GSH assays and Western blotting. Bioinformatics analyses and luciferase reporter assays were performed and revealed targeted relationships between circ-CDK8 and miR-615-5p, miR-615-5p and SLC7A11. Interference with circ-CDK8 expression reduced SLC7A11 expression by sponging miR-615-5p, suppressed OSCC cell migration and invasion, and promoted ferroptosis by increasing ROS, MDA, and iron levels and decreasing GSH and GPX4 levels in OSCC cells. Furthermore, in vivo, animal experiments confirmed that circ-CDK8 interference inhibited OSCC cell proliferation and SLC7A11 expression. Results: Collectively, this study revealed a novel strategy to upregulate erastin-induced ferroptosis in OSCC cells via the circ-CDK8/miR-615-5p/SLC7A11 axis, providing new insights into OSCC and a potential therapeutic strategy for OSCC.

Role of O-linked N-acetylglucosamine protein modification in oxidative stress-induced autophagy: a novel target for bone remodeling.

O-linked N-acetylglucosamine protein modification (O-GlcNAcylation) is a dynamic post-translational modification (PTM) involving the covalent binding of serine and/or threonine residues, which regulates bone cell homeostasis. Reactive oxygen species (ROS) are increased due to oxidative stress in various pathological contexts related to bone remodeling, such as osteoporosis, arthritis, and bone fracture. Autophagy serves as a scavenger for ROS within bone marrow-derived mesenchymal stem cells, osteoclasts, and osteoblasts. However, oxidative stress-induced autophagy is affected by the metabolic status, leading to unfavorable clinical outcomes. O-GlcNAcylation can regulate the autophagy process both directly and indirectly through oxidative stress-related signaling pathways, ultimately improving bone remodeling. The present interventions for the bone remodeling process often focus on promoting osteogenesis or inhibiting osteoclast absorption, ignoring the effect of PTM on the overall process of bone remodeling. This review explores how O-GlcNAcylation synergizes with autophagy to exert multiple regulatory effects on bone remodeling under oxidative stress stimulation, indicating the application of O-GlcNAcylation as a new molecular target in the field of bone remodeling.

Research on the Influence of Cold Drawing and Aging Heat Treatment on the Structure and Mechanical Properties of GH3625 Alloy.

With the development of the petroleum industry, the demand for materials for oilfield equipment is becoming increasingly stringent. The strength increase brought about by time strengthening is limited in meeting the needs of equipment development. The GH3625 alloy with different strength levels can be obtained through cold deformation and heat treatment processes. A study should be carried out to further develop the potential mechanical properties of GH3625. In this study, the GH3625 alloy was cold drawn with different reductions in area (0-30%) and heat treated, and its mechanical properties were tested. The microstructure of the alloy during deformation and heat treatment was characterized by methods such as optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) based on the principles of physical metallurgy. The strength increase caused by dislocation strengthening was calculated from the dislocation density, tested by X-ray diffraction (XRD). The calculated value was compared to the measured value, elucidating the strengthening effect of cold deformation and heat treatment. The results showed that the yield strength and yield ratio of the cold-drawn alloy significantly reduced after aging at 650 °C and 760 °C. Heat treatment can make a cold-deformed material recover, ablate dislocations, and greatly reduce the dislocation density in the microstructure of the GH3625 alloy, which was the main factor in the decrease in yield strength. The work-hardening gradient of the cold-drawn material varied greatly with different reductions in area. When the reduction in area was small (10%), the hardness gradient was obvious. When it increased to 30%, the alloy was uniformly strengthened as the deformation was transmitted to the axis. This study can provide more mechanical performance options for GH3625 alloy structural components in the petrochemical industry.

Quantification of the provenance contribution and sedimentary mixing effect of sediments in the Yellow River Basin, China.

Quantifying the source contributions of sediments in large fluvial systems with active wind erosion problems has crucial implications for understanding morphological evolution and ecological progression in the Earth system. Much effort have been focused on characterizing sediments of the Yellow River, but quantitation of the sediment source proportions at the basin-wide scale is lacking. To this end, the research aims to quantitatively elucidate the potential source contributions of sediments in the Yellow River based on geochemical characteristics and sediment fingerprinting technique, in order to identify sedimentary mixing effect and propose sustainable development strategies. In total, samples of four source groups (n = 107) and target floodplain sediments (n = 61) were collected and tested for elemental composition, grain size, magnetic susceptibility, and quartz grain microtextures. The results indicated that the optimal tracer combination was determined as P, Zn, and Ca. The average contributions of the "Tibetan Plateau", "Sandy deserts-Loess Plateau", "Loess Plateau", and "Loess Plateau-Qinling Mountains" source groups to the target sediments were 23.0 %, 21.5 %, 31.6 %, and 23.9 %, respectively. The accuracy of source apportionments was supported by the goodness of fit (GOF) and virtual mixtures tests. Meanwhile, large amounts of debris from surrounding mountains was transported to the Loess Plateau through fluvial processes and ultimately mixed with aeolian deposits, leading to sedimentary mixing effect. To maintain water balance and minimize erosion risk, the drought-resistant perennial planting and moderate grazing were recommended. The findings are instrumental in promoting soil and water conservation and disclosing fluvial and aeolian interaction on a global scale.

O-GlcNAcylation: roles and potential therapeutic target for bone pathophysiology.

O-linked N-acetylglucosamine (O-GlcNAc) protein modification (O-GlcNAcylation) is a critical post-translational modification (PTM) of cytoplasmic and nuclear proteins. O-GlcNAcylation levels are regulated by the activity of two enzymes, O-GlcNAc transferase (OGT) and O­GlcNAcase (OGA). While OGT attaches O-GlcNAc to proteins, OGA removes O-GlcNAc from proteins. Since its discovery, researchers have demonstrated O-GlcNAcylation on thousands of proteins implicated in numerous different biological processes. Moreover, dysregulation of O-GlcNAcylation has been associated with several pathologies, including cancers, ischemia-reperfusion injury, and neurodegenerative diseases. In this review, we focus on progress in our understanding of the role of O-GlcNAcylation in bone pathophysiology, and we discuss the potential molecular mechanisms of O-GlcNAcylation modulation of bone-related diseases. In addition, we explore significant advances in the identification of O-GlcNAcylation-related regulators as potential therapeutic targets, providing novel therapeutic strategies for the treatment of bone-related disorders.

Prognostic effect of surgical treatment in elderly oral squamous cell carcinoma patients: A retrospective study.

BACKGROUND: Oral squamous cell carcinoma (OSCC) is one of the most prevalent malignant tumors in head and neck. However, few studies have focused on the postoperative prognosis of elderly OSCC patients undergoing surgical resection and reconstruction. METHODS: We conducted a retrospective study of 349 patients diagnosed OSCC in the Department of Oral and Maxillofacial Surgery, The Affiliated Hospital of Qingdao University from January 2016 to December 2022. Demographic and clinicopathological characteristics were recorded. Kaplan-Meier analysis was performed to identify the impact of age and reconstruction types on the prognosis of OSCC patients. Univariable regression analysis and multivariable Cox analysis were conducted to find independent prognostic factors of the younger and elderly OSCC patients. RESULTS: Among 349 OSCC patients included in this retrospective study, 241 (69.1 %) were elderly patients and 108 (30.9 %) were younger patients. The two groups were comparable according to the demographic records. The elderly group presented a better recurrence-specific prognosis than that of the younger group (RFS: p = 0.0324). There are no remarkable differences on the prognosis of different reconstructive types. Gender, current address, life habit, invasion patterns, and TNM stage were identified as independent prognostic factors of the younger and elderly OSCC patients. CONCLUSION: Elderly OSCC patients achieve a better recurrence-free survival than that of the younger patients. Meanwhile, the recurrence of OSCC patients is independent of their demographic and clinicopathological features. Elderly OSCC patients will benefit from aggressive surgical treatment as the younger patients.

Primary cutaneous anaplastic large-cell lymphoma resembling infratemporal space infection: a case report.

BACKGROUND: Primary cutaneous anaplastic large-cell lymphoma (PC-ALCL) is a rare T-cell lymphoma belonging to the CD30 + T-cell lymphoproliferative disorders. The case of PC-ALCL in the temporal region is exceedingly rare. Herein, we report a case of PC-ALCL involving the temporal region mimicking infratemporal space infection. CASE PRESENTATION: A 78-year-old woman presented to maxillofacial surgery service with a 6-month history of swelling and pain in the left side of her face. Laboratory investigations found an elevated C-reactive protein (CRP). Imaging findings showed enlarged lymph nodes and extensive thickening of subcutaneous tissue of the left temples. Based on these findings, the infratemporal space infection was suspected initially. The patient underwent incision and drainage, and we unexpectedly found no pus in the lesion area. Incisional biopsy showed necrosis and extensive involvement of the left temples by a diffuse infiltrate containing large, atypical cells. The tumor cells were positive for CD30, CD3, Ki67. They were negative for ALK (SP8), CD5, CD8, CD20 and PAX5. After considering these findings, a diagnosis of PC-ALCL was rendered. The patient was admitted to the lymphoma department for systemic chemotherapy and no relapse occurred during a follow-up period of six months. CONCLUSIONS: This report suggests that if there are suspicious intraoperative manifestations, carrying out a biopsy simultaneously, using Hematoxylin and eosin (HE) staining, and a comprehensive Immunohistochemistry (IHC) panel are essential to diagnosing PC-ALCL to prevent misdiagnosis.

Heterogeneity of molecular subtyping and therapy-related marker expression in primary tumors and paired lymph node metastases of small cell lung cancer.

The classification of molecular subtypes and the identification of targetable molecules have been proposed for small cell lung cancer (SCLC) patients. Our aim was to investigate whether the expression of these markers evaluated using lymph node (LN) metastases represents that of primary tumors. We enrolled 46 surgically resected SCLC patients' primary tumors and paired mediastinal LN metastases. The protein expression of subtype-defining markers (ASCL1, NEUROD1, POU2F3, and YAP1) and therapeutic markers (DLL3, MYC, PD-L1, and MHC I) was examined by immunohistochemistry and was correlated with clinicopathological parameters and prognoses. In primary and metastatic tumors, the expression of these markers was 78.3% and 87.0%, 50.0% and 63.0%, 13.0% and 6.5%, 17.4% and 15.2%, 84.8% and 87.0%, 17.4% and 6.5%, 50.0% and 34.8%, and 60.9% and 37.0%, respectively. Positive tumor PD-L1 expression was less present in LN metastases (p = 0.015), and the same was true for MHC I expression (p = 0.036). NEUROD1 and DLL3 expression levels in metastatic tumors were stronger (p < 0.001 and p = 0.002, respectively); conversely, POU2F3, MYC, PD-L1, and MHC I expression levels were weaker (p = 0.018, p = 0.019, p = 0.001, and p < 0.001, respectively). In 15 (32.6%) patients, we observed a change in the molecular subtyping pattern, and a higher number of neuroendocrine (NE)-high phenotype patients were diagnosed when using the LN specimens (91.3% vs. 84.8%). TNM stage and postoperative chemotherapy were independent prognostic factors in surgically resected SCLC patients, and no prognostic differences were found among molecular subtypes. This study highlights the discordance of subtype-specific proteins and therapeutic markers between SCLC primary tumors and LN metastases. Additionally, our findings have therapeutic and prognostic implications and warrant further clinical investigation.

Functional significance of O-linked N-acetylglucosamine protein modification in regulating autophagy.

Autophagy is a core molecular pathway that preserves cellular and organismal homeostasis. Being susceptible to nutrient availability and stress, eukaryotic cells recycle or degrade internal components via membrane transport pathways to provide sustainable biological molecules and energy sources. The dysregulation of this highly conserved physiological process has been strongly linked to human disease. Post-translational modification, a mechanism that regulates protein function, plays a crucial role in autophagy regulation. O-linked N-acetylglucosamine protein modification (O-GlcNAcylation), a monosaccharide post-translational modification of intracellular proteins, is essential in nutritional and stress regulatory mechanisms. O-GlcNAcylation has emerged as an essential regulatory mechanism of autophagy. It regulates autophagy throughout its lifetime by targeting the core components of the autophagy regulatory network. This review provides an overview of the O-GlcNAcylation of autophagy-associated proteins and their regulation and function in the autophagy pathway. Therefore, this article may contribute to further understanding of the role of O-GlcNAc-regulated autophagy and provide new perspectives for the treatment of human diseases.

Review: Protein O-GlcNAcylation regulates DNA damage response: A novel target for cancer therapy.

The DNA damage response (DDR) safeguards the stable genetic information inheritance by orchestrating a complex protein network in response to DNA damage. However, this mechanism can often hamper the effectiveness of radiotherapy and DNA-damaging chemotherapy in destroying tumor cells, causing cancer resistance. Inhibiting DDR can significantly improve tumor cell sensitivity to radiotherapy and DNA-damaging chemotherapy. Thus, DDR can be a potential target for cancer treatment. Post-translational modifications (PTMs) of DDR-associated proteins profoundly affect their activity and function by covalently attaching new functional groups. O-GlcNAcylation (O-linked-N-acetylglucosaminylation) is an emerging PTM associated with adding and removing O-linked N-acetylglucosamine to serine and threonine residues of proteins. It acts as a dual sensor for nutrients and stress in the cell and is sensitive to DNA damage. However, the explanation behind the specific role of O-GlcNAcylation in the DDR remains remains to be elucidated. To illustrate the complex relationship between O-GlcNAcylation and DDR, this review systematically describes the role of O-GlcNAcylation in DNA repair, cell cycle, and chromatin. We also discuss the defects of current strategies for targeting O-GlcNAcylation-regulated DDR in cancer therapy and suggest potential directions to address them.

Dynamic real-time forecasting technique for reclaimed water volumes in urban river environmental management.

In recent years, the utilization of wastewater recycling as an alternative water source has gained significant traction in addressing urban water shortages. Accurate prediction of wastewater quantity is paramount for effective urban river water resource management. There is an urgent need to develop advanced forecasting technologies to further enhance the accuracy and efficiency of water quantity predictions. Decomposition ensemble models have shown excellent predictive capabilities but are challenged by boundary effects when decomposing the original data sequence. To address this, a rolling forecast decomposition ensemble scheme was developed. It involves using a machine learning (ML) model for prediction and progressively integrating prediction outcomes into the original sequence using complementary ensemble empirical mode decomposition with adaptive noise (CEEMDAN). Long short-term memory (LSTM) is then applied for sub-signal prediction and ensemble. The ML-CEEMDAN-LSTM model was introduced for wastewater quantity prediction, compared with non-decomposed ML models, CEEMDAN-based LSTM models, and ML-CEEMDAN-based LSTM models. Three ML algorithms-linear regression (LR), gradient boosting regression (GBR), and LSTM-were examined, using real-time prediction data and historical monitoring data, with historical data selected using the decision tree method. The study used daily water volumes data from two reclaimed water plants, CH and WQ, in Beijing. The results indicate that (1) ML models varied in their selection of real-time factors, with LR performing best among ML models during testing; (2) the ML-CEEMDAN-LSTM model consistently outperformed ML models; (3) the ML-CEEMDAN-LSTM hybrid model performed better than the CEEMDAN-LSTM model across different seasons. This study offers a reliable and accurate approach for reclaimed water volumes forecasting, critical for effective water environment management.

p16 and p53 can Serve as Prognostic Markers for Head and Neck Squamous Cell Carcinoma.

OBJECTIVE: The present study aimed to explore the expression and clinical significance of human papilloma virus-related pathogenic factors (p16, cyclin D1, p53) in patients with head and neck squamous cell carcinoma (HNSCC) and construct a predictive model. METHODS: The Cancer Genome Atlas was used to obtain clinical data for 112 patients with HNSCC. Expression of p16, p53, and cyclin D1 was quantified. We used the survival package of the R program to set the cut-off value. Values above the cut-off were considered positive, while values below the cut-off were negative. Kaplan-Meier analysis and univariate and multivariate Cox regression analyses were performed to investigate prognostic clinicopathological indicators and the expression of p16, p53, and cyclin D1. A predictive model was constructed based on the results of multifactor Cox regression analysis, and the accuracy of the predictive model was verified through final calibration analysis. Follow-up of patients with HNSCC at the Affiliated Hospital of Binzhou Medical University was conducted from 2015 to 2017, and reliability of the predictive model was validated based on follow-up data and molecular expression levels. RESULTS: According to the results, expression of p16 and p53 was significantly associated with prognosis (P < .05). The predictive model constructed based on the expression levels of p16 and p53 was useful for evaluating the prognosis of patients with HNSCC. The predictive model was validated using follow-up data obtained from the hospital, and the trend of the follow-up results was consistent with the predictive model. CONCLUSION: p16 and p53 can be used as key indicators to predict the prognosis of HNSCC patients and as critical immunohistochemical indicators in clinical practice. The survival model constructed based on p16 and p53 expression levels reliably predicts patient prognosis.

The mitochondrial regulation in ferroptosis signaling pathway and its potential strategies for cancer.

Ferroptosis is an iron-dependent regulated cell death, mainly manifested by the production of reactive oxygen species and accumulation of lipid peroxides. It is distinct from other forms of cell death with regard to morphology and biochemistry, particularly in disrupting mitochondrial function. Mitochondria are essential compartments where the organism generates energy and are closely associated with the fate of ferroptosis. Currently, researchers focus on the potential value of ferroptosis and mitochondria for overcoming drug sensitivity and assisting in cancer therapy. In this review, we summarize the main mechanisms of ferroptosis (the GPX4-realated pathway, FSP1-related pathway, and iron metabolism pathway) and the functions and regulating pathways of mitochondria (the TCA cycle, oxidative phosphorylation, mitochondrial regulation of iron ions, and mtDNA) in ferroptosis. We believe that exploring the role of mitochondria in ferroptosis will help us understand the potential regulatory mechanisms of ferroptosis in cancer and help us find new therapeutic targets.

The role of novel programmed cell death in head and neck squamous cell carcinoma: from mechanisms to potential therapies.

Head and neck squamous cell carcinoma (HNSCC) is a common oral cancer with poor prognosis and for which no targeted therapeutic strategies are currently available. Accumulating evidence has demonstrated that programmed cell death (PCD) is essential in the development of HNSCC as a second messenger. PCD can be categorized into numerous different subroutines: in addition to the two well-known types of apoptosis and autophagy, novel forms of programmed cell death (e.g., necroptosis, pyroptosis, ferroptosis, and NETosis) also serve as key alternatives in tumorigenesis. Cancer cells are not able to avoid all types of cell death simultaneously, since different cell death subroutines follow different regulatory pathways. Herein, we summarize the roles of novel programmed cell death in tumorigenesis and present our interpretations of the molecular mechanisms with a view to the development of further potential therapies.

Molecular subtypes, predictive markers and prognosis in small-cell lung carcinoma.

AIMS: A new molecular subtype classification was proposed for small-cell lung carcinoma (SCLC). We aimed to further validate the classification in various SCLC patient samples using immunohistochemistry (IHC) to highlight its clinical significance. METHODS: We analysed the protein expression of four subtype (achaete-scute family BHLH transcription factor 1 (ASCL1), neuronal differentiation 1 (NEUROD1), POU class 2 homeobox 3 (POU2F3) and Yes1-associated transcriptional regulator (YAP1)) and two predictive markers (delta-like ligand 3 (DLL3) and MYC) using IHC in 216 specimens from 195 SCLC patients, including 21 pairs of resected biopsy tumours. Associations among molecular subtypes, clinicopathological features and prognostic implications were also explored. RESULTS: The ASCL1, NEUROD1, POU2F3, YAP1, DLL3 and MYC-positive expression rates were 70.3%, 56.9%, 14.9%, 19.0%, 75.4% and 22.6%, respectively. DLL3 expression had positive and negative associations with that of ASCL1 and POU2F3/YAP1, respectively, whereas MYC had the opposite effect. Strong associations of ASCL1 (Ρ=0.8603, p<0.0001), NEUROD1 (Ρ=0.8326, p<0.0001), POU2F3 (Ρ=0.6950, p<0.0001) and YAP1 (Ρ=0.7466, p<0.0001) expressions were detected between paired resected biopsy tumours. In addition to SCLC-A (ASCL1-dominant), SCLC-N (NEUROD1-dominant) and SCLC-P (POU2F3-dominant), unsupervised hierarchical cluster analyses identified a fourth, quadruple-negative SCLC subtype (SCLC-QN) characterised by the low expression of all four subtype-specific proteins, and 55.4% (n=108), 27.2% (n=53), 11.8% (n=23) and 5.6% (n=11) were categorised as SCLC-A, SCLC-N, SCLC-P and SCLC-QN, respectively. Significant enrichment of SCLC-P in the combined SCLC cohort was observed, and adenocarcinoma was more prevalent in SCLC-A, while large-cell neuroendocrine carcinoma was more commonly seen in SCLC-P. No survival difference was found among molecular subtypes. CONCLUSIONS: Our results provide clinical insights into the diagnostic, prognostic and predictive significance of SCLC molecular subtype classifications.