Comparative Study of Circulating MMP-7, CCL18, KL-6, SP-A, and SP-D as Disease Markers of Idiopathic Pulmonary Fibrosis

Serum biomarkers in neuroendocrine cell hyperplasia of infancy

BACKGROUND

Neuroendocrine cell hyperplasia of infancy (NEHI) is a form of childhood interstitial lung disease of unknown origin associated with hyperplasia of pulmonary neuroendocrine cells (PNECs). Diagnosis is based on the characteristic clinical picture and typical radiological imaging, and, in some cases, on lung biopsies. To date, no biochemical indicators of the disease have been identified.

AIM

We aimed to determine biomarkers that could be useful in the management of children diagnosed with NEHI.

METHODS

Patients with NEHI and healthy children were enrolled. Concentrations of serum biomarkers secreted by PNECs (calcitonin gene-related peptide and gastrin-releasing peptide) and biomarkers of the destruction of alveolar capillary membrane (surfactant proteins A and D [SP-A and SP-D]; glycoprotein Krebs von den Lungen-6 [KL-6]; metalloproteinases 7 and 9 [MMP-7 and MMP-9]; tissue inhibitor of metalloprotease 1) were measured.

RESULTS

Fifty-two children with NEHI and 23 healthy children were included in the study. The median age of children with NEHI was 3.9 years. There were no differences in serum levels of biomarkers secreted by PNECs between groups. KL-6 levels were significantly higher in children with NEHI than in healthy ones (median 119.6 vs. 92.1 U/mL, p = 0.003); however, concentrations of KL-6 were low in both groups. No significant differences existed between groups for the remaining biomarkers associated with the destruction of the alveolar-capillary membrane.

CONCLUSIONS

Measurement of serum biomarkers released by PNECs and those associated with the destruction of the alveolar-capillary membrane does not appear to be useful in the management of children with NEHI.

The fibroblast activation protein alpha as a biomarker of pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a rare, chronic, and progressive interstitial lung disease with an average survival of approximately 3 years. The evolution of IPF is unpredictable, with some patients presenting a relatively stable condition with limited progression over time, whereas others deteriorate rapidly. In addition to IPF, other interstitial lung diseases can lead to pulmonary fibrosis, and up to a third have a progressive phenotype with the same prognosis as IPF. Clinical, biological, and radiological risk factors of progression were identified, but no specific biomarkers of fibrogenesis are currently available. A recent interest in the fibroblast activation protein alpha (FAPα) has emerged. FAPα is a transmembrane serine protease with extracellular activity. It can also be found in a soluble form, also named anti-plasmin cleaving enzyme (APCE). FAPα is specifically expressed by activated fibroblasts, and quinoline-based specific inhibitors (FAPI) were developed, allowing us to visualize its distribution in vivo by imaging techniques. In this review, we discuss the use of FAPα as a useful biomarker for the progression of lung fibrosis, by both its assessment in human fluids and/or its detection by imaging techniques and immunohistochemistry.

Prognostic performance of Krebs von den Lungen-6, surfactant protein A, surfactant protein D levels in the serum and bronchoalveolar lavage fluid in chronic fibrosing interstitial pneumonia: a retrospective study

BACKGROUND

The serum markers Krebs von den Lungen-6 (KL-6), surfactant protein A (SP-A), and surfactant protein D (SP-D) have been used for the diagnosis, differential diagnosis, and prognosis prediction of interstitial pneumonia. However, the significance of measuring the serum and bronchoalveolar lavage fluid (BALF) KL-6, SP-D, and SP-A levels in predicting the prognosis of chronic fibrosing interstitial pneumonia (CFIP), idiopathic pulmonary fibrosis, and idiopathic nonspecific interstitial pneumonia remains unclear. We aimed to clarify the significance of measuring the serum and BALF KL-6, SP-A, and SP-D levels in predicting the prognosis of patients with CFIP.

METHODS

Among 173 patients who were diagnosed with CFIP between September 2008 and February 2021, 39 who underwent bronchoalveolar lavage were included in this study. Among these, patients experiencing an annual decrease in forced vital capacity (FVC) of ≥10% or those facing challenges in undergoing follow-up pulmonary function tests owing to significant deterioration in pulmonary function were categorized as the rapidly progress group. Conversely, individuals with an annual decrease in the FVC of <10% were classified into the slowly progress group. The serum and BALF KL-6, SP-D, and SP-A levels, as well as BALF/serum SP-D and SP-A ratios were compared between the two groups.

RESULTS

Among the patients with CFIP, the BALF SP-D level (p=0.0111), BALF SP-A level (p<0.0010), BALF/serum SP-D ratio (p=0.0051), and BALF/serum SP-A ratio (p<0.0010) were significantly lower in the rapidly than in the slowly progress group (p<0.0010). The receiver operating characteristics analysis results demonstrated excellent performance for diagnosing patients with CFIP, with the BALF SP-D level (area under the curve [AUC], 0.7424), BALF SP-A level (AUC, 0.8842), BALF/serum SP-D ratio (AUC, 0.7673), and BALF/serum SP-A ratio (AUC, 0.8556). Moreover, the BALF SP-A level showed a notably superior CFIP diagnostic capability. Survival analysis using the Kaplan-Meier method revealed that patients with a BALF SP-A level of <1500 ng/mL and BALF/serum SP-A ratio of <15.0 had poor prognoses.

CONCLUSIONS

Our results suggest that BALF SP-A measurement may be useful for predicting the prognosis in patients with CFIP.

[Diagnosis of anti-melanoma differentiation-associated gene 5 antibody-positive dermatomyositis led by sarcoplasmic myxovirus resistance protein A expression on muscle pathology]

A 44-year-old woman with autism spectrum disorder developed bulbar symptoms and generalized muscle weakness 7 months before referral. Six months before, she was administered glucocorticoid for liver involvement. During the course, while she presented alopecia, skin ulcers, and poikiloderma, hyperCKemia was observed only twice. Due to complications including cardiac involvement and hearing loss as well, we suspected mitochondrial disease and performed a muscle biopsy. The muscle pathology showed sarcoplasmic myxovirus resistance A (MxA) expression with scattered pattern. Since anti-melanoma differentiation-associated gene 5 (MDA5) antibody was detected, we diagnosed the patient with anti-MDA5 antibody-positive dermatomyositis (DM). We reinforced immunosuppressive therapy, and her clinical symptoms and liver involvement were improved. When we diagnose a case of anti-MDA5 antibody-positive DM who is difficult to make clinical diagnosis, it may be valuable to evaluate sarcoplasmic MxA expression on muscle pathology.

Circulating biomarkers and progression of idiopathic pulmonary fibrosis: data from the INMARK trial

Background

We used data from the INMARK trial to investigate associations between circulating biomarkers of extracellular matrix (ECM) turnover, inflammation and epithelial dysfunction and disease progression in subjects with idiopathic pulmonary fibrosis (IPF).

Methods

Subjects with IPF and forced vital capacity (FVC) ≥80% predicted were randomised 1:2 to receive nintedanib 150 mg twice daily or placebo for 12 weeks followed by open-label nintedanib for 40 weeks. Associations between baseline biomarker levels and the proportion of subjects with disease progression (decline in FVC ≥10% predicted or death) over 52 weeks were assessed in subjects randomised to placebo using logistic regression. Associations between baseline demographic/clinical characteristics and biomarker levels and disease progression over 52 weeks were analysed using multivariate models.

Results

Of 230 subjects who received placebo for 12 weeks then open-label nintedanib for 40 weeks, 70 (30.4%) had disease progression over 52 weeks. Baseline levels of CRPM (C-reactive protein (CRP) degraded by matrix metalloproteinase (MMP)-1/8), C3M (collagen 3 degraded by MMP-9), CRP, KL-6 (Krebs von den Lungen-6) and SP-D (surfactant protein D) were not significantly associated with disease progression over 52 weeks in analyses corrected for multiple comparisons. In models including only baseline demographic/clinical characteristics, 61.2-64.2% of subjects were correctly classified as having or not having disease progression over 52 weeks. When both demographic/clinical characteristics and biomarker levels were included in the models, 50.0-64.5% of the test set were correctly classified.

Conclusions

Among subjects with IPF and preserved FVC, multivariate models based on demographic/clinical characteristics and biomarker levels at baseline did not provide an accurate prediction of which patients would progress.

The role of biomarkers in the diagnosis and treatment follow-up of idiopathic pulmonary fibrosis

BACKGROUND AND AIM

Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive lung disease of unknown cause with a poor prognosis. The aim of our study is to determine the role of Krebs von den Lungen-6(KL-6),Matrix metalloproteinase (MMP)-7, Surfactant protein A (SP-A), Surfactant protein D(SP-D), vascular endothelial growth factor (VEGF) and periostin in the diagnosis of IPF and in the response monitoring of patients treated.

METHOD

47 IPF patients, 27 non-IPF interstitial lung disease (ILD) patients and 21 healthy individuals were included in the study. Demographic data, pulmonary function test- Diffusing capacity of the lung for carbon monoxide (PFT-DLCO) measurements, High-resolution computed tomography (HRCT) findings of the patients were recorded, and serum samples were taken.

RESULTS

While periostin and SP-A levels were not significantly different between IPF and non-IPF ILD, they were significantly higher in both IPF and non-IPF ILD compared to healthy control group (p=0.002,p=0.006 for periostin and p=0.002,p<0.001 for SP-A, respectively).By receiver operating characteristic (ROC) analysis, the cut-off point for periostin to distinguish IPF is >594.5 pg/ml (sensitivity 72%, specificity 76%), while the cut-off point for SP-A is found >6.62 ng/ml (sensitivity 87.2%,specificity 57.1%). In the combined ROC analysis based on SP-A=6.62 ng/ml and periostin >634.6 pg/ml values, sensitivity was found to be 85% and specificity was 57%.Considering the correlation of forced expiratory volume in the first second  (FEV1)(%), forced vital capacity (FVC)(%), restriction and diffusion severities with biomarker levels in the 6th month of IPF patients treated, a correlation was detected between MMP-7 levels and restriction severities (p=0.020), between KL-6 levels and restriction and diffusion severities (p=0.002), and between SP-A levels and FVC(%)(p=0.006).

CONCLUSION

It is thought that biomarkers SP-A and periostin may contribute significantly to the diagnosis of patients with IPF, and SP-A, MMP-7 and KL-6 levels may contribute significantly to treatment follow-up.

Research progress of KL-6 in respiratory system diseases

This article comprehensively elucidates the discovery of Krebs von den Lungen-6 (KL-6), its structural features, functional mechanisms, and the current research status in various respiratory system diseases. Discovered in 1985, KL-6 was initially considered a tumor marker, but its elevated levels in interstitial lung disease (ILD) led to its recognition as a relevant serum marker for ILD. KL-6 is primarily produced by type 2 alveolar epithelial cell regeneration. Over the past 30 years since the discovery of KL-6, the number of related research papers has steadily increased annually. Following the coronavirus disease 2019 (COVID-19) pandemic, there has been a sudden surge in relevant literature. Despite KL-6's potential as a biomarker, its value in the diagnosis, treatment, and prognosis varies across different respiratory diseases, including ILD, idiopathic pulmonary fibrosis (IPF), COVID-19, and lung cancer. Therefore, as an important serum biomarker in respiratory system diseases, the value of KL-6 still requires further investigation.

Evaluating the diagnostic and therapeutic significance of KL-6 in patients with interstitial lung diseases

Background

This study aimed to assess the diagnostic value of Krebs von den Lungen-6 (KL-6), Surfactant protein-A (SP-A), SP-D and molecular matrixmetalloproteinase-7 (MMP-7) in discriminating patients with interstitial lung diseases (ILDs) from disease control subjects.

Methods

Serum levels of KL-6, SP-A, SP-D and MMP-7 were measured in both the ILD and non-ILD (NILD) groups. Receiver operating characteristic (ROC) curve analysis was conducted to evaluate the diagnostic potential of these markers and laboratory indices. High-resolution computed tomography (HRCT) fibrosis scores were determined, and their correlation with the serum markers was analyzed.

Results

Serum levels of KL-6 and MMP-7 were significantly elevated in the ILD group compared to the control group, while no significant differences were observed for SP-A and SP-D. ROC analysis of KL-6 demonstrated superior diagnostic accuracy, with a sensitivity of 76.36%, specificity of 91.07%, and an area under curve (AUC) of 0.902 (95%CI 0.866-0.945). These findings were consistent across an additional cohort. Correlation analysis revealed a link between KL-6 levels at initial diagnosis and HRCT fibrosis scores, indicating disease severity. Moreover, a negative correlation was found between KL-6 and pulmonary function indices, reflecting disease progression. Patients with increased 12-month HRCT fibrosis score showed higher lactate dehydrogenase (LDH) levels, with LDH exhibiting an AUC of 0.767 (95% CI: 0.520-0.927) as a predictor of progression.

Conclusions

Serum KL-6 detection proves to be a valuable tool for accurately distinguishing ILDs from control subjects. While KL-6 shows a correlation with HRCT fibrosis scores and a negative association with pulmonary function indices, its predictive value for ILDs prognosis is limited.

Trial registration

This study received retrospective approval from the Ethical Committee of Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China (institutional review board ID: TJ-IRB20210331, date: 2021.03.30).

Targeting Progression in Pulmonary Fibrosis: An Overview of Underlying Mechanisms, Molecular Biomarkers, and Therapeutic Intervention

Interstitial lung diseases comprise a heterogenous range of diffuse lung disorders, potentially resulting in pulmonary fibrosis. While idiopathic pulmonary fibrosis has been recognized as the paradigm of a progressive fibrosing interstitial lung disease, other conditions with a progressive fibrosing phenotype characterized by a significant deterioration of the lung function may lead to a burden of significant symptoms, a reduced quality of life, and increased mortality, despite treatment. There is now evidence indicating that some common underlying biological mechanisms can be shared among different chronic fibrosing disorders; therefore, different biomarkers for disease-activity monitoring and prognostic assessment are under evaluation. Thus, understanding the common pathways that induce the progression of pulmonary fibrosis, comprehending the diversity of these diseases, and identifying new molecular markers and potential therapeutic targets remain highly crucial assignments. The purpose of this review is to examine the main pathological mechanisms regulating the progression of fibrosis in interstitial lung diseases and to provide an overview of potential biomarker and therapeutic options for patients with progressive pulmonary fibrosis.

Soluble E-cadherin participates in BLM-induced pulmonary fibrosis by promoting EMT and lung fibroblast migration

Soluble E-cadherin (sE-cad) is an 80 kDa fragment derived from E-cadherin that is shed from the cell surface through proteolytic cleavage and is a biomarker in various cancers that promotes invasion and migration. Alveolar epithelial destruction, aberrant lung fibroblast migration and inflammation contribute to pulmonary fibrosis. Here, we hypothesized that E-cadherin plays an important role in lung fibrosis. In this study, we found that E-cadherin was markedly increased in the bronchoalveolar lavage fluid (BALF) and serum of mice with pulmonary fibrosis and that blocking sE-cad with HECD-1, a neutralizing antibody targeting the ectodomain of E-cadherin, effectively inhibited myofibroblast accumulation and collagen deposition in the lungs after bleomycin (BLM) exposure. Moreover, transforming growth factor-β (TGF-β1) induced the shedding of sE-cad from A549 cells, and treatment with HECD-1 inhibited epithelial-mesenchymal transition (EMT) stimulated by TGF-β1. Fc-E-cadherin (Fc-Ecad), which is an exogenous form of sE-cad, robustly promoted lung fibroblast migration. E-cadherin participates in bleomycin (BLM)-induced lung fibrosis by promoting EMT in the alveolar epithelium and fibroblast activation. E-cadherin may be a novel therapeutic target for lung fibrosis.

Walking the path of treatable traits in interstitial lung diseases

Interstitial lung diseases (ILDs) are complex and heterogeneous diseases. The use of traditional diagnostic classification in ILD can lead to suboptimal management, which is worsened by not considering the molecular pathways, biological complexity, and disease phenotypes. The identification of specific "treatable traits" in ILDs, which are clinically relevant and modifiable disease characteristics, may improve patient's outcomes. Treatable traits in ILDs may be classified into four different domains (pulmonary, aetiological, comorbidities, and lifestyle), which will facilitate identification of related assessment tools, treatment options, and expected benefits. A multidisciplinary care team model is a potential way to implement a "treatable traits" strategy into clinical practice with the aim of improving patients' outcomes. Multidisciplinary models of care, international registries, and the use of artificial intelligence may facilitate the implementation of the "treatable traits" approach into clinical practice. Prospective studies are needed to test potential therapies for a variety of treatable traits to further advance care of patients with ILD.

Prognostic Value of Serum Biomarkers in Patients with Idiopathic Pulmonary Fibrosis in Relation to Disease Progression

BACKGROUND

The aim of this present study was to determine serum biomarker levels and their correlation with respiratory function and the clinical course of patients with idiopathic pulmonary fibrosis (IPF).

MATERIALS AND METHODS

This study included 72 IPF patients, according to the ATS/ERS criteria, in whom antifibrotic treatment was initiated. Blood samples were taken, and serum biomarkers, such as KL-6, SP-D, CCL18, CXCL13, VEGF-A, IL-8, IGFBP-1, IGFBP-2, IGFBP-7 and ICAM-1 were measured using ELISA methodology. Pulmonary function tests (FVC, TLC, DLCO-% pred) were determined at baseline and after 12 and 24 months and analyzed in correlation with the biomarkers.

RESULTS

The majority of patients (mean age 72 ± 6 years) were men (83%). The FVC and DLCO values at the 12-month follow-up were found to be statistically decreased in deceased patients (p < 0.05). The SP-D (p < 0.001) and the IGFBP-1 (p = 0.021) levels were found to be increased at the 1-year follow-up in deceased patients, and similarly, the SP-D (p = 0.005) and ICAM-1 (p = 0.043) levels at the 2-year follow-up. A chi-square test revealed that 70% of the category IV GAP index was found with cut-off elevated levels of a biomarker combination (KL-6, SP-D, VEGF-A) from the ROC curve analysis (p < 0.05).

CONCLUSION

This study provides evidence, for the first time in a Greek population, of the possibility of using a combination of KL-6, SP-D, and VEGF-A serum levels along with the GAP index.

Krebs von den Lungen-6 as a Potential Predictive Biomarker in Fibrosing Interstitial Lung Diseases

BACKGROUND

As fibrosing interstitial lung diseases (fILDs) are associated with high mortality, monitoring of disease activity under treatment is highly relevant. Krebs von den Lungen-6 (KL-6) is associated with the presence and severity of different fILDs, mainly in Asian patient populations.

OBJECTIVES

Our aim was to evaluate KL-6 as a predictive biomarker in fILDs in Caucasian patients.

METHODS

Consecutive patients with fILDs were recruited prospectively and serum concentrations of KL-6 were measured at baseline (BL), after 6 and 12 months (6 Months, 12 Months). Clinical characteristics including pulmonary function tests were assessed at 6-monthly visits and correlated with KL-6 BL levels as well as with KL-6 level changes.

RESULTS

A total of 47 fILD patients were included (mean age: 65 years, 68% male). KL-6 levels at BL were significantly higher in fILD patients than in healthy controls (n = 44, mean age: 45, 23% male) (ILD: 1,757 ± 1960 U/mL vs. control: 265 ± 107 U/mL, p < 0.0001). However, no differences were noted between ILD subgroups. KL-6 decreased significantly under therapy (6M∆BL-KL6: -486 ± 1,505 mean U/mL, p = 0.032; 12M∆BL-KL6: -547 ± 1,782 mean U/mL, p = 0.041) and KL-6 level changes were negatively correlated with changes in pulmonary function parameters (forced vital capacity [FVC]: r = -0.562, p < 0.0001; DLCOSB: r = -0.405, p = 0.013). While neither absolute KL-6 levels at BL nor KL-6 level changes were associated with ILD progression (FVC decline ≥10%, DLCOSB decline ≥15% or death), patients with a stable FVC showed significantly decreasing KL-6 levels (p = 0.022).

CONCLUSIONS

A decline of KL-6 under therapy correlated with a clinically relevant stabilization of lung function. Thus, KL-6 might serve as a predictive biomarker, which however must be determined by larger prospective cohorts.

Serum Krebs von den Lungen-6 is associated with in-Hospital mortality of patients with severe Community-Acquired Pneumonia: A retrospective cohort study

BACKGROUND

Currently, no ideal biomarker can accurately stratify the risk of patients with severe community-acquired pneumonia (SCAP). This study aimed to evaluate the role of serum Krebs von den Lungen-6 (sKL-6) in predicting in-hospital mortality in adults with SCAP.

METHODS

In this retrospective cohort study, 249 severe pneumonia adult patients were recruited between 6 May 2021 to 30 April 2023 in Xiangya Hospital of Central South University. The sKL-6 level within 48 h of admission was measured, and the primary outcome assessed was in-hospital mortality. Multivariable logistic regression analysis was performed to calculate adjusted odds ratios (OR) with 95% confidence intervals (CI). Survival curves were plotted and subgroup analyses were conducted, stratified by relevant covariates.

RESULTS

A total of 249 patients were included in the study,with 124 patients having normal sKL-6 levels, and 125 patients having abnormal sKL-6 levels. The overall in-hospital mortality rate was 28.9% (72 out of 249 patients). Univariate and multivariate logistic regression analysis revealed that the patients with abnormal sKL-6 levels had a higher risk of in-hospital mortality compared to those with normal sKL-6 levels, both in the total SCAP patient population (OR: 5.38, 95%CI: 2.41-12.01, P < 0.001) and the non-COVID-19 SCAP patients subgroup (OR: 8.12, 95%CI: 3.16-20.84, P < 0.001). Subgroup and interaction analyses confirmed the stability of the relationship between sKL-6 levels and in-hospital mortality(P for interaction > 0.05). Kaplan-Meier survival curves showed that patients with abnormal sKL-6 levels had a higher in-hospital mortality rate than those with normal sKL-6 levels (P < 0.05). However, the results of restricted cubic spline plots(RCS) analysis demonstrated a nonlinear association between sKL-6 levels (as a continuous variable) and in-hospital mortality in patients with SCAP. Similar results were observed in non-COVID-19 SCAP patients. Furthermore, the receiver operating characteristic curve (ROC) analysis revealed that sKL-6 had superior predictive performance compared to existing biomarkers (e.g., APACHE-II, SOFA, BUN/Cr, PCT, and D-dimer) for in-hospital mortality in non-COVID-19 SCAP patients.

CONCLUSION

sKL-6 is a practical and useful biomarker for predicting in-hospital mortality in patients with SCAP.

Evaluation of the Clinical Value of KL-6 and Tumor Markers in Primary Sjögren's Syndrome Complicated with Interstitial Lung Disease

OBJECTIVE

primary Sjögren's syndrome (pSS) is an autoimmune disease, of which the most common complication is interstitial lung disease (ILD). This study aimed to analyze the clinical value of Krebs von den Lungen-6 (KL-6), carcinoembryonic antigen (CEA), and carbohydrate antigen 153(CA153) in patients with pSS complicated with ILD (pSS-ILD), given that only few studies have evaluated this.

METHODS

This is a cross-sectional study. Serum KL-6 levels (U/mL) were measured using chemiluminescence immunoassay, and concentrations of serum tumor markers were determined using the immunofluorescence method in 64 cases of pSS-ILD (pSS-ILD group), 23 cases without ILD (non-ILD group), and 45 healthy controls. The correlation between KL-6 and tumor markers as well as lung function was analyzed, and the factors that were associated with pSS-ILD were screened.

RESULTS

The serum KL-6 was more abnormally increased in patients with pSS-ILD, and the serum KL-6, CEA, carbohydrate antigen 125 (CA125), and CA153 levels were significantly higher in the pSS-ILD group than in the non-ILD and healthy control groups (p < 0.05). KL-6, CEA, and CA153 were negatively correlated with forced vital capacity (FVC%), forced expiratory volume in 1 s (FEV1%), total lung capacity (TLC%), and diffusing capacity for carbon monoxide (DLCO%) (all p < 0.05). Multivariate logistic analysis showed that KL-6 was an independent factor associated with pSS-ILD.

CONCLUSIONS

In conclusion, we evaluated the association between clinical values of KL-6, tumor markers, and pSS-ILD, and found that KL-6 and tumor markers such as CEA, CA153, and CA125 in patients with pSS-ILD were higher than in patients with non-ILD, and KL-6 was more abnormally increased and significantly associated with ILD development in patients with pSS.

Usefulness and performance evaluation of serum KL-6 and SP-A assays in healthy individuals and patients with interstitial lung disease

BACKGROUND

Interstitial lung abnormalities (ILAs) are associated with the risk of progression to interstitial lung diseases (ILDs). Krebs von den Lungen 6 (KL-6) and surfactant protein (SP)-A have been used as biomarkers of ILDs. In this study, we evaluated the levels of these biomarkers and identified their clinical correlations in healthy individuals to assess their usefulness in the diagnosis of ILAs.

METHODS

The patient samples were categorized into three groups: healthy, disease, and ILD groups. We used the automated immunoassay HISCL KL-6 and SP-A assay kits. The analytical performance evaluation involved precision, linearity, comparison, establishment of reference intervals, and determination of the cutoff points. We also analyzed the correlations between presence of abnormalities on chest radiography and computed tomography (CT) or pulmonary function test (PFT) and serum levels in the healthy group.

RESULTS

KL-6 and SP-A assays showed good analytical performance. The KL-6 and SP-A cutoff values were 304 U/mL and 43.5 ng/mL between the ILD and healthy groups, respectively, which were lower than the values recommended by the manufacturer. In the clinical correlations with radiological findings, SP-A values in subjects with lung abnormalities on CT scans were significantly higher than those in normal scans. There was no significant difference in KL-6 and SP-A levels among PFT patterns; however, both serum levels in the mixed pattern showed higher values than those in the other patterns.

CONCLUSIONS

The results revealed a positive association between increased serum levels of SP-A and KL-6 and clinical characteristics as incidental findings on chest imaging and reduced lung function.

Clinical Utility of Bronchoalveolar Lavage Neutrophilia and Biomarkers for Evaluating Severity of Chronic Fibrosing Interstitial Lung Diseases

Introduction It is hypothesized that bronchoalveolar lavage (BAL) neutrophilia, Krebs von den Lungen-6 (KL-6), and C-reactive protein (CRP) predict the severity of chronic fibrosing interstitial lung diseases (CF-ILDs). Methods This cross-sectional study enrolled 30 CF-ILD patients. Using Pearson's correlation analysis, BAL neutrophils, KL-6, and CRP were correlated with forced vital capacity (FVC), diffusing lung capacity for carbon monoxide (DLCO), six-minute walk distance (6MWD), partial pressure of oxygen (PaO2), computed tomography fibrosis score (CTFS), and pulmonary artery systolic pressure (PASP). Using the receiver operator characteristic (ROC) curve, BAL KL-6 and CRP were evaluated against FVC% and DLCO% in isolation and combination with BAL neutrophilia for predicting the severity of CF-ILDs. Results BAL neutrophilia significantly correlated only with FVC% (r = -0.38, P = 0.04) and DLCO% (r = -0.43, P = 0.03). BAL KL-6 showed a good correlation with FVC% (r = -0.44, P < 0.05) and DLCO% (r = -0.50, P = 0.02), while BAL CRP poorly correlated with all parameters (r = 0.0-0.2). Subset analysis of BAL CRP in patients with CTFS ≤ 15 showed a better association with FVC% (r = -0.28, P = 0.05) and DLCO% (r = -0.36, P = 0.04). BAL KL-6 cut-off ≥ 72.32 U/ml and BAL CRP ≥ 14.55 mg/L predicted severe disease with area under the curve (AUC) values of 0.77 and 0.71, respectively. The combination of BAL neutrophilia, KL-6, and CRP predicted severity with an AUC value of 0.89. Conclusion The combination of BAL neutrophilia, KL-6, and CRP facilitates the severity stratification of CF-ILDs complementing existing severity parameters.

Potential biomarkers for diagnosis and disease evaluation of idiopathic pulmonary fibrosis

ABSTRACT

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive lung disease characterized by progressive lung fibrogenesis and histological features of usual interstitial pneumonia. IPF has a poor prognosis and presents a spectrum of disease courses ranging from slow evolving disease to rapid deterioration; thus, a differential diagnosis remains challenging. Several biomarkers have been identified to achieve a differential diagnosis; however, comprehensive reviews are lacking. This review summarizes over 100 biomarkers which can be divided into six categories according to their functions: differentially expressed biomarkers in the IPF compared to healthy controls; biomarkers distinguishing IPF from other types of interstitial lung disease; biomarkers differentiating acute exacerbation of IPF from stable disease; biomarkers predicting disease progression; biomarkers related to disease severity; and biomarkers related to treatment. Specimen used for the diagnosis of IPF included serum, bronchoalveolar lavage fluid, lung tissue, and sputum. IPF-specific biomarkers are of great clinical value for the differential diagnosis of IPF. Currently, the physiological measurements used to evaluate the occurrence of acute exacerbation, disease progression, and disease severity have limitations. Combining physiological measurements with biomarkers may increase the accuracy and sensitivity of diagnosis and disease evaluation of IPF. Most biomarkers described in this review are not routinely used in clinical practice. Future large-scale multicenter studies are required to design and validate suitable biomarker panels that have diagnostic utility for IPF.

Case Report: Nintedanib for immune-related pneumonitis triggered by anti-PD-1 treatment in a patient with SMARCA4-mutant NSCLC: a case report

SMARCA4-mutant lung cancer accounts for approximately 10% of non-small-cell lung cancers (NSCLCs), has few effective treatments, and has been associated with a poor prognosis. Our case report describes a 73-year-old man who was diagnosed with SMARCA4-mutant advanced lung adenocarcinoma. Routine driver gene mutation screening was negative, and tumor tissue immunohistochemistry analysis showed the absence of the BRG1 protein (encoded by SMARCA4). In addition to the standard chemotherapy regimens, programmed cell death protein 1 (PD-1) inhibitors were administered. After three cycles of combination therapy, the focus of the primary lung tumor shrunk evidently, but radiological interstitial abnormalities emerged in the basal and subpleural areas of the bilateral lungs. The patient's clinical condition deteriorated and he was diagnosed with immune checkpoint inhibitor (ICI)-associated pneumonia. Thus, the combination regimen was discontinued, corticosteroid therapy was administered according to guidelines, and nintedanib was added, given that interstitial abnormalities were observed on chest computed tomography (CT). Following the above treatment, the patient's condition improved, the standard chemotherapy regimen was restarted, and nintedanib treatment was maintained. The patient's clinical condition continued to improve, and follow-up CT showed significant resolution of the interstitial abnormalities and stabilization of the primary tumor lesion. In summary, we report the case of a patient with SMARCA4-mutant NSCLC, which is generally considered to be associated with a poor prognosis owing to a lack of effective treatments. The patient responded favorably to initial combination therapy with ICIs, although he subsequently developed immune-related adverse events. We also found that nintedanib, a multitargeted anti-fibrotic agent, was beneficial for the treatment of immune-related lung injury and showed potential anti-tumor effects.

Circulatory Serum Krebs von Den Lungen-6 and Surfactant Protein-D Concentrations Predict Interstitial Lung Disease Progression and Mortality

There is a need for biomarkers to predict outcomes, including mortality, in interstitial lung disease (ILD). Krebs von den Lungen-6 (KL-6) and surfactant protein D (SP-D) are associated with lung damage and fibrosis in all ILDs and are related to important clinical outcomes. Though these two biomarkers have been associated with ILD outcomes, there are no studies that have evaluated their predictive potential in combination. This study aims to determine whether KL-6 and SP-D are linked to poor disease outcomes and mortality. Additionally, we plan to examine whether changes in KL-6 and SP-D concentrations correspond with changes in lung function and whether serial measurements improve their predictive potential to identify disease progression and mortality. Forty-four patients with ILD participated in a prospective 6-month longitudinal observational study. ILD patients who succumbed had the highest KL-6 levels (3990.4 U/mL (3490.0-4467.6)) and highest SP-D levels (256.1 ng/mL (217.9-260.0)), followed by those who deteriorated: KL-6 levels 1357.0 U/mL (822.6-1543.4) and SP-D levels 191.2 ng/mL (152.8-210.5). The generalized linear model (GLM) analysis demonstrated that changes in forced vital capacity (FVC), diffusing capacity of lungs for carbon monoxide (DLCO), forced expiratory volume in 1 s (FEV1), and partial pressure of arterial oxygen (PaO₂) were correlated to changes in KL6 (p = 0.016, 0.014, 0.027, 0.047) and SP-D (p = 0.008, 0.012, 0.046, 0.020), respectively. KL-6 (odds ratio (OR): 2.87 (1.06-7.79)) and SPD (OR: 1.76 (1.05-2.97)) were independent predictors of disease progression, and KL-6 (hazard ratio (HR): 3.70 (1.46-9.41)) and SPD (HR: 2.58 (1.01-6.59)) were independent predictors of death by Cox regression analysis. Combined biomarkers (KL6 + SPD + CT + FVC) had the strongest ability to predict disease progression (AUC: 0.797) and death (AUC: 0.961), on ROC analysis. Elevated KL-6 and SPD levels are vital biomarkers for predicting the severity, progression, and outcomes of ILD. High baseline levels or an increase in levels over a six-month follow-up despite treatment indicate a poor prognosis. Combining KL6 and SPD with conventional measures yields a more potent prognostic indicator. Clinical studies are needed to test additional interventions, and future research will determine if this combined biomarker benefits different ethnicities globally.

Krebs von den Lungen-6 (KL-6) as a diagnostic marker for pulmonary fibrosis: A systematic review and meta-analysis

BACKGROUND

Pulmonary fibrosis (PF) is a respiratory disease with end-stage pathological changes of interstitial lung disease that severely affects the survival of patients. Among the many biomarkers that have been identified, serum Krebs von den Lungen-6 (KL-6) is by far the most frequent marker for detecting pulmonary fibrosis.

METHODS

We searched Medline (Pubmed), Embase, Web of science, and Cochrane databases for articles published between inception and August 2022 in order to explore the association between KL-6 and pulmonary fibrosis. Characteristics of patients and studies included in the articles were extracted by two independent investigators according to the inclusion and exclusion criteria. We reflected the accuracy of KL-6 in distinguishing between PF and non-PF by calculating sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and area under the curve by SROC curves. The presence of heterogeneity was reflected by I² in the forest plot, and then the source of heterogeneity was investigated by meta-regression.

RESULTS

We searched for 939 research papers, of which 16 met the inclusion criteria. Meta-analysis showed a sensitivity of 0.87 (95 % CI: 0.78-0.92), specificity of 0.91 (95 % CI: 0.86-0.95), positive likelihood ratio of 10.2 (95 % CI: 6.1, 17.0) and negative likelihood ratio of 0.14 (95 % CI: 0.08, 0.25) for KL-6 in diagnosing pulmonary fibrosis. The area under the receiver operating characteristic curve was 0.95 (95 % CI: 0.93-0.97). The results showed significant heterogeneity in both sensitivity and specificity (I² = 94.55 and 91.52, respectively). Meta-regression analysis identified race as the cause of sensitivity heterogeneity and assay methodology as the cause of specificity heterogeneity.

CONCLUSIONS

The analysis of this study suggests that serum KL-6 is a better tool for the diagnosis of pulmonary fibrosis when factors such as disease cause and control group category are not specifically considered.

Serum proteomics identify biomarkers associated with the pathogenesis of idiopathic pulmonary fibrosis

The heterogeneity of idiopathic pulmonary fibrosis (IPF) limits its diagnosis and treatment. The association between the pathophysiological features and the serum protein signatures of IPF currently remains unclear. The present study analyzed the specific proteins and patterns associated with the clinical parameters of IPF based on a serum proteomic dataset by Data-Independent Acquisition (DIA) using mass spectrometry. Differentiated proteins in sera distinguished in IPF patients into three subgroups in signal pathways and overall survival. Aging-associated signatures by WGCNA coincidently provided clear and direct evidence that aging is a critical risk factor for IPF rather than a single biomarker. LDHA and CCT6A expression, which were associated with glucose metabolic reprogramming, were correlated with high serum lactic acid content in the patients with IPF. Cross-model analysis and machine learning showed that a combinatorial biomarker accurately distinguished IPF patients from healthy subjects with an AUC of 0.848 (95% CI = 0.684-0.941) and validated from another cohort and ELISA assay. This serum proteomic profile provides rigorous evidence that enables understanding of the heterogeneity of IPF and protein alterations that could help in its diagnosis and treatment decisions.

Identification of immune biomarkers associated with basement membranes in idiopathic pulmonary fibrosis and their pan-cancer analysis

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive interstitial lung disease of unknown etiology, characterized by diffuse alveolitis and alveolar structural damage. Due to the short median survival time and poor prognosis of IPF, it is particularly urgent to find new IPF biomarkers. Previous studies have shown that basement membranes (BMs) are associated with the development of IPF and tumor metastasis. However, there is still a lack of research on BMs-related genes in IPF. Therefore, we investigated the expression level of BMs genes in IPF and control groups, and explored their potential as biomarkers for IPF diagnosis. In this study, the GSE32537 and GSE53845 datasets were used as training sets, while the GSE24206, GSE10667 and GSE101286 datasets were used as validation sets. In the training set, seven immune biomarkers related to BMs were selected by differential expression analysis, machine learning algorithm (LASSO, SVM-RFE, Randomforest) and ssGSEA analysis. Further ROC analysis confirmed that seven BMs-related genes played an important role in IPF. Finally, four immune-related Hub genes (COL14A1, COL17A1, ITGA10, MMP7) were screened out. Then we created a logistic regression model of immune-related hub genes (IHGs) and used a nomogram to predict IPF risk. The nomogram model was evaluated to have good reliability and validity, and ROC analysis showed that the AUC value of IHGs was 0.941 in the training set and 0.917 in the validation set. Pan-cancer analysis showed that IHGs were associated with prognosis, immune cell infiltration, TME, and drug sensitivity in 33 cancers, suggesting that IHGs may be potential targets for intervention in human diseases including IPF and cancer.

Development of a scoring system with multidimensional markers for fibrosing interstitial lung disease

Fibrosing interstitial lung disease (ILD) can cause high mortality and sensitive evaluation of fibrosing ILD could be critical. The aim of this study is to develop a scoring system to predict prognosis of fibrosing ILD. 339 patients with fibrosing ILD were enrolled as a derivation cohort. Cox multiple regression analysis indicated that smoking history (HR  =  3.826, p  =  0.001), age(HR  =  1.043, p  =  0.015), CEA(HR  =  1.059, p  =  0.049),CYFRA21-1(HR  =  1.177, p  =  0.004) and DLCO% predicted (HR  =  0.979, p  =  0.032) were independent prognostic factors for fibrosing ILD. The clinical scoring system for fibrosing ILD was established based on the clinical variables (age [A], CEA and CYFRA21-1 [C], DLCO% predicted [D], and smoking history [S]; ACDS). The area under the receiver operating characteristic curve (AUROC) of the scoring system for predicting prognosis of fibrosing ILD was 0.90 (95%CI: 0.87–0.94, p < 0.001). The cutoff value was 2.5 with their corresponding specificity (90.7%) and sensitivity (78.8%). To validate the value of ACDS score levels to predict the survival of patients with fibrosing ILD, 98 additional fibrosing ILD patients were included as a validation cohort. The log-rank test showed a significant difference in survival between the two groups(ACDS score < 2.5 and ACDS score ≥ 2.5) in validation cohort. The independent risk factors for mortality in patients with fibrosing ILD are higher CEA, higher CYFRA21-1, smoking history, lower DLCO%predicted at baseline and older age. ACDS is a simple and feasible clinical model for predicting survival of fibrosing ILD.

Krebs von den Lungen-6 glycoprotein circulating levels are not useful as prognostic marker in COVID-19 pneumonia: A large prospective cohort study

Coronavirus disease 2019 (COVID-19) has rapidly expanded worldwide. Currently, there are no biomarkers to predict respiratory worsening in patients with mild to moderate COVID-19 pneumonia. Small studies explored the use of Krebs von de Lungen-6 circulating serum levels (sKL-6) as a prognostic biomarker of the worsening of COVID-19 pneumonia. We aimed at a large study to determine the prognostic value of sKL-6 in predicting evolving trends in COVID-19. We prospectively analyzed the characteristics of 836 patients with COVID-19 with mild lung disease on admission. sKL-6 was obtained in all patients at least at baseline and compared among patients with or without respiratory worsening. The receiver operating characteristic curve was used to find the optimal cutoff level. A total of 159 (19%) patients developed respiratory worsening during hospitalization. Baseline sKL-6 levels were not higher in patients who had respiratory worsening (median {IQR} 315.5 {209–469} vs. 306 {214–423} U/ml p = 0.38). The last sKL-6 and the change between baseline and last sKL-6 were higher in the respiratory worsening group (p = 0.02 and p &lt; 0.0001, respectively). The best sKL-6 cutoff point for respiratory worsening was 497 U/ml (area under the curve 0.52; 23% sensitivity and 85% specificity). sKL-6 was not found to be an independent predictor of respiratory worsening. A conditional inference tree (CTREE) was not useful to discriminate patients at risk of worsening. We found that sKL-6 had a low sensibility to predict respiratory worsening in patients with mild-moderate COVID-19 pneumonia and may not be of use to assess the risk of present respiratory worsening in inpatients with COVID-19 pneumonia.

Loss of SP-A in the Lung Exacerbates Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a devastating and common chronic lung disease that is pathologically characterized by the destruction of lung architecture and the accumulation of extracellular matrix in the lung. Previous studies have shown an association between lung surfactant protein (SP) and the pathogenesis of IPF, as demonstrated by mutations and the altered expression of SP in patients with IPF. However, the role of SP in the development of lung fibrosis is poorly understood. In this study, the role of surfactant protein A (SP-A) was explored in experimental lung fibrosis induced with a low or high dose of bleomycin (BLM) and CRISPR/Cas9-mediated genetic deletion of SP-A. Our results showed that lung SP-A deficiency in mice promoted the development of fibrotic damage and exacerbated inflammatory responses to the BLM challenge. In vitro experiments with murine lung epithelial LA-4 cells demonstrated that in response to transforming growth factor-β1 (TGF-β1), LA-4 cells had a decreased protein expression of SP-A. Furthermore, exogenous SP administration to LA-4 cells inhibited the TGF-β1-induced upregulation of fibrotic markers. Overall, these findings suggest a novel antifibrotic mechanism of SP-A in the development of lung fibrosis, which indicates the therapeutic potential of the lung SP-A in preventing the development of IPF.

Mammalian Neuraminidases in Immune-Mediated Diseases: Mucins and Beyond

Mammalian neuraminidases (NEUs), also known as sialidases, are enzymes that cleave off the terminal neuraminic, or sialic, acid resides from the carbohydrate moieties of glycolipids and glycoproteins. A rapidly growing body of literature indicates that in addition to their metabolic functions, NEUs also regulate the activity of their glycoprotein targets. The simple post-translational modification of NEU protein targets-removal of the highly electronegative sialic acid-affects protein folding, alters protein interactions with their ligands, and exposes or covers proteolytic sites. Through such effects, NEUs regulate the downstream processes in which their glycoprotein targets participate. A major target of desialylation by NEUs are mucins (MUCs), and such post-translational modification contributes to regulation of disease processes. In this review, we focus on the regulatory roles of NEU-modified MUCs as coordinators of disease pathogenesis in fibrotic, inflammatory, infectious, and autoimmune diseases. Special attention is placed on the most abundant and best studied NEU1, and its recently discovered important target, mucin-1 (MUC1). The role of the NEU1 - MUC1 axis in disease pathogenesis is discussed, along with regulatory contributions from other MUCs and other pathophysiologically important NEU targets.

Low Molecular Weight Fucoidan Inhibits Pulmonary Fibrosis In Vivo and In Vitro via Antioxidant Activity

In this study, sulfated polysaccharides extracted from Laminaria japonica were degraded by free radicals to obtain low molecular weight fucoidan (LMWF). The in vivo and in vitro effects of LMWF on bleomycin-treated pulmonary fibrosis mice and TGF-treated A549 cells, respectively, were evaluated, and the role of antioxidant activity was assessed. H&E, Masson's trichrome, and Sirius red staining results showed that bleomycin induced obvious pathological changes and collagen deposition in the lung tissue of mice. However, LMWF effectively inhibited collagen deposition, and based on immunohistochemistry analyses, LMWF can also inhibit the expression of fibrosis markers. At the same time, LMWF could regulate related antioxidant factors in the lung tissue of pulmonary fibrosis mice and reduce the pressure of oxidative stress. Moreover, LMWF could improve the morphology of cells induced with TGF, which confirmed that LMWF could inhibit fibrosis via antioxidant activity modulation.

Post-COVID-19 Pulmonary Fibrosis

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has infected millions worldwide with a high mortality rate due to a lack of definitive treatment. Despite having a wide range of clinical features, acute respiratory distress syndrome (ARDS) has emerged as the primary cause of mortality in these patients. Risk factors and comorbidities like advanced age with limited lung function, pre-existing diabetes, hypertension, cardiovascular diseases, and obesity have increased the risk for severe COVID-19 infection. Rise in inflammatory markers like transforming growth factor β (TGF-β), interleukin-6 (IL-6), and expression of matrix metalloproteinase 1 and 7 (MMP-1, MMP-7), along with collagen deposition at the site of lung injury, results in extensive lung scarring and fibrosis. Anti-fibrotic drugs, such as Pirfenidone and Nintedanib, have emerged as potential treatment options for post-COVID-19 pulmonary fibrosis. A lung transplant might be the only life-saving treatment. Despite the current advances in the management of COVID-19, there is still a considerable knowledge gap in the management of long-term sequelae in such patients, especially concerning pulmonary fibrosis. Follow up on the current clinical trials and research to test the efficacy of various anti-inflammatory drugs is needed to prevent long-term sequelae early mortality in these patients.

Matrix Metalloproteinase 7 Expression and Apical Epithelial Defects in Atp8b1 Mutant Mouse Model of Pulmonary Fibrosis

Abnormalities in airway epithelia and lung parenchyma are found in Atp8b1 mutant mice, which develop pulmonary fibrosis after hyperoxic insult. Microarray and ingenuity pathway analysis (IPA) show numerous transcripts involved in ciliogenesis are downregulated in 14-month (14 M) -old Atp8b1 mouse lung compared with wild-type C57BL/6. Lung epithelium of Atp8b1 mice demonstrate apical abnormalities of ciliated and club cells in the bronchial epithelium on transmission electron microscopy (TEM). Matrix metalloproteinase 7 (MMP7) regulates of ciliogenesis and is a biomarker for idiopathic pulmonary fibrosis (IPF) in humans. Mmp7 transcript and protein expression are significantly upregulated in 14 M Atp8b1 mutant mouse lung. MMP7 expression is also increased in bronchoalveolar lavage fluid (BAL). Immunohistochemistry is localized MMP7 to bronchial epithelial cells in the Atp8b1 mutant. In conclusion, MMP7 is upregulated in the aged Atp8b1 mouse model, which displays abnormal ciliated cell and club cell morphology. This mouse model can facilitate the exploration of the role of MMP7 in epithelial integrity and ciliogenesis in IPF. The Atp8b1 mutant mouse is proposed as a model for IPF.

The Prognostic Value of Krebs von den Lungen-6 and Surfactant Protein-A Levels in the Patients with Interstitial Lung Disease

Background and Objectives

The highly variable clinical course of interstitial lung disease (ILD) makes it difficult to predict patient prognosis. Serum surfactant protein-A (SP-A) and Krebs von den Lungen-6 (KL-6) are known prognostic biomarkers. However, the clinical or pathophysiological differences in patients with these biomarkers have not been well evaluated. We investigated the clinical and pathophysiological differences through the comparison of SP-A and KL-6 levels before and after treatment.

Methods

This study included retrospective data from 91 patients who were treated for ILD between August 2015 and September 2019. Serum SP-A and KL-6 levels were measured before and after treatment. The patients were followed up for 3 months.

Results

Changes in the serum biomarkers (Delta SP-A and Delta KL-6) were found to be significantly correlated (rs = 0.523, P < 0.001); Delta SP-A and Delta KL-6 were inversely correlated with changes in pulmonary function (% predicted values of diffusing capacity for carbon monoxide [DLCO], forced vital capacity [FVC], and forced expiratory volume in 1 s [FEV1]). Patients were divided into four groups based on their Delta SP-A and Delta KL-6 levels in a cluster analysis (G1, G2, G3, and G4). Both SP-A and KL-6 were elevated in the G1 group, with all the patients enrolled classified as progressive or unchanged, and 86.4% of patients showed improved disease activity in the G4 group, where both SP-A and KL-6 levels were reduced. In the G2 group, only SP-A levels decreased post-treatment, indicating an improvement in respiratory function; the patients were not at the end stage of the disease. Only the SP-A levels increased in the G3 group with immunosuppressive treatment.

Conclusions

Reduced serum SP-A and/or KL-6 levels are associated with improved lung function in patients with ILD. Some patients only showed a decrease in SP-A levels could prognosis an improvement in respiratory function. When only SP-A is increased, it may imply that the patients are at an early stage of disease progression. As a result, for proper disease monitoring, measuring both markers is important.

Role of MUC1 rs4072037 polymorphism and serum KL-6 levels in patients with antisynthetase syndrome

Mucin 1/Krebs von den Lungen-6 (KL-6) is proposed as a serum biomarker of several interstitial lung diseases (ILDs), including connective tissue disorders associated with ILD. However, it has not been studied in a large cohort of Caucasian antisynthetase syndrome (ASSD) patients. Consequently, we assessed the role of MUC1 rs4072037 and serum KL-6 levels as a potential biomarker of ASSD susceptibility and for the differential diagnosis between patients with ILD associated with ASSD (ASSD-ILD +) and idiopathic pulmonary fibrosis (IPF). 168 ASSD patients (149 ASSD-ILD +), 174 IPF patients and 523 healthy controls were genotyped for MUC1 rs4072037 T > C. Serum KL-6 levels were determined in a subgroup of individuals. A significant increase of MUC1 rs4072037 CC genotype and C allele frequencies was observed in ASSD patients compared to healthy controls. Likewise, MUC1 rs4072037 TC and CC genotypes and C allele frequencies were significantly different between ASSD-ILD+ and IPF patients. Additionally, serum KL-6 levels were significantly higher in ASSD patients compared to healthy controls. Nevertheless, no differences in serum KL-6 levels were found between ASSD-ILD+ and IPF patients. Our results suggest that the presence of MUC1 rs4072037 C allele increases the risk of ASSD and it could be a useful genetic biomarker for the differential diagnosis between ASSD-ILD+ and IPF patients.

Identification of Hub Genes and Pathways Associated With Idiopathic Pulmonary Fibrosis via Bioinformatics Analysis

Idiopathic pulmonary fibrosis (IPF) is a progressive disease whose etiology remains unknown. The purpose of this study was to explore hub genes and pathways related to IPF development and prognosis. Multiple gene expression datasets were downloaded from the Gene Expression Omnibus database. Weighted correlation network analysis (WGCNA) was performed and differentially expressed genes (DEGs) identified to investigate Hub modules and genes correlated with IPF. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis, and protein-protein interaction (PPI) network analysis were performed on selected key genes. In the PPI network and cytoHubba plugin, 11 hub genes were identified, including ASPN, CDH2, COL1A1, COL1A2, COL3A1, COL14A1, CTSK, MMP1, MMP7, POSTN, and SPP1. Correlation between hub genes was displayed and validated. Expression levels of hub genes were verified using quantitative real-time PCR (qRT-PCR). Dysregulated expression of these genes and their crosstalk might impact the development of IPF through modulating IPF-related biological processes and signaling pathways. Among these genes, expression levels of COL1A1, COL3A1, CTSK, MMP1, MMP7, POSTN, and SPP1 were positively correlated with IPF prognosis. The present study provides further insights into individualized treatment and prognosis for IPF.

Serial Measurements of Circulating KL-6, SP-D, MMP-7, CA19-9, CA-125, CCL18, and Periostin in Patients with Idiopathic Pulmonary Fibrosis Receiving Antifibrotic Therapy: An Exploratory Study

Idiopathic pulmonary fibrosis (IPF) is a progressive and inevitably fatal disease with a heterogeneous clinical course. This study aimed to evaluate the usefulness of circulating biomarkers in routine IPF clinical practice. We conducted an exploratory study in a cohort of 28 IPF subjects qualified for anti-fibrotic therapy with up to 24 months serial measurements of seven IPF biomarkers, including those that are well-established, Krebs von den Lungen-6 (KL-6), surfactant protein D (SP-D), matrix metalloproteinase 7 (MMP-7), and more recently introduced ones, cancer antigen 19-9 (CA19-9), cancer antigen 125 (CA-125), chemokine (C-C motif) ligand 18 (CCL18), and periostin. Among studied biomarkers, SP-D had the highest diagnostic accuracy to differentiate IPF subjects from controls, followed by MMP-7 and KL-6. At each study timepoint, KL-6 levels correlated inversely with forced vital capacity % predicted (FVC% pred.), and transfer factor of the lung for carbon monoxide % predicted (T_L,CO% pred.), while SP-D levels correlated inversely with FVC% pred. and T_L,CO% pred. at 24 months of anti-fibrotic therapy. Baseline KL-6 and CA19-9 concentrations were significantly elevated in patients with progressive disease in comparison to patients with stable disease. In addition, in the progressors subgroup CA19-9 concentrations significantly increased over the second year of study follow-up. In patients with progressive disease, we observed a significant inverse correlation between a change in SP-D levels and a change in FVC% pred. in the first year of treatment, whereas in the second year a significant inverse correlation between a change in KL-6 levels and a change in FVC% pred. was noted. Our study findings support the view that both well-established IPF biomarkers, including KL-6, SP-D, and MMP-7, and more recently introduced ones, like CA19-9, have the potential to support clinical practice in IPF.

Upregulation of receptor tyrosine kinase-like orphan receptor 2 in idiopathic pulmonary fibrosis

BACKGROUND/AIMS

Receptor tyrosine kinase-like orphan receptor 2 (ROR2) is a major regulator of Wnt signaling, which is involved in fibroblast dysfunction. Because its role has not been evaluated in idiopathic pulmonary fibrosis (IPF), we examined the clinical implications of ROR2 expression.

METHODS

ROR2 mRNA expression was measured using reverse transcription polymerase chain reaction in lung tissue-derived fibroblasts from IPF patients (n = 14) and from controls (n = 10). ROR2 protein was measured using enzyme-linked immunosorbent assay in primary fibroblasts from IPF patients (n = 14) and controls (n = 10), and in bronchoalveolar lavage (BAL) fluids obtained from normal controls (NC; n = 30). IPF patients (n = 84), and other patients with interstitial lung diseases, including nonspecific interstitial pneumonia (NSIP; n = 10), hypersensitivity pneumonitis (HP; n = 10), and sarcoidosis (n = 10).

RESULTS

ROR2 mRNA and protein levels were significantly higher in IPF fibroblasts than in controls (p = 0.003, p = 0.0017, respectively). ROR2 protein levels in BAL fluids from patients with IPF were significantly higher than in those from NC (p < 0.001), and from patients with NSIP (p = 0.006), HP (p = 0.004), or sarcoidosis (p = 0.004). Receiver operating characteristic curves showed a clear difference between IPF and NC in ROR2 protein level (area under the curve, 0.890; confidence interval, 0.829 to 0.950; p < 0.001). ROR2 protein levels were significantly higher in GAP stage III than in GAP stages I and II (p = 0.016).

CONCLUSION

ROR2 may be related to the development of IPF, and its protein level may be a useful and severity-dependent candidate marker for IPF.

Molecular Biomarkers in Idiopathic Pulmonary Fibrosis: State of the Art and Future Directions

Idiopathic pulmonary fibrosis (IPF), the most lethal form of interstitial pneumonia of unknown cause, is associated with a specific radiological and histopathological pattern (the so-called "usual interstitial pneumonia" pattern) and has a median survival estimated to be between 3 and 5 years after diagnosis. However, evidence shows that IPF has different clinical phenotypes, which are characterized by a variable disease course over time. At present, the natural history of IPF is unpredictable for individual patients, although some genetic factors and circulating biomarkers have been associated with different prognoses. Since in its early stages, IPF may be asymptomatic, leading to a delayed diagnosis. Two drugs, pirfenidone and nintedanib, have been shown to modify the disease course by slowing down the decline in lung function. It is also known that 5-10% of the IPF patients may be affected by episodes of acute and often fatal decline. The acute worsening of disease is sometimes attributed to identifiable conditions, such as pneumonia or heart failure; but many of these events occur without an identifiable cause. These idiopathic acute worsenings are termed acute exacerbations of IPF. To date, clinical biomarkers, diagnostic, prognostic, and theranostic, are not well characterized. However, they could become useful tools helping facilitate diagnoses, monitoring disease progression and treatment efficacy. The aim of this review is to cover molecular mechanisms underlying IPF and research into new clinical biomarkers, to be utilized in diagnosis and prognosis, even in patients treated with antifibrotic drugs.

Interstitial Lung Disease in Connective Tissue Disease: A Common Lesion With Heterogeneous Mechanisms and Treatment Considerations

Connective tissue disease (CTD) related interstitial lung disease (CTD-ILD) is one of the leading causes of morbidity and mortality of CTD. Clinically, CTD-ILD is highly heterogenous and involves rheumatic immunity and multiple manifestations of respiratory complications affecting the airways, vessels, lung parenchyma, pleura, and respiratory muscles. The major pathological features of CTD are chronic inflammation of blood vessels and connective tissues, which can affect any organ leading to multi-system damage. The human lung is particularly vulnerable to such damage because anatomically it is abundant with collagen and blood vessels. The complex etiology of CTD-ILD includes genetic risks, epigenetic changes, and dysregulated immunity, which interact leading to disease under various ill-defined environmental triggers. CTD-ILD exhibits a broad spectra of clinical manifestations: from asymptomatic to severe dyspnea; from single-organ respiratory system involvement to multi-organ involvement. The disease course is also featured by remissions and relapses. It can range from stability or slow progression over several years to rapid deterioration. It can also present clinically as highly progressive from the initial onset of disease. Currently, the diagnosis of CTD-ILD is primarily based on distinct pathology subtype(s), imaging, as well as related CTD and autoantibodies profiles. Meticulous comprehensive clinical and laboratory assessment to improve the diagnostic process and management strategies are much needed. In this review, we focus on examining the pathogenesis of CTD-ILD with respect to genetics, environmental factors, and immunological factors. We also discuss the current state of knowledge and elaborate on the clinical characteristics of CTD-ILD, distinct pathohistological subtypes, imaging features, and related autoantibodies. Furthermore, we comment on the identification of high-risk patients and address how to stratify patients for precision medicine management approaches.

Prognostic role of Krebs von den Lungen-6 (KL-6) measurement in idiopathic pulmonary fibrosis: a systematic review and meta-analysis

OBJECTIVES

Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial disease with limited therapeutic options. The measurement of Krebs von den Lungen-6 (KL-6) glycoprotein has been proposed for evaluating the risk of IPF progression and predicting patient prognosis, but the robustness of available evidence is unclear.

METHODS

We searched Medline and Embase databases for peer-reviewed literature from inception to April 2020. Original articles investigating KL-6 as prognostic marker for IPF were retrieved. Considered outcomes were the risk of developing acute exacerbation (AE) and patient survival. Meta-analysis of selected studies was conducted, and quantitative data were uniformed as odds ratio (OR) or hazard ratio (HR) estimates, with corresponding 95% confidence intervals (CI).

RESULTS

Twenty-six studies were included in the systematic review and 14 were finally meta-analysed. For AE development, the pooled OR (seven studies) for KL-6 was 2.72 (CI 1.22-6.06; p=0.015). However, a high degree of heterogeneity (I²=85.6%) was found among selected studies. Using data from three studies reporting binary data, a pooled sensitivity of 72% (CI 60-82%) and a specificity of 60% (CI 52-68%) were found for KL-6 measurement in detecting insurgence of AE in IPF patients. Pooled HR (seven studies) for mortality prediction was 1.009 (CI 0.983-1.036; p=0.505).

CONCLUSIONS

Although our meta-analysis suggested that IPF patients with increased KL-6 concentrations had a significant increased risk of developing AE, the detection power of the evaluated biomarker is limited. Furthermore, no relationship between biomarker concentrations and mortality was found. Caution is also needed when extending obtained results to non-Asian populations.

Blood Transcriptomics Predicts Progression of Pulmonary Fibrosis and Associated Natural Killer Cells

Rationale: Disease activity in idiopathic pulmonary fibrosis (IPF) remains highly variable, poorly understood, and difficult to predict. Objectives: To identify a predictor using short-term longitudinal changes in gene expression that forecasts future FVC decline and to characterize involved pathways and cell types. Methods: Seventy-four patients from COMET (Correlating Outcomes with Biochemical Markers to Estimate Time-Progression in IPF) cohort were dichotomized as progressors (≥10% FVC decline) or stable. Blood gene-expression changes within individuals were calculated between baseline and 4 months and regressed with future FVC status, allowing determination of expression variations, sample size, and statistical power. Pathway analyses were conducted to predict downstream effects and identify new targets. An FVC predictor for progression was constructed in COMET and validated using independent cohorts. Peripheral blood mononuclear single-cell RNA-sequencing data from healthy control subjects were used as references to characterize cell type compositions from bulk peripheral blood mononuclear RNA-sequencing data that were associated with FVC decline. Measurements and Main Results: The longitudinal model reduced gene-expression variations within stable and progressor groups, resulting in increased statistical power when compared with a cross-sectional model. The FVC predictor for progression anticipated patients with future FVC decline with 78% sensitivity and 86% specificity across independent IPF cohorts. Pattern recognition receptor pathways and mTOR pathways were downregulated and upregulated, respectively. Cellular deconvolution using single-cell RNA-sequencing data identified natural killer cells as significantly correlated with progression. Conclusions: Serial transcriptomic change predicts future FVC decline. An analysis of cell types involved in the progressor signature supports the novel involvement of natural killer cells in IPF progression.

Serum KL-6 Could Represent a Reliable Indicator of Unfavourable Outcome in Patients with COVID-19 Pneumonia

KL-6 is a sialoglycoprotein antigen which proved elevated in the serum of patients with different interstitial lung diseases, especially in those with a poorer outcome. Given that interstitial pneumonia is the most common presentation of SARS-CoV2 infection, we evaluated the prognostic role of KL-6 in patients with COVID-19 pneumonia. Patients with COVID-19 pneumonia were prospectively enrolled. Blood samples were collected at the time of enrolment (TOE) and on day 7 (T1). Serum KL-6 concentrations were measured by chemiluminescence enzyme immunoassay using a KL-6 antibody kit (LUMIPULSE G1200, Fujirebio) and the cut-off value was set at >1000 U/mL. Fifteen out of 34 enrolled patients (44.1%) died. Patients with unfavourable outcome showed significantly lower P/F ratio and higher IL-6 values and plasmatic concentrations of KL-6 at TOE compared with those who survived (median KL-6: 1188 U/mL vs. 260 U/mL, p < 0.001). KL-6 > 1000 U/mL resulted independently associated with death (aOR: 11.29, p < 0.05) with a positive predictive value of 83.3%. Our results suggest that KL-6 is a reliable indicator of pulmonary function and unfavourable outcome in patients with COVID-19 pneumonia. A KL-6 value > 1000 U/mL resulted independently associated with death and showed good accuracy in predicting a poorer outcome. KL-6 may thus represent a quick, inexpensive, and sensitive parameter to stratify the risk of severe respiratory failure and death.

Serum Krebs von den Lungen-6 and lung ultrasound B lines as potential diagnostic and prognostic factors for rheumatoid arthritis-associated interstitial lung disease

INTRODUCTION

Rheumatoid arthritis (RA)-associated interstitial lung disease (ILD) (RA-ILD) is a serious systemic RA manifestation with high mortality that needs proper, accurate, and sensitive assessment tools.

OBJECTIVES

Firstly, evaluate serum Krebs von den Lungen-6 (KL-6) levels and lung ultrasound B lines (LUS B lines) score in RA-ILD correlating them with the severity of ILD assessed by high-resolution computed tomography (HRCT) and pulmonary function tests (PFTs). Secondly, determine cut-off values for LUS and KL-6 in RA-ILD assessment and outcome prediction.

METHODS

A case-control study included seventy-five RA-ILD patients with an equal number of matched RA patients without ILD. Clinical assessment includes DAS-28 and PFTs, laboratory assessment of serum KL-6 by latex-enhanced immunoturbidimetric assay, and radiological evaluation of ILD using semiquantitative CT grade and LUS B lines.

RESULTS

RA-ILD patients had significantly higher serum KL6 compared to those without ILD (1025.5 ± 419.6 vs. 237.5 ± 51.9, p ≤ 0.001). Serum KL6 was positively correlated with HRCT and LUS scores (r = 0.93, r = 0.97, respectively) with negative correlation with FVC% and FEV1% (r = - 0.93, r = - 0.91, respectively). LUS was positively correlated with KL6 and HRCT (r = 0.97, r = 0.944, respectively) while, negatively correlated with PFTs. Cut-off values of KL6 and LUS were 277.5 U/ml and < 5.5, with AUC 0.878 and 1, sensitivity 86.7% and 100%, and specificity 88% and 100%, respectively.

CONCLUSIONS

The non-invasive, radiation-free LUS with a score < 5.5 combined with serum KL6 could be helpful for RA-ILD assessment correlating with HRCT and disease severity. Serum KL6 combined with LUS is important new and potential prognostic factor predicting poor outcomes in RA-ILD. Further large-scale, multi-center, and prospective studies are needed to confirm these findings.

KEY POINTS

• Combination of the non-invasive, radiation-free LUS with a score < 5.5 and serum KL6 levels of 277.5 U/ml is recommended as prognostic tools for RA-ILD. • Easily obtainable tests such as serum KL-6, inflammatory markers, and LUS are sensitive for assessing RA-ILD and the risk of poor outcomes in patients with RA-ILD. • RA-ILD patients with higher KL6 levels, higher LUS scores had a poor prognosis with short survival. • LUS B lines could be used as the first imaging tool for the evaluation of RA-ILD decreasing the risk of HRCT radiation exposure in asymptomatic or mild RA-ILD patients.

Matrix metalloproteinase-2, -7, and -9 activities in dogs with idiopathic pulmonary fibrosis compared to healthy dogs and dogs with other respiratory diseases

BACKGROUND

Canine idiopathic pulmonary fibrosis (CIPF) is a chronic, interstitial lung disease that mainly affects West Highland white terriers (WHWTs) and is characterized by excessive deposition of extracellular matrix (ECM) in the lung. Matrix metalloproteinases (MMPs) participate in remodeling of ECM.

OBJECTIVES

To compare metalloproteinase-2, -7 and -9 activities in blood or bronchoalveolar lavage fluid (BALF) samples or both of CIPF WHWTs with healthy WHWTs, healthy dogs of other breeds, and dogs with other lung diseases and determine if these MMPs could be used as diagnostic and prognostic markers for CIPF.

ANIMALS

Forty-four CIPF WHWTs, 24 dogs with chronic bronchitis (CB), 17 with eosinophilic bronchopneumopathy (EBP), 10 with bacterial pneumonia, 39 healthy WHWTs, and 35 healthy dogs of other breeds.

METHODS

Cross-sectional observational study. Pro-MMP and active MMP activities were analyzed by zymography.

RESULTS

In serum, significantly higher (P < .01) pro-MMP-7 activities were observed in CIPF WHWTs compared to healthy dogs of other breeds, dogs with CB and dogs with EBP. In BALF of CIPF WHWTs, both pro-MMP-9 and pro-MMP-2 activities were significantly higher (P < .01) compared to healthy WHWTs, but these differences were not detected in plasma. The CIPF WHWTs had significantly higher (P < .05) activities of pro-MMP-9 compared to dogs with CB and of pro-MMP-2 compared to dogs with CB and EBP. No statistically significant prognostic factors were observed in CIPF WHWTs.

CONCLUSIONS AND CLINICAL RELEVANCE

Serum MMP-7 and BALF MMP-2 and -9 potentially may be useful diagnostic markers but not prognostic markers for CIPF.

Serum SP-A and KL-6 levels can predict the improvement and deterioration of patients with interstitial pneumonia with autoimmune features

BACKGROUND

Some patients with interstitial pneumonia with autoimmune features (IPAF) showed a progressive course despite therapy. This study aimed to evaluate whether serial changes in the serum levels of surfactant protein-A (SP-A) and Krebs von den Lungen-6 (KL-6) can predict disease progression.

METHODS

Sixty-four patients with IPAF and 41 patients with non-fibrotic lung disease (non-FLD) were examined. Based on long-term changes in lung function, 36 IPAF patients who were followed up for more than 3 months were divided into a progressive group (n = 9), an improvement group (n = 13), and a stable group (n = 14). Serum KL-6 and SP-A levels were measured. The sensitivity, specificity, cut-off value, and area under the curve (AUC) value for each of the indices were determined using receiver operating characteristic (ROC) curve analysis. The expression differences in these biomarkers and their correlation with disease severity were analyzed.

RESULTS

Compared with non-FLD patients, serum SP-A and KL-6 levels in IPAF patients were increased significantly [SP-A: (p < 0.001); KL-6: (p < 0.001)] and negatively correlated with DLCO (SP-A: r_S = - 0.323, p = 0.018; KL-6: r_S = - 0.348, p = 0.0011). In patients with progressive disease, the posttreatment serum SP-A and KL-6 levels were increased significantly compared with pretreatment levels [SP-A: (p = 0.021); KL-6: (p = 0.008)]. In patients showing improvement, the levels were decreased significantly [SP-A (p = 0.007) and KL-6 (p = 0.002)]. Changes in serum biomarkers (Delta SP-A and Delta KL-6) were significantly negatively correlated with changes in lung function (Delta FVC, Delta DLCO and Delta FEV1) (r_S = 0.482, p < 0.05). A significant positive correlation was found between Delta SP-A and Delta KL-6 (r_S = 0.482, p < 0.001).

CONCLUSIONS

Serum SP-A and KL-6 offer high sensitivity and specificity for the diagnosis of IPAF. The decrease in serum SP-A and/or KL-6 levels in patients with IPAF is related to the improvement in pulmonary function. SP-A and KL-6 may be important biomarkers for predicting disease progression in patients with IPAF.

Idiopathic pulmonary fibrosis: Current knowledge, future perspectives and its importance in radiation oncology

Idiopathic pulmonary fibrosis (IPF) is a progressive, fibrotic lung disease with an unknown cause. Uncertainties still remain regarding the pathogenesis of IPF, and the prognosis of this disease is poor despite some recent improvements in treatment. Radiation induced lung injury (RILI) is a common complication and a dose-limiting toxicity of thoracic radiotherapy. Importantly, IPF is a crucial risk factor for pulmonary toxicity after thoracic radiotherapy. Although IPF is not universally accepted as a definite contraindication for thoracic radiotherapy at present, it has been shown that IPF can increase the risk of severe and fatal complications after thoracic radiotherapy. Proton beam therapy has shown promising results in reducing the incidence of thoracic radiotherapy related life-threatening complications in IPF patients, but the current evidence is not sufficient to recommend the standard use of it. Many similarities are noticeable between IPF and RILI in terms of pathogenesis and underlying mechanisms. Better understanding of the mechanisms of IPF and RILI may enable clinicians to provide safer and more effective thoracic radiotherapy treatments in cancer patients with IPF. In this review, we summarize the current knowledge of IPF, present the importance of IPF in radiation oncology practice, and highlight the similarities and relationship between IPF and RILI.

Serum Krebs von den Lungen (KL-6) level as a marker of exacerbation of interstitial lung diseases

Background

Krebs von den Lungen (KL-6) is elevated in serum of interstitial lung disease (ILD) patients based on its leakage from the alveolar space into the blood; KL-6 is significantly higher in patients with acute exacerbation of ILDs (AE-ILD) compared with stable patients. This study aimed to determine the sensitivity and specificity of KL6 to detect AE-ILD.

Results

This is a prospective cross sectional observational study was carried out on 88 subjects at the Chest Department, Minia Cardiothoracic University Hospital, during the period from August 2018 to August 2019. This study was approved by the hospital research ethics board of Minia University and informed consent was obtained. History, examination, spirometry, ABGs, X-ray, HRCT, CBC, ESR, CRP, and KL6 levels were done to both stable and exacerbation groups of ILDs. The level of biomarkers is compared between both groups and control.

Statistical analysis done by using IBM SPSS statistical package version 20 (χ2 test and independent sample t test, ANOVA test, bivariate Pearson correlation analysis, and ROC curve analysis).

The study showed that there is a significant difference between stable and exacerbating groups regarding fever, signs of RHF, dyspnea scale, FVC, and PaO2.

Conclusion

KL-6 cutoff ≥ 187.5 U/ml could exhibit AE-ILDs with a sensitivity of 98% and a specificity of 97%. KL-6 is a more sensitive and specific marker to detect AE-ILD.

Molecular approach to the classification of chronic fibrosing lung disease-there and back again

Chronic diffuse parenchymal lung disease (DPLD) is an umbrella term for a very heterogeneous group of lung diseases. Over the last decades, clinical, radiological and histopathological criteria have been established to define and separate these entities. More recently the clinical utility of this approach has been challenged as a unifying concept of pathophysiological mechanisms and a shared response to therapy across the disease spectrum have been described. In this review, we discuss molecular motifs for subtyping and the prediction of prognosis focusing on genetics and markers found in the blood, lavage and tissue. As a purely molecular classification so far lacks sufficient sensitivity and specificity for subtyping, it is not routinely used and not implemented in international guidelines. However, a better molecular characterization of lung disease with a more precise identification of patients with, for example, a risk for rapid disease progression would facilitate more accurate treatment decisions and hopefully contribute to better patients' outcomes.

[Clinical value of biomarkers in diagnosis and treatment of idiopathic pulmonary fibrosis]

Idiopathic pulmonary fibrosis (IPF) is a chronic interstitial pneumonia characterized by progressive accumulation of fibroblastic foci and destruction of the alveolar structure. Due to an incomplete understanding of the mechanism of the occurrence and progression of IPF, currently no effective means have been available for its early screening or treatment. With a poor overall prognosis, the patients with IPF have a median survival of only 2-4 years. In recent years, several studies have confirmed that dozens of molecules are involved in the development of IPF and can be used as potential biomarkers. These biomarkers play important roles in early diagnosis (such as SP-D, MMP-7, and osteopontin), prognostic evaluation (such as telomerase length, KL-6, mtDNA, HSP-70, LOXL2, CXCL13, miRNA, ICAM-1, and CCL18), and guiding treatment of IPF (such as TOLLIP rs3750920 genotype, SAMS score, and SP-D), and also provide potential therapeutic targets (such as TERT, TERR, RTEC, and PARN).

Identification of a unique temporal signature in blood and BAL associated with IPF progression

Idiopathic pulmonary fibrosis (IPF) is a progressive and heterogeneous interstitial lung disease of unknown origin with a low survival rate. There are few treatment options available due to the fact that mechanisms underlying disease progression are not well understood, likely because they arise from dysregulation of complex signaling networks spanning multiple tissue compartments. To better characterize these networks, we used systems-focused data-driven modeling approaches to identify cross-tissue compartment (blood and bronchoalveolar lavage) and temporal proteomic signatures that differentiated IPF progressors and non-progressors. Partial least squares discriminant analysis identified a signature of 54 baseline (week 0) blood and lung proteins that differentiated IPF progression status by the end of 80 weeks of follow-up with 100% cross-validation accuracy. Overall we observed heterogeneous protein expression patterns in progressors compared to more homogenous signatures in non-progressors, and found that non-progressors were enriched for proteomic processes involving regulation of the immune/defense response. We also identified a temporal signature of blood proteins that was significantly different at early and late progressor time points (p < 0.0001), but not present in non-progressors. Overall, this approach can be used to generate new hypothesis for mechanisms associated with IPF progression and could readily be translated to other complex and heterogeneous diseases.