KL-6 as an Immunological Biomarker Predicts the Severity, Progression, Acute Exacerbation, and Poor Outcomes of Interstitial Lung Disease: A Systematic Review and Meta-Analysis

The mitigating effect of para-hydroxycinnamic acid in bleomycin-induced pulmonary fibrosis in mice through targeting oxidative, inflammatory and fibrotic pathways

This study investigated the therapeutic benefits of para-hydroxycinnamic acid in mice with bleomycin-induced lung fibrosis. Forty male BALB/c mice were randomly assigned to four groups: normal, which received 0.9% normal saline; induced, which received a single dose of bleomycin (5 mg/kg) by oropharyngeal challenge; pirfenidone-treated; and para-hydroxycinnamic acid-treated, which challenged with bleomycin and received a daily oral dose of 300 and 50 mg/kg, respectively, from day 7 to day 21. Tissue pro-fibrotic and inflammatory cytokines, oxidative indicators, pulmonary histopathology, immunohistochemistry of fibrotic proteins and the assessment of gene expression by RT-qPCR were evaluated on day 22 after euthanizing animals. Pirfenidone and para-hydroxycinnamic acid managed to alleviate the fibrotic endpoints by statistically improving the weight index, histopathological score and reduced expression of fibrotic-related proteins in immune-stained lung sections, as well as fibrotic markers measured in serum samples. They also managed to alleviate tissue levels of oxidative stress and inflammatory and pro-fibrotic mediators. para-Hydroxycinnamic acid enhanced the expression of crucial genes associated with oxidative stress, inflammation and fibrosis in vivo. para-Hydroxycinnamic acid has demonstrated similar effectiveness to pirfenidone, suggesting it could be a promising treatment for fibrotic lung conditions by inhibiting the TGF-β1/Smad3 pathway or through its anti-inflammatory and antioxidant properties.

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.

Vinpocetine alleviated alveolar epithelial cells injury in experimental pulmonary fibrosis by targeting PPAR-γ/NLRP3/NF-κB and TGF-β1/Smad2/3 pathways

This study aimed to investigate the potential anti-fibrotic activity of vinpocetine in an experimental model of pulmonary fibrosis by bleomycin and in the MRC-5 cell line. Pulmonary fibrosis was induced in BALB/c mice by oropharyngeal aspiration of a single dose of bleomycin (5 mg/kg). The remaining induced animals received a daily dose of pirfenidone (as a standard anti-fibrotic drug) (300 mg/kg/PO) and vinpocetine (20 mg/kg/PO) on day 7 of the induction till the end of the experiment (day 21). The results of the experiment revealed that vinpocetine managed to alleviate the fibrotic endpoints by statistically improving (P ≤ 0.05) the weight index, histopathological score, reduced expression of fibrotic-related proteins in immune-stained lung sections, as well as fibrotic markers measured in serum samples. It also alleviated tissue levels of oxidative stress and inflammatory and pro-fibrotic mediators significantly elevated in bleomycin-only induced animals (P ≤ 0.05). Vinpocetine managed to express a remarkable attenuating effect in pulmonary fibrosis both in vivo and in vitro either directly by interfering with the classical TGF-β1/Smad2/3 signaling pathway or indirectly by upregulating the expression of Nrf2 enhancing the antioxidant system, activating PPAR-γ and downregulating the NLRP3/NF-κB pathway making it a candidate for further clinical investigation in cases of pulmonary fibrosis.

Progressive Pulmonary Fibrosis: Where Are We Now?

Interstitial lung diseases (ILDs) are a diverse collection of lung disorders sharing similar features, such as inflammation and fibrosis. The diagnosis and management of ILD require a multidisciplinary approach using clinical, radiological, and pathological evaluation. Progressive pulmonary fibrosis (PPF) is a distinct form of progressive and fibrotic disease, occurring in ILD cases other than in idiopathic pulmonary fibrosis (IPF). It is defined based on clinical symptoms, lung function, and chest imaging, regardless of the underlying condition. The progression to PPF must be monitored through a combination of pulmonary function tests (forced vital capacity [FVC] and diffusing capacity of the lung for carbon monoxide), an assessment of symptoms, and computed tomography scans, with regular follow-up. Although the precise mechanisms of PPF remain unclear, there is evidence of shared pathogenetic mechanisms with IPF, contributing to similar disease behavior and worse prognosis compared to non-PPF ILD. Pharmacological treatment of PPF includes immunomodulatory agents to reduce inflammation and the use of antifibrotics to target progressive fibrosis. Nintedanib, a known antifibrotic agent, was found to be effective in slowing IPF progression and reducing the annual rate of decline in FVC among patients with PPF compared to placebos. Nonpharmacological treatment, including pulmonary rehabilitation, supplemental oxygen therapy, and vaccination, also play important roles in the management of PPF, leading to comprehensive care for patients with ILD. Although there is currently no cure for PPF, there are treatments that can help slow the progression of the disease and improve quality of life.

Identification of Idiopathic Pulmonary Fibrosis and Prediction of Disease Severity via Machine Learning Analysis of Comprehensive Metabolic Panel and Complete Blood Count Data

BACKGROUND

Diagnosis of idiopathic pulmonary fibrosis (IPF) typically relies on high-resolution computed tomography imaging (HRCT) or histopathology, while monitoring disease severity is done via frequent pulmonary function testing (PFT). More reliable and convenient methods of diagnosing fibrotic interstitial lung disease (ILD) type and monitoring severity would allow for early identification and enhance current therapeutic interventions. This study tested the hypothesis that a machine learning (ML) ensemble analysis of comprehensive metabolic panel (CMP) and complete blood count (CBC) data can accurately distinguish IPF from connective tissue disease ILD (CTD-ILD) and predict disease severity as seen with PFT.

METHODS

Outpatient data with diagnosis of IPF or CTD-ILD (n = 103 visits by 53 patients) were analyzed via ML methodology to evaluate (1) IPF vs CTD-ILD diagnosis; (2) %predicted Diffusing Capacity of Lung for Carbon Monoxide (DLCO) moderate or mild vs severe; (3) %predicted Forced Vital Capacity (FVC) moderate or mild vs severe; and (4) %predicted FVC mild vs moderate or severe.

RESULTS

ML methodology identified IPF from CTD-ILD with AUCTEST = 0.893, while PFT was classified as DLCO moderate or mild vs severe with AUCTEST = 0.749, FVC moderate or mild vs severe with AUCTEST = 0.741, and FVC mild vs moderate or severe with AUCTEST = 0.739. Key features included albumin, alanine transaminase, %lymphocytes, hemoglobin, %eosinophils, white blood cell count, %monocytes, and %neutrophils.

CONCLUSION

Analysis of CMP and CBC data via proposed ML methodology offers the potential to distinguish IPF from CTD-ILD and predict severity on associated PFT with accuracy that meets or exceeds current clinical practice.

Clinical characteristics and outcome of lung cancer in patients with fibrosing interstitial lung disease

BACKGROUND

Lung cancer (LC) is an important comorbidity of interstitial lung disease (ILD) and has a poor prognosis. The clinical characteristics and outcome of each ILD subtype in LC patients have not been sufficiently investigated. Therefore, this study aimed to evaluate the difference between idiopathic pulmonary fibrosis (IPF) and non-IPF ILD as well as prognostic factors in patients with ILD-LC.

METHODS

The medical records of 163 patients diagnosed with ILD-LC at Asan Medical Center from January 2018 to May 2023 were retrospectively reviewed. Baseline characteristics and clinical outcomes were compared between the IPF-LC and non-IPF ILD-LC groups, and prognostic factors were analyzed using the Cox proportional-hazard model.

RESULTS

The median follow-up period was 11 months after the cancer diagnosis. No statistically significant differences were observed in clinical characteristics and mortality rates (median survival: 26 vs. 20 months, p = 0.530) between the groups. The independent prognostic factors in patients with ILD-LC were higher level of Krebs von den Lungen-6 (≥ 1000 U/mL, hazard ratio [HR] 1.970, 95% confidence interval [CI] 1.026-3.783, p = 0.025) and advanced clinical stage of LC (compared with stage I, HR 3.876 for stage II, p = 0.025, HR 5.092 for stage III, p = 0.002, and HR 5.626 for stage IV, p = 0.002). In terms of treatment, surgery was the significant factor for survival (HR 0.235; 95% CI 0.106-0.520; p < 0.001).

CONCLUSIONS

No survival difference was observed between IPF-LC and non-IPF ILD-LC patients. A higher level of Krebs von den Lungen-6 may act as a prognostic marker in ILD-LC patients.

Lung toxicity induced by anti-HER2 antibody - drug conjugates for breast cancer

Human epidermal growth factor receptor 2 (HER2) serves as both a prognostic indicator and a therapeutic target for breast cancer. Therefore, anti-HER2 therapy plays a crucial role in the treatment of HER2-positive cancer. Antibody-drug conjugates (ADCs) are composed of a monoclonal antibody, a chemical linker and a payload, wherein their aim is to reduce the toxicity associated with chemotherapy drugs by utilizing specific antibodies. Among the anti-HER2 ADCs currently approved for clinical use, trastuzumab emtansine(T-DM1) and trastuzumab deruxtecan (T-Dxd) have demonstrated remarkable efficacy in treating HER2-positive breast cancer. However, it is essential to emphasize the occurrence of lung toxicity during the treatment process, which can be life-threatening. In this review, we provide an overview of the new epidemiological features associated with interstitial lung disease (ILD) related to anti-HER2 ADCs in breast cancer. We also summarize the potential pathogenesis and explore the diagnosis and treatment strategies within this field.

The effectiveness and pharmacoeconomic study of using different corticosteroids in the treatment of hypersensitivity pneumonitis

PURPOSE

Interstitial lung diseases (ILDs) are caused by inflammation and/or fibrosis of alveolar walls resulting in impaired gas exchange. Hypersensitivity pneumonitis (HP) is the third most common type of ILDs. Corticosteroids are the mainstay treatment for HP. The use of intramuscular (IM) betamethasone or intravenous (IV) dexamethasone as weekly pulse doses has shown higher benefit than daily oral prednisolone for HP patients. The aim of this study is to directly compare different corticosteroids in terms of effectiveness and in monetary values and perform an economic evaluation.

METHODS

One hundred and seven patients were tested for pulmonary function tests (PFTs) and inflammatory markers to assess the treatment effectiveness. A cost-effectiveness analysis (CEA) was performed. ICERs between 3 treatment groups were calculated.

RESULTS

Post treatment, Krebs von den Lungen-6 (KL-6) levels significantly improved in betamethasone group from 723.22 ± 218.18 U/ml to 554.48 ± 129.69 U/ml (p = 0.001). A significant improvement in erythrocyte sedimentation rate (ESR) occurred in the dexamethasone group from 56.12 ± 27.97 mm to 30.06 ± 16.04 mm (p = 0.048). A significant improvement in forced expiratory volume (FEV1), forced vital capacity (FVC) and six-minute walk distance (6MWD) was observed within the three treatment groups. A significant improvement in oxygen desaturation percentage (SpO2) occurred within dexamethasone and betamethasone groups. Betamethasone and dexamethasone were found more cost-effective than prednisolone as their ICERs fell in quadrant C. Furthermore, ICER between betamethasone and dexamethasone was performed; a small difference in cost was found compared to the higher benefit of betamethasone.

CONCLUSION

Betamethasone and dexamethasone were found to be more effective than prednisolone in improving the inflammatory reaction and the clinical features of HP patients. Betamethasone was found to be the best intervention in terms of cost against the effect.

Baseline Blood Levels of Mucin-1 Are Associated with Crucial On-Treatment Adverse Outcomes in Patients with Idiopathic Pulmonary Fibrosis Receiving Antifibrotic Pirfenidone

Mucin-1 is a multi-functional glycoprotein expressed by type II alveolocytes and may be detectable in the circulation following pulmonary fibrosis. The prognostic utility of baseline pre-treatment blood levels of mucin-1 in patients with idiopathic pulmonary fibrosis (IPF) receiving antifibrotics has not yet been fully established. We retrospectively studied a cohort of patients (from two hospitals) with IPF who were receiving pirfenidone for >12 weeks. Baseline blood mucin-1 levels were measured via sandwich enzyme-linked immunosorbent assays. We investigated the performance of mucin-1 levels in longitudinally predicting the risks of acute exacerbation of IPF (AE-IPF) and severe adverse outcomes (SAO), including lung transplantation and death. Seventy patients were included; 20 developed AE-IPF; and 31 had SAO during the follow-up period. Patients with baseline mucin-1 levels ≥2.5 ng/mL had enhanced risks of AE-IPF (adjusted hazard ratio [aHR], 14.07; 95% confidence interval [CI], 4.26-46.49) and SAO within 2 years (aHR, 7.87; 95% CI, 2.86-21.70) and anytime during the follow-up (aHR, 4.68; 95% CI, 2.11-10.39). The risks increased across subgroups with increasing mucin-1 levels. Patients in the "mucin-1 ≥ 2.5" group also exhibited an accelerated decline in DLCO. This study supports baseline blood mucin-1 levels as a biomarker for IPF that predicts adverse outcomes during pirfenidone treatment.

Clinical characteristics and prognostic impact of acute exacerbations in patients with interstitial lung disease and lung cancer: A single-center, retrospective cohort study

BACKGROUND

Although acute exacerbation (AE) after treatment for lung cancer (LC) is a poor prognostic factor in patients with interstitial lung disease associated with lung cancer (ILD-LC), the risk of AE according to cancer treatment type remains unclear. Therefore, in the present study, we aimed to investigate the association between AE and treatment received for LC in patients with ILD-LC.

METHODS

We conducted a retrospective study of patients with ILD-LC who had undergone treatment for LC between January 2018 and December 2022. The primary study outcome was the incidence of AE within 12 months of treatment for LC according to treatment type. The association between AE and all-cause mortality was evaluated as a secondary outcome.

RESULTS

Among a total of 137 patients, 23 (16.8%) developed AE within 12 months of treatment for LC. The incidence of AE according to treatment type was 4.3% for surgery, 16.2% for radiotherapy, 15.6% for chemotherapy, and 54.5% for concurrent chemoradiation therapy (CCRT). Patients who received CCRT were more likely to develop AE, even after adjustment for covariables (hazard ratio [HR], 15.39; 95% confidence interval [CI]: 4.00-59.19; p < 0.001). In addition, AE within 12 months of treatment for LC was associated with an increased risk of all-cause mortality (HR, 2.82; 95% CI: 1.13-7.04; p = 0.026).

CONCLUSION

Among treatment options for patients with ILD-LC, CCRT was associated with an increased risk for AE. In addition, patients with AE had a higher mortality rate than patients without AE.

Serum KL-6 levels predict the occurrence and severity of treatment-related interstitial lung disease in lung cancer

In this study, we aimed to investigate the feasibility of serum Krebs von den Lungen-6 (KL-6) as a potential biomarker for treatment-related ILD (TR-ILD) in lung cancer. We recruited patients with lung cancer in whom KL-6 was measured to differentiate between pneumonia and ILD (category 1), diagnose and assess the severity of suspicious ILD (category 2), or evaluate baseline levels before cancer treatment (category 3). Among 1,297 patients who underwent KL-6 testing, 422 had lung cancer, and TR-ILD was detected in 195 patients. In categories 1-2, median KL-6 level was higher in drug-induced ILD or acute exacerbation of underlying ILD than in no ILD or radiation-induced pneumonitis, and it was correlated with the severity of TR-ILD. High KL-6 level (cut-off: > 436U/mL) was an independent risk factor for severe TR-ILD, and low KL-6 level with high procalcitonin level (> 0.5 ng/mL) could exclude severe TR-ILD. Patients with severe TR-ILD had worse overall survival than those without, whereas high baseline KL-6 level was associated with worse survival, especially in patients without severe TR-ILD. Therefore, serum KL-6 may be a surrogate marker for predicting the occurrence and assessing the severity of TR-ILD at the time of suspected ILD and before lung cancer treatment.

IFN-γ: An overlooked cytokine in dermatomyositis with anti-MDA5 antibodies

Dermatomyositis with anti-melanoma differentiation-associated gene 5 antibody (anti-MDA5 DM) is a rare autoimmune disease, often complicated by life-threatening, rapidly progressive interstitial lung disease. Additional manifestations of the disease include skin lesions, vascular abnormalities, joints and muscles pain. Despite its clinical significance, the pathogenesis of anti-MDA5 DM remains largely unknown. Currently, the disease is perceived as driven by type I interferon (IFN) whose expression is increased in most of the patients. Importantly, the regulation of IFN-γ is also altered in anti-MDA5 DM as evidenced by the presence of IFN-γ positive histiocytes in the lungs of patients, and the identification of autoantibodies that directly stimulate the production of IFN-γ by mononuclear cells. This review critically examines the pathogenesis of the disease, shedding light on recent findings that emphasize a potential role of IFN-γ. A novel conceptual framework is proposed, which integrates the molecular mechanisms altering IFN-γ regulation in anti-MDA5 DM with the known functional effects of IFN-γ on key tissues affected during the disease, such as the lungs, skin, and vessels. Understanding the precise role and relevance of IFN-γ in the pathogenesis of the disease will not only enhance the selection of available therapies for anti-MDA5 DM patients but also pave the way for the development of new therapeutic approaches targeting the altered molecular pathways.

Treatable Traits in Systemic Sclerosis

Systemic sclerosis (SSc) is a chronic systemic disease within the spectrum of connective tissue diseases, specifically characterized by vascular abnormalities and inflammatory and fibrotic involvement of the skin and internal organs resulting in high morbidity and mortality. The clinical phenotype of SSc is heterogeneous, and serum autoantibodies together with the extent of skin involvement have a predictive value in the risk stratification. Current recommendations include an organ-based management according to the predominant involvement with only limited individual factors included in the treatment algorithm. Similar to what has been proposed for other chronic diseases, we hypothesize that a "treatable trait" approach based on relevant phenotypes and endotypes could address the unmet needs in SSc stratification and treatment to maximize the outcomes. We provide herein a comprehensive review and a critical discussion of the literature regarding potential treatable traits in SSc, focusing on established and candidate biomarkers, with the purpose of setting the bases for a precision medicine-based approach. The discussion, structured based on the organ involvement, allows to conjugate the pathogenetic mechanisms of tissue injury with the proposed predictors, particularly autoantibodies and other serum biomarkers. Ultimately, we are convinced that precision medicine is the ideal guide to manage a complex condition such as SSc for which available treatments are largely unsatisfactory.

Post-COVID-19 pulmonary fibrosis: An ongoing concern

Coronavirus disease (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 rapidly spread across the globe causing over 6 million deaths and major compromization of health facilities. The vast majority of survivors post-COVID-19 are left with variable degrees of health sequelae including pulmonary, neurological, psychological, and cardiovascular complications. Post-COVID-19 pulmonary fibrosis is one of the major concerns arising after the recovery from this pandemic. Risk factors for post-COVID-19 pulmonary fibrosis include age, male sex, and the severity of COVID-19 disease. High-resolution computed tomography provides diagnostic utility to diagnose pulmonary fibrosis as it provides more details regarding the pattern and the extent of pulmonary fibrosis. Emerging data showing similarities between post-COVID-19 pulmonary fibrosis and idiopathic pulmonary fibrosis, finding that needs further exploration. The management of post-COVID-19 pulmonary fibrosis depends on many factors but largely relies on excluding other causes of pulmonary fibrosis, the extent of fibrosis, and physiological impairment. Treatment includes immunosuppressants versus antifibrotics or both.

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.

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.

KL-6 levels in the connective tissue disease population: typical values and potential confounders-a retrospective, real-world study

Background

Krebs von den Lungen 6 (KL-6) is a potential biomarker for determining the severity of interstitial lung disease (ILD) in patients with connective tissue disease (CTD). Whether KL-6 levels can be affected by potential confounders such as underlying CTD patterns, patient-associated demographics, and comorbidities needs further investigation.

Methods

From the database created by Xiangya Hospital, 524 patients with CTD, with or without ILD, were recruited for this retrospective analysis. Recorded data included demographic information, comorbidities, inflammatory biomarkers, autoimmune antibodies, and the KL-6 level at admission. Results of CT and pulmonary function tests were collected one week before or after KL-6 measurements. The percent of predicted diffusing capacity of the lung for carbon monoxide (DLCO%) and computed tomography (CT) scans were used to determine the severity of ILD.

Results

Univariate linear regression analysis showed that BMI, lung cancer, TB, lung infections, underlying CTD type, white blood cell (WBC) counts, neutrophil (Neu) counts, and hemoglobin (Hb) were related to KL-6 levels. Multiple linear regression confirmed that Hb and lung infections could affect KL-6 levels independently; the β were 9.64 and 315.93, and the P values were 0.015 and 0.039, respectively. CTD-ILD patients had higher levels of KL-6 (864.9 vs 463.9, P < 0.001) than those without ILD. KL-6 levels were closely correlated to the severity of ILD assessed both by CT and DLCO%. Additionally, we found that KL-6 level was an independent predictive factor for the presence of ILD and further constructed a decision tree model to rapidly determine the risk of developing ILD among CTD patients.

Conclusion

KL-6 is a potential biomarker for gauging the incidence and severity of ILD in CTD patients. To use this typical value of KL-6, however, doctors should take Hb and the presence of lung infections into account.

Acute Exacerbations of Interstitial Lung Diseases: Focus on Biomarkers

Interstitial lung diseases (ILDs) are a large group of pulmonary disorders characterized histologically by the cardinal involvement of the pulmonary interstitium. The prototype of ILDs is idiopathic pulmonary fibrosis (IPF), an incurable disease characterized by progressive distortion and loss of normal lung architecture through unchecked collagen deposition. Acute exacerbations are dramatic events during the clinical course of ILDs, associated with high morbidity and mortality. Infections, microaspiration, and advanced lung disease might be involved in the pathogenesis of acute exacerbations. Despite clinical scores, the prediction of the onset and outcome of acute exacerbations is still inaccurate. Biomarkers are necessary to characterize acute exacerbations better. We review the evidence for alveolar epithelial cell, fibropoliferation, and immunity molecules as potential biomarkers for acute exacerbations of interstitial lung disease.

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.

Serum KL-6 as a Biomarker of Progression at Any Time in Fibrotic Interstitial Lung Disease

The development of a progressive phenotype of interstitial lung disease (ILD) is still unpredictable. Whereas tools to predict mortality in ILD exist, scores to predict disease progression are missing. The aim of this study was to investigate whether baseline serum KL-6 as an established marker to assess disease activity in ILD, alone or in combination with clinical variables, could improve stratification of ILD patients according to progression risk at any time. Consecutive patients with fibrotic ILD, followed at our institution between 2008 and 2015, were investigated. Disease progression was defined as relative decline of ≥10% in forced vital capacity (FVC) or ≥15% in diffusing capacity of the lung for carbon monoxide (DLco)% from baseline at any time. Serum KL-6 was measured using an automated immunoassay (Fujirebio Europe, Gent, Belgium). A stepwise logistic regression was performed to select variables to be included in the score. A total of 205 patients (49% idiopathic pulmonary fibrosis (IPF), 51% fibrotic nonspecific interstitial pneumonia (NSIP)) were included, of them 113 (55%) developed disease progression during follow up. Male gender (G) and serum KL-6 strata (K) were significant predictors of progression at regression analysis and were included in the GK score. A threshold of 2 GK score points was best for discriminating patients at high risk versus low risk to develop disease progression at any time. Serum KL-6 concentration, alone or combined in a simple score with gender, allows an effective stratification of ILD patients for risk of disease progression at any time.

Interstitial lung disease in rheumatoid arthritis: A multidisciplinary problem in rheumatology and pulmonology

Rheumatoid arthritis (RA) is an immune-mediated rheumatic disease (IMRDs) characterized by chronic erosive arthritis and systemic damage to internal organs, leading to early disability and reduced life expectancy in patients. A particularly important place among the systemic manifestations of RA is occupied by interstitial lung diseases (ILD) – the most severe form of pulmonary pathology in RA, defined as RA-ILD, which is pathogenetically associated with risk factors (smoking, etc.) and autoimmune mechanisms underlying RA. RA-ILD is a subtype of RA characterized by a severe course and a poor prognosis и неблагоприятным прогнозом. The review presents new data regarding risk factors and biomarkers for RA-ILD; modern diagnostic capabilities based on the use of functional lung tests, high-resolution computed tomography, ultrasound examination of the lungs. Particular attention is paid to the efficacy and safety of pharmacotherapy, including methotrexate, biologics, JAK inhibitors, and antifibrotic therapy. An algorithm for the pharmacotherapy of RA-ILD has been proposed.

Krebs von den lungen-6 as a clinical marker for hypersensitivity pneumonitis: A meta-analysis and bioinformatics analysis

Aim

Hypersensitivity pneumonitis (HP), also referred to as exogenous allergic alveolitis, is one of the most common interstitial lung diseases (ILDs). A potential immune biomarker, Krebs von den lgen-6 (KL-6) characterizes the progression and severity of HP. The meta-analysis in this study was conducted to elucidate the variations in the concentrations of KL-6 in different types of HP.

Methods

A systematic search of various databases such as EMBASE, Pubmed, CNKI, VIP, Web of Science, and WanFang was carried out to find relevant published articles between January 1980 and August 2022 that explored the relationship between KL-6 and allergic pneumonia. Standardized mean difference (SMD) and 95% confidence interval (CI) were used as effect sizes for comparison among different groups. The GSE47460 and GSE150910 datasets were downloaded to extract and validate the differences in KL-6 mRNA expression between HP lung tissue and healthy controls. Furthermore, the single-cell sequencing dataset GSE135893 was downloaded to extract KL-6 mRNA expression in type II alveolar epithelial cells to validate the differences between HP and healthy controls. Two researchers evaluated the quality of the included studies by employing Newcastle-Ottawa Scale. All the qualified studies were subjected to statistical analyses carried out utilizing RevMan 5.2, Stata 11.0, and R software 4.1.3.

Results

Twenty studies aligned perfectly with the inclusion criteria of the meta. The concentrations of KL-6 were substantially higher in the blood of HP patients as compared to the control group. Subgroup analyses were carried out in accordance with the allergen source and the results revealed that patients with different allergens had higher blood KL-6 concentrations than healthy controls. Additionally, different subgroups of subjects were created for meta-analysis as per the fibrosis status, race, measurement method, and sample type. The concentration of KL-6 in blood was much higher in all HP subgroups than in healthy control groups. Moreover, the bioinformatics analysis revealed that KL-6 mRNA expression was higher in HP lung tissue and type II alveolar epithelial cells as compared to healthy controls.

Conclusion

The present meta-analysis and bioinformatics analysis suggested that the concentration levels of KL-6 varied between HP patients and healthy individuals, and the KL-6 concentrations may be higher in the blood samples of HP patients.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, CRD42022355334.

Prediction Value of KREBS Von Den Lungen-6 (KL-6) Biomarker in COVID-19 Patients: A Systematic Review and Meta-Analysis

The SARS-CoV-2 (COVID-19) pandemic is a major issue that necessitates the use of cutting-edge disease prediction models. The aim of the study was to assess the existing evidence regarding association between Krebs von den Lungen-6 levels and COVID-19 severity. A literature search was performed on Web of Science, PubMed, Scopus and Cochrane Central Register of Controlled Trials databases from 1 January 2020 up to 2 August 2022. The electronic database search was supplemented by searching Google Scholar. In addition, reference lists of relative articles were also reviewed. KL-6 levels among COVID-19 positive vs. negative patients varied and amounted to 443.37 ± 249.33 vs. 205.73 ± 86.8 U/mL (MD = 275.33; 95%CI: 144.57 to 406.09; p < 0.001). The KL-6 level was 402.82 ± 261.16 U/mL in the severe group and was statistically significantly higher than in the non-severe group (297.38 ± 90.46 U/mL; MD = 192.45; 95%CI: 118.19 to 266.72; p < 0.001). The KL-6 level in the mild group was 272.28 ± 95.42 U/mL, compared to 268.04 ± 55.04 U/mL in the moderate COVID-19 group (MD = −12.58; 95%CI: −21.59 to −3.57; p = 0.006). Our meta-analysis indicates a significant association between increased KL-6 levels and SARS-CoV-2 infection. Moreover, KL-6 levels are significantly higher in patients with a more severe course of COVID-19, indicating that KL-6 may be a useful predictor to identify patients at risk for severe COVID-19.

Roles of biomarkers in anti-MDA5-positive dermatomyositis, associated interstitial lung disease, and rapidly progressive interstitial lung disease

BACKGROUND

Anti-melanoma differentiation-associated gene 5 (MDA5)-positive dermatomyositis (MDA5⁺ DM) is significantly associated with interstitial lung disease (ILD), especially rapidly progressive ILD (RPILD) due to poor prognosis, resulting in high mortality rates. However, the pathogenic mechanism of MDA5⁺ DM-RPILD is unclear. Although some MDA5⁺ DM patients have a chronic course of ILD, many do not develop RPILD. Therefore, the related biomarkers for the early diagnosis, disease activity monitoring, and prediction of the outcome of RPILD in MDA5⁺ DM patients should be identified. Blood-based biomarkers are minimally invasive and can be easily detected.

METHODS

Recent relative studies related to blood biomarkers in PubMed were reviewed.

RESULTS

An increasing number of studies have demonstrated that dysregulated expression of blood biomarkers related to ILD such as ferritin, Krebs von den Lungen-6 (KL-6), surfactant protein-D (SP-D), and cytokines, and some tumor markers in MDA5⁺ DM may provide information in disease presence, activity, treatment response, and prognosis. These studies have highlighted the great potentials of blood biomarker values for MDA5⁺ DM-ILD and MDA5⁺ DM-RPILD. This review provides an overview of recent studies related to blood biomarkers, besides highlighted protein biomarkers, including antibody (anti-MDA5 IgG subclasses and anti-Ro52 antibody), genetic (exosomal microRNAs and neutrophil extracellular traps related to cell-free DNA), and immune cellular biomarkers in MDA5⁺ DM, MDA5⁺ DM-ILD, and MDA5⁺ DM-RPILD patients, hopefully elucidating the pathogenesis of MDA5⁺ DM-ILD and providing information on the early diagnosis, disease activity monitoring, and prediction of the outcome of the ILD, especially RPILD.

CONCLUSIONS

Therefore, this review may provide insight to guide treatment decisions for MDA5⁺ DM-RPILD patients and improve outcomes.

Establishment and validation of nomogram for predicting immuno checkpoint inhibitor related pneumonia

Objective

Cancer is one of the main causes of death worldwide. Although immunotherapy brings hope for cancer treatment, it is also accompanied by immune checkpoint inhibitor-related adverse events (irAEs). Immune checkpoint inhibitor pneumonia (CIP) is a potentially fatal adverse event, but there is still a lack of effective markers and prediction models to identify patients at increased risk of CIP.

Methods

A total of 369 cancer patients treated between 2017 and 2022 with immune checkpoint inhibitors at Shengjing Hospital of China Medical University and Liaoning People's Hospital were recruited for this study. Independent variables were selected by differences and binary logistic regression analysis, and a risk assessment nomogram was constructed for CIP risk. The accuracy and discriminative abilities of the nomogram were evaluated by calibration plots, receiver operating characteristic curves (ROCs) and decision curve analyses (DCAs).

Results

Binary logistic regression analysis showed that smoking history, acute phase proteins [interleukin (IL-6) and C-reactive protein (CRP)], CD8 + T lymphocyte count and serum alveolar protein [surface protein-A (SP-A) and Krebs Von den Lungen-6 (KL-6)] were significantly associated with CIP risk. A nomogram consisting of these variables was established and validated by different analyses.

Conclusions

We developed an effective risk nomogram for CIP prediction in immune-checkpoint inhibitor administrated cancer patients, which will further assist early detection of immunotherapy-related adverse events.

Krebs von den Lungen 6 (KL-6) levels in COVID-19 ICU patients are associated with mortality

Background

Krebs von den Lungen 6 (KL-6) is a high-molecular-weight mucin-like glycoprotein, which is also known as MUC1. KL-6 is mainly produced by type 2 pneumocytes and bronchial epithelial cells, and, therefore, elevated circulating KL-6 levels may denote disorders of the alveolar epithelial lining.

The objective of this study is to verify if KL-6 serum level might support ICU physicians in predicting mortality, risk stratifying and triaging severe COVID-19 patients.

Methods

A retrospective cohort study, including all the COVID-19 patients who measured KL-6 serum values at least once during their ICU stay, was performed. The study sample, 122 patients, was divided in two groups, according to the median KL-6 value at ICU admission (median log-transformed KL-6 value: 6.73 U/ml; group A: KL-6 lower than the median and group B: KL-6 higher than the median).

Results

One-hundred twenty-two ICU patients were included in this study. Mortality was higher in group B than in group A (80 versus 46%; p < 0.001); both linear and logistic multivariate analyses showed ratio of arterial partial pressure of oxygen to fraction of inspired oxygen (P/F) significantly and inversely related to KL-6 values.

Conclusion

At ICU admission, KL-6 serum level was significantly higher in the most hypoxic COVID-19 patients and independently associated with ICU mortality.

Blood Krebs von den Lungen-6 levels predict treatment response to antifibrotic therapy in patients with idiopathic pulmonary fibrosis

BACKGROUND

Antifibrotic therapy can slow disease progression (DP) in patients with idiopathic pulmonary fibrosis (IPF). However, the prognostic biomarkers for DP in patients with IPF receiving antifibrotic therapy have not been identified. Therefore, we aimed to evaluate the prognostic efficacy of serum Krebs von den Lungen-6 (KL-6) for DP in patients with IPF receiving antifibrotic therapy.

METHODS

The clinical data of 188 patients with IPF who initiated antifibrotic therapy at three tertiary hospitals was retrospectively analyzed. DP was defined as a relative decline in forced vital capacity (FVC) ≥ 10%, diffusing capacity for carbon monoxide ≥ 15%, acute exacerbation, or deaths during 6 months after antifibrotic therapy.

RESULTS

The mean age of patients was 68.9 years, 77.7% were male, and DP occurred in 43 patients (22.9%) during follow-up (median, 7.6 months; interquartile range, 6.2-9.8 months). There was no difference in baseline KL-6 levels between the DP and no-DP groups; however, among patients with high baseline KL-6 levels (≥ 500 U/mL), changes in KL-6 levels over 1 month were higher in the DP group than those in the non-DP group, and higher relative changes in KL-6 over 1 month were independently associated with DP (odds ratio, 1.043; 95% confidence interval 1.005-1.084) in the multivariable logistic analysis adjusted for age and FVC. In the receiver operating characteristic curve analysis, the 1-month change in KL-6 was also useful for predicting DP (area under the curve = 0.707; P < 0.012).

CONCLUSIONS

Our data suggest that the relative change in KL-6 over 1 month might be useful for predicting DP in patients with IPF receiving antifibrotic therapy when baseline KL6 is high.