DNA methylation of PTGER4 in peripheral blood plasma helps to distinguish between lung cancer, benign pulmonary nodules and chronic obstructive pulmonary disease patients.

BACKGROUND/INTRODUCTION: In contrast to patients who present with advanced stage lung cancer and associated poor prognosis, patients with early-stage lung cancer may be candidates for curative treatments. The results of the NELSON lung cancer screening trial are expected to stimulate the development and implementation of a lung cancer screening strategy in most countries. Widespread use of chest computed tomography scans will also result in the detection of solitary pulmonary nodules. Because reliable biomarkers to distinguish between malignant and benign lesions are lacking, tissue-based histopathological diagnostics remain the gold standard. In this study, we aimed to establish a test to assess the predictive ability of DNA hypermethylation of SHOX2 and PTGER4 in plasma to discriminate between patients with 1.) lung cancer, 2.) benign lesions, and 3.) patients with chronic obstructive pulmonary disease (COPD). PATIENTS AND METHODS: We retrospectively analysed SHOX2 and PTGER4 methylation in 121 prospectively collected plasma samples of patients with lung cancer (group 1A), benign lesions (group 1B), and COPD without nodules (group 2). RESULTS: PTGER4 DNA hypermethylation was more frequently observed in patients with lung cancer than in controls (p = 0.0004). Results remained significant after correction for tumour volume, smoking status, age, and eligibility for the NELSON trial. CONCLUSIONS: Detection of methylated PTGER4 in plasma DNA may serve as a biomarker to support clinical decision-making in patients with pulmonary lesions at lung cancer screening in high-risk populations. Further exploration in prospective studies is warranted.

A prediction model based on DNA methylation biomarkers and radiological characteristics for identifying malignant from benign pulmonary nodules.

BACKGROUND: Lung cancer remains the leading cause of cancer deaths across the world. Early detection of lung cancer by low-dose computed tomography (LDCT) can reduce the mortality rate. However, making a definitive preoperative diagnosis of malignant pulmonary nodules (PNs) found by LDCT is a clinical challenge. This study aimed to develop a prediction model based on DNA methylation biomarkers and radiological characteristics for identifying malignant pulmonary nodules from benign PNs. METHODS: We assessed three DNA methylation biomarkers (PTGER4, RASSF1A, and SHOX2) and clinically-relevant variables in a training cohort of 110 individuals with PNs. Four machine-learning-based prediction models were established and compared, including the K-nearest neighbors (KNN), random forest (RF), support vector machine (SVM), and logistic regression (LR) algorithms. Variables of the best-performing algorithm (LR) were selected through stepwise use of Akaike's information criterion (AIC). The constructed prediction model was compared with the methylation biomarkers and the Mayo Clinic model using the non-parametric approach of DeLong et al. with the area under a receiver operator characteristic curve (AUC) analysis. RESULTS: A prediction model was finally constructed based on three DNA methylation biomarkers and one radiological characteristic for identifying malignant from benign PNs. The developed prediction model achieved an AUC value of 0.951 in malignant PNs diagnosis, significantly higher than the three DNA methylation biomarkers (0.912, 95% CI:0.843-0.958, p = 0.013) or Mayo Clinic model (0.823, 95% CI:0.739-0.890, p = 0.001). Validation of the prediction model in the testing cohort of 100 subjects with PNs confirmed the diagnostic value. CONCLUSION: We have shown that integrating DNA methylation biomarkers and radiological characteristics could more accurately identify lung cancer in subjects with CT-found PNs. The prediction model developed in our study may provide clinical utility in combination with LDCT to improve the over-all diagnosis of lung cancer.

[DNA methylation detection of SHOX2 and PTGER4 in plasma contributes to differential diagnosis of pulmonary nodule patients].

Objective To investigate the clinical significance of plasma cell free DNA (cfDNA) methylation in short stature homeobox 2 (SHOX2) and prostaglandin E receptor 4 (PTGER4) for diagnosing pulmonary nodule patients. Methods We collected 10 mL venous blood from patients. And the plasma DNA was extracted. Real-time quantitative PCR was performed to amplify the DNA after bisulfite conversion. Valid Ct values were input into specialized software to analyze the methylation status of SHOX2 and PTGER4. Histological classification of lung malignant tissues was carried out by immunohistochemistry. Results The 22 of 57 patients were positive and 35 were negative for SHOX2 and PTGER4 DNA methylation detection. Computed tomography (CT) indicated that 31 of 57 patients were diagnosed with pulmonary nodules, among which 19 patients were positive for DNA methylation; 3 of 16 patients with inflammation on CT were positive for DNA methylation; 10 patients with normal or ground glass CT images were negative for DNA methylation. Significant differences in SHOX2 and PTGER4 DNA methylation were observed in the patients with different CT findings. The highest positive rate of CT nodular lesions was 61.3%. The 20 patients with pulmonary nodules were pathologically diagnosed with lung cancer, of which 18 were positive for SHOX2 and PTGER4 DNA methylation, with a positive rate of 90%. Only 1 case of benign pulmonary nodules was positive. Significant difference in SHOX2 and PTGER4 methylation status was observed between benign and malignant pulmonary nodules. The positive rate of SHOX2 and PTGER4 methylation were both 100% in squamous cell lung carcinoma and small cell lung carcinoma, while 75% in adenocarcinoma. Conclusion SHOX2 and PTGER4 methylation detection in blood plasma has certain value in the early diagnosis of lung cancer and can be a complementary tool of CT in diagnosing pulmonary nodule patients.

Prostaglandin E2 levels and platelet function are different in cord blood compared to adults.

Neonatal platelets support primary haemostasis and thrombin generation as well as adult platelets, despite observable hypoaggregability in vitro. High prostaglandin E2 levels at accouchement could account for inhibited platelet function via the EP4 receptor. We set out to determine prostaglandin E2 plasma levels in cord blood of healthy neonates and evaluate the impact of prostaglandin E2 on platelet function in adult and cord blood samples. Prostaglandin E2 plasma levels were measured in cord blood and venous adult blood using GC-MS. Impact of prostaglandin E2 on platelet aggregation was measured by spiking cord blood and adult samples. Contributions of EP3 and EP4 receptors were evaluated using respective antagonists. Intracellular cAMP concentrations were measured using a commercial ELISA-kit. Prostaglandin E2 plasma levels were substantially higher in cord blood than in adult samples. Spiking with prostaglandin E2 resulted in a slight but consistent reduction of platelet aggregation in adult blood, but response to PGE2 was blunted in cord blood samples. Aggregation response of spiked adult samples was still higher than with non-spiked cord blood samples. Blockage of EP4 receptors resulted in improved platelet aggregation in adult platelets upon prostaglandin E2 spiking, while aggregation in cord blood samples remained unaltered. Intracellular cAMP concentrations after preincubation with prostaglandin E2 were only increased in adult samples. In conclusion, very high prostaglandin E2 concentrations in cord blood affect platelet function. This effect may partially explain neonatal platelet hypoaggregability. Peak levels of prostaglandin E2 can potentially protect against birth stress-induced platelet activation.

PGE(2) reverses G(s)-mediated inhibition of platelet aggregation by interaction with EP3 receptors, but adds to non-G(s)-mediated inhibition of platelet aggregation by interaction with EP4 receptors.

Prostaglandin E(2) (PGE(2)) has intriguing effects on platelet function in the presence of agents that raise cyclic adenosine 3'5'-monophosphate (cAMP). PGE(2) reverses inhibition of platelet aggregation by agents that stimulate cAMP production via a G(s)-linked receptor, but adds to the inhibition of platelet function brought about by agents that raise cAMP through other mechanisms. Here, we used the EP receptor antagonists DG-041 (which acts at the EP3 receptor) and ONO-AE3-208 (which acts at the EP4 receptor) to investigate the role of these receptors in mediating these effects of PGE(2). Platelet aggregation was measured in platelet-rich plasma obtained from healthy volunteers in response to adenosine diphosphate (ADP) using single platelet counting. The effects of a range of concentrations of PGE(2) were determined in the presence of (1) the prostacyclin mimetic iloprost, which operates through G(s)-linked IP receptors, (2) the cAMP PDE inhibitor DN9693 and (3) the direct-acting adenylate cyclase stimulator forskolin. Vasodilator-stimulated phosphoprotein (VASP) phosphorylation was also determined as a measure of cAMP. PGE(2) reversed the inhibition of aggregation brought about by iloprost; this was prevented in the presence of the EP3 antagonist DG-041, indicating that this effect of PGE(2) is mediated via the EP3 receptor. In contrast, PGE(2) added to the inhibition of aggregation brought about by DN9693 or forskolin; this was reversed by the EP4 antagonist ONO-AE3-208, indicating that this effect of PGE(2) is mediated via the EP4 receptor. Effects on aggregation were accompanied by corresponding changes in VASP phosphorylation. The dominant role of EP3 receptors circumstances where cAMP is increased through a Gs-linked mechanism may be relevant to the situation in vivo where platelets are maintained in an inactive state through constant exposure to prostacyclin, and thus the main effect of PGE(2) may be prothrombotic. If so, the results described here further support the potential use of an EP3 receptor antagonist in the control of atherothrombosis.