Abstract
BACKGROUND: Lymphangioleiomyomatosis is an incurable cystic lung disease primarily affecting women whose pathophysiologic features are only partially elucidated. Vascular endothelial growth factor D (VEGF-D) is a diagnostic biomarker for lymphangioleiomyomatosis, but about one-third of patients have low levels, necessitating invasive lung biopsy.
RESEARCH QUESTION: Does high-throughput proteomics reveal new diagnostic biomarkers and disease mechanisms in lymphangioleiomyomatosis?
STUDY DESIGN AND METHODS: We used the high-throughput proteomic Somascan assay (Somalogic) to measure approximately 10,000 plasma proteins in 20 patients with lymphangioleiomyomatosis and 10 healthy control participants. Enzyme-linked immunosorbent assay (ELISA) confirmed key protein levels in a validation cohort for a total of 53 patients with lymphangioleiomyomatosis and 64 control participants. A least absolute shrinkage and selection operator logistic regression model was used to develop a multiprotein diagnostic score.
RESULTS: We identified 662 differentially expressed proteins. Matrix metalloproteinase 8 (MMP8) was the top upregulated protein in the plasma of patients with lymphangioleiomyomatosis, and neutrophil degranulation was the most enriched pathway. Fifty-eight neutrophil proteins were enriched in lymphangioleiomyomatosis plasma. Premelanosome protein (PMEL) was 2-fold higher in the plasma of patients with lymphangioleiomyomatosis (log2-fold change, 1.47; P = .006), and it was expressed selectively by lymphangioleiomyomatosis cells. ELISA analysis confirmed that plasma MMP8 levels were elevated significantly in lymphangioleiomyomatosis (662 pg/mL vs 255 pg/mL in control participants) and were correlated negatively with baseline FEV1 % predicted (P = .0014). A 6-protein diagnostic score (the LAMScore) achieved 100% specificity (area under the receiver operating characteristic curve, 0.997) in discriminating patients with lymphangioleiomyomatosis from control participants, including those with low VEGF-D.
INTERPRETATION: Our comprehensive proteomic analysis highlights the potential role of neutrophils in lymphangioleiomyomatosis pathogenesis, with MMP8 and other proteases as potential drivers of lung destruction. PMEL and the 6-protein LAMScore are promising biomarkers for lymphangioleiomyomatosis, especially in patients with low VEGF-D levels. The high precision and reproducibility, the wide array of analytes measured, and the lowering costs of proteomics platforms indicate that in the future, lymphangioleiomyomatosis diagnosis could rely on clinically approved custom analyte panels without lung biopsy.