MS-Based Biomarker Discovery in Bronchoalveolar Lavage Fluid for Lung Cancer.

Bronchoalveolar lavage fluid (BALF) is a lung fluid. BALF is extracted from the lungs by a bronchoscope. The first step is to instill saline liquid into the lungs followed by extraction. The extracted liquid is depleted from cells by low spin centrifugation. The biochemical content of BALF is mainly composed of phospholipids and proteins and to less extent nucleic acids (DNA, miRNA, mRNA). The proteins, mRNAs, miRNAs, and lipids mirror the pathophysiological state of the patient and are consequently regarded as a rich source of biomarkers with already some examples of established clinical applications. Recently, in Proteomics Clin. Appl. 2019, 13, 1900028, Sim et al. established a novel MS-based proteomics protocol for BALF lung cancer sample analysis by combining antibody-based depletion of high abundant BALF proteins, high pH peptide fractionation, and label free quantitation on a high resolution Orbitrap Fusion instrument. They demonstrate an improvement in BALF sample coverage compared with some previous published methodologies. Notably, the result from the study supports the hypothesis that BALF more than serum reflects the lung cancer proteome and for this reason is a promising source for lung cancer biomarkers.