Identification of Proteomic Features To Distinguish Benign Pulmonary Nodules from Lung Adenocarcinoma

We hypothesized that distinct protein
expression features of benign
and malignant pulmonary nodules may reveal novel candidate biomarkers
for the early detection of lung cancer. We performed proteome profiling
by liquid chromatography–tandem mass spectrometry to characterize
34 resected benign lung nodules, 24 untreated lung adenocarcinomas
(ADCs), and biopsies of bronchial epithelium. Group comparisons identified
65 proteins that differentiate nodules from ADCs and normal bronchial
epithelium and 66 proteins that differentiate ADCs from nodules and
normal bronchial epithelium. We developed a multiplexed parallel reaction
monitoring (PRM) assay to quantify a subset of 43 of these candidate
biomarkers in an independent cohort of 20 benign nodules, 21 ADCs,
and 20 normal bronchial biopsies. PRM analyses confirmed significant
nodule-specific abundance of 10 proteins including ALOX5, ALOX5AP,
CCL19, CILP1, COL5A2, ITGB2, ITGAX, PTPRE, S100A12, and SLC2A3 and
significant ADC-specific abundance of CEACAM6, CRABP2, LAD1, PLOD2,
and TMEM110-MUSTN1. Immunohistochemistry analyses for seven selected
proteins performed on an independent set of tissue microarrays confirmed
nodule-specific expression of ALOX5, ALOX5AP, ITGAX, and SLC2A3 and
cancer-specific expression of CEACAM6. These studies illustrate the
value of global and targeted proteomics in a systematic process to
identify and qualify candidate biomarkers for noninvasive molecular
diagnosis of lung cancer.