Abstract: OBJECTIVE： To identify cofilin-1， a characteristic peripheral blood marker for recurrent metastasis of lung adenocarcinoma， by enrichment and mass spectrometry of plasma low-abundance proteins from lung adenocarcinoma patients using novel nanomaterials and to explore its relationship with clinicopathological features and prognosis of lung adenocarcinoma. METHODS： Twenty-four patients with complete clinical information of lung adenocarcinoma and 52 patients with benign lung disorders (17 tuberculosis，25 inflammatory granuloma and 10 malignant tumors) diagnosed by postoperative pathology were selected. Peripheral blood was collected from the patients，and low abundance proteins in the samples were enriched by kit nanomagnetic beads and subsequently identified by high resolution mass spectrometry. The target-decoy (TDfdr) algorithm was applied to screen differentially expressed genes in R software to control the pseudo-discovery rate within 0.05. RNA expression profiles and clinical data of 598 lung adenocarcinoma tissues were downloaded from The Cancer Genome Atlas (TCGA) database for Kaplan-Meier survival analysis and Log-rank test. RESULTS： A total of 6 563 proteins were identified by mass spectrometry， and 105 differentially expressed proteins were obtained after screening by the TDfdr algorithm (39 of which were lowly expressed and 66 were highly expressed in lung cancer plasma samples. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the low-expressed proteins were mainly involved in pathways related to the maintenance of the cell's material exchange，structural stability，and normal motor functions，which are involved in constituting the molecular basis of tissue development， homeostasis， and damage repair. On the other hand， the highly expressed proteins were mainly involved in pathways related to metabolic reprogramming，cell division，and motor migration，which help to maintain the survival and growth of cancer cells and promote the proliferation and metastasis of cancer cells. Bioinformatics analysis revealed that the actin depolymerization factor cofilin-1 was highly expressed in the plasma of lung adenocarcinoma patients (P<0.05)， and the high expression of cofilin-1 in TCGA lung adenocarcinoma tissues was negatively correlated with the overall survival of the patients (r=-1.48，P<0.05). CONCLUSION： There are large differences in plasma low abundance protein expression between patients with lung adenocarcinoma and those with benign lung diseases. High expression of cofilin-1 in cancer plasma and tissue correlated with poor prognosis of the patients，and it may therefore be useful as a plasma molecular marker for lung adenocarcinoma.

Key words: lung adenocarcinoma, plasma low-abundance proteins, proteome, cofilin-1, prognosis