Quantitative Secretomic Analysis Identifies Extracellular Protein Factors That Modulate the Metastatic Phenotype of Non-Small Cell Lung Cancer

Lung cancer is the leading cause
of cancer-related deaths for men
and women in the United States, with non-small cell lung cancer (NSCLC)
representing 85% of all diagnoses. Late stage detection, metastatic
disease and lack of actionable biomarkers contribute to the high mortality
rate. Proteins in the extracellular space are known to be critically
involved in regulating every stage of the pathogenesis of lung cancer.
To investigate the mechanism by which secreted proteins contribute
to the pathogenesis of NSCLC, we performed quantitative secretomic
analysis of two isogenic NSCLC cell lines (NCI-H1993 and NCI-H2073)
and an immortalized human bronchial epithelial cell line (HBEC3-KT)
as control. H1993 was derived from a chemo-naïve metastatic
tumor, while H2073 was derived from the primary tumor after etoposide/cisplatin
therapy. From the conditioned media of these three cell lines, we
identified and quantified 2713 proteins, including a series of proteins
involved in regulating inflammatory response, programmed cell death
and cell motion. Gene Ontology (GO) analysis indicates that a number
of proteins overexpressed in H1993 media are involved in biological
processes related to cancer metastasis, including cell motion, cell–cell
adhesion and cell migration. RNA interference (RNAi)-mediated knock
down of a number of these proteins, including SULT2B1, CEACAM5, SPRR3,
AGR2, S100P, and S100A14, leads to dramatically reduced migration
of these cells. In addition, meta-analysis of survival data indicates
NSCLC patients whose tumors express higher levels of several of these
secreted proteins, including SULT2B1, CEACAM5, SPRR3, S100P, and S100A14,
have a worse prognosis. Collectively, our results provide a potential
molecular link between deregulated secretome and NSCLC cell migration/metastasis.
In addition, the identification of these aberrantly secreted proteins
might facilitate the development of biomarkers for early detection
of this devastating disease.