ABSTRACT
Mutually exclusive KIT and PDGFRA mutations are considered to be the earliest events in gastrointestinal stromal tumors (GIST), but insufficient for their malignant progression. Herein, we aimed to identify driver genes and signaling pathways relevant to GIST progression. We investigated genetic profiles of 707 driver genes, including mutations, gene fusions, copy number gain or loss, and gene expression for 65 clinical specimens of surgically dissected GIST, consisting of six metastatic tumors and 59 primary tumors from stomach, small intestine, rectum, and esophagus. Genetic alterations included oncogenic mutations and amplification-dependent expression enhancement for oncogenes (OG), and loss of heterozygosity (LOH) and expression reduction for tumor suppressor genes (TSG). We assigned activated OG and inactivated TSG to 27 signaling pathways, the activation of which was compared between malignant GIST (metastasis and high-risk GIST) and less malignant GIST (low- and very low-risk GIST). Integrative molecular profiling indicated that a greater incidence of genetic alterations of driver genes was detected in malignant GIST (96%, 22 of 23) than in less malignant GIST (73%, 24 of 33). Malignant GIST samples groups showed mutations, LOH, and aberrant expression dominantly in driver genes associated with signaling pathways of PI3K (PIK3CA, AKT1, and PTEN) and the cell cycle (RB1, CDK4, and CDKN1B). Additionally, we identified potential PI3K-related genes, the expression of which was upregulated (SNAI1 and TPX2) or downregulated (BANK1) in malignant GIST. Based on our observations, we propose that inhibition of PI3K pathway signals might potentially be an effective therapeutic strategy against malignant progression of GIST.
Subject(s)
Gastrointestinal Neoplasms/genetics , Gastrointestinal Stromal Tumors/genetics , Signal Transduction/physiology , Disease Progression , Genes, Tumor Suppressor , Humans , Loss of Heterozygosity , Mutation , Oncogenes , Phosphatidylinositol 3-Kinases/physiology , Receptor, Platelet-Derived Growth Factor alpha/geneticsABSTRACT
Exosomes are small vesicles found in extracellular environments including blood, urine, and cell culture medium. Their contents are celltype specific, and molecules embedded in exosomes can be useful fluidbased clinical biomarkers. To identify proteins with metastatic marker potential, we conducted a comparative exosomal proteome analysis using human pancreatic cancer cell lines derived from metastasis, ascites, and primary tumors. Metastatic potential of cell lines was assessed by migratory and invasive activities. A pancreatic cancer cell line from metastasis (SU.86.86) revealed 23fold and 20fold increases in cell migratory and invasive activities, respectively, compared to the MIA PaCa2 cell line derived from primary tumor cells. Liquid chromatographymass spectrometrybased proteome analysis and subsequent validation by immunoblot analysis revealed that epidermal growth factor receptor pathway substrate 8 (Eps8) was highly abundant in exosomes from metastasisderived SU.86.86 cells. Comparison of 12 pancreatic cancer cell lines derived from different stages of malignancy revealed a strong relationship between exosomal Eps8 protein levels and cell motile activities (migration: r=0.85, P=4.2x104; invasion: r=0.60, P=3.2x102). Conversely, relationships between intracellular Eps8 protein levels and cell motile activities were moderate (migration: r=0.65, P=2.0x102; invasion: r=0.51, P=9.2x102). It was therefore concluded that exosomal Eps8 protein levels were correlated with the migratory cell potential of human pancreatic cancer cells, indicating that exosomal Eps8 has the potential to be a metastatic biomarker for human pancreatic cancer.