A cell proteomic approach for the detection of secretable biomarkers of invasiveness in oral squamous cell carcinoma.

OBJECTIVE: To identify potential biomarkers of invasiveness in oral squamous cell carcinoma. DESIGN: A pilot proteomic study for the identification of secreted and cleaved proteins that can serve as potential biomarkers for head and neck carcinoma invasiveness. SUBJECTS: Two primary cell lines and their variants were established from 2 oral squamous cell carcinoma human tissue samples with distinct invasive phenotypes. The cell lines were confirmed to maintain the invasive capacity of the original cancer when implanted into the tongues of immunocompromised RAG-2/gamma(c) mice. INTERVENTIONS: Invasiveness was assessed by the capacity of cells to invade through a matrigel matrix using the Boyden chamber assay and correlated with the invasiveness seen clinically and histologically in patients. In parallel, cell lines were grown in serum-free conditioned medium, which was then used to identify secreted and/or cleaved proteins that emanate from cancer cells, using 2-dimensional gel electrophoresis and matrix-assisted laser desorption-ionization combined with tandem mass spectrometry. RESULTS: The invasion assays revealed a correlation between cell migration capacity through matrigel matrix and the aggressive phenotype seen in the clinical and histopathological assessments. More than 50 proteins were identified as being differentially secreted in media between the least and the more aggressive cell lines (P < .05). These include proteins that regulate cell metabolism, cell structure, cell adhesion, and cell motility, as well as proteins with undefined function. CONCLUSIONS: We report a sensitive and clinically relevant approach to screen for secreted biomarkers of oral squamous cell carcinoma invasiveness using proteomic technology. Both high- and low-abundant secreted proteins were identified and can represent potential biomarkers for oral cancer.

Serum proteomic approach for the identification of serum biomarkers contributed by oral squamous cell carcinoma and host tissue microenvironment.

The lack of serum biomarkers for head and neck carcinoma limits early diagnosis, monitoring of advanced disease, and prediction of relapses in patients. We conducted a comprehensive proteomics study on serum from mice bearing orthotopic human oral squamous cell carcinomas (OSCC) with distinct invasive phenotypes. Matched established cell lines were transplanted orthotopically into tongues of RAG-2/gamma(c) mice and mouse serum was analyzed by 2-dimensional-differential gel electrophoresis(2D-DIGE)/liquid chromatography (LC)-MS/MS and by online 2D-LC-MS/MS of iTRAQ labeled samples. We identified several serum proteins as being differentially expressed between control and cancer-bearing mice and between noninvasive and invasive cancer (p<0.05). Differentially expressed proteins of human origin included the epidermal growth factor receptor (EGFR), cytokeratins, G-protein coupled receptor 87, Rab11 GTPase, PDZ-domain containing proteins, and PEST-containing nuclear proteins. Identified proteins of mouse origin included clusterin, titin, vitronectin, vitamin D-binding protein, hemopexin, and kininogen I. The levels of serum and cell secreted EGFR were further validated to match proteomic data regarding the inverse correlation with the invasive phenotype. In summary, we report a comprehensive patient-based proteomics approach for the identification of potential serum biomarkers for OSCC using an orthotopic xenograft mouse model.