Cell-based sensor for analysis of EGFR biomarker expression in oral cancer

Oral cancer is the sixth most common cancer worldwide and has been marked by high morbidity and poor survival rates that have changed little over the past few decades. Beyond prevention, early detection is the most crucial determinant for successful treatment and survival of cancer. Yet current methodologies for cancer diagnosis based upon pathological examination alone are insufficient for detecting early tumor progression and molecular transformation. To address this clinical need, we have developed a cell-based sensor to detect oral cancer biomarkers, such as the epidermal growth factor receptor (EGFR) whose over-expression is associated with early oral tumorigenesis and aggressive cancer phenotypes. The lab-on-a-chip (LOC) sensor utilizes an embedded track-etched membrane, which functions as a micro-sieve, to capture and enrich cells from complex biological fluids or biopsy suspensions. Once captured, "on-membrane" immunofluorescent assays reveal the presence and isotype of interrogated cells via automated microscopy and fluorescent image analysis. Using the LOC sensor system, with integrated capture and staining technique, EGFR assays were completed in less than 10 minutes with staining intensity, homogeneity, and cellular localization patterns comparable to conventional labeling methods. Further examination of EGFR expression in three oral cancer cell lines revealed a significant increase (p < 0.05) above control cells with EGFR expression similar to normal squamous epithelium. Results obtained in the microfluidic sensor system correlated well with flow cytometry (r(2) = 0.98), the "gold standard" in quantitative protein expression analysis. In addition, the LOC sensor detected significant differences between two of the oral cancer cell lines (p < 0.01), accounting for disparity of approximately 34 000 EGFR per cell according to quantitative flow cytometry. Taken together, these results support the LOC sensor system as a suitable platform for rapid detection of oral cancer biomarkers and characterization of EGFR over-expression in oral malignancies. Application of this technique may be clinically useful in cancer diagnostics for early detection, prognostic evaluation, and therapeutic selection. Having demonstrated the functionality of this integrated microfluidic sensor system, further studies using clinical samples from oral cancer patients are now warranted.