Assessment of gene expression in head and neck carcinoma using laser capture microdissection and real-time reverse transcription polymerase chain reaction.

Abstract

To quantify gene expression in tumor cells from human head and neck squamous cell carcinomas (HNSCC) using laser capture microdissection (LCM). Histopathologically identified HNSCC cells were microdissected from frozen sections, RNA was isolated, and vascular endothelial growth factor (VEGF) gene expression was measured by real-time reverse transcriptase polymerase chain reaction (RT-PCR). Two human HNSCC tumor samples and matched normal mucosal biopsies and five human xenograft tumor specimens were harvested, embedded, and frozen in OCT. The frozen tumors were sectioned to 8 to 10 mum in thickness, and hematoxylin-eosin (H&E) staining was performed before LCM. An estimated 2,000 to 3,000 tumor cells were microdissected from frozen sections and processed for RNA isolation. mRNA for VEGF was analyzed by real time RT-PCR (TaqMan) with commercially available primers and probes. Two thousand to 3000 cells were necessary to obtain a suitable quantity of RNA for subsequent gene expression study by real-time RT-PCR. The gene expression of VEGF, a major tumor angiogenic factor, was tested in microdissected HNSCC and compared with uninvolved normal mucosal controls. A greater than seven-fold increase of VEGF expression in tumor specimens versus mucosal controls was observed. LCM is a novel sample conserving technique that allows the precise selection of tumor cells from a heterogeneous architecture. The combination of LCM and real-time RT-PCR appears particularly efficacious for studying HNSCC molecular pathogenesis and identifying tissue-specific biomarkers.