AMPLIFICATION AND EXPRESSION OF EMS-1 (CORTACTIN) IN HEAD AND NECK SQUAMOUS-CELL CARCINOMA CELL-LINES

Amplification of chromosome 11q13 DNA sequences is detected in approxi mately 30% of primary head and neck squamous cell carcinomas (HNSCC). The amplified region includes genes for cyclin D1, hst-1, int-2, and m ore recently, ems-1, Ems-1 encodes an 80/85kd cytoskeletal associated protein termed cortactin, which has been shown to bind F-actin and is a pp60src substrate. We investigated 16 HNSCC cell Lines for ems-1 DNA amplification and gene expression by western blotting and immunofluor escence using mAb 4F11. Amplification of ems-1 DNA was detected in 8/1 6 (50%) cell lines and was related directly to overexpression of corta ctin by western blotting and immunofluorescence, Western blotting dete cted both forms of cortactin, p80 and p85, at equal intensity. Immunof luorescent staining revealed low levels of cortactin localized to the cytoplasm and surface membrane in normal bronchial epithelial cells an d tumor cell cultures with single copy ems-1 DNA. In contrast, tumor c ell cultures with ems-1 DNA amplification demonstrated intense, homoge neous cortactin cytoplasmic staining. These results suggest that overe xpression of p80/85 may be a useful marker to identify 11q13 amplifica tion, a molecular alteration correlated with the presence of lymph nod e metastasis in head and neck cancer.