EGFR and squamous cell carcinoma: The gene expression program that accompanies mucociliary differentiation has led to the hypothesis that cultured 'undifferentiated' epithelial cells may more closely resemble damaged epithelium or neoplastic lesions in vivo because many genes associated with normal squamous epithelia, squamous cell carcinomas, or epidermal growth factor receptor signaling are more highly expressed in undifferentiated cells [24].