Differences in C/EBPs in normal tissue and papillomas of the larynx.

Transcription factors belonging to the family of CAAT enhancer binding proteins (C/EBPs) programme differentiation in a wide variety of cells. We asked about the expression of C/EBPs in squamous epithelium. Using immunohistochemistry, C/EBPalpha and C/EBPbeta were easily detected in tissue sections from normal larynx or laryngeal papillomas, benign tumours with a papillomavirus aetiology and characterized by abnormal differentiation. A temporal expression of these C/EBPs occured as keratinocytes differentiated. In both tissues, C/EBPbeta appeared to be exclusively nuclear. In normal tissue, the greatest amount of C/EBPbeta was present in the spinous layer, and much less occurred in the granular layer. The basal layer of the laryngeal papillomas contained the most C/EBPbeta. Less was present in the spinous layer. Little C/EBPbeta was in the granular layer. Much C/EBPalpha was in the cytoplasm in both tissues. In normal tissue, nuclear C/EBPalpha staining was virtually absent in the basal layer, and became present in the spinous layer. Nuclear C/EBPalpha was randomly distributed in all layers in papillomas. Using immunoblots and Southwestern blots, we detected abundant truncated isoforms of C/EBPalpha in the papillomas. Since differentiation of many tissues is determined by the relative amounts of different C/EBPs, our data supports a role for C/EBPs in the differentiation of squamous epithelium.