Intracellular epidermal interleukin 1-like factors in the human epidermoid carcinoma cell line A431

Normal human epidermal cells produce, in primary culture, activities which stimulate the release of PGE2 and collagenase by dermal fibroblasts; this factor(s) might play an important role in epidermal-dermal interactions. Since these activities were mainly found in the cell lysates with only little being detected in the conditioned media, we investigated further the problem of cell-associated versus released activity in the model of the human epidermoid carcinoma cell line A431. The activities were consistently found in the cell lysate and in the conditioned media only when the cells were leaky. No membrane-associated activities were identified. Purification of the cytosolic activities were identified. Purification of the cytosolic activities yielded two differently charged species both with a MW of approximately 17K. The copurification of PGE2- and collagenase-stimulating activities with thymocyte comitogenic activity suggests a close physiochemical relation to IL-1. The activities described here might therefore correspond to the intracellular counterpart of epidermal IL-1 formerly described as epidermal cell-derived thymocyte activating factor (ETAF) and identified in the conditioned medium of cultured epidermal cells. These observations are of importance when studying the modulation of these activities.