Localization of transforming growth factor-α in human appendageal tumors

Transforming growth factor-α (TGFα) is a potent mitogen for epithelial cells that has been localized to normal human appendageal epithelia. To further understand the role of TGFα in human appendages, we examined TGFα expression immunohistochemically in 17 types of human appendageal tumors differentiating toward hair follicles, eccrine, apocrine, and sebaceous glands. In order of decreasing degrees of differentiation, tumors could be divided into hyperplasias, adenomas, benign epitheliomas, and primordial epitheliomas. Using an antibody that recognizes primarily the 6-kd and 13-kd forms of TGFα, TGFα immunostaining in 16 of 17 tumor types analyzed was found to follow a similar pattern, with expression in hyperplasias > adenomas > benign epitheliomas > primordial epitheliomas. Within a given tumor, TGFα expression also correlated well with the known differentiation state of the tumor cell types. The results suggest that TGFα expression is directly correlated with the differentiation state of hair follicle, eccrine, apocrine, and sebaceous tumors in human skin, and raises the possibility that TGFα may play a role in the differentiation of appendageal epithelia.