Expression of proto-oncogenes in normal and tumor tissues of human skin.

The expression of c-fos, c-myc, Ha-ras, N-ras, EGF-receptor, and cardiac actin genes was examined in 7 normal epidermis, 3 cellular nevi, and 8 skin tumors including 6 malignant and 2 benign tumors of human origin. These genes were transcribed in most normal and tumor tissues, though no tumor-specific expression of proto-oncogenes (c-fos, c-myc, Ha-ras, and N-ras) could be detected. However, there was a characteristic parallelism between the expression of c-fos and c-myc in normal epidermis, while the parallelism was not always definite in skin tumors. The ratio of c-fos/c-myc transcripts in normal epidermis was constant compared with the expression of other genes examined. These data suggest that c-fos and c-myc are expressed in all normal skin tissues, and that maintenance of a constant ratio of c-fos/c-myc is closely related to ordered cell growth of the tissues.