MYC and actinic keratosis: Development of papillomatosis (a pre-malignant lesion of skin epidermis resembling actinic keratosis in humans) was induced in nine mice following activation of c-MycERTAM (c-Myc) in suprabasal keratinocytes of adult Involucrin-c-MycERTAM transgenic skin by daily topical administration of 4-OHT for 14 days as previously described [8].