SEM1 and neoplasm: Keratinocyte stem cells (KSCs) are a group of relatively quiescent cells with a broad proliferative potential and an unlimited capacity for self-renewal [53, 54]. DSS1 (deleted in split hand/split foot 1) is a 12-O-tetradecanoyl phorbol-13-acetate-(TPA-) inducible gene expressed in KSCs that plays an important role in skin carcinogenesis and is required for epidermal cell proliferation and oncogenic transformation [55].