EGFR and skin neoplasm: Activation of CDK2 in mouse epidermis reportedly induces keratinocyte proliferation, however did not affect skin tumor development [42, 43] Also SYK has been shown to act as a negative regulator in epidermal keratinocyte differentiation and is also involved in EGFR signaling, which may contribute to its regulatory role in keratinocyte terminal differentiation [44].