EGF and skin sensitization: However, it is known that HaCaT cells differentiate normally [45] and are known to provide the microenvironment relevant to skin sensitization, for example, by responding to epidermal growth factor, transforming growth factor (TGF)-β1, TGF-α, IL-6, interferon gamma, and TNF-α, to stimulate the production of IL-1α [36, 46].