Although the skin cancer promoter PMA is known to induce the gene expression and IL-1α production in normal keratinocytes [20, 21], HaCaT cells have been shown to have a PMA-specific defect that is associated with an impaired mitogen-activated protein kinases (MAPKs) down-stream to the MEK/ERK signalling pathway [39, 42]. Here, MAP2K7 is linked to skin cancer.