CXCL1 and melanoma: High basal NF-κB activity is another reason for increased CXCL1 expression in malignant melanoma [7,184,185] due to increased expression of NF-κB-inducing kinase (NIK), which directly activates inhibitor of NF-κB kinase (IKK) [185] and can indirectly activate NF-κB through the activation of extracellular signal-regulated kinase (ERK) and mitogen-activated protein kinase (MAPK), which phosphorylates NF-κB [185].