Constitutive IKK activity associated with increased IκBα phosphorylation and degradation contribute to the high level of endogenous nuclear factor-κB (NF-κB) activation in Hs294T melanoma cells as compared with RPE cells (R. L. Shattuck-Brandt and A. Richmond, Cancer Res., 57: 3032–3039, 1997; M. N. Devalaraja et al., Cancer Res., 59: 1372–1377, 1999). To determine whether this endogenous NF-κB activation was characteristic of melanoma, we examined the level of constitutive activation of NF-κB in a number of melanoma cell lines. We demonstrate here that eight melanoma cell lines exhibit increased IκB kinase (IKK) activity, enhanced phosphorylation of IκBα and p65, and enhanced nuclear localization of p65/p50 in comparison to normal human epidermal melanocytes. The chemokines, CXC ligand 1 (CXCL1) and CXCL8, but not CXCL5, are highly expressed in most of the melanoma cell lines, suggesting that the constitutive production of chemokines is highly correlated to endogenous NF-κB activity. Our failure to observe a direct relationship between the fold activation of IKK, CXCL1, or CXCL8 mRNA levels and secretion of these chemokines into the culture medium suggest that regulation of chemokine expression also occurs at the posttranscription level of mRNA stability and/or translational control. Moreover, recombinant CXCL1 can directly induce IKK activity in normal human epidermal melanocytes in a concentration-dependent manner after up-modulation of CXCL1 protein expression, whereas inhibition of IKKβ activity results in down-modulation of CXCL1 protein expression. Finally, CXCL1 antibody blocks IKK activity and inhibits the proliferation of melanoma cells to further support the concept that the constitutive activation of NF-κB and autocrine effects of CXCL1 play an important role in the pathogenesis of melanoma.