Aberrant NF-kappaB Activity in HaCaT Cells Alters Their Response to UVB Signaling

The immortalized keratinocyte cell line called HaCaT has been used in experiments as a convenient substitute for cultured normal human keratinocytes. However, some molecular differences have been identified that distinguish HaCaT cells from normal human keratinocytes, including differences in the NF-kappaB signaling pathway and in their response to UVB irradiation. NF-kappaB is a widely expressed transcription factor that is activated by a cacophony of stimuli, including inflammatory mediators such as TNFalpha and oxidative stressors such as UVB exposure. This report delineates and further elucidates the aberrant NF-kappaB signaling pathway and its effect in HaCaT cells exposed to UVB radiation or inflammatory mediators. We demonstrate that NF-kappaB DNA binding is activated by both UVB and TNFalpha, but discrepancies in the activation of key upstream signaling pathway components such as AKT phosphorylation and IkappaBalpha degradation exist. Disruption of the constitutive NF-kappaB activity in HaCaT cells resulted in alterations in NF-kappaB signaling that were more consistent with the NF-kappaB signaling pathway in normal human keratinocytes. These studies suggest that caution should be used in extrapolating the biological responses of HaCaT cells to those of normal human keratinocytes in the absence of confirmatory experiments.