Aberrant NF-κB 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-κB signaling pathway and in their response to UVB irradiation. NF-κB is a widely expressed transcription factor that is activated by a cacophony of stimuli, including inflammatory mediators such as TNFα and oxidative stressors such as UVB exposure. This report delineates and further elucidates the aberrant NF-κB signaling pathway and its effect in HaCaT cells exposed to UVB radiation or inflammatory mediators. We demonstrate that NF-κB DNA binding is activated by both UVB and TNFα, but discrepancies in the activation of key upstream signaling pathway components such as AKT phosphorylation and IκBα degradation exist. Disruption of the constitutive NF-κB activity in HaCaT cells resulted in alterations in NF-κB signaling that were more consistent with the NF-κB 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.