Malignant Transformation of Immortalized HaCaT Keratinocytes through Deregulated Nuclear Factor κB Signaling

This is the authors' abstract. We don't add key points for this paper.

Previous studies addressing functional aspects of nuclear factor kappaB (NF-kappaB) activation in normal and transformed keratinocytes revealed complex and seemingly contradictory roles of this transcription factor in this cell type. In normal skin, NF-kappaB signaling seems to inhibit squamous cell carcinoma development whereas, in squamous cell carcinoma themselves, deregulated NF-kappaB expression and/or signaling is frequently observed. To further investigate this paradox, we focused on NF-kappaB activation as it relates to the transformed phenotype of immortalized but nontumorigenic human keratinocytes (HaCaT cells). We observed that NF-kappaB activity contributed to survival and growth of cultured HaCaT keratinocytes as shown by use of pharmacologic NF-kappaB inhibitors, RNA interference, and inducible overexpression of a dominant interfering IkappaB construct. NF-kappaB activation was largely provided through interaction with extracellular matrix components because preventing cell attachment by forced suspension culture markedly reduced NFkappaB signaling associated with cell death (anoikis); conversely, anoikis was partially reversed by NF-kappaB activation induced either by tumor necrosis factor-alpha treatment or by overexpressing the NF-kappaB p65 subunit in HaCaT cells. Furthermore, overexpression of NF-kappaBp65 in HaCaT cells induced colony formation in soft agar and tumorigenicity in nude mice. In summary, as opposed to normal keratinocytes, immortalized HaCaT keratinocytes provide a cellular context in which deregulated NF-kappaB signaling supports multiple malignant traits in vitro and in vivo.