Enforced expression of nuclear factor kappa B in p53 deficient keratinocytes induces cell cycle, angiogenic potential and tumorigenesis

Multiple genetic mutations with subsequent molecular events are required for progression of normal epithelial cells to cancer, with p53 mutations being a very common event in squamous carcinogenesis. Upregulation of nuclear factor kappa B (NF-κB) is an associated feature of malignancy, however studies have not examined purposeful overexpression of the NF-κB p65 subunit in in vitro models of oral carcinogenesis. Our objective is to demonstrate that NF-κB p65 transfection into p53 deficient Rhek keratinocytes produces carcinogenic progression. We constitutively over-expressed NF-κB p65 in Rhek keratinocytes, previously immortalized by SV 40 thus inactivating p53, and studied NF-κB dependent events. NF-κB p65 overexpression provided functional upregulation of NF-κB and produced cyclin D1-mediated proliferation and interleukin 8 transcription and secretion. Consequently, we demonstrated tumorigenesis in athymic mice with NF-κB p65 overexpressing cells. We conclude NF-κB p65 overexpression in p53 inactivated immortalized keratinocytes produces tumorigenesis, and that this single alteration in NF-κB expression on a p53 inactivated background is sufficient for squamous carcinogenesis features, thus providing evidence that p65 may act as a gain of function oncogene in this setting.