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.

The effect of indomethacin on paclitaxel sensitivity and apoptosis in oral squamous carcinoma cells: the role of nuclear factor-κB inhibition.

OBJECTIVE: To investigate new strategies to intensify chemosensitivity in head and neck squamous cell carcinoma. DESIGN: Oral squamous carcinoma cells were examined for nuclear factor-κB (NF-κB) activation and binding activity by paclitaxel, an agent currently used in head and neck cancer chemotherapy. Electromobility shift assays were used to assess the effect of indomethacin on NF-κB binding activity. Cell proliferation assays were used to study cell sensitivity to paclitaxel. To examine whether cytotoxicity could be increased by specifically inhibiting NF-κB, a dominant negative cell line, inhibitor kappa B-alpha (IκBα), was stably expressed in CA-9-22 cells. RESULTS: Paclitaxel possessed the capacity to functionally activate NF-κB, as demonstrated by luciferase reporter gene assays and electromobility shift assay. Indomethacin was able to inhibit paclitaxel-mediated NF-κB activation and promote apoptosis of paclitaxel-treated cells at 24 hours. Indomethacin augmented the paclitaxel cell-killing effect. The dominant negative IκBα cell line exhibited increased chemosensitization to paclitaxel by 2- to 10-fold. CONCLUSIONS: Paclitaxel has the capacity to activate NF-κB in oral squamous carcinoma cells. Indomethacin can reverse this activation to decrease cell proliferation and increase apoptosis. Treatment strategies that combine paclitaxel with indomethacin may have therapeutic benefits attributable to paclitaxel chemosensitization through NF-κB inhibition.