Inhibition of transcription factor nuclear factor-κB by a mutant inhibitor-κBα attenuates resistance of human head and neck squamous cell carcinoma to TNF-α caspase-mediated cell death

Abstract

Tumour necrosis factor-α (TNF-α) is a cytokine that can induce cell death of different cancers via a cellular cascade of proteases, the caspases. However, TNF-α has been detected in tumour and serum of patients with head and neck squamous cell carcinoma (HNSCC), and tumour cell lines derived from this environment often exhibit resistance to TNF-α-induced cell death. Cell death mediated by TNF-α and caspases may be inhibited by cytoprotective genes regulated by transcription factor nuclear factor-κB (NF-κB). We recently showed that NF-κB is constitutively activated in HNSCC, and that inhibition of NF-κB by expression of a nondegradable mutant inhibitor of NF-κB, IκBαM, markedly decreased survival and growth of HNSCC cells in vivo. In the present study, we examined the TNF-α sensitivity and response of HNSCC with constitutively active NF-κB, and of HNSCC cells in which NF-κB is inhibited by stable expression of a dominant negative mutant inhibitor, IκBαM. Human lines UM-SCC-9, 11B and 38, previously shown to exhibit constitutive activation of NF-κB, were found to be highly resistant to growth inhibition by up to 104U/ml of TNF-α in 5 day MTT assay. These TNF-α resistant HNSCC lines expressed TNF receptor I, and exhibited constitutive and TNF-α-inducible activation of NF-κB as demonstrated by nuclear localization of NF-κB p65 by immunohistochemistry. UM-SCC-9 I11 cells which stably expressed an inhibitor of NF-κB, IκBαm, were susceptible to TNF-α-induced growth inhibition. DNA cell cycle analysis revealed that TNF-α induced growth inhibition was associated with accumulation of cells with sub-G0/G1 DNA content. Cell death was demonstrated by trypan blue staining, and was blocked by caspase inhibitor. We conclude that HNSCC that exhibit constitutive and TNF-α-inducible activation of transcription factor NF-κB are resistant to TNF-α, and that inhibition of NF-κB sensitizes HNSCC to TNF-α caspase-mediated cytotoxicity. The demonstration of the role of activation of NF-κB in resistance of HNSCC to TNF-α may be helpful in the identification of potential targets for pharmacological, molecular and immune therapy of HNSCC. © 2000 Cancer Research Campaign

Nuclear Factor-κB is an Important Modulator of the Altered Gene Expression Profile and Malignant Phenotype in Squamous Cell Carcinoma

“…Increased expression of IAP-1 (Birc2) was previously detected in metastatic SCC (4). The inhibition of IAP-1 expression with inhibition of NF-B in this study is consistent with the effect of inhibition of NF-B in sensitizing LY-2 cells to apoptosis and HNSCC to tumor necrosis factor-induced caspasemediated cell death (22). Decreased expression of ␤-catenin has been observed and associated with metastasis of human oral SCC (23).…”

“…Constitutive activation of NF-B and NF-B-inducible genes has been detected in prostate and breast cancers, melanomas, and lymphomas (25,(37)(38)(39)(40)(41). NF-B has been implicated in promoting expression of the phenotypic changes and genes involved in inhibition of programmed and therapeutic cell death (18,22,(41)(42)(43)(44), proliferation (15), tumorigenesis (7,25,34), angiogenesis, invasiveness, and metastatic potential (9,25,38).…”

Granulocyte macrophage-colony stimulating factor and interleukin-3 increase expression of type II tumour necrosis factor receptor, increasing susceptibility to tumour necrosis factor-induced apoptosis. Control of leukaemia cell life/death switching

“…25 The pathway which is initially chosen may depend on the presence or absence of low constitutive NF-kB activation. Inhibition of the induction of NF-kB sensitises cells to TNF-induced toxicity, 56 and inhibition of protein synthesis appears to have a similar effect. We have shown that the protein-synthesis inhibitor, cycloheximide, sensitised TF-1 cells to TNF-induced toxicity, and this was most likely by preventing induction of protective or survival factors.…”

Metastatic squamous cell carcinoma cells that overexpress c-Met exhibit enhanced angiogenesis factor expression, scattering and metastasis in response to hepatocyte growth factor

“…For example, the stepwise changes in patterns of growth and metastasis in this model have been linked to expression of angiogenesis factors, such as the C-X-C chemokine Gro-1/KC, and expression of other genes related to activation of the Nuclear Factor kappaB (NF-kB) signal pathway Loukinova et al, 2000). Identification of these factors has facilitated demonstration of the clinical and functional importance of expression of several angiogenesis factors and constitutive activation of NF-kB in human head and neck squamous cell carcinoma (HNSCC) Duffey et al, 1999).…”