NIH Research Festival
Head and neck squamous cell carcinomas (HNSCC) are highly inflammatory and preferentially metastasize to lymph nodes. NF-B, a key target and regulator of inflammatory and cancer genes is constitutively activated in HNSCC, but the upstream regulation, especially for activation of alternative pathway involving LTβ/LTβR is not clear. We hypothesized that LTβ/LTβR mediated alternative NF-kB pathway signaling is an important mechanism for activation and promotion of malignant and metastatic phenotypes in HNSCC. In this study, we have found that LTβ and LTβR are over expressed in subsets of HNSCC (UM-SCC) tissues and cell lines. In UM-SCC cell lines, LTβ mainly activated the alternative NF-κB pathway, enhancing nuclear translocation of RELB and NF-B2/p52.Knockdown of LTβR by siRNA decreased LTR mRNA by quantitative RT-PCR and protein expression by Western blots. Knockdown of LTβR decreased its target kinase NIK, and downstream NF-B subunits RELB and NF-kB2/p52 protein expression. Knockdown of NIK protein decreased RELB and p52 protein expression, while LTβ treatment stabilized NIK, RELB and NF-kB2/p52 expression. LTB mediated NF-B activity was examined by transient luciferase reporter assay or using stably transfected NF-kB reporter cell line through beta lactamase Fret Blazer activity. Knockdown of LTBR and NIK functionally decreased NF-B reporter activity, while treatment of LTB partially restored the NF-kB reporter activity. Our data has shown that constitutive LTβ induces activation of NIK and downstream NF-kB alternate pathway proteins, RELB and NF-kB2/p52 in HNSCC. LT and NIK activation of the alternative NF-B pathway may contribute to the malignant phenotype and metastasis of HNSCC.
Scientific Focus Area: Cancer Biology
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