Inhibitors of NF-kappaB reverse cellular invasion and target gene upregulation in an experimental model of aggressive oral squamous cell carcinoma

SummaryBackgroundOral squamous cell carcinoma (OSCC) is diagnosed in 640,000 patients yearly with a poor (50%) 5-year survival rate that has not changed appreciably in decades.Paitents and MethodsTo investigate molecular changes that drive OSCC progression, cDNA microarray analysis was performed using human OSCC cells that form aggressive poorly differentiated tumors (SCC25-PD) in a murine orthotopic xenograft model compared to cells that produce well-differentiated tumors (SCC25-WD).ResultsAs this analysis revealed that 59 upregulated genes were NF-κB target genes, the role of NF-κB activation in alteration of the transcriptional profile was evaluated. The mRNA and protein upregulation of a panel NF-κB target genes was validated by real-time qPCR and immunohistochemistry. Additionally, nuclear translocation of RelA was greatly increased in SCC25-PD, increased nuclear RelA was observed in oral tumors initiated with SCC25-PD compared with tumors initiated by SCC25-WD, and nuclear RelA correlated with stage of disease on two human OSCC tissue microarrays. Treatment of SCC25-PD cells with the IKKβ-inhibitor sc-514, that effectively prevents RelA phosphorylation on Ser 536, reversed nuclear-translocation of RelA and strongly inhibited NF-κB gene activation. Furthermore, blocking the phosphorylation of RelA using the MSK1/2 inhibitor SB 747651A significantly reduced the mRNA upregulation of a subset of target genes. Treatment with sc-514 or SB747651A markedly diminished cellular invasiveness.ConclusionsThese studies support a model wherein NF-κB is constitutively active in aggressive OSCC, while blocking the NF-κB pathway reduces NF-κB target gene upregulation and cellular invasiveness.