Inhibitors of Nf-kappaB Reverse Cellular Invasion and Target Gene Upregulation in an Experimental Model of Aggressive Oral Squamous Cell Carcinoma.

Background: Oral 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 methods: To 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). Results: As 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. Conclusions: These 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.