MAPK3 and squamous cell carcinoma: Our study used SCC4 oral squamous cell carcinoma cells, and our results indicate that kaempferol (1) inhibits the migration and invasion of SCC4 cells; (2) reduces the gene expression and enzyme activity of MMP-2; (3) decreases the nuclear translocation of AP-1 to the MMP-2 promoter; and (4) inhibits the phosphorylation of ERK1/2.