Abstract: Objective To observe the effects of curcumin on migration and invasion of papillary thyriod cancer B-CPAP cells. Methods B-CPAP cells were treated with 5, 10, 15, or 20 μmol/L curcumin, and the changes in cell survival, migration and invasion were examined using MTT assay and Transwell assay. ROS levels in the treated cells were detected with a DCFH-DA probe. The expression levels of Nrf2 and Keap1 in the cells were determined using Western blotting and qRT-PCR. Results Treatment with curcumin dose- and time-dependently suppressed the viability of B-CPAP cells (P<0.05 or P<0.01). Curcumin inhibited the migration and invasion (P<0.001) and promoted ROS production in B-CPAP cells in a dose-dependent manner, and application of NAC effectively reversed curcumin- induced increase of ROS. Curcumin at 20 μmol/L significantly decreased the protein and mRNA expressions of Nrf2 and increased the expressions of Keap1 protein and mRNA (P<0.05 or P<0.01), causing also significantly reduced expression of Nrf2 protein in the cell nuclei (P<0.05) without obviously affecting its expression in the cytoplasm (P>0.05). Conclusion Curcumin inhibits the proliferation, migration and invasion of papillary thyriod cancer B-CPAP cells probably via the Keap1-Nrf2 signaling pathway.

Key words: curcumin; B-CPAP; Keap1-Nrf2 pathway; papillary thyriod cancer