Tumor metastasis is the major cause of death for
prostate cancer (PCa) patients. However, the treatment options for metastatic PCa are very limited. Epithelial-mesenchymal transition (EMT) has been reported to be an indispensable step for
tumor metastasis and is suggested to associate with acquisition of cancer stem cell (CSC) attributes. We propose that small-molecule compounds that can reverse EMT or induce mesenchymal-epithelial transition (MET) of PCa cells may serve as
drug candidates for anti-
metastasis therapy. Methods: The promoters of CDH1 and VIM genes were sub-cloned to drive the expression of firefly and
renilla luciferase reporter in a lentiviral vector. Mesenchymal-like PCa cells were infected with the
luciferase reporter lentivirus and subjected to
drug screening from a 1274 approved small-molecule
drug library for the identification of agents to reverse EMT. The dosage-dependent effect of candidate compounds was confirmed by
luciferase reporter assay and immunoblotting. Wound-healing assay, sphere formation, transwell migration assay, and in vivo intracardiac and orthotopic
tumor xenograft experiments were used to evaluate the mobility,
metastasis and
tumor initiating capacity of PCa cells upon treatment. Possible downstream signaling pathways affected by the candidate compound treatment were analyzed by
RNA sequencing and immunoblotting. Results:
Drug screening identified
Amlexanox, a
drug used for recurrent
aphthous ulcers, as a strong agent to reverse EMT.
Amlexanox induced significant suppression of cell mobility, invasion, serial sphere formation and in vivo
metastasis and
tumor initiating capacity of PCa cells.
Amlexanox treatment led to downregulation of the IKK-ɛ/ TBK1/ NF-κB signaling pathway. The effect of
Amlexanox on EMT reversion and cell mobility inhibition can be mimicked by other IKK-ɛ/TBK1 inhibitors and rescued by reconstitution of dominant active NF-κB. Conclusions:
Amlexanox can sufficiently suppress PCa
metastasis by reversing EMT through downregulating the IKK-ɛ/TBK1/NF-κB signaling axis.