Invadopodia formation is a key driver of
cancer metastasis. The noncanonical IkB-related
kinase IKKε has been implicated in
cancer metastasis, but its roles in invadopodia formation and
colorectal cancer (CRC)
metastasis are unclear. Methods: Immunofluorescence,
gelatin-degradation assay, wound healing assay and transwell invasion assay were used to determine the influence of IKKε over-expression, knockdown and pharmacological inhibition on invadopodia formation and the migratory and invasive capacity of CRC cells in vitro. Effects of IKKε knockdown or pharmacological inhibition on CRC
metastasis were examined in mice. Immunohistochemistry staining was used to detect expression levels of IKKε in CRC patient tissues, and its association with prognosis in CRC patients was also analyzed. Immunoprecipitation, western blotting and in vitro
kinase assay were constructed to investigate the molecular mechanisms. Results: IKKε co-localizes with
F-actin and the invadopodia marker Tks5 at the
gelatin-degrading sites of CRC cells. Genetic over-expression/knockdown or pharmacological inhibition of IKKε altered invadopodia formation and the migratory and invasive capacity of CRC cells in vitro. In vivo, knockdown or pharmacological inhibition of IKKε significantly suppressed
metastasis of CRC cells in mice. IKKε knockdown also inhibited invadopodia formation in vivo. Clinical investigation of
tumor specimens from 191 patients with CRC revealed that high IKKε expression correlates with
metastasis and poor prognosis of CRC. Mechanistically, IKKε directly binds to and phosphorylates kindlin-2 at
serine 159; this effect mediates the IKKε-induced invadopodia formation and promotion of CRC
metastasis. Conclusions: We identify IKKε as a novel regulator of invadopodia formation and a unique mechanism by which IKKε promotes the
metastasis of CRC. Our study suggests that IKKε is a potential target to suppress CRC
metastasis.