DEAD-box RNA helicases in the multistep process of tumor metastasis

RNA helicases constitute a large family of proteins that share a catalytic core with high structural similarity. DEAD-box (DDX) proteins belong to the largest RNA helicase subfamily, and DDX members have been implicated in all facets of RNA metabolism, from transcription to translation, miRNA maturation, and RNA delay and degradation. Interestingly, an increasing number of studies have suggested a relationship between DDX proteins and cancer initiation and progression. The expression levels of many DDX proteins are elevated in a majority of cancers, and recent studies have demonstrated that some DDX proteins have a potent positive effect on promoting the metastasis of malignant cells. Metastasis is a complex, multistep cascade process that includes local invasion, intravasation and survival in the circulation, arrest at a distant organ site, extravasation and metastatic colonization; here, we review this process and present the suggested functions and mechanisms of DDX family proteins in particular steps of the invasion‒metastasis cascade.