5-Iodotubercidin inhibits epithelial to mesenchymal transition by inhibiting IKK/NFκB-dependent gene expression.

Epithelial to mesenchymal transition (EMT) is a process of trans-differentiation important for development, inflammation and cancer. Transforming Growth Factor-β (TGFβ) is a physiologically relevant inducer of EMT. We had recently characterized the adenosine analog, adenosine kinase inhibitor 5-Iodotubercidin (5-ITu), as a compound which preferentially sensitizes MK2-deficient cells to TNFα-induced, RIPK1-dependent cell death. Here we investigated the effect of 5-ITu on TGFβ-induced EMT. 5-ITu suppressed TGFβ-induced morphological changes and migration in A549 (lung cancer) and PANC1 (pancreatic cancer) cell lines. Consistent with these effects, there was significant suppression of EMT markers as indicated by qPCR, immunoblotting and immunofluorescence and confocal microscopy. Mechanistic investigations revealed that 5-ITu-mediated EMT suppression was independent of adenosine kinase inhibition and RIPK1 activation. 5-ITu suppressed NFκB activity in cells undergoing EMT and IKK inhibition phenocopied the effect of 5-ITu on EMT. The effect of 5-ITu on EMT was lost upon IκBα knockdown. Kinase assays revealed IKKβ as a potential direct target of 5-ITu. We identified a TGFβ-associated, NFκB-dependent gene signature consisting of four genes, that are differentially regulated upon 5-ITu treatment. Interestingly, this four gene signature could predict survival in lung and pancreatic cancer. The identification of this role for the multitarget kinase inhibitor 5-ITu in NFκB activity-dependent EMT, in addition to RIPK1-dependent necroptosis has potential implications in anticancer strategies.