SPAK mediates KCC 3‐enhanced cervical cancer tumorigenesis

Ste20‐related proline/alanine‐rich kinase ( SPAK ) plays a role in regulating many biological activities, and interacts with K‐Cl co‐transporter 3 ( KCC 3); however, the importance of SPAK for KCC 3 function has not been demonstrated. Here, we investigated the role of SPAK in KCC 3‐regulated cell invasiveness and tumor formation. We show that induction of KCC 3 expression triggers activation of the NF ‐κB and SPAK signaling cascades, leading to activation of p38 mitogen‐activated protein kinase ( MAPK ) and matrix metalloproteinase‐2 ( MMP 2). A small interference RNA ‐mediated reduction in SPAK protein levels suppressed the invasive ability and oncogenic potential of cervical cancer cells, and decreased tumor formation in mouse xenografts. A combination of experimental approaches, including RT ‐ PCR and real‐time RT ‐ PCR , gelatin zymography, NF ‐κB luciferase activity and chromatin immunoprecipitation assays, showed that the induction of KCC 3 over‐expression increased MMP 2 expression and augmented binding of NF ‐κB to its putative SPAK promoter binding site, suggesting that the SPAK / MMP 2 axis is up‐regulated by NF ‐κB. Pharmacological inhibition of NF ‐κB or MMP 2 abrogated KCC 3‐triggered, SPAK ‐dependent cell invasiveness. Furthermore, p38 MAPK was identified as the upstream regulator of KCC 3‐dependent MMP 2 activation. We conclude that SPAK may promote KCC 3‐mediated tumor aggressiveness via the NF ‐κB/p38 MAPK / MMP 2 axis. Structured digital abstract KCC3 physically interacts with SPAK by anti-bait co-immunoprecipitation ( view interaction )