Low STK25 expression drives colorectal cancer metastasis by activating TGF-β/SMAD2 signaling.

The metastatic spread of colorectal cancer (CRC) is the primary factor determining patient prognosis. A key driver of this aggressive phenotype is epithelial-mesenchymal transition (EMT), often orchestrated by the TGF-β/SMAD2/3 signaling pathway. While TGF-β is a known culprit, the specific downstream effectors mediating its pro-metastatic effects in CRC remain a critical gap. Understanding these mechanisms could unlock novel therapeutic targets to halt CRC progression.

Researchers investigated the role of Serine/threonine protein kinase 25 (STK25) in CRC metastasis. They first analyzed STK25 expression levels in CRC patients and correlated them with tumor metastasis and survival outcomes. Functional experiments were then conducted using in vitro CRC cells and in vivo animal models to assess the impact of STK25 knockdown on EMT and metastatic potential. Mechanistic studies explored how STK25 depletion influenced the TGF-β signaling pathway, specifically examining the requirement of STK25 kinase activity.

Low STK25 expression was significantly associated with increased tumor metastasis and poor survival in CRC patients. Functional studies demonstrated that STK25 knockdown profoundly promoted CRC cells' epithelial-mesenchymal transition (EMT) and enhanced their metastatic capabilities in vitro and in vivo. Mechanistically, the depletion of STK25 was found to promote cell migration and EMT progression primarily through the TGF-β signaling pathway. Crucially, the intrinsic kinase activity of STK25 was identified as a prerequisite for its inhibitory effect on TGF-β signaling activation. This establishes a direct link between STK25 and a major pro-metastatic pathway.

The kinase activity of STK25 was required to inhibit TGF-β signaling activation, directly linking its function to EMT and metastasis.