NKCC1 as a regulator of stemness and redox balance in colorectal cancer

Abstract Na⁺-K⁺-2Cl − cotransporter 1 (encoded by SLC12A2 ) is a solute carrier overexpressed in colorectal cancer (CRC), but its functional role remains unclear. Here, we identify NKCC1 as a marker of normal intestinal stem cells, supported by its crypt-base localization, single-cell transcriptomics, and patient-derived organoids, while analyses of public colorectal cancer single-cell datasets further link NKCC1 expression to cancer stem cell populations. Surprisingly, analysis of CRC patient datasets revealed that tumors with lower SLC12A2 expression were associated with poorer relapse-free survival. By stably knocking down NKCC1 in cell lines and organoids, we demonstrate enhanced expression of stemness markers, altered oxidative stress pathways, and increased radioresistance. In contrast, pharmacological inhibition with bumetanide activates AKT/mTORC1 signaling, elevates reactive oxygen species (ROS), and sensitizes cells to oxidative stress. Together, these results highlight NKCC1 as a dual regulator of stemness and redox homeostasis, supporting its role as a potential key player in colorectal carcinogenesis.