AQP5: A functional gastric cancer stem cell marker in mouse and human tumors.

Cancer stem cells (CSCs) represent a self-renewing population capable of fueling long-term tumor growth. In gastric cancer, the identity of CSC populations remains unclear. In this study, we established a gastric CSC population marked by the water channel protein aquaporin-5 (AQP5), which resides in human and mouse pyloric tumors. Using multiple organoid and mouse models, we found a requirement for AQP5+ CSCs in both initiating and sustaining cancer progression and demonstrated that AQP5 expression also directly promotes tumor growth and invasion in a WNT, PI3K (phosphatidylinositol 3-kinase), and MAPK (mitogen-activated protein kinase)-dependent manner. Beyond primary cancers, AQP5 further enriches for a functional CSC population in metastatic tumors. Together, our findings support a CSC model in gastric tumors that may have application for therapeutic strategies targeting CSCs.