SLC4A7 (NBCn1) is an electroneutral sodium-bicarbonate cotransporter that mediates bicarbonate import into the cytoplasm, playing a critical role in intracellular pH regulation and acid-base homeostasis 1. In normal physiology, SLC4A7 functions across diverse tissues including epithelial, neuronal, cardiac, and vascular tissues to maintain pH balance and support various cellular functions 1. The transporter is regulated by mTORC1 signaling, which selectively enhances SLC4A7 translation to promote bicarbonate import and support de novo nucleotide synthesis during cell growth 2. However, SLC4A7 exhibits context-dependent roles in cancer pathogenesis. In breast cancer, upregulated Na+,HCO3- cotransport via NBCn1/SLC4A7 facilitates net acid extrusion, maintaining permissive intracellular pH for cancer cell proliferation, with knockout mice showing delayed tumor progression 3. Conversely, in lung adenocarcinoma, SLC4A7 suppresses oncogenesis by reducing lactate transport and protein lactylation, inhibiting tumor stemness and metastatic capacity 4. In head and neck squamous cell carcinoma, SLC4A7 promotes epithelial-mesenchymal transition and metastasis through PI3K/AKT/mTOR pathway activation 5. The SLC4A7 variant rs4973768 is associated with increased breast cancer susceptibility 6. These divergent cancer-specific effects suggest SLC4A7's role depends on tumor type and metabolic context, presenting both therapeutic opportunities and challenges.