MCTP1 is a transmembrane calcium-sensing protein containing multiple C2 domains that functions as a calcium sensor essential for neuronal homeostasis and synaptic plasticity 1. In the nervous system, MCTP1 regulates neurotransmitter release and presynaptic plasticity through calcium-dependent signaling mechanisms [UniProt]. Brain proteomic studies identified MCTP1 downregulation as a risk factor for bipolar disorder, suggesting its role in neuropsychiatric disease 2. Beyond neurobiology, MCTP1 plays unexpected oncogenic roles in cancer progression. In prostate cancer, MCTP1 acts as a pivotal component of a calcium-sensing circuit (MCTP1/FYN/MEF2C axis) that drives therapy-induced neuroendocrine differentiation and epithelial-to-mesenchymal transition (EMT) following androgen deprivation therapy 13. MCTP1 stimulates calcium signaling and AKT activation to promote EMT markers and neuroendocrine differentiation 3. In esophageal cancer, MCTP1 downregulation through DNA hypermethylation correlates with chemotherapy resistance 4, while in ovarian cancer, MCTP1 expression is reduced across multiple drug-resistant variants 5. Conversely, in endometrial cancer, a long non-coding RNA (MCTP1-AS1) acts as a tumor suppressor through the miR-650/SMAD7 axis 6. These contrasting roles suggest context-dependent functions in cancer biology.