SLC31A1 and cancer: Copper (Cu) is an essential nutrient required for energy production, antioxidant defense, and connective tissue maturation, yet its metabolism has emerged as a unique vulnerability in cancer.1 Cellular copper uptake is primarily mediated by the high-affinity transporter CTR1 (SLC31A1), the principal gateway for copper entry and a key regulator of intracellular copper availability.2, 3 Global Ctr1 deletion in mice causes embryonic lethality,4 and intestinal loss results in systemic copper deficiency,5 underscoring its physiological importance.