Apart from its character as a signaling mediator intracellularly, meanwhile, lactate functions as an extracellular ligand.192–196 G-protein-coupled receptor 81 (GPR81), a G protein-coupled receptor for lactate, exists in colon, breast, lung, hepatocellular, salivary gland, cervical, and pancreatic cancer cell lines.197–200 Lactate supports energy metabolism in tumor cells through binding to GPR81. Here, HCAR1 is linked to familial pancreatic carcinoma.