FFAR2 and melanoma: Moreover, a diet-derived trans-vaccenic acid (TVA) inactivates the cell surface receptor G-protein-coupled receptor 43 (GPR43)-an immune regulatory G-protein-coupled receptor activated by its short-chain fatty acid ligand [314]-thereby activating the cAMP-PKA-CREB axis, enhancing CD8+ T cell cytotoxic effector function which suppress tumor growth in melanoma mouse models, and representing host-extrinsic reprogramming of CD8+ T cells [315].