VGF is an important regulator of metabolism and endoplasmic reticulum (ER) stress in neurons and endocrine cells [56–58], where it activates pro-survival signaling pathways such as PI3K/AKT/mTOR and MAPK/ERK1/2 [59, 60], but its role in regulation of cancer cells remained unclear for a long time. Here, MAPK3 is linked to cancer.