GDNF and keratoconus: Moreover, after assessing the expression of several NT, including NGF, brain-derived neurotrophic factor (BDNF), neurotrophic factor 3 (NTF3), NTF4, glial cell line-derived neurotrophic factor (GDNF), and Netrin-1 (encoded by NTN1), NGF demonstrated the highest expression in PDAC cell lines, KC mice, and KPC mice.