GDNF and neuroblastoma: This is in contrast with previous reports that demonstrate that GDNF can increase dopamine levels via the regulation of TH gene expression in a Ret-dependent response in human neuroblastoma cell lines (Xiao et al., 2002) and in grafts of human ESC-derived DaNs into an environment of GDNF overexpression (Gantner et al., 2020).