BDNF and neuroblastoma: 13-cis-retinoic acid treatment has been shown to induce dependence on neurotrophin and glial-derived neurotrophic factor signaling through the RET kinase [31, 32], suggesting that the observed synergistic effects of RET inhibition with 13-cis-retinoic acid are possibly due to the induction of oncogenic addiction to RET signaling [33, 34], which subsequently sensitizes neuroblastoma cells to RET inhibition.