Induction of MYCN-amplified neuroblastoma differentiation through NMYC suppression using PPAR-γ antagonist

Neuroblastomas are the most common extracranial solid tumors in children and have a unique feature of neuronal differentiation. Peroxisome proliferator-activated receptor (PPAR)-γ is reported to have neuroprotective effects in addition to having antitumor effects in various cancers. Thus, we aimed to clarify the role of PPAR-γ agonist and antagonist in malignant neuroblastomas, which also possess neuronal features. In MYCN-amplified neuroblastoma CHP212 cells, treatment with the PPAR-γ antagonist GW9662 induced growth inhibition in a dose-dependent manner. In addition, the PPAR-γ antagonist treatment changed cell morphology with increasing expression of the neuronal differentiation marker tubulin beta 3 (TUBB3) and induced G1 phase arrest and apoptosis in MYCN-amplified neuroblastoma. Notably, the PPAR-γ antagonist treatment significantly decreased expression of NMYC, B-cell lymphoma 2 (BCL2) and bromodomain-containing protein 4 (BRD4). It is implied that BRD4, NMYC, BCL2 suppression by the PPAR-γ antagonist resulted in cell growth inhibition, differentiation, and apoptosis induction. In our in vivo study, the PPAR-γ antagonist treatment induced CHP212 cells differentiation and resultant tumor growth inhibition. Our results provide a deeper understanding of the mechanisms of tumor cell differentiation and suggest that PPAR-γ antagonist is a new therapeutic and prevention option for neuroblastomas.