Bexarotene Promotes Neuroblastoma SH-SY5Y Cell Differentiation to Mature Neurons with Decreased Proliferation

Abstract

Bexarotene is a retinoid X receptor (RXR) pharmacological agonist that has been demonstrated to treat cutaneous T-cell lymphoma and promising therapeutic potential for neurological diseases. But it still remains unclear whether bexarotene participates in regulation of neuroblastoma. Human neuroblastoma SH-SY5Y cells were used as a model to investigate the neuronal differentiation impact of bexarotene. Bexarotene-cultured SH-SY5Y cells showed changes in cell morphology, adopting pyramidal shapes and extending neurites, increased expression of neuronal marker β-tubulin III and mature neurons marker neurofilament M and upregulation of neuronal differentiation markers including growth-associated protein 43 (GAP43) and synaptophysin (SYP). SH-SY5Y cells induced by bexarotene increased the expression of GABAergic marker glutamate decarboxylase (GAD1) and dopaminergic marker TH, but not glutamatergic marker glutamate-ammonia ligase (GLUL) and cholinergic marker solute carrier family 18 member 1 (SLC18A1). Functional enrichment analysis of RNAseq data and subsequent cell experiments revealed that the PI3K-Akt axis is the dominant signaling pathway promoting the differentiation of SH-SY5Y cells into mature and functional neurons in response to bexarotene. Additionally, we observed that SH-SY5Y cells show reduced proliferation rates accompanied by decreased expression of cyclin-dependent kinase 6 (CDK6) and increased expression of cyclin-dependent kinase 1 (CDK1) following 7-day exposure to bexarotene, suggesting bexarotene induces a quiescent state in SH-SY5Y cells. SH-SY5Y cells can be induced to mature neurons with decreased proliferation induced by bexarotene via PI3K-Akt axis. It indicates bexarotene has the potential to treat neuroblastoma.

Keywords: Bexarotene; Neuronal differentiation; PI3K-Akt signaling pathway; Proliferation; SH-SY5Y cells.