NF1 Is a Tumor Suppressor in Neuroblastoma that Determines Retinoic Acid Response and Disease Outcome

Abstract

Summary Retinoic acid (RA) induces differentiation of neuroblastoma cells in vitro and is used with variable success to treat aggressive forms of this disease. This variability in clinical response to RA is enigmatic, as no mutations in components of the RA signaling cascade have been found. Using a large-scale RNAi genetic screen, we identify crosstalk between the tumor suppressor NF1 and retinoic acid induced differentiation in neuroblastoma. Loss of NF1 activates RAS-MEK signaling, which in turn represses ZNF423, a critical transcriptional co-activator of the retinoic acid receptors. Neuroblastomas with low levels of both NF1 and ZNF423 have extremely poor outcome. We find NF1 mutations in neuroblastoma cell lines and in primary tumors. Inhibition of MEK signaling downstream of NF1 restores responsiveness to RA, suggesting a therapeutic strategy to overcome RA resistance in NF1 deficient neuroblastomas.

Retinoic Acid Receptor β Stimulates Hepatic Induction of Fibroblast Growth Factor 21 to Promote Fatty Acid Oxidation and Control Whole-body Energy Homeostasis in Mice

“…3, A-C, the mRNA levels of RAR␤ were effectively suppressed by siRNA RAR␤#7, with the greatest knockdown efficiency being ϳ60%, and, to a lesser extent, by siRNA RAR␤#8. Consistent with early studies showing that RAR␤ is greatly inducible by RA in both HepG2 cells and human livers with no significant changes in RAR␣ and RAR␥ (39), RA treatment caused a ϳ3-fold increase in mRNA amounts of RAR␤, the bona fide target gene of RA (40). Knockdown of RAR␤ by siRNA resulted in a profound reduction in the basal and RAstimulated RAR␤ expression, suggesting that RA is a more efficacious RAR ligand in HepG2 cells.…”

Overview and recent advances in the treatment of neuroblastoma

“…Furthermore, expression of the gene for the Ras GTPase-activating protein (RasGAP) NF1 is also associated with neuroblastoma patient outcomes, and recent studies have identified a potential role for NF1 as a mediator of retinoid resistance in neuroblastoma cells [156]. Additional studies have demonstrated efficacy of the novel MEK inhibitor binimetinib in preclinical models of neuroblastoma [155,157], suggesting that RAS-MAPK pathway inhibitors may be effective in patients with relapsed neuroblastoma.…”

Mastermind-Like 3 Controls Proliferation and Differentiation in Neuroblastoma

“…One way cells can become resistant to RA-induced differentiation is by loss of RA target gene expression (20,21). To determine if ectopic MAML3 expression leads to the loss of RA-responsive gene expression, we integrated our ChIP-seq and transcriptome data.…”

“…Loss of NF1 activates RAS signaling, which in turn represses ZNF423 expression, leading to RA resistance. Low expression levels of ZNF423 and/or NF1 in neuroblastoma patients predict poor outcome (21).…”