Combined Treatments with a Retinoid Receptor Agonist and Epigenetic Modulators in Human Neuroblastoma Cells

Abstract

Neuroblastoma (NB) is the most common extracranial solid childhood tumor accounting for around 15% of pediatric cancer deaths and most probably originates from a failure in the development of embryonic neural crest cells. Retinoids can inhibit the proliferation and stimulate differentiation of NB cells. In addition, epigenetic events involving changes in chromatin structure and DNA methylation can mediate the effects of retinoids; hence, the scope of this study is to investigate the use of retinoids and epigenetic drugs in NB cell lines. Here, we demonstrate that the combination of retinoid all trans-retinoic acid (ATRA) with inhibitors of either histone deacetylases (HDACs) or DNA methyltransferase is more effective in impairing the proliferation of human SH-SY5Y and SK-N-BE(2) NB cells than any drug given alone. Treatments also induced differential changes on the messenger RNA (mRNA) expression of retinoid receptor subtypes and reduced the protein content of c-Myc, the neuronal markers NeuN and β-3 tubulin, and the oncoprotein Bmi1. These results suggest that the combination of retinoids with epigenetic modulators is more effective in reducing NB growth than treatment with single drugs.

Targeting histone deacetylase activity to arrest cell growth and promote neural differentiation in Ewing sarcoma

“…Together, our results indicate that HDis can reduce EWS growth and survival and lead to a more differentiated state. It is noteworthy that these data are consistent with our previous findings indicating that HDis can impair cell growth and modulate differentiation of cells from other types of childhood pediatric tumors possibly originating from neural stem cells, medulloblastoma and neuroblastoma [62,63]. cells exposed to NaB for 72 h. c Percent of H3 phos-S10 mean intensity (immunofluorescence) from EWS cell lines exposed to NaB for 72 h; N = 3 independent experiments.…”

Translation of upstream open reading frames in a model of neuronal differentiation

“…Further, this led to the confirmation of decreased eIF2α phosphorylation in differentiated cells. We believe that this is indicative of a neuronal differentiation-dependent shift in eIF2α phosphorylation separate from an alleviation of stress, possibly associated with retinoic acid treatment itself (Roffe, Hajj et al 2013, Almeida, Vieira et al 2017, Nair, Das et al 2017. Thus, our data suggests that the presence of persistently translated uORFs can delay scanning ribosomes from reaching the CDS and potentially provide more time for them to acquire a ternary complex (Andreev, O'Connor et al 2015, Starck, Tsai et al 2016, Wek 2018.…”

“…We detected a significant decrease in the ratio of phosphorylated eIF2α to total eIF2α after 6 days of differentiation (Figure 7H). While a change in eIF2α phosphorylation has not been previously described in SH-SY5Y cell differentiation, RA treatment protects cells against endoplasmic reticulum stress, and RA differentiated SH-SY5Y cells have been shown to differ from non-differentiated cells in their buffering capacity against oxidative stress inducing agents (Almeida, Vieira et al 2017, Nair, Das et al 2017. Further, ATF4 is present in our list of constrained uORFs and its TE is increased in the nondifferentiated condition, consistent with past findings that ATF4 has two uORFs whose persistent expression is key to the increase in ATF4 protein during the integrated stress response (Lu, Harding et al 2004, Vattem and Wek 2004, Starck, Tsai et al 2016.…”

The secondary laticifer differentiation in rubber tree is induced by trichostatin A, an inhibitor of histone acetylation

“…Post-translational modifications of histones are involved in modulating dynamic changes in chromatin structure and gene activity [27] . Histone acetylation is generally associated with transcription activation, whereas histone deacetylation results in transcription repression [12,15] .…”