Nuclear receptor 4A2 (NR4A2) is a druggable target for glioblastomas

Karki et al., Journal of Neuro-Oncology, 2020 asked whether the orphan nuclear receptor NR4A2, best known from dopaminergic neurons, matters in glioblastoma. Screening four established glioblastoma lines and five lines grown from fresh patient tumours showed NR4A2 in all of them, and highly expressed in every patient derived line, where NR4A1 and NR4A3 were only variably expressed, which made those cells the model of choice.

Testing the receptor meant knocking it down, and the team says plainly what they found when they tried: small interfering RNA was less effective than antisense oligonucleotides for this target. They used AUMsilence sdASO, two oligonucleotides against NR4A2 and a matched scramble control, all three sequences printed in the Methods. The Methods make the delivery contrast explicit. The small interfering RNAs were transfected with a lipid reagent and the medium was changed afterwards. The antisense oligonucleotides were put straight into the well at 10 μM and the medium was not changed at all.

Both oligonucleotides lowered NR4A2 protein in the two patient derived lines and in U87-MG cells. Proliferation fell, invasion through a Boyden chamber fell, Annexin V staining rose and caspase 8, caspase 7 and PARP were cleaved. Putting the receptor back by overexpression reversed all three effects, which is the on target control. Silencing also blocked outward invasion from three dimensional tumour spheroids. Separately, small molecule antagonists of the receptor reproduced the same pattern, and combining a small molecule with the oligonucleotide added nothing beyond either alone, which the authors read as evidence that the drug acts through this receptor. Knocking down the neighbouring receptor NR4A3, which the paper did by RNA interference rather than with the oligonucleotides, had almost no effect on any of the same readouts. The mouse xenograft arm of this paper tested the small molecule only and used no oligonucleotide.