Poster Presentation 27th Lorne Cancer Conference 2015

Investigating a novel role for NR4A orphan nuclear receptors in DNA repair and resistance to BRAF inhibitors in melanocyte and melanoma cells (#265)

Aaron Smith 1 , Kelvin Yin 1 , Yash Chhabra 2 , Richard Sturm 3 , Wen Lim 1 , Kasturee Jagirdar 3
  1. School of Biomedical Sciences, University of Queensland, St Lucia, QLD
  2. Institute for Molecular Bioscience, University of Queensland, St Lucia, QLD, Australia
  3. School of Medicine, University of Queensland, St Lucia, Queensland, Australia

The NR4A nuclear receptors, NR4A1, NR4A2 and NR4A3, are a sub-group of the nuclear receptor family of transcriptional regulators that have been linked to numerous physiological processes including metabolism, stress responses and cancer.  We have previously reported that the rapid and transient induction of the NR4A family by the Melanocortin-1 Receptor (MCIR) in melanocytes plays a pivotal role in the augmentation of DNA repair by this pathway.  Moreover, melanocytes that are homozygous for loss-of-function variants in MC1R, considered to be melanoma susceptibility genes, exhibit significantly impaired induction of the NR4A gene family.  More recently, we have demonstrated a direct role for these genes in the repair of UV induced DNA lesions and observe a UV induced co-localisation of these factors with known DNA repair proteins. While the expression of the NR4A genes is tightly controlled in normal cells we have found constitutively high levels of expression in the majority of melanoma cell lines tested. Inhibition of the MAPK pathway using chemical inhibitors or BRAF siRNA dramatically reduces expression of the NR4A genes in melanoma cells.  We have found that over-expression of the NR4A proteins protects cells from genotoxic insults and conventional chemotherapies but also facilitates resistance to recently developed targeted BRAF inhibitors.  Current efforts in our laboratory are aimed at identifying mechanisms by which the NR4A proteins protect melanocytic cells from genotoxic stress and contribute to melanoma tumorigenicity and resistance to therapies.