Silencing and Re-Expression of Retinoic Acid Receptor Beta2 in Human Melanoma
Many melanoma cells are resistant to the anti-proliferative effect of all trans retinoic acid (ATRA). Retinoic Acid Receptor-β2 (RAR-β2) mediates the ATRA growth inhibition. We found a correlation between the anti-proliferative activity of ATRA and expression of RAR-β2. There was not a strict correlation between DNA methylation of RAR-β gene and its expression. There was no difference in global and RARβ specific nucleosome repeat length (NRL) in melanoma and melanocytes or between control and ATRA treated cells. Pan-acetylation of H3 and H4 within the RAR-β gene promoter was higher in cells expressing RAR-β2. All trans retinoic acid treatment of responsive cells did not change pan-acetylation of H3/H4, but addition of ATRA to non-responsive cells increased H4 pan-acetylation. Phytochemicals or the histone deacetylase inhibitor Trichostatin A did not restore expression of RAR-β2. Treatment of WM1366 melanoma cells with 5-aza 2′-deoxycytidine reactivated RAR-β2 gene expression and restored the ability of ATRA to further induce the expression of this gene. Therefore, promoter methylation is responsible for silencing of RAR-β2 in some melanoma cells and pan-acetylation of H3 likely plays a permissive role in expression of RAR-β2.
Fan, J., Eastham, L., Varney, M. E., Hall, A., Adkins, N. L., Sollars, V. E. , Georgel, P. and Niles, R. M. (2010), Silencing and re-expression of retinoic acid receptor beta2 in human melanoma. Pigment Cell & Melanoma Research, 23: 419–429. doi: 10.1111/j.1755-148X.2010.00702.x