AbstractMYCN-amplification is a high-risk factor in neuroblastoma which contributes to a poor prognostic outcome. Here data is presented showing that both short-interfering RNA depletion and treatment by small molecule inhibitors (SMI) of lysine-specific histone methyltransferase Euchromatic Histone Lysine Methyltransferase 2 (G9a) leads to impaired growth in all tested neuroblastoma cell lines. Furthermore, in cell lines representative of high-risk neuroblastomas with MYCN-amplification, there is a significant increase in apoptosis and cell death. There is also a significant reduction in MYCN protein in MYCN-overexpressing cells, including in SHEP-21N cell line with inducible MYCN expression, after both G9a knockdown and SMI treatment independently. This suggests there is a synthetic lethal relationship between G9a and MYCN.
G9a-associated reduction of MYCN leads to the re-expression of repressed tumour suppressor and pro-apoptotic factor BCL-2 Related Ovarian Killer (BOK). Quantitative gene expression analysis and immunoblotting of neuroblastoma cell lines shows an increase in BOK after both G9a depletion and SMI treatment independently which is only apparent in the MYCN-overexpressing cell lines; this increase in BOK leads to apoptosis, and BOK depletion was able to rescue G9a inhibition-associated apoptosis.
Together, these studies show that G9a is a major oncoprotein in neuroblastoma tumourigenesis and a novel regulator of MYCN protein; this suggests that together they repress pro-apoptotic factor BOK to block apoptosis in high-risk neuroblastoma.
|Date of Award||6 Nov 2018|
|Supervisor||Karim T A Malik (Supervisor)|