The role of MYCN in the failure of MYCN amplified neuroblastoma cell lines to G1 arrest after DNA damage.
We previously reported that 3 p53 wild type (wt) MYCN amplified (MNA) neuroblastoma cell lines failed to G1 arrest after DNA damage despite induction of p53, p21(WAF1) and MDM2. We hypothesised that this was due to high MYCN expression. p53 responses to DNA damage were examined in an additional 13 p53 wt neuroblastoma cell lines. MNA was significantly associated with a failure to G1 arrest after DNA damage (p < 0.001) and higher levels of apoptosis after irradiation (p < 0.05). p21(WAF1) and hypophosphorylated (hypo) RB accumulation post irradiation were significantly lower in cell lines that failed to G1 arrest (p < 0.05). Conditional MYCN expression in non-MNA SHEP Tet21N cells did not affect the G1 arrest after irradiation. MYCN knockdown using siRNA in 3 p53 wt MNA cell lines did not restore a G1 arrest after irradiation, but increased the baseline G1 population, p21(WAF1) and hypo RB expression. MYCN siRNA also caused a G1 arrest in a p53 mutant MNA cell line. This study is the first to determine that MNA correlates with a failure to G1 arrest and attenuated p21(WAF1) induction; however MYCN expression alone is not causally responsible.
Bell
Emma
E
Northern Institute for Cancer Research, University of Newcastle upon Tyne, Newcastle upon Tyne, UK.
Premkumar
Rakesh
R
Carr
Jane
J
Lu
Xiaohong
X
Lovat
Penny E
PE
Kees
Ursula R
UR
Lunec
John
J
Tweddle
Deborah A
DA
D017209:Apoptosis; D045744:Cell Line, Tumor; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D004249:DNA Damage / Q000528:radiation effects; D016193:G1 Phase; D005784:Gene Amplification; D006801:Humans; D000071447:N-Myc Proto-Oncogene Protein; D009447:Neuroblastoma / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology*; D015513:Oncogene Proteins / Q000235:genetics / Q000502:physiology*; D034622:RNA Interference; D014158:Transcription, Genetic; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism
C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; C459801:MYCN protein, human; D000071447:N-Myc Proto-Oncogene Protein; D009687:Nuclear Proteins; D015513:Oncogene Proteins; D016159:Tumor Suppressor Protein p53