CHD5, a tumor suppressor gene deleted from 1p36.31 in neuroblastomas.
BACKGROUND
Neuroblastomas are characterized by hemizygous 1p deletions, suggesting that a tumor suppressor gene resides in this region. We previously mapped the smallest region of consistent deletion to a 2-Mb region of 1p36.31 that encodes 23 genes. Based on mutation analysis, expression pattern, and putative function, we identified CHD5 as the best tumor suppressor gene candidate.


METHODS
We determined the methylation status of the CHD5 gene promoter in NLF and IMR5 (with 1p deletion) and SK-N-SH and SK-N-FI neuroblastoma cell lines using methylation-specific sequencing and measured CHD5 mRNA expression by reverse transcription polymerase chain reaction in cells treated with or without 5-aza-2-deoxycytidine, an inhibitor of DNA methylation. We transfected the cells with CHD5 and antisense (AS) CHD5 DNA to assess the effect of CHD5 overexpression and suppression, respectively, on colony formation in soft agar and growth of xenograft tumors in athymic mice. We also analyzed the association of CDH5 expression with outcomes of 99 neuroblastoma patients. Statistical tests were two-sided.


RESULTS
CHD5 expression was very low or absent in neuroblastoma cell lines. The CHD5 promoter was highly methylated in NLF and IMR5 lines, and CHD5 expression increased after treatment with 5-aza-2-deoxycytidine. Clonogenicity and tumor growth were abrogated in NLF and IMR5 cells overexpressing CHD5 compared with antisense CHD5 (clonogenicity: mean no. of colonies per plate, NLF-CHD5, 43 colonies, 95% confidence interval [CI] = 35 to 51 colonies, vs NLF-CHD5-AS, 74 colonies, 95% CI = 62 to 86 colonies, P < .001; IMR5-CHD5, 11 colonies, 95% CI = 2 to 20 colonies, vs IMR5-CHD5-AS, 39 colonies, 95% CI = 17 to 60 colonies, P = .01; tumor growth, n = 10 mice per group: mean tumor size at 5 weeks, NLF-CHD5, 0.36 cm(3), 95% CI = 0.17 to 0.44 cm(3), vs NLF-CHD5-AS, 1.65 cm(3), 95% CI = 0.83 to 2.46 cm(3), P = .002; IMR5-CHD5, 0.28 cm(3), 95% CI = 0.18 to 0.38 cm(3), vs IMR5-CHD5-AS, 1.15 cm(3), 95% CI = 0.43 to 1.87 cm(3); P = .01). High CHD5 expression was strongly associated with favorable event-free and overall survival (P < .001), even after correction for MYCN amplification and 1p deletion (P = .027).


CONCLUSIONS
CHD5 is the strongest candidate tumor suppressor gene that is deleted from 1p36.31 in neuroblastomas, and inactivation of the second allele may occur by an epigenetic mechanism.
Fujita
Tomoyuki
T
Division of Oncology, The Children's Hospital of Philadelphia, Philadelphia, PA 19104-4318, USA.
Igarashi
Jun
J
Okawa
Erin R
ER
Gotoh
Takahiro
T
Manne
Jayanthi
J
Kolla
Venkatadri
V
Kim
Jessica
J
Zhao
Huaqing
H
Pawel
Bruce R
BR
London
Wendy B
WB
Maris
John M
JM
White
Peter S
PS
Brodeur
Garrett M
GM
D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D045744:Cell Line, Tumor; D002878:Chromosomes, Human, Pair 1 / Q000235:genetics*; D003114:Colony-Forming Units Assay; D004265:DNA Helicases / Q000235:genetics*; D019175:DNA Methylation; D004252:DNA Mutational Analysis; D016373:DNA, Antisense; D000077209:Decitabine; D015536:Down-Regulation / Q000187:drug effects; D017353:Gene Deletion; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D016147:Genes, Tumor Suppressor; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D014411:Neoplastic Stem Cells; D009419:Nerve Tissue Proteins / Q000235:genetics*; D009447:Neuroblastoma / Q000235:genetics*; D011237:Predictive Value of Tests; D011379:Prognosis; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012307:Risk Factors; D014162:Transfection; D014183:Transplantation, Heterologous; D015854:Up-Regulation / Q000187:drug effects
D000964:Antimetabolites, Antineoplastic; D016373:DNA, Antisense; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D000077209:Decitabine; D004265:DNA Helicases; C471926:CHD5 protein, human; D001374:Azacitidine