title: Methylation-associated silencing of the thrombospondin-1 gene in human neuroblastoma.
abstract: Tumor angiogenesis, a major requirement for tumor outgrowth and metastasis, is regulated by pro- and antiangiogenic factors. Methylation-associated inactivation of the angiogenesis inhibitor thrombospondin-1 (TSP-1) has been observed recently in some adult tumors. To investigate the role of TSP-1 in pediatric cancer, we examined its pattern of expression and mechanisms of regulation in neuroblastoma (NB). TSP-1 was silenced in a subset of undifferentiated, advanced-stage tumors and NB cell lines. In contrast, most localized tumors expressed this angiogenesis inhibitor, and a significant correlation between morphological evidence of neuroblast differentiation and TSP-1 expression was observed. Luciferase assays demonstrated the presence of nuclear factors required for TSP-1 transcription in both TSP-1-positive and -negative cell lines, but no correlation between TSP-1 promoter activity and the level of TSP-1 mRNA expression was seen. Our studies indicate that the transcriptional silencing of TSP-1 was caused by methylation. TSP-1 promoter methylation was detected in all of the NB cell lines lacking TSP-1 mRNA and in 37% of the NB clinical tumors analyzed. Furthermore, treatment with the demethylating agent, 5-Aza-2'-deoxycytidine (5-Aza-dC), restored TSP-1 expression in NB cell lines. Disrupting methylation with 5-Aza-dC also led to significant inhibition of NB in vivo and re-expression of TSP-1 in a subset of NB xenografts. These results suggest that 5-Aza-dC inhibits NB growth by augmenting the expression of TSP-1 along with other genes that suppress tumor growth. Demethylating agents may prove to be effective candidates for the treatment of children with NB.
authors.affiliation: The Robert H. Lurie Comprehensive Cancer Center, Feinberg School of Medicine, Northwestern University, Chicago, IL 60614, USA.
authors.forename: Qi-Wei
authors.initials: QW
authors.lastname: Yang
authors.forename: Shuqing
authors.initials: S
authors.lastname: Liu
authors.forename: Yufeng
authors.initials: Y
authors.lastname: Tian
authors.forename: Helen R
authors.initials: HR
authors.lastname: Salwen
authors.forename: Alexandre
authors.initials: A
authors.lastname: Chlenski
authors.forename: Joanna
authors.initials: J
authors.lastname: Weinstein
authors.forename: Susan L
authors.initials: SL
authors.lastname: Cohn
mesh_terms: D000818:Animals; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D045744:Cell Line, Tumor; D018899:CpG Islands; D019175:DNA Methylation; D000077209:Decitabine; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D009447:Neuroblastoma / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D019700:Thrombospondin 1 / Q000096:biosynthesis / Q000235:genetics*; D014158:Transcription, Genetic / Q000187:drug effects; D014183:Transplantation, Heterologous
chemical_list: D019700:Thrombospondin 1; D000077209:Decitabine; D001374:Azacitidine