trichostatin-a and Teratoma

Supratentorial primitive neuroectodermal tumors (sPNET) and atypical teratoid/rhabdoid tumors (AT/RT) of the CNS represent a biological and clinical enigma, despite advances in both molecular techniques and clinical management for these two rare embryonal brain tumors of childhood. Epigenetic changes hold great potential as possible disease mechanisms and may be manipulated therapeutically. We thus studied aberrant methylation of the genes RASSF1A and CASP8 and its consequence on expression in cell lines and primary tumors using a combination of semiquantitative methylation specific PCR (MSP), bisulfite sequencing and RT-PCR. In all, 17 samples of autopsy-derived normal appearing brain served as controls. Opposed to control tissues 19/24 sPNET and 4/6 AT/RT demonstrated aberrant methylation for the RASSF1A promoter region. Treatment of cell lines using 5-Aza-2'-deoxycytidine (5AZA) alone or in combination with trichostatin A (TSA) succeeded in re-establishing expression of RASSF1A in cell lines derived from a renal rhabdoid, an AT/RT and a medulloblastoma. A 5' CpG-rich region of CASP8 was methylated in normal tissues and in tumors. However, CASP8 showed inconsistent expression patterns in normal and tumor tissues. Our results indicate that aberrant methylation of the RASSF1A promoter region may be of importance in the origin and progression of sPNET and AT/RT while the analysed 5'-CpG rich region of the CASP8 gene does not seem to play an important role in these tumors. Further studies of epigenetic changes in these rare tumors are warranted as their biology remains obscure and treatment efforts have been rather unsuccessfull.

Topics: Adolescent; Adult; Azacitidine; Brain Neoplasms; Caspase 8; Caspases; Child; Child, Preschool; CpG Islands; Decitabine; DNA Methylation; Epigenesis, Genetic; Female; Gene Silencing; Humans; Hydroxamic Acids; Infant; Male; Neuroectodermal Tumors, Primitive; Promoter Regions, Genetic; Rhabdoid Tumor; Teratoma; Tumor Suppressor Proteins

Treatment of cultured cells with sodium butyrate, that is the histone deacetylase inhibitor, induces the histone hyperacetylation and the expressions of various mammalian genes without affecting the level of protein synthesis. However, butyrate is a non-specific inhibitor of deacetylase because of its effects on various other enzymes and nuclear proteins other than histones. On the other hand, Trichostatin A (TSA) was recently found to be a potent and specific inhibitor of histone deacetylase. We examined the effect of TSA on the expression of mouse cytokeratin A (endo A). TSA increased endoA expression in F9 cells, and was effective at a much lower concentration than sodium butyrate. We also examined the changes of chromatin structure induced by the two drugs by a DNase I-hypersensitivity assay. Both drugs induced the formation of a DNase I-hypersensitive site (DH site) in only the promoter region. The precise mechanism(s) by which the two drugs increase endoA gene expression is unknown, but these results suggest that endoA expression is induced by inhibition of histone deacetylase and that the effect is at the transcriptional level.

Topics: Animals; Binding Sites; Butyrates; Butyric Acid; Chromatin; Deoxyribonuclease I; DNA; Enhancer Elements, Genetic; Gene Expression; Histone Deacetylase Inhibitors; Hydroxamic Acids; Keratins; Mice; Promoter Regions, Genetic; RNA, Messenger; Teratoma; Tumor Cells, Cultured