title: Silencing of the tumor suppressor gene FHIT is highly characteristic for MLL gene rearranged infant acute lymphoblastic leukemia.
abstract: MLL rearranged acute lymphoblastic leukemia (MLL) is an aggressive type of acute lymphoblastic leukemia (ALL), diagnosed predominantly in infants (<1 years of age). Since current chemotherapy fails in >50% of patients with MLL, new therapeutic strategies are desperately needed. For this, understanding the biological features characterizing MLL is necessary. Analysis of gene expression profiles revealed that the expression of the tumor suppressor gene FHIT is reduced in children with MLL rearranged ALL as compared to ALL patients carrying germ line MLL. This finding was confirmed by quantitative real-time PCR. In 100% of the infant MLL cases tested, methylation of the FHIT 5'CpG region was observed, resulting in strongly reduced mRNA and protein expression. In contrast, FHIT methylation in infant and non-infant ALL patients carrying germ line MLL was found in only approximately 60% (P< or =0.004). FHIT expression was restored upon exposing leukemic cells to the demethylating agent decitabine, which induced apoptosis. Likewise and more specifically, leukemic cell death was induced by transfecting MLL rearranged leukemic cells with expression vectors encoding wild-type FHIT, confirming tumor suppressor activity of this gene. These observations imply that suppression of FHIT may be required for the development of MLL, and provide new insights into leukemogenesis and therapeutic possibilities for MLL.
authors.affiliation: Erasmus MC/Sophia Children's Hospital, Department of Pediatric Oncology/Hematology, Rotterdam, The Netherlands.
authors.forename: R W
authors.initials: RW
authors.lastname: Stam
authors.forename: M L
authors.initials: ML
authors.lastname: den Boer
authors.forename: M M C J
authors.initials: MM
authors.lastname: Passier
authors.forename: G E
authors.initials: GE
authors.lastname: Janka-Schaub
authors.forename: S E
authors.initials: SE
authors.lastname: Sallan
authors.forename: S A
authors.initials: SA
authors.lastname: Armstrong
authors.forename: R
authors.initials: R
authors.lastname: Pieters
mesh_terms: D017766:Acid Anhydride Hydrolases / Q000235:genetics*; D045744:Cell Line, Tumor; D018899:CpG Islands / Q000235:genetics; D019175:DNA Methylation; D020869:Gene Expression Profiling; D015321:Gene Rearrangement; D020868:Gene Silencing; D011495:Histone-Lysine N-Methyltransferase; D006801:Humans; D007223:Infant; D051788:Myeloid-Lymphoid Leukemia Protein / Q000235:genetics*; D009363:Neoplasm Proteins / Q000235:genetics*; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000175:diagnosis / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000099170:Bis(5'-adenosyl)triphosphatase
chemical_list: D017766:Acid Anhydride Hydrolases; D011495:Histone-Lysine N-Methyltransferase; D051788:Myeloid-Lymphoid Leukemia Protein; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D000099170:Bis(5'-adenosyl)triphosphatase; C497422:KMT2A protein, human