ABSTRACT
The Myc antagonists Mad1, Mxi1 and Rox proteins share two highly conserved domains, Sin3-interacting domain (SID) and basic helix-loop-helix leucine zipper domain (bHLHzip), which are essential for these proteins to function during molecular switching from proliferation to differentiation. In an attempt to identify mutations in Mad1, Mxi1 and Rox genes in human haematological malignancies, we screened 10 haematopoietic cell lines, bone marrow mononuclear cells (BMMNC) from 26 patients with haematological malignancies and peripheral blood mononuclear cells (PBMNC) from 30 healthy volunteers, using reverse transcription-polymerase chain reaction, single strand conformation polymorphism analysis and sequencing. Mad1, Mxi1 and Rox genes were expressed in all samples. Four polymorphisms were found in cell lines BMMNC and PBMNC: two in Mad1, one in Mxi1 and one in Rox. Nine missense mutations were detected: two in Mad1 in patients, four in Mxi1 (three in patients and one in KG-1 cell line), and three in Rox in patients. No mutations were detected in PBMNC from healthy volunteers. Among six patients with acute lymphoblastic leukaemia, two had Mxi1 mutations and another two had Rox mutations. These mutations were associated with poorer clinical outcomes. This is the first report to show that Mad1, Mxi1 and Rox genes were expressed and displayed mutations in haematological malignancies.
Subject(s)
Basic Helix-Loop-Helix Leucine Zipper Transcription Factors/genetics , Basic Helix-Loop-Helix Transcription Factors/genetics , Cell Cycle Proteins/genetics , DNA Mutational Analysis , Leukemia/genetics , Nuclear Proteins/genetics , Proto-Oncogene Proteins c-myc/antagonists & inhibitors , Repressor Proteins/genetics , Tumor Suppressor Proteins/genetics , Acute Disease , Adolescent , Adult , Aged , Amino Acid Sequence , Base Sequence , Basic Helix-Loop-Helix Leucine Zipper Transcription Factors/metabolism , Basic Helix-Loop-Helix Transcription Factors/metabolism , Bone Marrow Cells/metabolism , Cell Cycle Proteins/metabolism , Cell Line, Tumor , Female , Gene Expression , HL-60 Cells , Humans , K562 Cells , Male , Middle Aged , Molecular Sequence Data , Nuclear Proteins/metabolism , Repressor Proteins/metabolism , Sequence Homology, Amino Acid , Tumor Suppressor Proteins/metabolism , U937 CellsABSTRACT
Previous studies demonstrated that interleukin-12 (IL-12) enhances the non-MHC-restricted cytotoxic activity of NK cells and facilitate specific allogeneic human cytotoxic T lymphocyte responses against fresh leukemia cells and cell lines. The Wilms' tumor gene, WT1 mRNA, has been used as a marker of minimal residual disease (MRD) for evaluating therapeutic efficacy of patients with leukemia or myelodysplastic syndrome (MDS). This study was aimed to investigate whether in vitro IL-12 can lower WT1 gene expression in peripheral blood monuclear cells (PBMNC) from patients with leukemia or MDS. PBMNC from these 30 patients and 5 healthy volunteers were cultured at 5 x 10(5) cells/ml alone with or without 100 units/ml of IL-12 for 3 days. WT1 mRNA was measured by competitive reverse transcription polymerase chain reaction (RT-PCR) since WT1 mRNA is considered as a marker of minimal residual disease (MRD) in leukemia and MDS. The results demonstrated that WT1 mRNA in PBMNC of 5 healthy volunteers was less than 10(3) copies/microg of total RNA. Following the 3-day IL-12 treatment, mean WT1 mRNA of PBMNC was reduced from 10(4.8) to 10(4.2) copies/microg of total RNA in 6 CML patients, from 10(5.4) to 10(4.8) copies/microg in 12 MDS patients and from 10(5.0) to 10(4.2) copies/microg in 5 AML patients in CR, but not reduced in 5 of 7 AML in non-CR. It is concluded that IL-12 significantly decrease the quantity of leukemia cells in PBMNC of most patients with MDS, CML and AML in CR. IL-12 may be of considerable benefit in the elimination of MRD in patients with hematological malignancies.
