Detection of leukemia-associated MLL-GAS7 translocation early during chemotherapy with DNA topoisomerase II inhibitors.
ABSTRACT Leukemias with MLL gene translocations are a complication of primary cancer treatment with DNA topoisomerase II inhibitors. How early translocations appear during primary cancer treatment has not been investigated. We tracked the leukemic clone with an MLL gene translocation during neuroblastoma therapy in a child who developed acute myeloid leukemia. The karyotype of the leukemic clone showed del(11)(q23). We used panhandle PCR-based methods to isolate the breakpoint junction involving MLL and an unknown partner gene. Marrow DNA from neuroblastoma diagnosis and DNA and RNA from serial preleukemic marrows were examined for the translocation. The karyotypic del(11)(q23) was a cryptic t(11;17). GAS7, a growth arrest-specific gene at chromosome band 17p13, was the partner gene of MLL. Two different MLL-GAS7 fusion transcripts were expressed. The translocation was already detectable by 1.5 months after the start of neuroblastoma treatment. The translocation was not detectable in the marrow at neuroblastoma diagnosis or in peripheral blood lymphocyte DNAs of six normal subjects. GAS7 is a new partner gene of MLL in treatment-related acute myeloid leukemia. MLL gene translocations can be present early during anticancer treatment at low cumulative doses of DNA topoisomerase II inhibitors. Although MLL has many partner genes and most have not been characterized, panhandle PCR strategies afford new means for detecting MLL gene translocations early during therapy when the partner gene is unknown.
Article: Leucine-zipper dimerization motif encoded by the AF17 gene fused to ALL-1 (MLL) in acute leukemia.[show abstract] [hide abstract]
ABSTRACT: Chromosome region 11q23 is involved in reciprocal chromosome translocations associated with human acute leukemias. These aberrations fuse the ALL-1 gene located at 11q23 to a series of partner genes positioned on a variety of human chromosomes. The fused genes encode chimeric proteins. Here we report the cloning and characterization of the ALL-1 partner at 17q21, the AF17 gene. The AF17 gene encodes a protein of 1093 amino acids, containing a leucine-zipper dimerization motif located 3' of the fusion point and a cysteine-rich domain at the N terminus. The latter can be arranged in three zinc fingers and shows homology to a domain within the protein Br140 (peregrin). AF17 contains stretches of amino acids previously associated with domains involved in transcriptional repression or activation. Based on features of AF17 and of the proteins encoded by the other partner genes analyzed and in conjunction with other recent studies, we propose a model in which ALL-1 rearrangements result in loss of function of the gene. In this model, the partner polypeptide plays an accessory role either by repressing activity of the truncated ALL-1 protein or by blocking the function of the normal protein presumably present in the leukemic cells.Proceedings of the National Academy of Sciences 09/1994; 91(17):8107-11. · 9.68 Impact Factor
Article: Secondary acute myeloid leukemia in children previously treated with alkylating agents, intercalating topoisomerase II inhibitors, and irradiation.[show abstract] [hide abstract]
ABSTRACT: Patient records were reviewed to identify cases of secondary acute myeloid leukemia (AML) with clinical and cytogenetic features characteristic of classic epipodophyllotoxin-related AML in patients whose prior treatment for cancer did not include these agents. Four cases of secondary AML with chromosomal abnormalities involving bands 11q23 and 21q22, in the absence of prior treatment with etoposide or teniposide, were identified among patients treated at St Jude Children's Research Hospital between January 1980 and April 1992. The four identified patients were initially treated for rhabdomyosarcoma, non-Hodgkin's lymphoma (n = 2), and Hodgkins' disease. Prior chemotherapy included relatively low cumulative doses of doxorubicin (median, 150 mg/m2; range, 120 to 375 mg/m2) and cyclophosphamide (median, 3,100 mg/m2; range, 2,250 to 11,400 mg/m2). All four patients had received radiation therapy: 59.4 Gy to the right middle ear for rhabdomyosarcoma; 15 Gy and 12 Gy to the abdomen and right lower quadrant, respectively, for non-Hodgkin's lymphoma; 27 Gy to the right orbit for non-Hodgkin's lymphoma; and 36.6 Gy to the mantle-paraaortic-spleen regions plus 20.4 Gy inverted-Y radiation at relapse for Hodgkin's disease. Secondary AML was diagnosed a median of 38 months after initial diagnosis (range, 14 to 55). Leukemic cell translocations involved band 11q23 in two cases and band 21q22 in two. Although all patients obtained a complete remission (CR), only one remains disease-free (at 34 months), following an allogeneic bone marrow transplant. Intercalating topoisomerase II inhibitors (doxorubicin, dactinomycin), when combined with alkylating agents and irradiation, may cause secondary AML.Journal of Clinical Oncology 07/1993; 11(6):1039-45. · 18.37 Impact Factor
Article: The human MLL gene: nucleotide sequence, homology to the Drosophila trx zinc-finger domain, and alternative splicing.[show abstract] [hide abstract]
ABSTRACT: We have previously reported the cloning of several cDNAs corresponding to the MLL gene. The predicted primary amino acid sequence of two of these clones, 14p-18B and 14-7, reveals nearly complete identity with parts of the sequences of HRX, ALL-1, and Htrx-1, including a Zinc-finger region with homology to the Drosophila trithorax gene. However, we found that there is a stretch of 39 amino acids that is absent from 14p-18B when compared to ALL-1 and HRX. Another sequence of three amino acids is present in ALL-1, but is absent from 14p-18B and HRX. Nucleotide sequence examination reveals that these differences arise from alternative splicing, suggesting that MLL, HRX, and ALL-1 each represents a different alternative splicing product from the same gene. At least two cDNA clones, 14-7 and 14p-18C, correspond to incompletely processed transcripts including intron sequences. Northern blots using a subclone of 14p-18B revealed mRNA species of 14-16 kb in size in various human tissues. RNase protection assays show that the splice variant containing exon 8 and lacking a 9-bp extension 3' of exon 12 is predominantly expressed in hematopoietic cell lines.DNA and Cell Biology 07/1995; 14(6):475-83. · 2.07 Impact Factor