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Query: UMLS:C0596978 (Leukemia)
 15,069 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The human tri-thorax gene (HRX) also called ALL-1 (Acute Lymphocytic Leukemia-1) as well as MLL (Myeloid-lymphoid or Mixed-lineage Leukemia) gene, is disrupted in the majority of leukemias with chromosomal abnormalities involving 11q23. The alteration of the gene is related to leukemogenesis of various types such as acute myelogenous leukemia (AML), acute lymphoblastic leukemia (ALL), and acute mixed lineage leukemia. The gene is also rearranged in cases of secondary AML developing after exposure to chemotherapeutic agents, especially topoisomerase II inhibitors. In at least one report, genomic analysis of this recombination site showed the breakpoint to be a topoisomerase II binding site and that exposure to the inhibitor could induce the rearrangement. If exposure induces the rearrangement of the gene, secondary ALL as well as secondary AML could occur after exposure to these agents, because the type of leukemias with rearranged HRX gene is not limited to AML. We present here such a case of secondary ALL with this gene rearrangement which occurred during adjuvant chemotherapy for breast cancer. Although less cases of secondary ALL are reported in comparison with those of secondary AML, such case reports have been accumulating. The incidence of this type of leukemia should be clarified in the future.
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PMID:HRX gene rearrangement in secondary acute lymphoblastic leukemia. 754 29

The clinical heterogeneity of acute lymphoblastic leukemia (ALL) of B cell lineage reflects the presence of distinct molecular pathways leading to well-defined ALL molecular subtypes. These molecular pathways include the formation of the fusion transcripts BCR/ABL and E2A/PBX1, due to t(9;22) and t(1;19), respectively, as well as rearrangements of the MLL gene at 11q23 and of c-MYC at 8q24. Hyperdiploid ALL in the absence of chromosomal structural abnormalities is an additional ALL molecular subtype. Mutations of the RAS family genes and of the p53 tumor suppressor gene represent additional genetic lesions detected in a fraction (10-20%) of ALL cases. RAS activation in ALL may be detected in all molecular subtypes of ALL and denotes poor prognosis. Conversely, little is known regarding the clinical and biological features of ALL cases carrying p53 mutations. In order to help clarify the role of p53 inactivation in ALL development, we have determined the frequency of p53 mutations throughout the molecular spectrum of B cell lineage ALL. We report that p53 inactivation in ALL of B cell lineage is restricted to cases carrying a rearrangement of MLL or c-MYC, whereas it is consistently negative in other molecular subgroups. These data underline the molecular heterogeneity of ALL of B cell lineage and indicate that at least some of the molecular pathways involved in ALL pathogenesis require more than one genetic lesion.
Leukemia 1995 Jun
PMID:p53 gene inactivation in acute lymphoblastic leukemia of B cell lineage associates with chromosomal breakpoints at 11q23 and 8q24. 759 84

We report on three patients with acute non-lymphoblastic leukemia (ANLL) displaying the same chromosomal translocation t(11;15)(q23;q14). The clinical course of the disease was aggressive, and survival was short. The FAB subtype was M-2 in two cases, and M-1 in the remaining patient. Immunologically two cases showed aberrant expression of a lymphoid antigen (CD19 and TdT, respectively). HTRX1/MLL gene was rearranged in one patient studied at the time of diagnosis. These results plus data scattered in the literature show that the t(11;15)(q23;q14) can be added to the list of recurrent rearrangements in ANLL involving 11q23.
Leukemia 1995 Jul
PMID:Translocation (11;15)(q23;q14) in three patients with acute non-lymphoblastic leukemia (ANLL): clinical, cytogenetic and molecular studies. 763 Jan 91

Cytogenetic abnormalities of band 11q23 have been found in more than 50% of infant leukemias regardless of the phenotype. Using probes for the MLL gene at 11q23, MLL rearrangements have been identified in 70-80% of all infant leukemias including virtually all of the cases with 11q23 translocations, as well as cases with apparently normal karyotypes. We reviewed the chromosomal pattern of 26 cases of infant leukemias (12 ALL, 12 AML, two AUL). Eleven had 11q23 translocations, five had other abnormalities, and 10 had a normal karyotype. To determine whether 11q23/MLL rearrangements were present in the leukemia cells of patients with a normal karyotype, we performed FISH and molecular studies of eight of these patients who had adequate material. Three were found to have 11q23/MLL abnormalities, two of them detected by FISH; one ALL case had a t(11;19) (q23;p13.3), and one AML case had a t(11;19) (q23;p13.1). Retrospective review confirmed the presence of the t(11;19) in a small percentage of poor quality metaphase cells in both cases. A rearrangement of the MLL gene was detected by Southern blot analysis of leukemic cells from a third patient with ALL; one cell with a deletion of 11q23 was found on karyotypic review. Therefore, in our series the actual incidence of 11q23 abnormalities in infant leukemias was 54% (14/26): 67% in ALL (8/12) and 50% in AML (6/12). Our findings suggest that most infant leukemias with apparently normal karyotypes that have a molecular rearrangement of the MLL gene are undetected subtle translocations.(ABSTRACT TRUNCATED AT 250 WORDS)
Leukemia 1995 Aug
PMID:Detection of 11q23/MLL rearrangements in infant leukemias with fluorescence in situ hybridization and molecular analysis. 764 16

Rearrangements of the MLL (Mixed Lineage Leukemia) gene in the human 11q23 cytogenetic locus have been detected in secondary (therapy-related) acute leukemias in patients who have received topoisomerase II inhibitors for prior, independent neoplasms. The topoisomerase II inhibitors implicated in MLL/11q23 secondary leukemias all inhibit the religation step of reaction catalyzed by topoisomerase II. This results in the stabilization of a 'cleavable complex' with double-strand DNA breaks at the point of topoisomerase II binding. This raises the possibility that the cleavable complex participates in the translocation process in MLL/11q23 secondary leukemias. Here we report that the MLL/11q23 breakpoints in 13/13 patients with secondary leukemia map to the same breakpoint cluster region (bcr) noted in de novo MLL/11q23 acute leukemias and the presence of in vivo topoisomerase II inhibitor-induced cleavage sites in MLL/11q23 bcr. We have also cloned and sequenced the breakpoint from a MLL/11q23 secondary acute leukemia. This analysis revealed sequences similar to the consensus sequence for vertebrate topoisomerase II binding and cleavage close to the 11q23 and 4q21 breakpoints. These results support a role for topoisomerase II in mechanism generating translocations in MLL/11q23 secondary acute leukemia.
Leukemia 1995 Aug
PMID:Molecular analysis of 13 cases of MLL/11q23 secondary acute leukemia and identification of topoisomerase II consensus-binding sequences near the chromosomal breakpoint of a secondary leukemia with the t(4;11). 764 17

We report a case of therapy-related acute myeloid leukemia (t-AML), M4 FAB subtype, with t(10;11)(p14;q21) chromosome abnormality developed in a patient treated for acute promyelocytic leukemia (APL) after 4 years of continuous complete remission (CCR). Two distinct forms of t-AML have been described: the classical type and the second type. Our case has many characteristics in common with the second type of t-AML such as: exposure to topoisomerase II active agents (idarubicin (IDA), mitoxantrone (MITOX), etoposide (VP16)), M4 FAB subtype, a latency period of 39 months and absence of a preleukemic phase. However, it differs in the chromosome 11 breakpoint (band q21 instead of q23) and absence of ALL-1 (Hrx, MLL, Htrx) gene involvement. This can represent the second observation of t-AML occurring after treatment for APL.
Leukemia 1995 Sep
PMID:Therapy-related acute myelomonocytic leukemia following successful treatment for acute promyelocytic leukemia. 765 28

A number of gene arrangements have been described as characteristic abnormalities associated with different types of leukemia, and this list is still growing. In view of the biological, clinical and prognostic relevance of the pathological fusion products, techniques permitting their detection are of paramount importance in the clinical setting. In some instances, permanent leukemic cell lines carrying the abnormality of interest are available for the establishment and standardization of molecular assays. For a number of newly discovered gene rearrangements, however, this may not be the case. It is therefore of great interest for clinical laboratories to have alternative technical possibilities for the set-up of standardized molecular tests. This problem provided the stimulus to design a simple and rapid method for in vitro generation of chimeric RNA molecules corresponding to pathological fusion transcripts typical for chromosomal translocations in leukemias. Two separate fragments are generated in a four-primer multiplex PCR. Due to a PCR-generated overlap, a chimeric fragment can be synthesized in a second round of PCR. This PCR product is then purified with the help of magnetic beads. Due to the SP6 promotor sequence incorporated during the second round of PCR, transcription into RNA is easily facilitated while the template DNA is still bound to the solid phase. Following this strategy we were able to synthesize the fusion transcripts m-BCR/ABL, CBF beta/MYH11, and MLL/AFp1 which are the molecular equivalents of t(9;22)(q34,q11), inv16(p13;q22) and t(1;11)(p32;q23), respectively. The chimeric RNA will be useful as a control template in diagnostic RT-PCR strategies. It can also be further processed in translation systems leading to the corresponding chimeric oncoprotein. This approach can be easily used to create any hybrid RNA of interest.
Leukemia 1995 Apr
PMID:Rapid synthesis of hybrid RNA molecules associated with leukemia-specific chromosomal translocations. 772 8

The leukemias of infancy, characterized by an equal distribution of lymphoid and myeloid subtypes, account for 2.5-5% of the acute lymphoblastic leukemias (ALL) and 6-14% of the acute myeloid leukemias (AML) of childhood. Rearrangements of the MLL gene on chromosome 11q23 are the most common genetic abnormalities in both ALL and AML, occurring in 70-80% and approximately 60% of cases, respectively. Infants with ALL and a rearrangement of MLL typically present with hyperleukocytosis, massive organomegaly, CNS involvement, CD10- B-lineage phenotype and myeloid-associated antigen (CD15) expression. Prognosis in these cases is uniformly poor, whereas in similar cases without the genetic defect, it is good to intermediate. The presenting features of infant AML include monoblastic or myelomonoblastic morphology, hyperleukocytosis and extramedullary involvement. Expected outcome approximates that for ALL (approximately 30% long-term survival rate). Rare congenital forms of lymphoid or myeloid leukemia, manifested at birth or during the first month of life, carry a dismal prognosis, especially when a MLL/11q23 rearrangement is present; such cases should be carefully distinguished by chromosomal/molecular analysis and cell culture techniques from transient myeloproliferative disorders which require only supportive care but close follow-up for subsequent development of leukemia. Juvenile chronic myeloid leukemia also can occur in infants and may be responsive to chemotherapy alone. Rapid progress has been made over the past decade in understanding the biology of infant leukemias. The biggest challenge now is to develop more effective treatment, especially for patients with MLL rearrangements.
Leukemia 1995 May
PMID:Biology and treatment of infant leukemias. 776 37

A patient with acute monocytic leukemia (AMoL) and t(6;11)(q27;q23) developed acute lymphoblastic leukemia (ALL) and t(4;11)(q21;23), 10 months after complete remission of the AMoL. The MLL gene, normally located at band 11q23, appeared differently rearranged in the cells of these two leukemias, showing a different origin for the two malignant clones. The responsibility of etoposide, used in treatment of the AML, in the occurrence of the ALL is probable in this patient.
Leukemia 1994 Dec
PMID:Distinct MLL gene rearrangements associated with successive acute monocytic and lymphoblastic leukemias in the same patient. 780 11

A nested polymerase chain reaction (PCR) protocol was developed for rapid detection of four different 11q23 abnormalities by a single PCR assay. During each of the two PCR rounds a sense primer located within exon 5 of the MLL gene at 11q23 was combined with four different antisense primers, each located within possible translocation partner genes at chromosomes 4, 6, 9, and 19, respectively. Except for the MLL primer all primers used during the second round of nested-PCR carried a characteristic fluorescence label at their 5'-end. Agarose gel analysis of the PCR products was sufficient to discriminate between the absence of any of the four MLL rearrangements and the presence of at least one of them. Discrimination of the four different MLL translocation partner genes was not possible by agarose gel analysis due to a molecular heterogeneity of the 11q23 breakpoints resulting in PCR products of variable size. For this reason, automatic fluorescence-based DNA-fragment analysis was used to exactly define the MLL translocation partner genes if a positive result had been obtained by agarose gel analysis. In patients with leukemia, this assay may enable a fast and highly sensitive detection of different 11q23 abnormalities, which usually correlate with poor clinical prognosis.
Leukemia 1995 Jan
PMID:Detection of four different 11q23 chromosomal abnormalities by multiplex-PCR and fluorescence-based automatic DNA-fragment analysis. 784 20


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