Meiotic pachytene arrest in MLH1-deficient mice

Germ line mutations in DNA mismatch repair genes including MLH1 cause hereditary nonpolyposis colon cancer. To understand the role of MLH1 in normal growth and development, we generated mice that have a null mutation of this gene. Mice homozygous for this mutation show a replication error phenotype, and extracts of these cells are deficient in mismatch repair activity. Homozygous mutant males show normal mating behavior but have no detectable mature sperm. Examination of meiosis in these males reveals that the cells enter meiotic prophase and arrest at pachytene. Homozygous mutant females have normal estrous cycles and reproductive and mating behavior but are infertile. The phenotypes of the mlh1 mutant mice are distinct from those deficient in msh2 and pms2. The different phenotypes of the three types of mutant mice suggest that these three genes may have independent functions in mammalian meiosis.

Congenital chromosome breakage clusters within Giemsa-light bands and identifies sites of chromatin instability

Analysis of the distribution of published chromosome breaks in cells with constitutional chromosome aberrations showed a nonrandom distribution of breaks among chromosomes and chromosome regions. A significant amount of breakage occurred at Giemsa-negative bands. In addition, chromosome sites associated with a number of fragile sites and cellular oncogene sites were affected nonrandomly. The data are consistent with the hypothesis that chromosome breakage occurs in somatic or germ cells as a result of recombinational errors involving actively transcribing chromatin regions or regions of unstable DNA sequence structure placed in proximity during interphase.

Relationship of Auer rods and chromosome findings to outcome in eighty-nine adults with acute nonlymphoblastic leukemia

We performed cytogenetic analyses using banding techniques on 89 adults with acute nonlymphoblastic leukemia prior to receiving protocol chemotherapy. The relationships of cytogenetic findings both to outcome and to other pretreatment variables (particularly the presence or absence of Auer rods) were analyzed. Patients were followed up to 90+ months. When patients were grouped according to cytogenetic findings (NN: all normal metaphases; AA: all abnormal metaphases; AN: both normal and abnormal metaphases; F: no evaluable metaphases; I: insufficient (less than three) metaphases) no significant differences were noted with regard to age, sex, terminal transferase positivity, complete remission rate, remission duration or survival. The marrow aspirates of patients with only normal (69%) metaphases or no evaluable metaphases (64%) were more likely to display Auer rods than specimens from individuals with only abnormal (26%) or a mixture of normal and abnormal (42%) metaphases (p = 0.03). The presence of Auer rods in the pretreatment marrow aspirate was associated with an increased complete remission rate (71% vs 41%, p = 0.004), median remission duration (12 months vs 9 months, p = 0.02), and median survival (13 months vs 4 months, p = 0.01). Using multivariable analyses, the presence or absence of Auer rods was the pretreatment factor that most significantly predicted response and survival in this group of patients. The presence of a normal karyotype in the initial cytogenetic preparation is associated with the presence of Auer rods. The finding of Auer rods in the initial bone marrow predicts greater response and longer survival in acute nonlymphoblastic leukemia.

Philadelphia chromosome and terminal transferase-positive acute leukemia: similarity of terminal phase of chronic myelogenous leukemia and de novo acute presentation

Twenty-eight patients with Philadelphia chromosome (Ph1)--positive and terminal transferase (TdT)--positive acute leukemia (AL) were treated with intensive chemotherapy used for adult acute lymphoblastic leukemia (L-10 and L-10M protocols). Fifteen patients had a documented chronic phase of Ph1-positive chronic myelogenous leukemia preceding the acute transformation (TdT + BLCML) while the remaining 13 patients did not (TdT + Ph1 + AL). An overall complete remission (CR) rate of 71% was obtained with a median survival of 13 months in the responders. Clinical presentation, laboratory data, cytogenetics, response to treatment, and survivals of the two groups of patients are compared. These results appear to be similar, suggesting a common or closely related origin. Since the overall survival of those receiving chemotherapy maintenance is poor, three patients underwent allogeneic bone marrow transplantation (BMT) from histocompatibility leukocyte antigen--matched siblings after they achieved CR. One of them is a long-term survivor (35 + months) with a Ph1-negative bone marrow. New techniques such as BMT should be considered in young patients with a histocompatibility leukocyte antigen--compatible sibling once a CR has been achieved.

Application of monoclonal anti-HY antibody for human H-Y typing

We have successfully produced monoclonal anti- H-Y antibody by fusing NS-1 myeloma cells with splenocytes from C57BL/6 females immunized with syngeneic male splenocytes. We have proved that the antibody is male specific and that it cross reacts with human H-Y. We have further tested 80 normal individuals for H-Y antigen and obtained significant differences between males and females. Therefore, the monoclonal anti- H-Y antibody is useful for clinical typing of human H-Y antigen.

Acute myeloblastic leukemia following non-Hodgkin lymphoma in an adolescent. A report of a case with preleukemic syndrome, and review of the literature

Reports of acute nonlymphoblastic leukemia occurring after successful treatment of Hodgkin and non-Hodgkin lymphoma (NHL) are appearing with increasing frequency. Two years after completion of LSA2-L2 therapy for stage III, poorly differentiated lymphocytic lymphoma, a 16-year-old boy developed a preleukemic state characterized by a refractory macrocytic anemia with excess blasts, dyshematopoiesis, abnormal cluster:colony ratio on in vitro bone marrow culture, and acquired deficiencies of erythrocyte pyruvate kinase, triose phosphate isomerase, and adenylate kinase. Four months later acute myeloblastic leukemia was evident. The RNA index determined by flow cytofluorometry was increased. Four marker chromosomes were found and involved complex translocation of chromosomes 11 and 17 (t11;l17) in 100% of the cells, and chromosomes 4 (t4q;4) in 10% of the cells. A thorough literature search uncovered four other reports of acute nonlymphoblastic leukemia occurring in children treated for NHL and a total of 58 cases in the adult and pediatric age groups. Over 50% of the patients had AML, were mean over 50 years of age, and were treated with radiotherapy and chemotherapy. It is anticipated that additional cases of second malignancies will be reported in this population of patients whose outlook for the curability of the primary malignancy is 75%.

The coexistence of acute myeloblastic leukemia and diffuse histiocytic lymphoma in the same patient as demonstrated by multiparameter analysis

Measurement of cellular DNA content by flow cytometry demonstrated presence of two distinct aneuploid neoplasms in a patient who developed acute myeloblastic leukemia (AML) 4 mo after diagnosis of a diffuse histiocytic lymphoma (DHL). A lymph node aspirate contained peroxidase-negative, "null," hyperdiploid (2.6C) DHL cells, while the bone marrow (BM) contained 84% primitive peroxidase-positive tetraploid AML cells (4.0C). Minor populations of hyperdiploid HDL and normal diploid cells could be detected by flow-cytometry in the BM, and all three populations were also seen in the peripheral blood.

Results of treatment of Ph'+ chronic myelogenous leukemia with an intensive treatment regimen (L-5 protocol)

Thirty-seven patients with Philadelphia-chromosone-positive (Ph'+) chronic myelogenous leukemia who were untreated or minimally pretreated were entered on the L-5 protocol. This protocol consisted of sequential treatment with splenic irradiation, splenectomy, arabinosylcytosine and 6-thioguanine, and L-asparaginase. Maintenance therapy was hydroxyurea or a multiple-drug regimen. The median survival of the 37 patients is 50 mo. Twelve patients showed a temporary reduction in the percentage of Ph'+ marrow metaphases to less than one-third of the initial values and in 7 of these patients none were found. The duration of the Ph'+ chromosome reduction ranged from 1 to 43 mo. The median survival of the responders has not yet been reached. It is concluded that whereas overall survival is not appreciably extended, patients who have a reduction in Ph'+ cells in the marrow may survive longer than the average; also, the reduction occurs most frequently in patients who have relatively small spleens at diagnosis. The reduction is difficult to maintain, and it may be reinduced in some patients with intensive chemotherapy.