Detection of minimal residual disease in an AML patient with trisomy 8 using interphase fish.

Patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS) often exhibit clonal chromosomal abnormalities. Using a probe for the centromeric region of chromosome 8, fluorescence in situ hybridization (FISH) on interphase cells was used to detect trisomy 8 in an AML patient whose leukemia was characterised by the karyotype 47, XY, +8, del(9) (q21.1q32). We have demonstrated using FISH the presence of the trisomy at all stages of the patient's disease course (including remission, peripheral blood cell harvest and relapse), whereas conventional karyoptypic analysis was only able to detect the trisomy at diagnosis and clinical relapse. We have also shown using immunophenotyping, cell sorting and FISH, that the trisomic cells in this patient were restricted to the CD34+ subset of blood and bone marrow and could not be found in the CD 34-, T or B cell compartment. Overall we have shown FISH to be a rapid, quantitative method for the detection of cells with numerical chromosome abnormalities. FISH analysis of interphase cells provides valuable information on the status of the whole population, rather than just cycling cells, and can be applied successfully to monitor the level of leukemic cells.

Inhibition of granulocyte-macrophage colony-stimulating factor prevents dissemination and induces remission of juvenile myelomonocytic leukemia in engrafted immunodeficient mice.

Granulocyte-macrophage colony-stimulating factor (GM-CSF ) and tumor necrosis factor alpha (TNFalpha) have been implicated in the pathogenesis of the fatal childhood disease termed juvenile myelomonocytic leukemia (JMML). We used a severe combined immunodeficient/nonobese diabetic (SCID/NOD) mouse model of JMML and examined the effect of inhibiting these cytokines in vivo with the human GM-CSF antagonist and apoptotic agent E21R and the anti-TNFalpha monoclonal antibody (MoAb) cA2 on JMML cell growth and dissemination in vivo. We show here that JMML cells repopulated to high levels in the absence of exogeneous growth factors. Administration of E21R at the time of transplantation or 4 weeks after profoundly reduced JMML cell load in the mouse bone marrow. In contrast, MoAb cA2 had no effect on its own, but synergized with E21R in virtually eliminating JMML cells from the mouse bone marrow. In the spleen and peripheral blood, E21R eliminated JMML cells, while MoAb cA2 had no effect. Importantly, studies of mice engrafted simultaneously with cells from both normal donors and from JMML patients showed that E21R preferentially eliminated leukemic cells. This is the first time a specific GM-CSF inhibitor has been used in vivo, and the results suggest that GM-CSF plays a major role in the pathogenesis of JMML. E21R might offer a novel and specific approach for the treatment of this aggressive leukemia in man.

Apoptosis regulatory gene NEDD2 maps to human chromosome segment 7q34-35, a region frequently affected in haematological neoplasms.

Developmentally regulated mouse gene Nedd2 encodes a protein similar to the product of the nematode Caenorhabditis elegans cell death gene ced-3 and the mammalian interleukin-1 beta-converting enzyme. Overexpression of Nedd2 in cultured mammalian cells induces apoptosis that can be blocked by proto-oncogene BCL2. We have isolated cDNA clones for the human homologue of the mouse gene and, by using these as probes, mapped the human NEDD2 gene to 7q34-35 by fluorescence in situ hybridisation. The potential tumour suppressor function of NEDD2 is discussed.

Paracentric inversion of chromosome 14 plus rare 9p variant in a couple with habitual spontaneous abortion.

A couple presenting with habitual spontaneous abortion both showed a chromosome rearrangement. The male had an apparently balanced paracentric inversion of chromosome 14 - 46,XY,inv(14) (q11q32). The female had a karyotype with a rare large short arm variant of chromosome 9 - 46,XX,var(9) (p11p21). Testing of a living normal child showed that he had inherited both rearrangements. Family testing showed the chromosome 9 variant in three generations, with all carriers being of normal phenotype and intelligence. This study confirms that the presence of more than one chromosomal rearrangement can be compatible with normal development. This is useful for genetic counselling. Nevertheless when such cases arise, each must be individually assessed.