Tissue culture in microgravity.

Attempts to simulate normal tissue microenvironments in vitro have been thwarted by the complexity and plasticity of the extracellular matrix, which is important in regulating cytoskeletal and nuclear matrix proteins. Gravity is one of the problems, tending to separate components that should be kept together. For space shuttle experiments, NASA engineers devised a double-walled rotating bioreactor, which is proving to be a useful tissue culture device on earth as well as in space.

A role for mitochondrial DNA in the pathogenesis of radiation-induced myelodysplasia and secondary leukemia.

The onset of acute myeloid leukemia following ionizing radiation or alkylating agent exposure is antedated months to years by the development of 'preleukemia', or secondary myelodysplastic syndrome (sMDS). Mitochondrial abnormalities induced by chloramphenicol and clonal deletions of mitochondrial DNA (mt DNA) in the bone marrow create hematological defects similar to sMDS, and abnormal dimers of mt DNA are observed in acute leukemia. This suggests a role for mt DNA in the pathogenesis of sMDS and secondary leukemia. We outline disparate experimental evidence to support this concept and suggest a role for select protease inhibitors in the clinical management of this disorder.

Apoptotic megakaryocyte dysplasia in the myelodysplastic syndromes.

The terminal phase of the megakaryocyte life span is characterized by the onset of apoptosis to form compact, denuded megakaryocyte nuclei (DMK) surrounded by a thin rim of cytoplasm. Increased numbers of DMK have been reported in patients with acquired immune deficiency syndrome (AIDS) and chronic myeloproliferative disorders. In this study the bone marrow biopsies of 20 patients with various FAB subtypes of myelodysplastic syndrome (MDS) were examined for the presence of DMK cells and semiquantified for marrow reticulin level. For all MDS subtypes, a 9% or greater incidence of DMK in the total megakaryocyte population of the bone marrow was associated with a significant deposit of reticulin in the marrow. Immunocytochemical staining for Factor VIII (Von Willebrand factor), showed the abnormal deposition of this megakaryocyte protein in the extravascular stroma around many of the DMK cells. These findings are consistent with a hypothesis for excess stromal reticulin based on the defective maturation and intramedullary death of large numbers of megakaryocytes. The number of DMK in the marrow biopsies of MDS patients may have prognostic significance.

Immunocytochemical identification of nuclear estrogen-receptors in human acute myeloid leukemia.

The peripheral and bone marrow blast cells of twenty patients newly-diagnosed as acute myeloid leukemia (AML), subtypes M1-M5, were analysed for the presence of estrogen-receptors by ER-ICA immunocytochemistry and dextran-coated charcoal cytosolic (DCC) assay. Two patients demonstrated myeloblasts with nuclear staining patterns consistent with the presence of estrogen-receptors. The positive immuno-staining results were confirmed by DCC in one patient with AML, subtype M4. This patient demonstrated an unusual myeloblast karyotype with a reciprocal translocation t(6;11)(q27;q23.3) involving the designated locus of the ESR gene on chromosome 6 (6q24-qter). The abnormal juxtaposition of DNA control elements close to the promoter of the ESR gene may be one mechanism by which aberrant synthesis of estrogen-receptor protein can occur to provide a growth advantage for leukemia cell clones.

Induction of morphological differentiation in the human leukemic cell line K562 by exposure to thalidomide metabolites.

The lineage and state of differentiation of cells in the mammalian haemopoietic compartment is associated with specific patterns of homeobox gene expression (EMBO J. 7, 2131, 1988). Agents which influence homeobox gene expression are thus of great interest in the study of human leukemias. Retinoic acid has direct regulatory actions on homeobox gene transcription (TIBS 158, 52, 1989; Differentiation 37, 773, 1988) and can induce select human leukemia cell lines to undergo terminal differentiation in vitro (Proc. natl Acad. Sci. U.S.A. 77, 2936, 1980). Retinoic acid is also a known teratogen for vertebrate foetal limb-bud development. Some of the teratogenic effects are duplicated by the drug Thalidomide (Embryopathic Activity of Drugs, Little Brown, Boston, p. 167, 1965; Haematological Cytology, Wolf Med. Pub. Ltd, London, p. 118, 1982). To investigate Thalidomide for other retinoid-like effects, we exposed cultures of human leukemia K562 cells to the metabolites generated in a Thalidomide hepatic-microsomal enzyme drug metabolizing system (Proc. natl Acad. Sci. U.S.A. 78, 2545, 1981). Here we report evidence that a single 2 h pulse-exposure to Thalidomide metabolites, induces K562 cells to undergo morphological differentiation in vitro. We also demonstrate a significant cytotoxic effect for these metabolites.

Hyperprolactinemia in acute myeloid leukemia and indication of ectopic expression of human prolactin in blast cells of a patient of subtype M4.

The sera of 28 patients with acute myeloid leukemia AML--subtypes M1 to M6 were screened for human prolactin (h-PRL). Serum TSH (thyroid stimulating hormone), LH (luteinizing hormone), FSH (follicle stimulating hormone), beta-estradiol, free T4 (tetra-iodotyronine) and testosterone were also determined. It was found that in 16 of the 28 patients h-PRL was significantly elevated while all other endocrine values were normal. In a patient subtype M4 with elevated serum h-PRL we demonstrate by immunoblotting that the hormone and its dimer are present in the blast cells. This may reflect ectopic synthesis due to altered expression of homeobox genes and a requirement of h-PRL as a growth stimulant of the leukemic myeloblast.