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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mice were infected with the exogenous Moloney leukemia virus (M-MuLV) at two different stages of development. Either newborn mice (which can be considered as essentially fully differentiated animals) or preimplantation mouse embryos (at the 4-8 cell stage) were infected with M-MuLV. In both cases, animals that had developed an M-MuLV-induced leukemia were obtained. Two lines of evidence indicate that infection of preimplantation embryos, in contrast to infection of newborns, can lead to integration of the virus into the germ line. 1. Viremic males of the first backcross generation (N-1 generation) transmitted the virus to 50% of their offspring (N-2 generation) when mated with uninfected females. Likewise, a 50% transmission was observed from viremic N-2 and N-3 males to the next generations. 2. Molecular hybridization experiments revealed that viremic N-1 and N-2 animals carried one copy of M-MuLV per diploid mouse genome equivalent in all "non-target" organs tested. Together, both experiments indicate that the exogenous M-MuLV can be converted to an endogenous virus after infection of preimplantation embryos. The available evidence suggests that M-MuLV integrated into the germ line at one out of two possible integration sites. Thus, viremic backcross animals are heterozygous for a single Mendelian locus carrying the M-MuLV gene. During leukemogenesis an amplification of the M-MuLV from one copy to a maximum of four copies per diploid mouse genome equivalent takes place in the tumor tissues.
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PMID:Germ line integration and Mendelian transmission of the exogenous Moloney leukemia virus. 106 7

A case of epithelial thymoma occurring synchronously with Philadelphia chromosome-positive chronic myelogenous leukemia and urinary bladder carcinoma in a 76-year-old man is described. Thymomas have been associated with numberous hematologic, collagen-vascular and autoimmune disease states, as well as with an increased incidence of nonthymic malignancy. Human thymoma-associated leukemia is, however, extremely unusual, despite the well-documented role of the thymus in leukemogenesis in experimental animals. No previous literature reports of thymoma associated with chronic myelogeneous leukemia were found. A review of long-term followup data of surviving thymoma patients is necessary to determine if an increased propensity to develop leukemia is present in present in patients with thymoma.
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PMID:Thymoma and chronic myelogenous leukemia: a case report. 106 82

Differentiation of hemopoietic cells appears to depend upon specific interactions of certain cell-factors. The phenotypic abnormality in leukemia may involve an impairment in these interactions. In this report we present some of our views of leukemogenesis with respect to cell-factor interaction and the feasibility of experimental approaches to this problem. In culture, the interaction of myelogenous cells with factor(s) leading to differentiation can be measured either with a suspension mass culture method or by a solid (semi-soft) clonal method. The protein factors that support the growth of hemopoietic cells in suspension culture are termed growth stimulating factors (GSA) and in semi-solid culture, colony stimulating factors (CSA). Studies using conditioned medium prepared from phytohemagglutinin stimulated human lymphocytes (PHA-LyCM) and whole human embryo cells (WHE) revealed that GSA and CSA were not identical for growth of either normal human or leukemic leukocytes. In some cases maturation of leukemic leukocytes was observed. Fractionation of PHA-LyCM showed that there are three peaks for CSA. Each peak contains different fractions for supporting cellular proliferation, differentiation, and self-renewal of precursor cells in suspension culture. Apparently, each contains heterogenous species of protein factors some of which functionally overlap, while others do not.
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PMID:The phenotypic abnormality in leukemia: a defective cell-factor interaction? 108 22

Studies of Rauscher virus-induced erythroleukemia have demonstrated immunodepressive effects in the host and enhanced leukemogenesis with adjuvant administration. These observations led to the study of leukemic development in the NZB strain as a natural model of the experimentally adjuvant-stimulated animal. The results of such investigation would attribute the increased susceptibility of NZB mice to the possession of an enlarged population of pluripotent hemopoietic stem cells in active cell cycle. Studies with radiation chimeras have further shown that elevated endogenous spleen colony formation, the increased potential for autoimmunity, and for susceptibility to Rauscher viral leukemogenesis are all linked through the NZB hemopoietic system. It is concluded that the presence of an enlarged compartment of cyclically active stem cells may be an etiologic factor in the susceptibility to both virus-induced leukemia and the development of autoimmune disease.
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PMID:Tumor virus effects on immunocyte precursor cells. Hemopoietic stem cell behavior and leukemogenic susceptibility. 108 86

Chromosomal findings are reported in three patients with acute myelomonocytic leukemia and in one with reticulosarcoma leukemia who had been treated for multiple myeloma with melphalan and X-ray. All four patients had striking chromosomal anomalies. An iatrogenic causation of aneuploidy is suggested. This is supported by chromosomal findings in patients with acute leukemia following polycythemia vera and Hodgkin's disease; practically all of the leukemias have been aneuploid. A comparison is made of such "secondary" acute leukemias with "primary" acute leukemias that are aneuploid in only 40% of the cases. Chromosomal changes are not considered to be the initial event in leukemogenesis.
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PMID:Chromosome studies in acute leukemias developing in patients with multiple myeloma. 109 66

Radiation which induces leukemogenesis in the unirradiated mouse, inhibits leukemogenesis if given again to the previously irradiated, but not yet leukemic mouse. The objective of this experiment was to identiry nonmalignant late radiation in jury in the bone marrow, the modification of which by a second exposure may account for postponement of radiogenic leukemia. To this end, leukemogenically irradiated RFM/Up mice were reirradiated under conditions known to bring about postponement of the leukemias due to the first radiation exposure. Quantitative analysis of the femoral pone marrow of these mice shows that leukemia incidence is positively correlated with the number of immature myeloid cells, and negatively correlated with the percentage of the mature myeloid cells in the entire myeloid series. The implications of this for the understanding of preleukemic change are discussed.
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PMID:Experimental manipulation of preleukemic change in whole-body irradiated RFM/Up mice (38542). 112 85

Lipid composition of thymuses investigated during the development of thymic leukemogenesis induced by exposing C57BL/6J mice to gamma radiation led to the following conclusions. 1. Alkyldiacylglycerols, a class of lipids that are generally elevated in most neoplastic tissues, occurred only in small quantities (less than 1% of the total lipids) in the thymuses of both control and irradiated mice. However, we found a 3- to 8-fold increase in this fraction in thymic tumors of mice at 5 mo after irradiation when compared to controls of similar age. However, the small quantity of this lipid class in thymic leukemia and the fact that similar levels were found in some samples of involuted thymuses of mice 3 days after irradiation, suggests to us that the level of alkyldiacylglycerols is not sufficiently specific or sensitive for detecting early stages of thymic leukemogenesis. 2. Thymuses 3 days after irradiation and leukemic thymuses contain 2- to 3-fold greater quantities of cholesterol esters than control thymuses. No major differences were found in the distribution of acyl moieties in the cholesterol esters of the various thymus samples from the same aged mice except that in thymic tumors the quantity of 18:1 esters was increased by about 25% over that of the controls. The apparent lack of specificity of increased cholesterol esters for neoplasia indicates that its measurement would not provide a suitable indicator of early neoplastic transformation. 3. Acyl composition of the triacylglycerols of thymuses revealed an increase in the 18:1 and a decrease in the 18:2 acids at 3 days after irradiation when compared to the same aged controls. However, thymic tumors occurring at 5 mo after irradiation contained less 14:0, 16:0, and 16:1 acids and increased amounts of 18:1 and 18:2 acids esterified as triacylglycerols compared to controls. The fatty acid distribution in the phospholipid fraction of thymuses was not altered by the appearance of leukemia.
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PMID:Analysis of tumor-associated alkyldiacylglycerols and other lipids during radiation-induced thymic leukemogenesis. 114 68

Administration of N-butylnitrosourea (BNU) induces leukemia in thymectomized C57BL/6J and C3Hf/Bi mice with almost the same high frequency as in non-thymectomized mice. Thymectomized and BNU-treated (C3Hf/Bi times CBA/H-T6T6)F1 mice receiving neonatal thymus tissues from C3Hf donors developed leukemias with or without marked enlargement of the grafts. The origin of leukemic cells was analysed by T6 marker chromosome and thymus allo-antigen theta in this hybrid system. Cells from leukemia with enlarged thymus grafts possessed the sigma-antigen detected by cytotoxicity tests. Cells from leukemia without thymus involvement had no sigma antigen. The leukemic cells arising at the site of thymus grafts were derived from the graft itself (C3Hf) or from the host (C3Hf times CBA/H-T6T6)F1 cells, most probably bone marrow cells which are repopulating into the graft. When the mice were treated with BNU after the lymphoid elements in the grafted thymus had been replaced by host cells, leukemia mainly composed of host-origin cells developed. Leukemia in which neoplastic cells in the thymus grafts were of donor origin and those in other hematopoietic tissues were of host origin was found not infrequently. The present results mean that the target cells in BNU leukemogenesis are distributed within and outside the thymus and that some leukemias are of multifocal tissue origin.
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PMID:Origin of leukemic cells in mouse leukemia induced by N-butylnitrosourea. 115 1

Comparative considerations are made between human acute leukemia (AL) and mouse transplantable L-1210 leukemia. The main kinetic parameters, such as the growth fraction (GF), growth rate, and cell cycle times, of both human and mouse diseases, are compared. The striking differences in cell kinetics and in response to treatment may be viewed as depending on different leukemogenesis mechanisms. Therefore, some improvement in human AL chemotherapy is considered possible both by researching a more rational employment of cytostatic drugs, and studying other animal models quite similar to the human disease, such as AKR leukemia.
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PMID:L-1210 and human acute leukemia kinetics as related to therapy. 116 6

The frequent occurrence of TF gene involvement in translocations associated with leukemia is remarkable, although not yet explained. The wide variety of TFs involved in these translocations and the different stages of cellular maturation argue against a unifying mechanism. Recombinases, active during B-cell and T-cell development, have been implicated in gene arrangements involving TCR genes and in the SIL/SCL rearrangement, which involves two genes not normally rearranged. However, other mechanisms must clearly be active in generating these molecular abnormalities and perhaps they relate to the multistep maturation and differentiation processes and continuous cell turnover seen in hematopoietic cells. The difficulties in obtaining human solid tumor samples may make it more difficult to identify translocations involving TF genes in solid tumors. Recently, the cytogenetic analysis of solid tumors has improved and specific cytogenetic abnormalities have been associated with specific types of tumors. With advanced techniques, such as fluorescent in situ hybridization (a technique that does not depend on cell growth) and PCR, abnormalities involving TF genes will be discovered. Abnormalities of TF genes, other than translocations, have been seen in a broad variety of nonhematopoietic malignancies. The p53 protein has been shown to bind DNA in a sequence-specific fashion and interact with a variety of DNA tumor virus oncoproteins. The broad range of cell types that harbor p53 abnormalities suggests that TF abnormalities will likely be implicated in many solid tumors. We have detailed several examples of how gene rearrangements that accompany chromosomal translocations in acute leukemia can alter the expression or activity of cellular TFs. Several translocations generate fusion RNA transcripts and fusion TF proteins with altered functional characteristics. Other translocations result in the expression of a gene not normally detectable in hematopoietic cells or alter the level of its expression, or affect the promoter usage or exon structure of the gene (Table 2). Studies are underway in many laboratories to characterize the biologic activity of these abnormal TFs and it remains to be proven that these molecular abnormalities are directly linked with leukemogenesis. The identification of abnormal fusion transcripts and proteins may allow specific therapies to be directed against "tumor-specific" DNA, mRNA, or protein targets. Therapeutic strategies based on antisense or ribozyme technology may be used to turn off expression of these genes and inhibit leukemia cell growth. Immunologic methods can also be used to direct therapy against the malignant cells.
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PMID:Transcription factors, translocations, and leukemia. 136 70


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