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Biomedical subjects

S K Ma

Publications and source records attributed to S K Ma.

At least 91 records · Page 5Linked to original sources
PubMed2000

Acute myeloid leukaemia with giant granules: association with t(10; 11)(p13; q14) and disseminated intravascular coagulation.

A 16-year-old Chinese girl presented with AML-M5a. A bone marrow examination showed that the myeloblasts which were overwhelming the marrow contained giant granules (pseudo-Chediak-Higashi anomaly). Her karyotype showed a rare translocation t(10; 11)(p13; q14). Molecular delineation of the translocation breakpoints was not possible. Nonetheless, this case further demonstrates the morphological and phenotypic heterogeneity of acute leukaemia with this translocation. In this girl it was associated with disseminated intravascular coagulation.

Adolescent↗
PubMed2000

Effects of antioxidants and a caspase inhibitor on chloramphenicol-induced toxicity of human bone marrow and HL-60 cells.

Chloramphenicol (CAP), a board spectrum antibiotic widely used in many developing countries, has toxic side effects on bone marrow, the most serious of which is aplastic anemia. Recent studies suggest that effects of CAP on suppressing hematopoietic colony formation may be abrogated by antioxidants. In addition, there is preliminary evidence that CAP induces apoptosis in hemopoietic stem cells, leading to aplastic anemia. We have been unable to demonstrate the protective effects of a variety of antioxidants on CAP-induced suppression of burst-forming unit erythroid (BFU-E) and colony-forming unit granulocyte/monocyte (CFU-GM). Using flow cytometry, we have, however, confirmed that CAP can induce apoptosis in purified human bone marrow CD34+ cells. We also showed that a caspase inhibitor, Z-VAD.fmk, can ameliorate the apoptotic-inducing effects of CAP in the HL-60 cell line.

Amino Acid Chloromethyl Ketones↗
PubMed2000

Absence of microsatellite instability in primary myelodysplastic syndrome.

Using polymerase chain reaction (PCR), we examined a panel of 10 microsatellite markers (BAT26, BAT40, D2S123, D4S171, D8S87, D10S197, D12S89, Tp53, D18S58, PLCpr) covering nine chromosomal arms for microsatellite instability (MSI) in 29 patients with primary MDS. Bone marrow DNA was compared with corresponding constitutional DNA derived from buccal epithelial cells. Apart from BAT26 and BAT40 that were mononucleotide (poly A) repeats, the others were dinucleotide (CA) repeats. The patients comprised 10 cases of refractory anemia (RA), three cases of refractory anemia with ringed sideroblasts (RARS), nine cases of refractory anemia with excess of blasts (RAEB), four cases of refractory anemia with excess of blasts in transformation (RAEBt), and three cases of chronic myelomonocytic leukemia (CMML). Serial samples were available in seven patients, in which four showed transformation into higher disease grade or acute myeloid leukemia (AML). Genetic alterations at one locus (three at D2S123, one at D4S171) were evident in four cases, and loss of heterozygosity at Tp53 was detected in one case. Accordingly, none of the 29 patients with primary MDS nor the seven with disease progression in this study exhibited MSI. This shows that MSI may not be important in the pathogenesis or progression of MDS in contrast to other genetic mechanisms, notably recurrent chromosomal abnormalities that dysregulate the expression or function of genes controlling cell growth, differentiation and apoptosis.

Aged↗
PubMed1999

Atypical chronic myeloid leukemia with der(20)t(17;20)(q21;q13).

We present a case of atypical chronic myeloid leukemia that developed blastic transformation four months after initial presentation, with the blast cells showing multilineage antigen expression. A novel karyotypic abnormality, der(20)t(17;20)(q21;q13), was found in bone marrow cells at diagnosis. The potential role of such an aberration in leukemogenesis is discussed.

Adult↗
PubMed1999

Extra-medullary relapse of leukemia following allogeneic bone marrow transplantation.

The curative effect of allogeneic bone marrow transplantation (BMT) for acute and chronic leukemia is attributed to the intensive conditioning chemotherapy with or without radiotherapy, as well as an immune-mediated graft versus leukemia (GVL) effect. A different pattern of relapse has been observed after allogeneic BMT for patients with leukemia. Compared with treatment using conventional chemotherapy alone, isolated extra-medullary relapse of disease appears to be seen more commonly after allogeneic BMT. While a full donor's hematopoiesis may be retained, prolonged morphological remission has been observed in the recipient's bone marrow. There appears to be a population of leukemic cells with an affinity to extra-medullary tissues. The failure of the leukemic clone to repopulate the recipient's marrow suggests the presence of a more profound GVL effect in the marrow environment. The optimal treatment for extra-medullary relapse of leukemia following allogeneic BMT remains uncertain. In the case of isolated extra-medullary relapses following BMT, the leukemia may still be responsive to further treatment with chemotherapy and/or radiotherapy. The prognosis is poor in general, but prolonged survival has been observed in some of these patients. With the preservation of donor's hematopoiesis in the recipient's marrow, the use of intensive chemotherapy followed by donor lymphocyte or stem cell re-infusion is a promising option.

Bone Marrow Transplantation↗
PubMed1999

Cytogenetics and molecular genetics of childhood leukemia.

Childhood leukemia is the commonest form of childhood cancer and represents clonal proliferation of transformed hemopoietic cells as a result of genetic changes. Molecular characterization of these changes, in particular chromosomal translocations, has yielded a wealth of information on the mechanisms of leukemogenesis. These findings have also allowed the development of sensitive assays for the identification of underlying molecular defects, which is applicable to disease diagnosis and to monitor response to treatment. Genetic alterations in childhood leukemia are powerful prognostic indicators. TEL-AML1 fusion and hyperdiploidy >50 chromosomes are associated with a good prognosis in childhood acute lymphoblastic leukemia, whereas BCR-ABL fusion and MLL rearrangements are associated with a poor prognosis. Hence cytogenetic and molecular genetic classification of childhood leukemia will significantly improve the ability of clinicians to predict therapeutic response and prognosis, which paves the way for risk stratification based on clinical and genetic features. Finally, deciphering of genetic lesions in leukemia has allowed elucidation of the molecular basis of current treatment, as typified by the success of all-trans retinoic treatment in acute promyelocytic leukemia, and has identified targets for novel therapeutic approaches. It is envisaged that efforts in characterization of molecular defects in childhood leukemia will ultimately be translated into better clinical outcome for patients.

Biomarkers, Tumor↗
PubMed1999

The role of trisomy 8 in the pathogenesis of chronic eosinophilic leukemia.

A case of chronic eosinophilic leukemia (CEL) manifesting as spinal cord compression by an extradural eosinophilic chloroma in a 32-year-old Chinese man was presented, who subsequently developed extramedullary transformation at the skin and then peritoneal cavity. Cytogenetic study of bone marrow cells at diagnosis showed a clonal karyotypic abnormality of trisomy 8 (+8), which on fluorescence in situ hybridization (FISH) was shown to be present in a clone of abnormal eosinophils, hence showing the neoplastic nature of the eosinophilic proliferation. There was another population of abnormal eosinophils that did not show +8. At blastic transformation, all blast cells in ascitic fluid were shown by FISH to harbor +8. These findings suggest that +8 in this case may have arisen from clonal evolution and is not the primary genetic event in leukemogenesis, but +8 most probably imparts a further survival advantage to the clone responsible for subsequent blastic transformation.

Adult↗
PubMed1999

Trisomy 21 as the sole acquired karyotypic abnormality in acute myeloid leukemia and myelodysplastic syndrome.

We report five cases of myeloid disorders in which trisomy 21 (+21) was found as the sole acquired karyotypic abnormality, comprising two cases of acute myeloid leukemia (AML) and three cases of myelodysplastic syndrome (MDS). In this series, MDS patients with +21 presented as high grade disease, which included two cases of refractory anemia with excess of blasts (RAEB) and one case of refractory anemia with excess of blasts in transformation (RAEBt), and showed rapid disease progression. Significant thrombocytopenia was observed in all three patients, and bone marrow examination showed a marked reduction in megakaryocytes. AML patients with +21 included one case each of AML-M2 and M4. Despite the poor prognosis reported in AML patients with +21 as the sole abnormality, the patient in our series who was able to complete intensive treatment was cured of disease. The role of +21 in leukemogenesis is reviewed.

Acute Disease↗
PubMed1999

Complex variant 15;17 translocations in acute promyelocytic leukemia. A case report and review of three-way translocations.

Complex variant 15;17 translocations are increasingly recognized in acute promyelocytic leukemia (APL). We report a novel three-way translocation in APL involving chromosomes 15, 17, and X in the form of t(X;17;15)(q13;q12;q21). Southern blot analysis showed retinoic acid receptor alpha (RARA) gene rearrangement at intron 2. Clinical and morphologic findings are typical of APL, and a complete remission was attained with a course of conventional chemotherapy. A review of three-way complex variants of 15;17 translocation in the literature reveals 21 published cases in addition to ours. PML/RARA fusion was observed in all 8 cases in which molecular genetic analysis had been performed. More cases need to be analyzed to determine if clustering to particular chromosomal bands occurs in variant translocations, and whether APL cases harboring complex 15;17 variants differ clinically from those with classical 15;17 translocation.

Adult↗