Sertad1 antagonizes iASPP function by hindering its entrance into nuclei to interact with P53 in leukemic cells.

BACKGROUND: As the important suppressor of P53, iASPP is found to be overexpressed in leukemia, and functions as oncogene that inhibited apoptosis of leukemia cells. Sertad1 is identified as one of the proteins that can bind with iASPP in our previous study by two-hybrid screen. METHODS: Co-immunoprecipitation and immunofluorescence were perfomed to identified the interaction between iASPP and Sertad1 protein. Westernblot and Real-time quantitative PCR were used to determine the expression and activation of proteins. Cell proliferation assays, cell cycle and cell apoptosis were examined by flow cytometric analysis. RESULTS: iASPP combined with Sertad1 in leukemic cell lines and the interaction occurred in the cytoplasm near nuclear membrane. iASPP could interact with Sertad1 through its Cyclin-A, PHD-bromo, C terminal domain, except for S domain. Overexpression of iASPP in leukemic cells resulted in the increased cell proliferation and resistance to apoptosis induced by chemotherapy drugs. While overexpression of iASPP and Sertad1 at the same time could slow down the cell proliferation, lead the cells more vulnerable to the chemotherapy drugs, the resistance to chemotherapeutic drug in iASPPhi leukemic cells was accompanied by Puma protein expression. Excess Sertad1 protein could tether iASPP protein in the cytoplasm, further reduced the binding between iASPP and P53 in the nucleus. CONCLUSIONS: Sertad1 could antagonize iASPP function by hindering its entrance into nuclei to interact with P53 in leukemic cells when iASPP was in the stage of overproduction.

Significance of transmission electron microscopy in subtyping of monocytic leukemia.

The objective of this paper is to produce an ultrastructural classification of acute monocytic leukemia (AML-M5) in relation to clinical behaviors. The ultrastructural characteristics of blasts of the monocytic series were analyzed in 72 M5 patients by transmission electron microscopy (TEM), in terms of their content of typical monoblasts, atypical monoblasts, atypical promonocytes, and typical promonocytes in bone-marrow aspirates. Four kinds of monocytic blasts were identified by cell size and shape, nuclear profile, nucleocytoplasmic ratio, heterochromatin content, nucleolus, granules, vesicles, and Golgi apparatus. Their characteristics of remission rate, cytochemistry, immunophenotype, and cytogenetics were also investigated. The data obtained permitted M5 patients to be divided into monoblast and promonocyte types. Monoblast-type patients expressed weaker monocytic enzymograms and specific antigen staining for CD14 and CD64, compared with promonocyte-type patients. Monoblast patients had higher CR than promonocyte patients. Therefore, TEM subclassification of patients differs from and improves upon the light microscopical criteria for distinguishing monoblasts and promonocytes and has clinical significance.

[Ultrastructural analysis of 5' nucleotides distribution in acute myeloid leukemia subtypes].

5' nucleotides (5'NT), a purine degradative enzyme, is capable of hydrolyzing nucleotide and acting as a phosphotransferase simultaneously. It has critical role in maintaining nucleotide metabolism balance. The present study was aimed to investigate the expression of 5'NT in bone marrow granulocytes (BMGs) from patients with acute myeloid leukemia (AML) and healthy donors comparatively. The BMGs were isolated from bone marrow of 33 patients with AML and 6 healthy donors by using lymphocyte isolating solution. The reactivity of 5'NT was detected by electron microscope and cytochemistry of cytidine monophosphate (CMP). The positive BMG ratio and their index were calculated on the base of ultrastructural observation semiquantitatively. The results indicated that electron microscopy revealed plasma membrane reacting pattern of CMP. Most BMGs from normal donors were CMP negative or exhibited lower active degree. All cases of M(0), M(1), M(2) and t (8; 21) showed high positive percentages and high indexes of BMGs, but no statistic differences between them. APL of t (15; 17) shared lower percentages and indexes than other subtypes. There was no significant difference between APL and normal donors statistically. In conclusions, the results suggested the expression of 5'NT may be associated with BMG differentiation in AML, and APL of t (15; 17) may be a highly differentiated leukemia subtype.