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Checkpoint protein Chk1 has been identified as an Hsp90 client. Treatment with 100 nM geldanamycin (GM) for 24 h markedly reduced the Chk1 amount in Jurkat and ML-1 leukemia cell lines. Because Chk1 plays a central role in G2 checkpoint, we added GM to G2-arrested Jurkat and HL-60 cells pretreated with 50 nM doxorubicin for 24 h. GM slowly released both cell lines from doxorubicin-induced G2 arrest into G1 phase. GM also abrogated ICRF-193-induced decatenation G2 checkpoint in Jurkat and HL-60 cells. Western blot analysis showed that addition of GM attenuates doxorubicin- and ICRF-193-induced Chk1 phosphorylation at Ser345. GM, however, failed to abrogate G2 arrest in p53-positive ML-1 cells maybe due to the p21 induction. GM released HeLa cells from doxorubicin-induced G2 arrest but trapped them at M phase. Flow cytometric analysis showed that addition of GM converted doxorubicin-induced necrosis into apoptosis in Jurkat cells. Colony assay indicated that although GM has a weak cytotoxic effect as a single agent, it dramatically intensifies the cytotoxicity of doxorubicin and ICRF-193 in Jurkat and HL-60 cells. These results suggest that abrogation of G2 checkpoint by GM may play a central role in sensitizing p53-negative tumor cells to DNA-damaging and decatenation-inhibiting agents.Oncogene (2008) 27, 3091–3101; doi:10.1038/sj.onc.1210978; published online 10 December 2007 [ABSTRACT FROM AUTHOR]

Natural killer (NK) cell-type lymphoproliferative disease of granular lymphocytes (LDGL) is characterized by the outgrowth of CD3-CD16/56+ NK cells, and can be further subdivided into two distinct categories: aggressive NK cell leukemia (ANKL) and chronic NK lymphocytosis (CNKL). To gain insights into the pathophysiology of NK cell-type LDGL, we here purified CD3-CD56+ fractions from healthy individuals (n=9) and those with CNKL (n=9) or ANKL (n=1), and compared the expression profiles of >12?000 genes. A total of 15 ‘LDGL-associated genes’ were identified, and a correspondence analysis on such genes could clearly indicate that LDGL samples share a ‘molecular signature’ distinct from that of normal NK cells. With a newly invented class prediction algorithm, ‘weighted distance method’, all 19 samples received a clinically matched diagnosis, and, furthermore, a detailed cross-validation trial for the prediction of normal or CNKL status could achieve a high accuracy (77.8%). By applying another statistical approach, we could extract other sets of genes, expression of which was specific to either normal or LDGL NK cells. Together with sophisticated statistical methods, gene expression profiling of a background-matched NK cell fraction thus provides us a wealth of information for the LDGL condition.Leukemia (2004) 18, 556-565. doi:10.1038/sj.leu.2403261 Published online 22 January 2004 [ABSTRACT FROM AUTHOR]

The effects of corticosteroids on the natural killer (NK) cell activity of human peripheral blood lymphocytes were evaluated. When six untreated female patients with systemic lupus erythematosus were compared with fifteen age-matched, corticosteroid-treated female patients. NK activity in the latter was significantly suppressed. Although the administration of high doses seemed lo suppress cytotoxicity to a greater extern, there was no close correlation between the daily doses of steroids and NK activity. When cytotoxicity levels were followed before and during corticosteroid therapy in the same patient, NK activity decreased markedly during treatment, particularly in patients on high-dose corticosteroids. [ABSTRACT FROM AUTHOR]

Cell co-operation in the generation of secondary cytotoxic responses was studied by selectively sensitizing lymphocytes in mixed lymphocyte culture (MLC) across I or D region difference and by combining the primed lymphocytes in the secondary MLC. Secondary cytotoxic responses were induced in D-region-primed lymphocytes by restimulation with the original priming D-region antigens, by co-culturing with the I-region-primed lymphocytes in the presence of the priming I-region antigens, or by cell-free supernatants obtained 24 h after the restimulation of D-region-primed lymphocytes and I-region-primed lymphocytes. The active MLC supernatants produced by both I-region-primed and D-region-primed cells also induced accelerated proliferative responses in D-region-primed lymphocytes. Heat-treatment or ultraviolet irradiation of the stimulator cells eliminated the capacity of the cells to induce the production of CTL-helper factor in I-region-primed and D-region-primed lymphocytes. It was concluded that both I-region-primed and D-region-primed lymphocytes produce a cell-free factor which induces proliferation and secondary cytotoxicity in D-region-primed lymphocytes. The possible participation of D-region reactive helper T cells and D-region reactive cytotoxic T cells in the cytotoxic responses to D-region antigens in the absence of I-region difference is discussed. [ABSTRACT FROM AUTHOR]

Medullasin, a serine protease found in human bone marrow cells, has been shown to induce activated killer (AK) cells that lyse both natural killer (NK)-sensitive and -resistant cloned target cells from human lymphocytes. In addition to all the tested malignant cell lines, malignant cells obtained from all patients with acute myelocytic leukaemia, chronic lymphocytic leukaemia and lymphoblastic leukaemia were lysed by AK cells induced by medullasin. Maximum induction was achieved when lymphocytes were incubated at 37 for 60 min in the presence of medullasin (20 µg/ml). The cytotoxicity of AK cells induced by medullasin treatment (200 µg/ml, 37 for 60 min) was greater than that of lymphokine-activated killer (LAK) cells produced by 500 U/ml of interleukin-2 (IL-2). Cytokines such as IL-2 or interferon (IFN) are not considered to be involved in the medullasin induction of AK cells for the following reasons: (1) neither IL-2 nor IFN activity were detected in the supernatant of lymphocytes treated with medullasin; (2) the supernatant of lymphocytes treated with medullasin failed to induce AK cells, and (3) the presence of antibodies against IL-2 or IFN did not influence the effect of the protease. By employing monoclonal antibodies to the surface antigens of lymphocytes and a panning method using plastic dishes coated with anti-mouse IgG goat Fab', progenitor as well as effector cells were found to be CD16-positive cells. [ABSTRACT FROM AUTHOR]