Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P10415 (Bcl-2)
 33,771 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

All-trans retinoic acid (ATRA) increases the sensitivity of AML blast cells to cytosine arabinoside (Ara-C) or daunorubicin (DNR) when ATRA is given after drug. We have proposed that down-regulation of bcl-2 is part of the mechanism by which ATRA regulates drug sensitivity. To test this hypothesis cDNA encoding bcl-2 was transfected into cells of the continuous lines OCI/AML-2 and OCI/AML-5. Four transfectant lines were isolated; three contained transfected bcl-2 in the sense orientation (AML5-BCL2sa, AML5-BCL2sb and 2-bcl2) and one with anti-sense bcl-2(AML5-bcl2as). The presence of the transfected gene was demonstrated by Northern blot; translation of the sense transfected genes into protein was demonstrated by Western blotting. Lines with sense-oriented transfected bcl-2 were significantly less sensitive to Ara-C or H2O2 than the parental lines; the cells with anti-sense transfected genes were more sensitive than their parent but the difference did not reach statistical significance. The effect of ATRA on bcl-2 expression was compared in sense-transfected cells and their parents; by Northern blotting it was shown that the endogenous but not the transfected genes were down-regulated after ATRA exposure. The capacity of cells with transfected genes to respond to ATRA was tested by obtaining Ara-C survival curves for ATRA-treated cells. Compared to controls not exposed to ATRA, the transfected cells showed little or statistically insignificant changes in Ara-C sensitivity after ATRA treatment. We conclude that data from the transfectants provides evidence that expression of bcl-2 is a determinant of sensitivity to Ara-C and H2O2; and that the effect of ATRA on sensitivity requires the presence of bcl-2 genes in association with regulatory elements.
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PMID:Direct evidence for the participation of bcl-2 in the regulation by retinoic acid of the Ara-C sensitivity of leukemic stem cells. 756 7

We examined the effects of high intracellular levels of Bcl-2 on the metabolism and DNA incorporation of high-dose Ara-C (HIDAC) as well as on Ara-C-induced DNA strand breaks and apoptosis of human AML HL-60 cells. HL-60/Bcl-2 and HL-60/neo cells were created by retrovirally transfecting the human AML HL-60 cells with the pZip-bcl-2 and pZip-neo plasmids, respectively. As compared to HL-60/neo, HL-60/Bcl-2 cells contained significantly higher (approximately 10-fold) p26Bcl-2, but equivalent levels of Bax and undetectable levels of Bcl-xL. HIDAC (10 or 100 microM for 4 h) produced the kilobase size and internucleosomal DNA fragmentation associated with apoptosis in HL-60/neo but not in HL-60/Bcl-2 cells. Significantly greater loss of survival (by MTT assay) and flowcytometric and morphologically recognizable apoptosis were observed in HL-60/neo cells. HIDAC did not affect Bcl-2 levels in either cell type. The intracellular accumulation of Ara-CTP relative to dCTP, Ara-C DNA incorporation and Ara-C-induced early DNA damage in the form of strand breaks (detected by alkaline elution assay) were not significantly different between HL-60/Bcl-2 and HL-60/neo cells. In addition, HIDAC treatment caused similar DNA synthesis inhibition in the two cell types. These results indicate that high intracellular levels of Bcl-2 operate distally to inhibit the final apototic cell death pathway by preventing the conversion of HIDAC-induced early DNA damage into lethal DNA fragmentation associated with apoptosis.
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PMID:Intracellular metabolism of Ara-C and resulting DNA fragmentation and apoptosis of human AML HL-60 cells possessing disparate levels of Bcl-2 protein. 889 76

Overexpression of P-glycoprotein (PGP), MRP or LRP has been characterized as the 'proximal', while overexpression of the anti-apoptosis Bcl-2 or Bcl-xL relative to the pro-apoptosis Bax protein has been recognized as the 'distal' mechanism of multidrug resistance in human AML cells. In the present studies, we examined whether these mechanisms can co-exist in human AML HL-60 cells. We also determined how these mechanisms would affect the accumulation and cytotoxicity of a PGP substrate, such as Taxol (paclitaxel). For this, immunoblot analyses were performed to determine the expression of PGP, MRP, Myc, Bcl-2, Bcl-xL and Bax on either the multidrug-resistant HL-60 sublines created under the selection pressure of doxorubicin (HL-60/AR), paclitaxel (HL-60/TAX1000) or vincristine (HL-60/VCR), or sublines created by transfection and overexpression of the bcl-2 (HL-60/Bcl-2) or bcl-xL gene (HL-60/Bcl-xL). As compared to the control HL-60, HL-60/AR cells possess high MRP while HL-60/TAX1000 and HL-60/VCR cells express high levels of the mdr-1 encoded PGP. In addition, these multidrug-resistant cells possess 1.5- to 2.5-fold higher Bcl-2, while their Bax and Myc levels are similar to those in the control HL-60 cells. HL-60/TAX1000 and HL-60/VCR cells also express three- and 2.5-fold higher Bcl-xL levels. PGP, but not MRP, overexpression significantly impaired paclitaxel accumulation and paclitaxel-induced apoptosis, as well as reduced its cytotoxic effects as determined by the MTT assay. In contrast, enforced and much higher expression of Bcl-2 in HL-60/Bcl-2 (five-fold) or Bcl-xL in HL-60/Bcl-xL cells (10-fold) significantly reduced paclitaxel-induced apoptosis and the loss of cell viability, without affecting its intracellular accumulation. These results confirm the possibility of co-expression of multiple mechanisms of multidrug resistance in human leukemic cells which had been selected by exposure to a single drug. The results also indicate that MRP overexpression does not confer resistance against paclitaxel. In addition, these findings suggest that, for Bcl-2 and Bcl-xL, enforced overexpression to high levels is necessary to induce paclitaxel resistance in HL-60 cells.
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PMID:Co-expression of several molecular mechanisms of multidrug resistance and their significance for paclitaxel cytotoxicity in human AML HL-60 cells. 900 89

Paclitaxel has been shown to activate Raf-1 and cause phosphorylation of Bcl-2, which has been correlated with paclitaxel-induced apoptosis of cancer cells. In the present studies, we demonstrate that in human AML HL-60 cells that express Bcl-2 but little Bcl-xL (HL-60/neo cells), paclitaxel-induced phosphorylation of Bcl-2 is followed by increased intracellular free Bax levels. This, in turn, is followed by the cleavage and activation of the key cysteine protease, CPP32beta/Yama, and cleavage of poly(ADP-ribose) polymerase, resulting in the DNA fragmentation of apoptosis. Cotreatment with the benzoquinone ansamycin Geldanamycin depleted Raf-1 but did not decrease Bcl-2 levels or impair paclitaxel-induced Bcl-2 phosphorylation in HL-60/neo cells. Also, Geldanamycin did not affect paclitaxel-induced apoptosis of HL-60/neo cells. As compared to the control HL-60/neo, HL-60/Bcl-xL cells contain Bcl-2 as well as an enforced overexpression of Bcl-xL. Immunoprecipitation studies with anti-Bcl-2 and/or anti-Bcl-x antibodies demonstrated that HL-60/Bcl-xL cells possess lower free Bax but higher levels of Bax heterodimerized to Bcl-2 and Bcl-xL. Following treatment of HL-60/Bcl-xL cells with paclitaxel, although Bcl-2 phosphorylation was observed, it was not followed by increased free Bax levels, cleavage of CPP32beta/Yama and poly(ADP-ribose) polymerase, or induction of the DNA fragmentation of apoptosis. These findings indicate the order of molecular events leading to paclitaxel-induced apoptosis and show that Raf-1 may not be involved in paclitaxel-induced phosphorylation of Bcl-2 or apoptosis of HL-60 cells.
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PMID:Bcl-xL overexpression inhibits progression of molecular events leading to paclitaxel-induced apoptosis of human acute myeloid leukemia HL-60 cells. 906 80

Bcl-2 over-expression has been shown to inhibit apoptosis induced by a variety of stimuli, whereas a predominance of Bax alpha to Bcl-2 accelerates apoptosis upon apoptotic stimuli. We sought to study the relevance of these apoptotic regulating gene products in leukaemia. In a panel of leukaemia and lymphoma cell lines (HL60, DoHH2, CEM C7, L1210 and S49), the Bax alpha-to-Bcl-2 ratio as assessed by Western-blot analysis correlated with sensitivity to dexamethasone treatment. In addition, in HAbax alpha-transfected CEM C7 clones, a similar correlation was found for dexamethasone and thapsigargin sensitivity. In bone-marrow aspirates from patients with childhood acute lymphoblastic or myelocytic leukaemia (ALL, n = 48; AML, n = 8), the Bcl-2 and Bax alpha levels were highly variable, but well within the range found in the Bax alpha transfectants and in the established cell lines. Bcl-2 levels were lower in T- than in B-lineage ALL, which could be ascribed to simultaneous inverse relation between Bcl-2 and WBC. By contrast, Bax alpha:Bcl-2 was independent of any presenting feature and was largely dependent on Bax alpha levels. Results suggest that Bax alpha:Bcl-2, rather than Bcl-2 alone is important for the survival of drug-induced apoptosis in leukemic cell lines and ALL.
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PMID:The Bax alpha:Bcl-2 ratio modulates the response to dexamethasone in leukaemic cells and is highly variable in childhood acute leukaemia. 918 97

Although the Bcl-2 protein inhibits apoptosis (programmed cell death) of lymphoid cells induced by a variety of stimuli, its effects on myeloid cell short- and long-term survival after chemotherapy are less defined. We sought to elucidate the short- and long-term effect of Bcl-2 in a well-studied myeloid cell line (HL-60) treated with specific anti-AML chemotherapy. HL-60 cells overexpressing Bcl-2 (HL-60/BCL-2) were more resistant than parental HL-60 cells to multiple chemotherapeutic agents in short-term apoptosis and viability assays. Significantly, HL-60/BCL-2 cells retained greater long-term proliferative capacity than HL-60 cells when treated with low doses of doxorubicin. To assess the importance of Bcl-2 expression in pediatric AML we correlated clinical outcome and levels of Bcl-2 protein in 22 patient specimens. The correlation did not achieve statistical significance with patient response to chemotherapy or long-term outcome, suggesting that analysis of larger numbers of patient samples would not be useful. Our study suggests that although Bcl-2 clearly promotes short and long-term survival in a myeloid cell line, measurement of Bcl-2 levels alone are not sufficient to be of prognostic significance in pediatric AML.
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PMID:BCL-2 expression does not not correlate with patient outcome in pediatric acute myelogenous leukemia. 958 84

Bcl-2 expression and its prognostic value were evaluated in 42 children with acute leukemia. The Bcl-2 expression of the leukemic blast cells was measured quantitatively by flow cytometry and was further analyzed by the simultaneous immunostaining of Bcl-2 with the surface membrane antigens, DNA, Ki-67 antigen. All of the cases showed a consistent expression of Bcl-2 protein; virtually all leukemic lymphoblasts were Bcl-2 positive. Although the expression of Bcl-2 varied widely from 7 to 80 x 10(3) MESF units, no significant difference was found in the mean value between the patients with acute lymphoblastic leukemia and those with acute myeloblastic leukemia. In more than half of the patients with AML, intraclonal heterogeneity of Bcl-2 expression was observed. The expression of Bcl-2 showed no apparent fluctuations during the different phases of the cell cycle. However, the proportion of Bcl-2-positive and -negative cells during the cell cycle was different between ALL and AML patients. In the ALL patients, few Bcl-2-negative cells were detected only in the GI phase, whereas in the AML patients Bcl-2-negative cells were detected in the S and G2/M phases, as well as in the G1 phase. No apparent difference was found in Bcl-2 expression between the Ki-67-negative noncycling population and the Ki-67-positive cycling population. Of the clinical features of these patients, only CD34 expression in the ALL patients was associated with high levels of Bcl-2 expression. In the 28 untreated cases of ALL, high expression of Bcl-2 was not an unfavorable factor for the outcome of this disease.
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PMID:Bcl-2 expression and prognosis in childhood acute leukemia. Children's Cancer and Leukemia Study Group. 959 36

The major vault lung resistance protein LRP is a cytoplasmic protein involved in drug resistance, especially in acute myeloid leukemia. We looked for LRP overexpression, using immunocytochemistry with LRP 56 monoclonal antibody, on marrow slides from 41 cases of myelodysplastic syndromes (MDS). LRP overexpression (LRP+) was defined by expression of LRP 56 in at least 20% of marrow blasts. LRP overexpression was seen in 19 (46%) cases. Concordant results between LRP overexpression and P-glycoprotein (PGP) expression were seen in 66% of the cases (p = 0.03), and discordant results (LRP+ and PGP-, or LRP- and PGP+) in 33% of the cases. No correlation was seen between LRP overexpression and FAB type, karyotype, CD34, p53 expression and bcl2 overexpression in blasts. Furthermore, in the 18 cases treated with anthracycline-AraC intensive chemotherapy and the 7 cases treated with low dose AraC, the response rate was not significantly different in LRP+ and LRP- patients. Survival was also similar in LRP+ and LRP- patients. In conclusion, LRP overexpression is probably more frequent in MDS than in de novo AML and, as in AML, is only partially correlated with PGP expression. In our experience, however, LRP was not a prognostic factor for response to chemotherapy and survival in MDS.
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PMID:Expression of lung resistance protein and correlation with other drug resistance proteins and outcome in myelodysplastic syndromes. 964 68

Fas-deficient (Fas(lpr/lpr)) mice constitutively expressing Bcl-2 in myeloid cells by the hMRP8 promoter often develop a fatal disease analogous to human acute myeloblastic leukemia (AML-M2). Hematopoietic cells from leukemic Fas(lpr/lpr)hMRP8bcl-2 animals form clonogenic blast colonies in vitro and can transfer disease to wild-type mice. In vitro ligation of Fas on Fas+/+ hMRP8bcl-2 marrow cells depletes approximately 50% of myeloid progenitor activity, demonstrating that Bcl-2 can only partially block Fas-mediated death signals in myelomonocytic progenitors. In addition, Fas(lpr/lpr) marrow contains greatly increased numbers of myeloid colony-forming cells as compared to Fas+/+ controls. Taken together, these data suggest that Fas has a novel role in the regulation of myelopoiesis and that Fas may act as a tumor suppressor to control leukemogenic transformation in myeloid progenitor cells.
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PMID:Mice defective in two apoptosis pathways in the myeloid lineage develop acute myeloblastic leukemia. 969 35

The expression of Bcl-2 family members was examined in normal and leukemic hematopoietic cells. Immature hematopoietic progenitor cells (CD34+/33-/13-) did not express Bcl-2 but Bcl-XL, the majority of CD34 cells expressed Bcl-2, Bcl-XL and BAD, and normal promyelocytes (CD34-/33+) lacked expression of both Bcl-2 and Bcl-XL, while leukemic CD34+progenitors and promyelocytes expressed these anti-apoptotic proteins. In AML, Bcl-2 expression was higher on CD34+ than on all AML cells, however, expression of Bcl-2 or Bcl-XL did not predict achievement of complete remission. Surprisingly, low Bcl-2 content was associated with poor survival in a group of patients with poor prognosis cytogenetics. The anti-apoptotic BAD protein was found to be expressed in AML, but was phosphorylated in 41/42 samples. Phosphorylation was found at both sites, Ser 112 and Ser 136. During induction chemotherapy, Bcl-2 levels of CD34 cells increased significantly. In the context of evidence for small numbers of leukemic CD34+ cells expressing very high levels of Bcl-2 prior to therapy, this finding is interpreted as a survival advantage of Bcl-2 overexpressing progenitors and rapid elimination of cells with low Bcl-2. Bcl-2 and Bcl-XL were both expressed in minimal residual disease cells. Downregulation of Bcl-2 mRNA and protein was observed by ATRA and the combination of Ara-C, followed by ATRA, resulted in markedly increased cytotoxicity in HL-60 cells, as compared to Ara-C alone or ATRA followed by Ara-C. Implications of these findings for the development of new therapeutic strategies for AML are discussed.
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PMID:Expression of Bcl-2-related genes in normal and AML progenitors: changes induced by chemotherapy and retinoic acid. 1055 66


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