Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.5.1.1 (asparaginase)
2,695 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In vitro resistance to anthracyclines is related to a poor prognosis in childhood acute lymphoblastic leukemia (ALL), but the underlying mechanisms are poorly understood. Using flow cytometry, we studied the contribution of daunorubicin (DNR) accumulation and retention, cell size, expression of the major vault protein/lung resistance protein (LRP), P-glycoprotein (P-gp) and multidrug resistance-associated protein (MRP) to the cytotoxicity of DNR (by MTT assay) in childhood ALL. The accumulated and retained DNR content was not related to the degree of DNR resistance, nor did the content differ between 53 initial and 20 relapse ALL samples (P >0. 05), although the latter were median two-fold more resistant to DNR (P = 0.004). Leukemic cell volume correlated with resistance to the anthracyclines DNR (Rs 0.32, P = 0.012) and idarubicin (Rs 0.46, P = 0.011) but not to other classes of drugs such as prednisolone, vincristine, L-asparaginase and etoposide. Relapsed patients had 1. 5-fold larger cells than patients at initial diagnosis of ALL (P = 0. 001). After cell volume correction, the intracellular DNR concentration was lower in relapsed compared with initial ALL cells (eg 60 min accumulation, P = 0.003). Moreover, the intracellular DNR concentration inversely correlated with DNR resistance, both in the accumulation (Rs -0.44, P < 0.001) and retention (Rs -0.33, P = 0. 016) test condition. The accumulated DNR concentration inversely correlated with expression of LRP (Rs -0.36, P = 0.012) but not with P-gp and MRP. Expression of LRP, but not of P-gp and MRP, significantly correlated with DNR resistance in childhood ALL (Rs 0. 33, P = 0.03). In conclusion, the intracellular DNR concentration and the expression level of LRP may contribute to DNR resistance in childhood ALL. The strength of the correlations also indicates that resistance to anthracyclines can not be explained by one single mechanism.
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PMID:Relationship between the intracellular daunorubicin concentration, expression of major vault protein/lung resistance protein and resistance to anthracyclines in childhood acute lymphoblastic leukemia. 1060 24

The t(12;21) translocation resulting in TEL/AML1 gene fusion is present in approximately 25% of patients with precursor B-lineage pediatric acute lymphoblastic leukemia (ALL). Studies suggest an association with a good prognosis; however, relapse can occur. We studied the relation between t(12;21), determined by fluorescence in situ hybridization or polymerase chain reaction, and in vitro drug resistance, measured by the MTT assay, in childhood B-lineage ALL at diagnosis. A total of 180 ALL samples were tested, 51 (28%) of which were positive for t(12;21). The median LC(50) values did not differ significantly between TEL/AML1-positive and -negative samples for prednisolone, dexamethasone, daunorubicin, thiopurines, epipodophyllotoxins, and 4-HOO-ifosfamide. However, the TEL/AML1-positive patients were relatively more sensitive to L-asparaginase (ASP; 5.9-fold; P =.029) and slightly but significantly more resistant to vincristine (1.5-fold; P =.011) and cytarabine (1.5-fold; P =.014). After matching for unevenly distributed patient characteristics-that is, excluding patients younger than 12 months, patients with CD10-negative immature B-lineage ALL, patients with Philadelphia chromosome, and patients who were hyperdiploid (more than 50 chromosomes) from the TEL/AML1 negative group-the only remaining difference was a relative sensitivity for ASP in the TEL/AML1-positive samples (10.8-fold; P =. 012). In conclusion, the presence of TEL/AML1 gene fusion in childhood precursor B-lineage ALL does not seem to be associated with a high in vitro drug sensitivity, except for ASP, indicating that these patients could benefit from treatment schedules with significant use of this drug.
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PMID:TEL/AML1 gene fusion is related to in vitro drug sensitivity for L-asparaginase in childhood acute lymphoblastic leukemia. 1091 Sep 27

MTT analysis has yielded data on the sensitivity of leukemia cells isolated from 64 patients with acute leukemia to the cytokines G-KSF?, GM-KSF, interferon-alpha 2b and their combined use with drugs, such as cytosar, vepeside, doxorubicin, vincrastine, L-asparaginase. The mean in vitro survival of leukemia cells in children with acute lymphoblast cell leukemia (ALCL) was 1.9 times less than that in acute myeloblast cell leukemia (AMCL) (p < 0.001), that in new cases of ALL was 2.3 times less than in relapses (p = 0.024). The stimulating effect of GM-KSF on the survival rates of leukemia cells was seen in 64.7% of patients with AML. That of GM-KSF was recorded in 21.4% of cases. The survival of lymphoblast cells isolated from children with ALL did not differ greatly in the absolute majority of cases (by more than 30%) in the presence of growth factor in the medium. The cytotoxicity of XII with medium growth factor decreased in most cases. However, some cases (more frequently in AML than ALCL) displayed a higher cytotoxicity of XII, particularly cytosar in the presence of G-KSF and GM-KSFG; LC50 of Ara-C decreased by 30% or more in the presence of growth factor in 36% of patients. Incubation with interferon alpha 2b caused a reduction in the survival of leukemia cells, which was more pronounced in children with ALL. Interferon-alpha 2b caused an increase in the cytotoxic effect of XII on leukemia cells in ALL to a greater extent; cytosar, vepeside, and doxorubicin enhanced the effect by 1.47, 1.39, and 2.35 times, respectively.
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PMID:[Study of tumor cells sensitivity in patients with acute leukemia to cytokines and their combined use with drugs in vitro by MTT analysis]. 1094 55

The difference in the current cure rates between adult and childhood acute lymphoblastic leukaemia (ALL) may be caused by differences in drug resistance. Earlier studies showed that in vitro cellular drug resistance is a strong independent adverse risk factor in childhood ALL. Knowledge about cellular drug resistance in adult ALL is still limited. The present study compared the in vitro drug resistance profiles of 23 adult ALL patients with that of 395 childhood ALL patients. The lymphoblasts were tested by the MTT assay. The group of adult ALL samples was significantly more resistant to cytosine arabinoside, L-asparaginase, daunorubicin, dexamethasone and prednisolone. The resistance ratio (RR) was highest for prednisolone (31.7-fold) followed by dexamethasone (6.9-fold), L-asparaginase (6. 1-fold), cytosine arabinoside (2.9-fold), daunorubicin (2.5-fold) and vincristine (2.2-fold). Lymphoblasts from adult patients were not more resistant to mercaptopurine, thioguanine, 4-HOO-ifosfamide, mitoxantrone and teniposide. There were no significant differences in drug resistance between adult T-cell (T-) ALL (n = 11) and adult common/pre-B-cell (B-) ALL (n = 10). Additionally, adult T-ALL did not differ from childhood T-ALL (n = 69). There were significant differences between adult common/pre-B-ALL and childhood common/pre-B-ALL (n = 310) for prednisolone (RR = 302, P = 0.008), dexamethasone (RR = 20.9, P = 0.017) and daunorubicin (RR = 2.7, P = 0.009). Lymphoblasts from adults proved to be relatively resistant to drugs commonly used in therapy. This might contribute to the difference in outcome between children and adults with ALL.
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PMID:In vitro drug resistance profiles of adult versus childhood acute lymphoblastic leukaemia. 1105 62

We have developed an in vitro model of 38 T-lymphoblastic leukemia lines resistant to cytosine arabinoside (ara-C) and L-asparaginase (ASNase). Of these, 26 cell lines resistant to both drugs, 6 resistant to ara-C, and 6 resistant to ASNase were isolated. In 18 of these cell lines, all randomly selected, resistance to ara-C, ASNase and gamma radiation was documented by the MTT and trypan blue assays, as well as flow cytometry with Annexin V and propidium iodide (PI) staining. In these lines, p53, p21WAF1, and bcl-2 levels were measured by ELISA. Results show that P21WAF1 upregulation following p53 induction did not occur, suggesting that p53 function may be lost. Moreover, the data imply that upregulation of bcl-2 is critical in the development of resistance to ara-C and ASNase in these leukemic lines. In the CEM/0 parent line, p53 maintained its ability to interact with its DNA binding site as documented by the electrophoretic mobility shift assay (EMSA). But in one single- and one double-resistant leukemic cell line examined, p53 was not shown to maintain this ability. We conclude that double-resistant clones to ara-C and ASNase are refractory to both drugs, providing an excellent leukemic model to investigate the multiple-drug resistance.
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PMID:Development of a double-drug-resistant human leukemia model to cytosine arabinoside and L-asparaginase: evaluation of cross-resistance to other treatment modalities. 1129 23

Recent studies have shown that angiogenesis, which is induced by VEGF, may be involved in the pathogenesis of hematopoietic malignancies. A human leukemia model consisting of T-lymphoblastic CEM/0, 7 monoclonal refractory clones resistant to both cytosine arabinoside (ara-C) and L-asparaginase (ASNase), Jurkat/E6-1 and U937, representing the leukemic blasts from relapsed patients with leukemias was investigated for secretion of VEGF before and after treatment with various agents. The T-lymphoblastic cell line, Jurkat/E6-1, was used as the negative control, which has been characterized as not expressing mRNA nor the VEGF protein, and did not secrete VEGF. With no treatment, U937, the positive control, secreted the highest VEGF concentration of 1612.7 pg/ml. The CEM/O wild type cell line and 5 other drug-resistant clones secreted VEGF at levels ranging from 180.9 to 414.2 pg/ml. Two CEM drug-resistant clones, CEM/ara-C/G/ASNase-0.5-1 and CEM/ara-C/G/ASNase-1-1, lacked VEGF production. Docetaxel (Taxotere, TXR), Vincristine (VCR), ASNase, and the Fit-1/Fc chimera, a specific inhibitor of VEGF-dependent human umbilical vein endothelial cell (HUVEC) proliferation, were tested for inhibition of VEGF secretion. Treatment of the leukemic cell lines with 2 microg/ml Flt-1/Fc chimera for 24 hours completely inhibited VEGF secretion to the detection limit of the assay (<10pg/ml). After 24 hours incubation with Flt-1/Fc chimera, the leukemic cells appeared to be undergoing apoptosis, based on microphotography examination, suggesting that VEGF could be used in an autocrine loop to promote cell survival by the leukemic cells. Treatment with 0.5, 1, and 2 microg/ml Flt-1/FC chimera for 48 hours demonstrated a 15-25% growth inhibition by MTT assay. Strong inhibition of VEGF secretion in the culture media was observed after 10 microM TXR or 0.1 microM VCR for 24 hours in the wild-type and drug-resistant clones, except CEM/ara-C/I, in comparison with controls. In contrast, treatment with 1 IU/ml ASNase, a specific T-cell protein inhibitor, in 5 cell lines for 24 hours demonstrated no inhibition of VEGF in CEM/0 3 drug-resistant clones and the myeloid U937 line. We conclude that the leukemia cell lines actively secrete VEGF, in vitro. TXR and VCR, but not ASNase, strongly inhibit the VEGF production, suggesting that inhibition of this growth factor may be a mechanism of antileukemic activity. Moreover, the leukemic cell lines examined here may constitute a useful model to study antiangiogenic drugs, alone or in combination with established drug regimens used against refractory leukemias.
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PMID:Taxotere and vincristine inhibit the secretion of the angiogenesis inducing vascular endothelial growth factor (VEGF) by wild-type and drug-resistant human leukemia T-cell lines. 1172 83

To determine the clinical relevance of in vitro drug chemoresistance in childhood acute myeloid leukemia, we used an MTT assay to test leukemic cells from 132 newly diagnosed children. Patients were diagnosed according to the French-American-British (FAB) classification as follows: M0 (n = 12), M1 (n = 16), M2 (n = 53), M4 (n = 17), M5 (n = 19) and M7 (n = 15). The results revealed that, compared to leukemic cells from complete-responders (n = 107), those from non-responders who failed induction therapy (n = 17) were 1.4 to 5.0 times more resistant in vitro to cytarabine (P = 0.005), melphalan (P = 0.003), etoposide (P = 0.011), L-asparaginase (P = 0.017), aclarubicin (P = 0.026) and dexamethasone (P = 0.039). For seven other drugs tested, the median lethal dose of 70% and leukemic cell survival of non-responders were higher than those of complete-responders, but the difference was not statistically significant. We sought correlations between FAB subtypes and in vitro drug resistance. Leukemias of the FAB M4 and M5 subtype were more sensitive to L-asparaginase (P = 0.01, P = 0.0036) than those of the FAB M2 subtype. FAB M5 leukemia was more sensitive to etoposide than were the FAB M2, M4 and M7 subtypes (P = 0.001, P = 0.034, P = 0.023, respectively). By contrast, FAB M5 leukemia was significantly more resistant to prednisolone and dexamethasone than were the FAB M0, M1, M2, M4 and M7 subtypes. We sought correlations between in vitro drug resistance and long-term clinical outcome, but found no associations in this case. These results suggest that in vitro resistance to cytarabine, melphalan, etoposide, L-asparaginase, aclarubicin and dexamethasone might represent factors that can predict response to the early course of therapy. Selecting an appropriate anti-cancer drug according to the FAB classification together with drug sensitivity testing may contribute to improved prognoses in childhood acute myeloid leukemia.
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PMID:Clinical relevance of in vitro chemoresistance in childhood acute myeloid leukemia. 1175 10

Glufosfamide is a new agent for cancer chemotherapy. The objective of the study was the comparison of the in vitro drug resistance profile of glufosfamide with other oxazaphosphorines in 106 samples of childhood acute leukemia by means of the MTT assay. The following drugs were tested: glufosfamide, 4-HOO-ifosfamide, 4-HOO-cyclophosphamide, mafosfamide cyclohexylamine salt, prednisolone, vincristine, L-asparaginase, daunorubicin and cytarabine. In the group of initial Acute Lymphoblastic Leukemia (ALL) samples, equivalent cytotoxicity values for glufosfamide, 4-HOO-ifosfamide, 4-HOO-cyclophosphamide and mafosfamide were 5.95, 9.92, 4.60 and 3.90 microg/ml, respectively. In comparison to initial ALL samples, the relative resistance for glufosfamide and 4-HOO-ifosfamide in relapsed ALL samples were 1.9 (p=0.049) and 1.3 (ns), and in initial Acute Myeloblastic Leukemia (AML) samples, respectively, 31 (p<0.001) and 5 (p=0.001). All oxazaphosphorines showed highly significant cross-resistance. In conclusion, in vitro activity of glufosfamide is comparable to ifosfamide. Glufosfamide shows high activity against lymphoblasts both on diagnosis and on relapse, however it cannot circumvent resistance to other oxazaphosphorines.
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PMID:In vitro activity of glufosfamide in childhood acute leukemia. 1201 97

Up-regulation of Bcl-2 protein may contribute to drug resistance, by decreasing apoptosis after treatment, in pre-B and B-cell leukemias in pediatric patients. By contrast, augmented caspase-3 activity, an effector caspase, may be indicative of drug sensitivity due to increased cellular apoptosis. We have reported the development of an in vitro human T-lymphoblastic leukemia model resistant to ara-C and/or native E. coli L-asparaginase (ASNase), mimicking the drug resistance to the Capizzi II regimen. We have investigated the potential drug synergism between Idarubicin (IDA) and Taxotere (TXR) that may be active in the ara-C and ASNase double drug-resistant cell lines. The additive or synergistic activity between IDA and TXR is drug concentration-dependent in inducing caspase-3 activation and cellular apoptosis. We exposed two human drug-resistant cell lines that do not express the MDRI phenotype, one resistant to ASNase alone (CEM/ASNase-1-3) and the other resistant to both ara-C and ASNase (CEM/ara-C/I/ASNase-0.5-2), to physiologically achievable concentrations of IDA, TXR, or their combination. Both lines showed either synergistic drug activity to the combination regimen in comparison to either drug used alone, as determined by MTT assay, or additivity as demonstrated by flow cytometry after Annexin V and propidium iodide (PI) staining. After exposure of the ASNase-resistant line to various concentrations, the intracellular levels of Bcl-2 protein decreased to near zero relative to untreated control cells. The Bcl-2 protein reductions in these cells ranged from 30% to <1%, 49% to <1%, and 27% to 3% when treated with IDA or TXR as a single drug or IDA + TXR combination, respectively. Similarly, intracellular Bcl-2 levels in the double-resistant cell line decreased with reductions ranging from 24% to <1%, 87% to <1%, and 46% to <1% of the untreated control after treatment with IDA, TXR, or their combination, respectively. Conversely, the caspase-3 activity increased in a dose-dependent manner and inversely-correlated with loss of cell viability (r= 0.91) after exposure to IDA + TXR combination in the double drug-resistant line to both ara-C and ASNase. We conclude that the combination of the IDA + TXR regimen is highly synergistic or additive in drug resistant human leukemic cell clones. The molecular mechanism of action is due to the down-regulation of Bcl-2 protein and up-regulation of caspase-3 activity. This drug combination warrants further investigation for use in the treatment of patients with ara-C and/or ASNase refractory leukemias.
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PMID:The combination regimen of idarubicin and taxotere is effective against human drug-resistant leukemic cell lines. 1216 12

Acute lymphoblastic leukemia (ALL) in infants under 1 year is strongly associated with translocations involving 11q23 (MLL gene), CD10-negative B-lineage (proB) immunophenotype, and poor outcome. The present study analyses the relationship between age, MLL rearrangements, proB-lineage, and in vitro drug resistance determined using the MTT assay. Compared to 425 children aged over 1 year with common/preB (c/preB) ALL, the 44 infants were highly resistant to steroids (for prednisolone (PRED) more than 580-fold, P=0.001) and L-asparaginase (L-ASP) (12-fold, P=0.001), but more sensitive to cytarabine (AraC) (1.9-fold, P=0.001) and 2-chlorodeoxyadenosine (2-CdA) (1.7-fold, P<0.001). No differences were found for vincristine, anthracyclines, thiopurines, epipodophyllotoxines, or 4-hydroperoxy (HOO)-ifosfamide. ProB ALL of all ages had a profile similar to infant ALL when compared with the group of c/preB ALL: relatively more resistant to L-ASP and PRED (and in addition thiopurines), and more sensitive to AraC and 2-CdA. Age was not related to cellular drug resistance within the proB ALL group (<1 year, n=32, vs >/=1 year, n=19), nor within the MLL-rearranged ALL (<1 year, n=34, vs >/=1 year, n=8). The translocation t(4;11)(q21;q23)-positive ALL cases were more resistant to PRED (>7.4-fold, P=0.033) and 4-HOO-ifosfamide (4.4-fold, P=0.006) than those with other 11q23 abnormalities. The expression of P-glycoprotein, multidrug-resistance protein, and lung-resistance protein (LRP) was not higher in infants compared to older c/preB ALL patients, but LRP was higher in proB ALL and MLL-rearranged ALL of all ages. In conclusion, infants with ALL appear to have a distinct in vitro resistance profile with the proB immunophenotype being of importance. The role of MLL cannot be excluded, with the t(4;11) being of special significance, while age appears to play a smaller role.
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PMID:In vitro drug-resistance profile in infant acute lymphoblastic leukemia in relation to age, MLL rearrangements and immunophenotype. 1471 91


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