Ganciclovir-mediated in vivo elimination of myeloid leukemic cells expressing the HSVtk gene induces HSVtk loss variants.
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The in vivo elimination of suicide gene-expressing tumor cells with prodrug treatment can induce protective immunity against wild-type tumors. In this study, we determined the efficacy and safety of the in vivo elimination of HSVtk expressing cells with ganciclovir treatment of a bystander cell killing-insensitive leukemic cell line. The retroviral construct pLTk+NeoDeltaMo, containing the HSVtk gene and the NeoR gene in a bicistronic unit, was introduced into rat leukemic LT12 cells. LT12/Tk+N cells showed a 1000- to 10 000-fold increased sensitivity to ganciclovir in vitro. In vitro mixing experiments demonstrated that LT12 cells were not susceptible to bystander cell lysis by LT12/Tk+N-2 cells exposed to ganciclovir. Rats injected s.c. with cloned LT12/Tk+N-2 cells developed tumors reaching a diameter of 3-4 cm after 40 days. Rats treated with gan- ciclovir twice daily for 5 consecutive days starting at day 7 did not develop s.c. tumors. Large established s.c. LT12/Tk+N-2 tumors completely regressed after ganciclovir treatment. However, recurrences of s.c. tumors were observed that were no longer sensitive to ganciclovir treatment. In vitro analysis of aspirates from the recurrent tumors demonstrated loss of HSVtk expression. In vitro culture of LT12/Tk+N-2 cells in soft agar in the presence of ganciclovir indicated that the frequency with which HSVtk-loss variants occurred is approximately one per 104 cells. The in vivo occurrence of HSVtk-loss variants escaping ganciclovir-induced elimination may have important implications for vaccination protocols using HSVtk gene expressing tumor cells that are not susceptible to bystander cell killing. (+info)
Prognostic significance of magnetic resonance imaging of femoral marrow in patients with myelodysplastic syndromes.
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PURPOSE: To investigate whether the abnormalities observed on femoral marrow magnetic resonance images are related to the development of leukemia and survival of patients with myelodysplastic syndromes (MDS). PATIENTS AND METHODS: The findings on magnetic resonance images of the femoral marrow were evaluated over periods of 1 to 92 months (median, 18 months) in 42 consecutive adult patients with newly diagnosed MDS. Magnetic resonance images were obtained by the T1-weighted spin echo method and the short T1 inversion recovery technique. RESULTS: Magnetic resonance images showed that the femoral marrow patterns changed from fatty, faint, or nodular to scattered or uniform as the disease progressed. Development of acute myeloid leukemia was observed in only 13 patients whose marrow exhibited a scattered or uniform pattern. The overall survival of the 29 patients with a scattered or uniform marrow pattern was significantly shorter than that of the 13 patients with a fatty, faint, or nodular marrow pattern (10.7% v 73.3% at 7 years; P < .01). The period of leukemia-free survival was also significantly shorter in the patients with a scattered or uniform marrow pattern versus a fatty, faint, or nodular pattern (37.7% v 100% at 7 years; P < .01). CONCLUSION: Magnetic resonance images of the femoral marrow can provide valuable information for assessing the prognosis and determining the most appropriate management of patients with MDS. (+info)
Etoposide (VP-16) is extensively used to treat cancer, yet its efficacy is calamitously associated with an increased risk of secondary acute myelogenous leukemia. The mechanisms for the extremely high susceptibility of myeloid stem cells to the leukemogenic effects of etoposide have not been elucidated. We propose a mechanism to account for the etoposide-induced secondary acute myelogenous leukemia and nutritional strategies to prevent this complication of etoposide therapy. We hypothesize that etoposide phenoxyl radicals (etoposide-O(.)) formed from etoposide by myeloperoxidase are responsible for its genotoxic effects in bone marrow progenitor cells, which contain constitutively high myeloperoxidase activity. Here, we used purified human myeloperoxidase, as well as human leukemia HL60 cells with high myeloperoxidase activity and provide evidence of the following. 1) Etoposide undergoes one-electron oxidation to etoposide-O(.) catalyzed by both purified myeloperoxidase and myeloperoxidase activity in HL60 cells; formation of etoposide-O(.)radicals is completely blocked by myeloperoxidase inhibitors, cyanide and azide. 2) Intracellular reductants, GSH and protein sulfhydryls (but not phospholipids), are involved in myeloperoxidase-catalyzed etoposide redox-cycling that oxidizes endogenous thiols; pretreatment of HL60 cells with a maleimide thiol reagent, ThioGlo1, prevents redox-cycling of etoposide-O(.) radicals and permits their direct electron paramagnetic resonance detection in cell homogenates. VP-16 redox-cycling by purified myeloperoxidase (in the presence of GSH) or by myeloperoxidase activity in HL60 cells is accompanied by generation of thiyl radicals, GS(.), determined by HPLC assay of 5, 5-dimethyl-1-pyrroline glytathionyl N-oxide glytathionyl nitrone adducts. 3) Ascorbate directly reduces etoposide-O(.), thus competitively inhibiting etoposide-O(.)-induced thiol oxidation. Ascorbate also diminishes etoposide-induced topo II-DNA complex formation in myeloperoxidase-rich HL60 cells (but not in HL60 cells with myeloperoxidase activity depleted by pretreatment with succinyl acetone). 4) A vitamin E homolog, 2,2,5,7, 8-pentamethyl-6-hydroxychromane, a hindered phenolic compound whose phenoxyl radicals do not oxidize endogenous thiols, effectively competes with etoposide as a substrate for myeloperoxidase, thus preventing etoposide-O(.)-induced redox-cycling. We conclude that nutritional antioxidant strategies can be targeted at minimizing etoposide conversion to etoposide-O(.), thus minimizing the genotoxic effects of the radicals in bone marrow myelogenous progenitor cells, i.e., chemoprevention of etoposide-induced acute myelogenous leukemia. (+info)
5,6-trans-16-ene-vitamin D3: a new class of potent inhibitors of proliferation of prostate, breast, and myeloid leukemic cells.
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The 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] is the physiologically active form of vitamin D3 that inhibits proliferation and induces differentiation of a variety of malignant cells. We evaluated a newly synthesized vitamin D3 analogue [1,25(OH)2-16-ene-5,6-trans-D3 (Ro 25-4020)] that has a novel 5,6-trans motif. Dose-response studies showed that 1,25(OH)2-16-ene-5,6-trans-D3 had 10-100-fold greater antiproliferative activities than 1,25(OH)2D3 when measuring clonal growth of breast (MCF-7) and prostate (LNCaP) cancer cell lines as well as a myeloid leukemia cell line (HL-60). Because the chief toxicity of vitamin D3 is hypercalcemia, we examined the calcemic activity of 1,25(OH)2-16-ene-5,6-trans-D3 in mice. Remarkably, 1,25(OH)2-16-ene-5,6-trans-D3 was at least 40-fold less calcemic as compared with 1,25(OH)2D3 and 1,25(OH)2-16-ene-D3 (Ro 24-2637). To explore the mechanism by which the 1,25(OH)2-16-ene-5,6-trans-D3 analogue mediated its antiproliferative activity, several studies were performed. Pulse-exposure studies showed that a 4-day pulse exposure to 1,25(OH)2-16-ene-5,6-trans-D3 (10(-7) M) in liquid culture was adequate to achieve a 40% inhibition of MCF-7 clonal growth in the absence of the analogue, suggesting that the growth inhibition mediated by 1,25(OH)2-16-ene-5,6-trans-D3 was at least in part irreversible. Cell cycle studies showed that 1,25(OH)2-16-ene-5,6-trans-D3 increased the proportion of MCF-7 cells in the G0-G1 phase and decreased those in the S phase. Furthermore, 1,25(OH)2-16-ene-5,6-trans-D3 induced an elevated expression of the cyclin-dependent kinase inhibitors, p21waf1 and p27kip1. In addition, 1,25(OH)2-16-ene-5,6-trans-D3 almost completely inhibited telomerase activity, as measured by telomeric repeat amplification protocol assay and human telomerase reverse transcriptase mRNA. For each of the growth-related parameters that were examined, the vitamin D3 analogue was more active than 1,25(OH)2D3. In contrast, 1,25(OH)2D3 was more calcemic than 1,25(OH)2-16-ene-5,6-trans-D3. In summary, 1,25(OH)2-16-ene-5,6-trans-D3, having a novel 5,6-trans motif, strongly inhibited clonal proliferation and reduced telomerase activity with low calcemic activity, suggesting further testing in in vivo cancer models. This analogue may gain a therapeutic niche for selected malignancies. (+info)
Bezafibrate as differentiating factor of human myeloid leukemia cells.
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Bezafibrate belongs to the class of fibric acid derivatives usually used as antihyperlipidemia agents. From the biochemical point of view, these drugs show intriguing properties which leads one to think they may promote a differentiation process in tumour cells. This new pharmacological activity of fibrates could partially depend on the induction of an oxidative stress. To test this hypothesis, the effect of bezafibrate, as well as of clofibric acid and gemfibrozil, on growth, functional and cytochemical characteristics of human leukaemia-derived cell lines HL-60, U-937 and K-562 has been studied in some details. The results show that bezafibrate, gemfibrozil and clofibric acid, do induce differentiation in human myeloid leukaemia cell lines as indicated by several differentiation markers. Moreover fibrates, in dose dependent manner, significantly alter the cell cycle distributions, mainly leading to G0/G1 phase increment and G2/M phase reduction. The differentiating activity of fibrates could have significant implications both for the pharmacotoxicological profile of this class of compounds and for the pathophysiology of neoplastic disease. (+info)
Out-patient management of acute myeloid leukemia after consolidation chemotherapy. Role of a hematologic emergency unit.
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BACKGROUND AND OBJECTIVE: Increasing attention to quality of life and to health care costs has recently induced several cancer centers to change in-patient management into an out-patient setting even during high risk phases of disease. The aim of this prospective study was to evaluate feasibility and safety, as well as clinical characteristics, of out-hospital management of AML patients during their post-consolidation phase. DESIGN AND METHODS: All patients who were treated over a three year period by the three following protocols were included in the study: AML10 EORTC/GIMEMA for patients with AML, except for APL, aged 60 years; AIDA GIMEMA for APL patients. All patients submitted to the AML10 and AML13 protocols and those patients submitted to the AIDA protocol with difficult peripheral vein access had a central venous catheter (CVC) sited. Patients treated as in-patients were discharged at the end of consolidation chemotherapy provided they were in a good clinical condition. They were routinely evaluated on an out-patient basis twice weekly. In the event of any complication they were referred to the Emergency Unit of our Department dedicated to out-patients with hematologic diseases. RESULTS: One hundred and eleven patients with AML were eligible for intensive chemotherapy. After achievement of complete remission they received a total of 133 consolidation courses and in 127 instances they were followed on an out-patient basis during the aplastic phase. There were 69 cases (54%) of rehospitalization, 68 because of fever and only one because of severe anemia. Rehospitalization occurred in 90%,70% and 38% of courses in AML10, AML13 and AIDA protocols, respectively. Only one patient died: the cause of death was a brain hemorrhage. Coagulase negative staphylococci and viridans streptococci were the organisms most frequently isolated from blood. Most coagulase negative staphylococci were isolated in patients submitted to AML10 and AML13 protocols, who had an indwelling CVC. Empiric once-a-day antibacterial therapy with ceftriaxone and amikacin was effective in 75% of the cases and made early discharge possible in 28% of the cases with antibiotic therapy continued in an out-patient setting. Overall, patients were managed out of the hospital for 66% of the period of post-consolidation neutropenia (77%, 48% and 50% of the post-consolidation neutropenia period in patients treated with AIDA, AML10 and AML13 protocols, respectively). INTERPRETATION AND CONCLUSIONS: Thanks to the availability of an emergency unit specifically dedicated to out-patients with hematologic diseases, selected out-hospital management of AML patients during post-consolidation cytopenia is a feasible, well accepted and cost-saving option, and can contribute to lower the risk of developing severe nosocomial infections. The empiric therapy with once-a-day ceftriaxone plus amikacin was effective, with the exception of staphylococcal infections, and made it possible to discharge patients early to continue treatment in an out-patient setting. (+info)
Fusion of a novel gene, BTL, to ETV6 in acute myeloid leukemias with a t(4;12)(q11-q12;p13).
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The ETV6 gene (also known as TEL) is the main target of chromosomal translocations affecting chromosome band 12p13. The rearrangements fuse ETV6 to a wide variety of partner genes in both myeloid and lymphoid malignancies. We report here 4 new cases of acute myeloid leukemia (AML) with very immature myeloblasts (French-American-British [FAB]-M0) and with a t(4;12)(q11-q12;p13). In all cases, ETV6 was found recombined to a new gene, homologous to the mouse Brx gene. The gene was named BTL (Brx-like Translocated in Leukemia). Reverse transcriptase-polymerase chain reaction (RT-PCR) experiments indicate that the expression of the BTL-ETV6 transcript, but not of the reciprocal ETV6-BTL transcript, is a common finding in these leukemias. In contrast to the majority of other ETV6 fusions, both the complete helix-loop-helix (HLH) and ETS DNA binding domains of ETV6 are present in the predicted BTL-ETV6 fusion protein, and the chimeric gene is transcribed from the BTL promoter. (+info)
Use of peripheral blood stem cells for autologous transplantation in acute myeloid leukemia patients allows faster engraftment and equivalent disease-free survival compared with bone marrow cells.
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We compared the feasibility and efficacy of autologous bone marrow (ABMT) and peripheral blood progenitor cell transplantation (PBSCT) performed after an identical induction/consolidation in adults with acute myeloid leukemia (AML). From January 1993 to June 1996 91 consecutive AML patients were enrolled in a program consisting of anthracycline-based induction and high-dose cytarabine consolidation (NOVIA). Until May 1994 ABMT was performed; from June 1994, if PBSC collection was adequate, PBSCT was performed. Out of 88 evaluable patients, 73 obtained a complete remission (CR) and 15 were resistant. Allogeneic bone marrow transplantation was performed in 16 patients. Forty-four (50%) were given autologous stem cell transplantation. ABMT was performed in 21 cases; twenty-nine patients were given G-CSF mobilization after NOVIA administration. An adequate number of PBSC was obtained in 23/29 (79%) cases, which were then re-infused. Median times to both neutrophil and platelet recovery from transplant were significantly shorter for the PBSC group (17 vs 36 days to 500 PMN/microl, P < 0.01; 20 vs 150 days to 20000 platelets/microl, P < 0.02; 37 vs 279 days to 50000 platelets/microl, P < 0.03), as were days of hospitalization after the reinfusion (18 vs 33, P < 0.03) and median days to transfusion independence. Toxicity was not significant in either group. After a minimum follow-up for live patients of 24 months (longer than the mean time for relapse observed for the PBSC series - 14 months) the percentage of relapses was similar: 11 of 21 (52.4%) and 12 of 23 (52.1%) in the ABMT and PBSC groups, respectively. Our results indicate that autologous PBSC transplantation, performed after an intensive chemotherapy regimen, is not inferior to ABMT in terms of disease-free survival and allows faster recovery times and reduced need for transfusion support. (+info)