Effects of CFU-S inhibitors on murine bone marrow during Ara-C treatment—I. Effects on stem cells

In order to determine whether the dialysable extract of fetal calf bone marrow, which has previously been shown to inhibit CFU-S entry into DNA synthesis, was also capable of protecting bone marrow CFU-S during chemotherapy, experiments were performed in which the dialysate was injected to mice simultaneously with Ara-C. The number of modullary CFU-S was significantly higher in mice receiving the dialysate with the drug than in mice receiving the drug alone, while the numbers of nucleated cells and of GM-CFC were not different in the two groups. These results suggest a specific protective effect on bone marrow CFU-S survival. By chromatography on Sephadex G10 it was possible to isolate a low molecular weight fraction which inhibits significantly the percentage of CFU-S in DNA synthesis but does not increase CFU-S number when assayed in the same protocol. These experiments seem to imply that there is little, if any, correlation between the inhibition of CFU-S entry into cycle and an increase in survival of these cells after Ara-C treatment. These observations as well as the mechanism of the protective effect (increase of the number of CFU-S) of the dialysate will be discussed.     

Low Dose Cytosine Arabinoside Therapy in Myelodysplastic Syndrome and Acute Myeloid Leukemia

Four patients with acute myeloid leukemia (AML) and three withmyelodysplastic syndrome (MDS) were given low dose cytosinearabinoside (Ara-C) therapy. One patient with de novo AML andtwo patients having refractory anemia with excess of blasts(RAEB) achieved responses. Although the responses lasted foronly a short duration (2–3 months), the therapy was welltolerated and not accompanied by severe complications, whilesevere cytopenia was a frequent side effect with transfusionsbeing necessary in most patients. This therapy could be clinicallyeffective for certain types of AML and MDS (especially RAEBand RAEB in transformation).     

低剂量照射增强白血病化疗的疗效及其机理的研究

为了增强化疗药物对白血病细胞的杀伤效应，而又最大限度地减少化疗的毒副作用，本研究探讨了低剂量照射增强Ara-C抗白血病的作用及其作用机理。实验用小鼠急性淋巴细胞性白血病模型（L615）进行，先确定低剂量全身照射与小剂量Ara-C最佳联合治疗方案；在此基础上观察该方案对血液系统的毒副作用，并从骨髓病理形态学的动态观察、残留白血病细胞检测、骨髓基质细胞GM-CSF表达（免疫酶标法）、骨髓条件培养上清液GM-CSF水平（微孔滤膜免疫金银染色法）等探讨其疗效机理。研究结果表明，小鼠于接种白血病细胞后第4天给予300cGy全身照射后，间隔1，2或3天连续有天给予30mg/kg Ara-C，有58%-72%的动物存活＞30天，其中17%的小鼠获得治愈，30天内因白血病死亡小鼠的存活时间也比单纯照射和单纯Ara-C组明显延长（P＜0.05)。该治疗方案对外周血白细胞数和骨髓有核细胞数有一过性减少，但恢复较快。骨髓病理形态学观察发现，300cGy照射后小鼠骨髓轻度抑制，血窦扩张充血；骨髓基质细胞GM-CSF表达高于正常；骨髓细胞条件培养液的GM-CSF水平也高于正常。由此可见，低剂量照射与小剂量Ara-C联合具有明显的协同作用，其机理可能与低剂量照射增加骨髓血窦的通透性，诱导骨髓基质细胞产生细胞因子，促使白血病细胞进入增殖周期，因而增加其对化疗敏感性有关。本研究提供了一种低毒高效治疗白血病的新途径。     

Pharmacology of intracellular cytosine-arabinoside-5′-triphosphate in malignant cells of pediatric patients with initial or relapsed leukemia and in normal lymphocytes

Purpose The prodrug cytosinearabinoside (ara-C) is widely used in the treatment of acute leukemias. The active drug is the intracellular metabolite cytosine-arabinoside-5′-triphosphate (ara-CTP). The purpose of the present study was to investigate the relation between sensitivity and pharmacokinetic parameters C _max, t _1/2 and AUC of ara-CTP. The obtained results were compared to previous studies. Experimental design C _max, t _1/2 and AUC of ara-CTP were assessed in leukemic cells of 17 pediatric patients with acute lymphoblastic leukemia (ALL) and in 6 lymphoblastic cell lines and compared with normal lymphocytes of 9 healthy donors by high pressure liquid chromatography (HPLC). The sensitivity of the cells against ara-C was determined by the MTT assay. Results The intracellular accumulation of ara-CTP was significantly lower in normal lymphocytes (C _max 47.7–60.9 pmol/10⁶ cells) compared to leukemic cell lines (C _max 11–1128 pmol/10⁶ cells) and leukemic cells of our patients (C _max 85.9–631 pmol/10⁶ cells). Similar results were found for the AUC. There was no significant difference between initial and relapsed leukemias in our small cohort. A correlation between sensitivity in terms of IC₅₀ values and the intracellular ara-CTP accumulation was observed in cell lines, but not in leukemic cells and normal lymphocytes from healthy donors. Conclusions Pharmacokinetic parameters varied tremendously in leukemic cells in contrast to normal lymphocytes without a difference in sensitivity. It is worthwhile to compare literature data to assess an optimal dosage of ara-C in pediatric patients.     

Contrasting in vitro effects for the combination of fludarabine, cytosine arabinoside (Ara-C) and granulocyte colony-stimulating factor (FLAG) compared with daunorubicin and Ara-C in P-glycoprotein-positive and P-glycoprotein-negative acute myeloblastic leukaemia

It has been suggested that the FLAG remission induction regimen comprising fludarabine (F-ara), cytosine arabinoside (Ara-C) and granulocyte colony-stimulating factor (G-CSF) may be capable of overcoming P-glycoprotein (P-gp)-related multidrug resistance (MDR) in patients with acute myeloblastic leukaemia (AML). We have investigated the in vitro response of P-gp-positive and -negative AML clones to FLAG and compared this with their response to treatment with Ara-C and daunorubicin (DNR). Twenty-four cryopreserved samples from patients with AML were studied using a flow cytometric technique for the enumeration of viable (7-amino actinomycin D negative) cells. Samples consisted of 12 P-gp-positive and 12 P-gp-negative cases, as measured by the MRK16 antibody. The results were analysed by calculating the comparative drug resistance (CDR), i.e. the percentage cell death caused by Ara-C + DNR subtracted from the percentage cell death, caused by FLAG after 48 h incubation in suspension culture. P-gp-positive clones were shown to have a significantly higher CDR than P-gp-negative clones (P = 0. 001). Furthermore, a significant positive correlation (r2 = 0.40, P < 0.01) was found between P-gp protein expression and CDR. However, P-gp function, measured using cyclosporin modulation of rhodamine 123 (R123) uptake, was not associated with the CDR, demonstrating that there are other properties of P-gp, besides its role in drug efflux, that modulate the responsiveness of AML blasts to chemotherapy. These results are consistent with a potential benefit for FLAG in P-gp-positive AML, but not P-gp-negative AML, compared with standard anthracycline and Ara-C therapy.     

Combination Chemotherapy with High-dose Methotrexate and Cytarabine with or without Brain Irradiation for Primary Central Nervous System Lymphomas

Due to the limited clinical experience there is no standard treatment of primary CNS-lymphomas (PCNSL). Based on the actual data it seems that high-dose methotrexate (HTMRX) and high-dose cytarabine (ARA-C) qualify as treatments of choice for this disease. The role of radiation therapy is still unclear, due to the high long-term toxicity, especially in elderly patients. We treated 14 HIV negative patients with 4–5 cycles of methotrexate (MTX) at 3500 mg/m² and MTX 15 mg intrathecal weekly or MTX 8000 mg/m² weekly without intrathecal treatment. Younger patients (< 60 y) received 3 weeks after last MTX dose a whole-brain irradiation (45 Gy + 9 Gy boost), older patientsts were not irradiated and continued CT. The following treatment consisted in ARA-C 3000 mg/m² d1 + 2 every 3 weeks for two cycles. All patients received steroids for two months or until the end of radiotherapy. The overall response rate was 100%, 12/14 CR (86%). Two patients died still on treatment but not due to lymphoma (1 pulmonary embolism, 1 herpes encephalitis). Toxicity was very mild with no grade 3–4 non-haematological toxic events and almost 100% grade 3–4 leucopenia without episodes of neutropenic fever. After a median follow up of 39 months the PFS and OS are 65% (9/14) and 78% (11/14) respectively, and compare well with other trial results.     

Pericarditis Associated with High-Dose Cytarabine Therapy for Acute Myeloblasts Leukemia: a Rare Complication of Therapy

Drug induced pericarditis is rare. We describe a 51 year old patient with acute myeloblasts leukemia (AML) who developed pericarditis during treatment with high dose cytarabine. The cytarabine was subsequently stopped and the patient recovered with steriod therapy. The platelet count was carefully monitored, and multiple platelet transfusions were given to prevent cardiac tamponade. Early recognition of this potentially life-threatening complication and appropriate management will usually result in the patient's recovery.     

Cytosine arabinoside modulation of the mitotic index in treatment of adult acute leukemia

Twenty-three unselected adult acute leukemic patients were treated with an initial intravenous pulse of cytosine arabinoside (Ara-C) 5 mg/kg. The mean mitotic index dropped from 7.7/1,000 to 2.8/1,000 at 4 hours after Ara-C pulse and rebounded to 6.7/1,000 at 18 hours. Infusions of Ara-C 7-10 mg/kg were given for 9 or 12 hours, depending on changes in the mitotic index. The group of responders (M₁ or M₂ marrows) could be predicted by the initial blast count in the marrow and the change in the mitotic index 18 hours after the Ara-C pulse. There were 9 (39%) complete and partial remissions. Six patients remained in remission more than 200 days. Since the changes in the mitotic indices induced by Ara-C were indistinguishable from those of another more successful trial, we infer that factors other than modulation of the cell cycle are critical to the success of this mode of therapy.     

High-Dose Cytosine Arabinoside and Viridans Streptococcus Sepsis in Children with Leukemia

We report three cases of fulminant sepsis due to viridans streptococci in leukemic children treated with high-dose cytosine arabinoside (Ara-C). The major predisposing factors to this occurrence are the presence of oropharingeal mucositis, which is the entry of streptococci into the bloodstream, and the use of antibiotic prophylactic regimens against gram-negative bacteria. In order to avoid fatal events during viridans streptococci sepsis, specific measures such as penicillin prophylaxis or early antibiotic treatment are needed. We suggest that the prompt empiric use of a glycopeptide antibiotic in addition to the conventional association of a β-lactam plus an aminoglycoside may significantly decrease the mortality rate due to fulminant streptococci sepsis while the patient is severely neutropenic. In this regard, our current policy considers the addition of an anti-gram-positive antibiotic to the first-choice fever treatment in neutropenic patients who have received high-dose Ara-C.     

High dose Ara-C related leukoencephalopathy

Summary Two patients with acute myelomonocytic leukemia in central nervous system relapse developed clinical signs and computerized tomographic evidence of leukoencephalopathy five to seven days after intravenous high dose Ara-C therapy. The first patient had received 30 gm of intravenous Ara-C with cranial irradiation (1680 rad in 2 fractions) and intrathecal Ara-C (100 mg × twice) for an intracerebral chloroma and leptomeningeal leukemia. In this patient the leukoencephalopathy was probably a result of a synergistic effect of the concomitant triple therapy. The second patient had received intrathecal administration of Ara-C and methotrexate for five and one-half months prior to intravenous Ara-C therapy. He developed altered mental status after 24 gm of intravenous Ara-C infusion. CT scan showed changes in the white matter compatible with leukoencephalopathy. In this patient the intravenous Ara-C probably was the precipitating factor of the development of leukoencephalopathy. The possible mechanism of the Ara-C induced leukoencephalopathy is discussed.