pH-sensitive immunoliposomes specific to the CD33 cell surface antigen of leukemic cells

A promising avenue in cancer therapy using liposomal formulations is the combination of site-specific delivery with triggered drug release. The use of trigger mechanisms in liposomes could be relevant for drugs susceptible to lysosomal hydrolytic/enzymatic degradation. Here, we propose a polymeric pH-sensitive liposome system that is designed to release its content inside the endosomes through a polymer structural change following receptor-mediated internalization. Specifically, pH-sensitive immunoliposomes (ILs) were obtained by including a terminally alkylated copolymer of N-isopropylacrylamide (NIPAM) in the liposome bilayer and by coupling the anti-CD33 monoclonal antibody to target leukemic cells. In vitro release of encapsulated fluorescent probes and cytosine arabinoside (ara-C) revealed that pH-sensitivity of the vector was retained in the presence of the antibody upon incubation in plasma. Flow cytometry and confocal microscopy analyses demonstrated that the pH-sensitive ILs were efficiently internalized by various CD33+ leukemic cell lines while limited interaction was found for liposomes decorated with an isotype-matched control antibody. Finally, the pH-sensitive ILs-CD33 formulation exhibited the highest cytotoxicity against HL60 cells, confirming the role of the NIPAM copolymer in promoting the escape of intact ara-C in the endosomes. These results suggest that this pH-sensitive liposomal formulation could be beneficial in the treatment of acute myeloid leukemia.     

Anti-leukemic activity of Wattakaka volubilis leaf extract against human myeloid leukemia cell lines

Ethnopharmacological relevance

Wattakaka volubilis has been traditionally used in Ayurvedic medicine in India for treatment of several ailments such as bronchial asthma, inflammations, tumors, piles, leucoderma, application to boils, rat bite etc.

Aim of the study

The present study was designed to investigate anti-leukemic activity of the crude aqueous methanolic extract and to identify active compounds from the leaves of Wattakaka volubilis.

Materials and methods

The leaves of Wattakaka volubilis were extracted with aqueous methanol. Liquid–liquid fractionation of the crude methanolic extract with different organic solvents was done and the fractions were screened for in vitro anti-leukemic activity using different leukemic cell lines. The active fractions were then subjected to chromatographic separation for isolation of bioactive compounds. Structure of isolated compound was elucidated by spectroscopic methods. The in vitro anti-leukemic activities of different extracts of the leaves and isolated compound WVP were studied in U-937, HL-60 and K-562 cell-lines by using cell count, MTT [(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide] and DNA laddering assays, flow-cytometric and confocal microscopic techniques.

Results

Kaempferol-3-O-[α-l-rhamnopyranosyl-(1→4)-O-α-l-rhamnopyranosyl-(1→6)-O]-β-d-glucopyranoside (WVP) was isolated from crude leaves extract of Wattakaka volubilis. Both the n-butanolic extract (WVB) of Wattakaka volubilis and its isolate WVP were found to be responsible for in vitro anti-leukemic activity. The IC₅₀ values of WVB were found be 120, 100 and 50 (μg/ml) in U937, K562, and HL-60 cell lines, respectively. Whereas, the pure isolate WVP exhibited anti-leukemic activity with IC₅₀ values of 13.5, 10.8, and 13.2 (μg/ml) in U937, K562, and HL-60 cell lines, respectively. The flow-cytometric analysis confirms that the cell cycle arrest occurs at G1 phase in case of U937 and K562 cell lines and G2/M phase in case of HL60 cell lines. Similarly both confocal microsocopic analysis and DNA laddering assay confirm the apoptosis and cell cycle arrests of leukemic cells.

Conclusion

The overall results provide evidence for the ethnopharmacological relevance for use of the plant Wattakaka volubilis in developing novel agents for the treatment of leukemia.     

Fludarabine-mediated circumvention of cytarabine resistance is associated with fludarabine triphosphate accumulation in cytarabine-resistant leukemic cells

The combination of cytarabine (ara-C) with fludarabine is a common approach to treating resistant acute myeloid leukemia. Success depends on a fludarabine triphosphate (F-ara-ATP)-mediated increase in the active intracellular metabolite of ara-C, ara-C 5’-triphosphate (ara-CTP). Therapy-resistant leukemia may exhibit ara-C resistance, the mechanisms of which might induce cross-resistance to fludarabine with reduced F-ara-ATP formation. The present study evaluated the effect of combining ara-C and fludarabine on ara-C-resistant leukemic cells in vitro. Two variant cell lines (R1 and R2) were 8-fold and 10-fold more ara-C resistant, respectively, than the parental HL-60 cells. Reduced deoxycytidine kinase activity was demonstrated in R1 and R2 cells, and R2 cells also showed an increase in cytosolic 5’-nucleotidase II activity. Compared with HL-60 cells, R1 and R2 cells produced smaller amounts of ara-CTP. Both variants accumulated less F-ara-ATP than HL-60 cells and showed cross-resistance to fludarabine nucleoside (F-ara-A). R2 cells, however, accumulated much smaller amounts of F-ara-ATP and were more F-ara-A resistant than R1 cells. In HL-60 and R1 cells, F-ara-A pretreatment followed by ara-C incubation produced F-ara-ATP concentrations sufficient for augmenting ara-CTP production, thereby enhancing ara-C cytotoxicity. No potentiation was observed in R2 cells. Nucleotidase might preferentially degrade F-ara-A monophosphate over ara-C monophosphate, leading to reduced F-ara-ATP production and thereby compromising the F-ara-A-mediated potentiation of ara-C cytotoxicity in R2 cells. Thus, F-ara-A-mediated enhancement of ara-C cytotoxicity depended on F-ara-ATP accumulation in ara-C-resistant leukemic cells but ultimately was associated with the mechanism of ara-C resistance.     

老年慢性粒细胞性白血病临床治疗体会

目的通过比较联合化疗HA方案（高三尖杉酯碱,阿糖胞苷）,DA方案（柔红霉素,阿糖胞苷）与单药口服化疗（羟基脲,马利兰）治疗老年慢性粒细胞白血病（CML）的结果分析,探索适合老年患者的常规治疗方法。方法将25例CML老年患者随机分成两组（联合化疗组13例,单药口服化疗组12例）,分别应用以上方案进行化疗,比较两组的临床疗效,不良反应及长期存活状况。结果联合化疗组及单药口服化疗组首次血液学完全缓解（CR）分别为9例（占81.82%）、7例（占58.33%）,部分缓解（PR）2例（占18.18%）、5例（占41.67%）。两组均出现一定程度的骨髓抑制,但联合化疗组出现的早,持续时间长且较严重,联合化疗组患者死亡2例,1例死于严重感染,1例死于颅内出血。单药口服化疗组无死亡病例,费用也与联合化疗组相差悬殊。结论虽联合标准化疗治疗（也就是所说的慢粒急治）使老年CML患者获得首次化疗缓解率比单药化疗高,但单药化疗患者病情变化较平稳,化疗不良反应较少,从而对症、支持治疗少,花费明显较低,对于基层医院及老年患者来说仍应首先考虑。     

Accelerated Radiotherapy with Concomitant ACNU/Ara-C for the Treatment of Malignant Glioma

Purpose To evaluate activity and toxicity of simultaneous ACNU and Ara-C with concurrent accelerated hyperfractionated radiotherapy in the treatment of high-grade glioma. Patients and Methods Thirty patients aged 23–71 years (median 47.5), 16 patients with glioblastoma multiforme (GBM) and 14 patients with grade-III glioma, received 93 courses of ACNU/Ara-C (median 4 courses) at following dose levels (ACNU/Ara-C in mg/m²/day): 70/90 (11 courses), 75/100 (36 courses) and 90/120 (46 courses). ACNU was administered IV on day 1 of each cycle, Ara-C as a 2h-intravenous infusion on days 1–3. Patients received concomitant radiation therapy with 2 daily fractions of 1.75Gy up to 57Gy (median). Results Median survival of all patients was 13 months, 11 months for GBM and >28 months for grade-III glioma; 31% (9 patients) survived longer than 24 months. The percentage of grade IV hematological toxicity was dose-dependent: 33% at the 70/90 dose level, 40% at 75/100 and 58% at 90/120. Six patients required platelet transfusion, 1 patient red blood cells; no febrile neutropenia occurred. Among 18 patients evaluable for response, 3 (17%) showed PR, 8 (44%) NC and 7 (39%) PD at completion of chemoradiation. No acute or late neurological toxicity occurred in this study. Younger age (p = 0.0001) and grade-III histology (p = 0.0009) were important prognostic factors for prolonged survival. Conclusion This chemoradiation regimen is active in malignant gliomas and can be safely recommended at a dose level using 70mg/m² ACNU together with 90mg/m² Ara-C.     

Effect of cytokines on the toxicity of cytostatic drugs to normal bone marrow cells in vitro

We evaluated in vitro how growth factors influenced the effect of cytostatic drugs on normal hematopoietic progenitor cells. Bone marrow was obtained from 15 donors for bone marrow transplantation. After separation the mononuclear fraction was incubated with granulocyte colony-stimulating factor (G-CSF) at 5 and 50 ng/ml, with granulocyte/macrophage colony-stimulating factor (GM-CSF) at 1 and 10 ng/ml, and with interleukin 3 (IL-3) at 0.5 and 5 ng/ml for 24 h prior to incubation with cytostatic drugs. These incubations were performed with 0.05 μM mitoxantrone and 0.2 μM daunorubicin for 1 h, and cells were thereafter cultured for colony-forming units – granulocyte/macrophage (CFU-GM) in soft agar for 10–12 days. Incubation with 0.05 μM cytosine arabinoside was performed continuously throughout the culture period. The proliferation of normal hematopoietic progenitor cells stimulated with GM-CSF at 10 ng/ml and with IL-3 at 5 ng/ml was significantly increased to 218% and 215% colonies, respectively, as compared with the control stimulated with conditioned medium only. Stimulation with G-CSF, on the other hand, did not induce any significantly enhanced proliferation relative to the control. Daunorubicin applied in combination with G-CSF at 5 ng/ml or with IL-3 at 0.5 ng/ml exerted a significantly higher degree of cytotoxicity on normal hematopoietic progenitor cells, resulting in 21% and 30% surviving colonies as compared with the 38% recorded for daunorubicin alone (P<0.05). Neither G-CSF nor IL-3 at a higher concentration nor GM-CSF exerted a significantly altered degree of toxicity relative to cells incubated with daunorubicin alone. The cytotoxic effect exerted on normal hematopoietic cells by mitoxantrone or ara-C was unchanged or significantly decreased after stimulation with growth factors as compared with the effect on cells incubated with cytostatic drugs alone. We conclude that G-CSF and IL-3 augment the effect of daunorubicin on normal hematopoietic progenitor cells. Received: 6 May 1997 / Accepted: 4 February 1998     

超大剂量阿糖胞苷在小儿急性髓细胞白血病的治疗探讨

目的应用超大剂量阿糖胞苷(SHDAra-C)对急性髓细胞白血病(AML)患儿进行缓解后治疗,探讨其疗效及安全性。方法在患者取得骨髓缓解后应用SHDAra-C共五个疗程,第一疗程Ara-C总剂量达36 g/m2,其后每疗程Ara-C总剂量18 g/m2,累计Ara-C总剂量达108 g/m2。结果8例AML患儿有7例完成了5个疗程HDAra-C化疗(1例只完成4疗程),除1例骨髓复发放弃治疗外,余7例均获CCR至今,CCR时间6~76月,无一例化疗相关性死亡。结论SHDAra-C是小儿AML化疗获得长期无病生存的重要治疗方法,有效且相对安全,其治疗效果值得更大规模的临床病例观察,治疗机理有待更深入的实验研究。     

Possible differentiation of human acute myeloblastic leukemia cells by daily and intermittent administration of aclacinomycin-A

A rapid decrease of myeloblasts and a remarkable increase of mature neutrophils, mostly with Pelger anomaly, were observed in the peripheral blood of a 51-year-old woman with terminal acute myeloblastic leukemia during 16 days of daily i.v. administration of 20 mg aclacinomycin-A (ACM-A). When the same dose was administered later on three consecutive days each week, a similar hematore neutrophils, mostly with Pelger anomaly, were observed in the peripheral blood of a 51-year-old woman with terminal acute myeloblastic leukemia during 16 days of daily i.v. administration of 20 mg aclacinomycin-A (ACM-A). When the same dose was administered later on three consecutive days each week, a similar hematore neutrophils, mostly with Pelger anomaly, were observed in the peripheral blood of a 51-year-old woman with terminal acute myeloblastic leukemia during 16 days of daily i.v. administration of 20 mg aclacinomycin-A (ACM-A). When the same dose was administered later on three consecutive days each week, a similar hematological change occurred again. An increase of myeloblasts observed between the third and the fifth week of this intermittent schedule was accompanied by that of mature neutrophils. Thrombopenia and anemia did not improve significantly. These findings may indicate the induction of leukemic myeloblasts by ACM-A into mature neutrophils. Administration of relatively small dose anthracyclines including ACM-A may be another potential choice in the treatment of refractory acute non-lymphocytic leukemia (ANLL) or ANLL after relapse.     

Cytarabin (Ara-C) induced radioresistance of mouse jejunal stem cells following single or fractionated doses of radiation

The effects of a single injection of cytosine arabinoside on crypt cell kinetics and intestinal cell radiosensitivity have been assessed. Tritiated thymidine labelling and mitotic indices indicate that synchrony was induced in crypt cells after administration of Ara-C and cryptogenic cell survival could be related to the presence of cells in S phase. Maximal radioresistance was noted 12 hr after Ara-C administration; however, the magnitude of this was greater than that which could exclusively be accounted for by synchronization of cells into a radioresistant S phase. A shorter mitotic delay in Ara-C pretreated mice was consistent with an early removal of the mitotic block; this contributed very little to the overall Ara-C protective effect, which was mainly one of induction of radioresistance rather than enhanced proliferation. The circumstances in which Ara-C pre-treatment might be clinically useful have been discussed.     

Phase II trial of amsacrine plus intermediate-dose Ara-C (IDAC) with or without etoposide as salvage therapy for refractory or relapsed acute leukemia

OBJECTIVE: The current trial attempted to evaluate the efficacy and toxicity of a salvage therapy consisting of amsacrine plus intermediate-dose Ara-C (IDAC) with or without etoposide for acute leukemia patients in refractory or relapsed states. METHODS: A total of 51 patients with refractory or relapsed acute leukemia were included in the current trial. Twenty-nine patients with acute myeloid leukemia (AML) received a salvage therapy of amsacrine plus IDAC and etoposide, while 22 patients with acute lymphoblastic leukemia (ALL) received amsacrine plus IDAC. RESULTS: The overall complete remission rate was 55% (45% for AML, 68% for ALL) and the median duration of overall survival was 144 days (95% confidence interval = 101-186 days). Grade 3, 4 infectious toxicities were observed in 43 patients (87%), while treatment-related toxicity, excluding infectious causes, included heart failure from myocarditis (n = 1) and central nervous system toxicity (n = 1). CONCLUSION: A salvage therapy consisting of amsacrine plus IDAC with or without etoposide appears to be safe and an effective bridge therapy into a stem cell transplantation programme for patients with refractory or relapsed acute leukemia.