Bufalin Induces the Apoptosis of Acute Promyelocytic Leukemia Cells via the Downregulation of Survivin Expression

Background and Aims: Bufalin is a cardiotonic steroid isolated from the Chinese toad venom preparation Chan'su and has been shown to induce leukemia cell differentiation and apoptosis under certain experimental conditions. However, the detailed mechanism by which bufalin induces the apoptosis of acute promyelocytic leukemia cells is largely unexplored. Methods: The acute promyelocytic leukemia cell line NB4 was treated with bufalin, then the proliferation was evaluated by cell viability assay and apoptosis was detected by flow cytometry analysis. In addition, NB4 cells were treated by MEK inhibitor PD98059 in combination with bufalin, and the expression of survivin and activation of caspase-3 were detected by Western blot analysis. Results: Bufalin inhibited the proliferation and induced the apoptosis of NB4 cells in a dose- and time-dependent manner. Moreover, bufalin synergized with PD98059 to inhibit the proliferation and induce the apoptosis of NB4 cells, which was associated with the downregulation of survivin expression and the upregulation of caspase-3 activation. Conclusions: Bufalin is a potential regimen to be used in combination with conventional chemotherapeutic drugs to improve acute promyelocytic leukemia therapy.     

Trivalent Antimonials Induce Degradation of the PML-RARalpha Oncoprotein and Reorganization of the Promyelocytic Leukemia Nuclear Bodies in Acute Promyelocytic Leukemia NB4 Cells

Acute promyelocytic leukemia (APL) is characterized by a specifict(15;17) chromosomal translocation that fuses the genes encoding thepromyelocytic leukemia protein (PML) and the retinoic acid receptor (RAR). The resulting PML-RAR protein induces a block in thedifferentiation of the myeloid progenitor cells, which can be releasedby retinoic acid (RA) in vitro and in vivo. The RA-induceddifferentiation of APL blasts is paralleled by the degradation of thefusion protein and the relocation of wild-type PML from aberrantnuclear structures to its normal localization in nuclear bodies.Recently, arsenic trioxide (As₂O₃) treatment was proposed as an alternative therapy in APL, because it can inducecomplete remission in both RA-sensitive and -resistant APL patients.Intriguingly, As₂O₃ was also shown to inducedegradation of the PML-RAR chimera and to reorganize PML nuclearbodies. Here we show that trivalent antimonials also have strikingeffects on RA-sensitive and RA-resistant APL cells. Treatment of theAPL-derived NB4 cells and the RA-resistant subclone NB4R4 with antimonytrioxide or potassium antimonyl tartrat triggers the degradation of the fusion protein and the concomitant reorganization of the PML nuclear bodies. In addition, as reported for As₂O₃, theantimonials provoke apoptosis of NB4 and NB4R4 cells. The mechanism ofantimony action is likely to be similar to that ofAs₂O₃, notably both substances induce theattachment of the ubiquitin-like SUMO-1 molecule to the PML moiety ofPML-RAR. From these data, we propose that, in analogy toAs₂O₃, antimonials might have a beneficialtherapeutic effect on APL patients, perhaps with less toxicity thanarsenic.     

用RT—PCR法检测急性白血病患者MDR1基因表达

化疗是治疗急性白血病（Ａｃｕｔｅ Ｌｅｕｋｅｍｉａ ＡＬ）的主要手段。然而，由人ＭＤＲ１基因编码的Ｐｇｐ过表达引起的ＭＤＲ（Ｍｕｌｔｉｄｒｕｇ ｒｅｓｉｓｔａｎｃｅ）往往导致化疗的失败。利用检测ＭＤＲ１ＭＲＮＡ的ＲＴ－ＰＣＲ法，对１４份正常骨髓标本、２９例ＡＬ患者３０份骨髓标本的ＭＤＲ１ＭＰＲＮＡ进行了检测。结果表明：化疗前、后ＡＬ患者的ＭＤＲ１ＭＲＮＡ阳性率分别为１９％和７５％（Ｐ〈０．０１）：     

Fas／Apo—1抗原在急性白血病中的表达及其意义

目的：了解Fas表达与临床疗效的关系。方法：应用卵白素-生物素复合物法（ABC法）检测54例急性白血病（AL）Fas抗原表达，并做MTT药敏试验。结果：发现AL患者Fas抗原阳性表达率明显低于非恶性血液疾病（急淋：4．12％±2．43％，急非淋：5．95％±3．97％，对照组：30．81％±12．21％，P＜0．01）。结论：Fas介导的细胞凋亡路径障碍在白血病的形成和维持中具有重要的病理生理意义。Fas抗原阳性细胞表达率与MTT药敏试验二者无相关性（r＝－0．127）。     

急性早幼粒细胞性白血病:全反式维甲酸诱导分化治疗中出血并发症的处理

16例急性早幼粒细胞性白血病(APL)采用全反式维甲酸(RA)进行诱导分化治疗。入院时和病程中80%(13/16例)的患者发生弥散性血管内凝血(DIC),4例发生严重出血。经配合包括肝素抗凝、新鲜血及血小板输注,并用地塞米松、脱水和防治感染等积极的综合性治疗,渡过危险期,有效保障 RA 诱导分化作用的发挥,全部病例取得骨髓完全缓解.     

Invasive Fungal Infections in Acute Promyelocytic Leukemia on Dual Differentiating Agents: Real World Data

Invasive fungal infection (IFI) in patients with acute promyelocytic leukemia (APL) is a common phenomenon in developing countries. In a systematic study (Dual Inducing Differentiating agents—Indian Trial: DID-IT) using dual differentiating agents (ATO and ATRA) in 98 APL patients at our center we report 18.3% incidence of IFI (n-18). Among all cases of IFI three were definitive, 14 were probable and one was possible IFI. We conclude that incidence of IFI in APL is affected by environmental and therapy related factors and mere usage of dual differentiating agents need not necessarily decrease the incidence of fungal infections.     

Role of GSTP1-1 in mediating the effect of As2O3 in the Acute Promyelocytic Leukemia cell line NB4

Arsenic trioxide (As₂O₃) is a highly effective agent in the treatment of acute promyelocytic leukemia (APL), whereas other hematopoietic tumors are less responsive to this agent and mechanisms underlying As₂O₃,-resistance are poorly understood. To better understand the complex network of GSH-related pathways in As₂O₃ sensitivity, we investigated the role of GSH and GSH-relevant enzymes in an APL cell line sensitive to As₂O₃ (NB4) and in a resistant subclone (AsR). Cell proliferation, viability, and apoptosis were investigated in NB4 cells before and after treatment with 1 μM As₂O₃ and in AsR cells. In these experimental cell models, GSTP1-1, JNK1 and JNK2 proteins were analyzed by immunoblotting, and a kinase assay for JNK1 was performed. GSH levels as well as the activities of the enzymes glutathione peroxidase, glutathione transferase, γ-Glutamylcysteynilsinthetase and superoxide dismutase were measured. NB4 cells treated with As₂O₃ showed a high level of oxidative stress and an increase of GSH levels. GSTP1-1 polymerization and JNK1 activation were detectable after 24 h and were followed by an increase of the apoptotic rate starting at 72 h. Neither GSTP1-1 polymerization nor JNK activation was found in AsR cells that showed a very low apoptotic rate. Our results suggest that APL sensitivity to As₂O₃ might be, at least in part, mediated by the balance between association and dissociation of JNK from GSTP1-1, depending on the redox status of the cell. Further investigation is warranted to find a way to interfere with this balance, whenever it might represent a mechanism of drug resistance.