Breaking chemoresistance and radioresistance with [213Bi]anti-CD45 antibodies in leukemia cells

Chemoresistance and radioresistance are considered one of the primary reasons for therapeutic failure in leukemias and solid tumors. Targeted radiotherapy using monoclonal antibodies radiolabeled with alpha-particles is a promising treatment approach for high-risk leukemia. We found that targeted radiotherapy using monoclonal CD45 antibodies radiolabeled with the alpha-emitter (213)Bi ([(213)Bi]anti-CD45) induces apoptosis, activates apoptosis pathways, and breaks beta-irradiation-, gamma-irradiation-, doxorubicin-, and apoptosis-resistance in leukemia cells. In contrast to beta-irradiation-, gamma-irradiation-, and doxorubicin-mediated apoptosis and DNA damage, [(213)Bi]anti-CD45-induced DNA damage was not repaired, and apoptosis was not inhibited by the nonhomologous end-joining DNA repair mechanism. Depending on the activation of caspase-3, caspase-8, and caspase-9, [(213)Bi]anti-CD45 activated apoptosis pathways in leukemia cells through the mitochondrial pathway but independent of CD95 receptor/CD95 ligand interaction. Furthermore, [(213)Bi]anti-CD45 reversed deficient activation of caspase-3, caspase-8, and caspase-9, deficient cleavage of poly(ADP-ribose) polymerase, and deficient activation of mitochondria in chemoresistant and in radioresistant and apoptosis-resistant leukemia cells. These findings show that [(213)Bi]anti-CD45 is a promising therapeutic agent to break chemoresistance and radioresistance by overcoming DNA repair mechanisms in leukemia cells and provide the foundation for discovery of novel anticancer compounds.     

Selective apoptotic killing of malignant hemopoietic cells by antibody-targeted delivery of an amphipathic peptide

The alpha-helical amphipathic peptide D-(KLAKLAK)2 is toxic to eukaryotic cells if internalized by a suitable targeting mechanism. We have targeted this peptide to malignant hemopoietic cells via conjugation to monoclonal antibodies, which recognize lineage-specific cell surface molecules. An anti-CD19/peptide conjugate efficiently killed 3/3 B lymphoid lines. However, an anti-CD33/peptide conjugate was cytotoxic to only one of three CD33-positive myeloid leukemia lines. The IC50 towards susceptible lines were in the low nanomolar range. Conjugates were highly selective and did not kill cells that did not express the appropriate cell surface cognate of the antibody moiety. Anti-CD19/peptide conjugates efficiently killed cells from patients with chronic lymphocytic leukemia but anti-CD33/peptide reagents were less effective against fresh acute myeloid leukemia cells. We therefore suggest that amphipathic peptides may be of value as targeted therapeutic agents for the treatment of a subset of hematologic malignancies.     

Novel conventional therapies in onco-hemathology

Cytogenetic, molecular and phenotyping features of malignant hematologic diseases succeeded in improving their management by a more accurate stratification of patients according to several groups of risk and by providing a rational for targeted therapy. Three major types of treatment (excluding cellular therapy) are currently available in onco-hematology: conventional chemotherapy, small molecules for targeted therapy and monoclonal antibodies. Conventional chemotherapy with optimization of doses and multidrug-based regimens allowed to substantially improve survival of patients and keeps a place of choice in treatment of these diseases. Targeted treatments came from the cytogenetic and molecular characterization of hemopathies. Thus, the kinase Bcr-Abl, as a result of the translocation t(9;22)(q34;q11), has been successfully targeted by tyrosine kinase inhibitors (TKI) in chronic myeloid leukemia and Ph+ acute lymphoblastic leukemia. Molecular abnormalities like internal-tandem duplication/point activating mutations in FLT3 in some acute myeloblastic leukemia or epigenetic dysregulations in some blood malignancies can also be targeted by small molecules. Hematopoietic malignant cells are phenotypically characterized by expression of cluster of differentiation (CD) on their surface. These CD are detected by flow cytometry using specific antibodies. Monoclonal antibodies targeting different CD have been developed for treatment. Rituximab, an anti-CD20 antibody, was the first monoclonal antibody successfully developed for treatment of malignant hematologic diseases. Since rituximab, many other monoclonal antibodies are being developed. Trends in malignant hematologic diseases presented here will include treatments, which have at least entered phase I/II clinical trials in adult or childhood leukemia. They include some novel drugs of conventional chemotherapy like second-generation nucleoside analogues. We will give an overview of the small molecules targeting the different cellular pathways and we will highlight those appearing as the most promising like novel TKIs. The large field of monoclonal antibodies will be also approached focusing on antibodies developed in leukemias.     

抗CD123抗体靶向治疗急性髓系白血病

白血病干细胞（leukemic stem cells,LSCs）被认为是白血病发生、发展、耐药、复发的根源,如何彻底根除LSCs已成为白血病治疗研究的一个重要方向。CD123是LSCs表面相对特异的抗原,针对其研发的靶向抗体治疗药物可有效杀伤急性髓系白血病（acute myeloid leukemia,AML）的LSCs,本文对抗CD123抗体靶向治疗AML的最新进展做一综述。     

益气养阴方诱导急性白血病细胞凋亡的实验研究

目的 :观察益气养阴方诱导急性白血病模型小鼠细胞凋亡的作用 ,探讨益气养阴方治疗急性白血病的作用机制。方法 :以L72 12 白血病小鼠为研究对象 ,用益气养阴方浓缩液给小鼠灌胃 8d后处死 ,利用光学显微镜、DNA琼脂糖凝胶电泳等手段观察益气养阴方对急性白血病的作用。结果 :形态学观察可见细胞凋亡特征 ,DNA琼脂糖凝胶电泳图谱显示细胞凋亡现象。结论 :本研究提示诱导白血病细胞凋亡是益气养阴方治疗急性白血病的重要机制之一     

Apoptosis induction by hypercross-linking of the surface antigen CD5 with anti-CD5 monoclonal antibodies in B cell chronic lymphocytic leukemia.

We evaluated cells from 24 patients with B cell chronic lymphocytic leukemia (B-CLL) to determine apoptosis induced by CD5 hypercross-linking. Following the CD5 hypercross-linking with anti-CD5 monoclonal antibodies (MoAbs), we identified 10 patients where CD5 hypercross-linking induced apoptosis (group A) and 14 patients whose cells were resistant to the anti-CD5 MoAbs (group B). The programmed cell death pathway of the cells from patient group A was caspase-3 and poly (ADP-ribose) polymerase (PARP)-dependent, involved a reduction of the mitochondrial transmembrane potential DeltaPsi and a down-regulation of the anti-apoptotic Bcl-2, Mcl-1 and iNOS proteins. Early activation-associated molecules such as CD25 and CD69 were expressed at higher levels than in controls after 6 h of culture with anti-CD5 MoAb. The expression of CD5 and of CD72, the ligand for CD5, were significantly lower in group A compared with group B. Anti-CD20 MoAb had similar activity with anti-CD5 MoAb and the combination of the two MoAbs seemed to be additive. In this study, it is suggested that the cells from some B-CLL patients can be induced into programmed cell death by CD5 hypercross-linking with anti-CD5 MoAbs.     

Immunotherapy for acute myeloid leukemia

Immunotherapeutic strategies have become part of standard cancer treatment. Chimeric and humanized antibodies have demonstrated activity against a variety of tumors. Although the humanized anti-CD33 antibody HuM195 has only modest activity against overt acute myeloid leukemia (AML), it can eliminate minimal residual disease in acute promyelocytic leukemia. High-dose radioimmunotherapy with β-particle-emitting isotopes targeting CD33, CD45, and CD66 can potentially allow intensification of antileukemic therapy before hematopoietic stem cell transplantation. Conversely, α-particle immunotherapy with isotopes such as bismuth-213 or actinium-225 offers the possibility of selective tumor cell kill while sparing surrounding normal tissues. Targeted chemotherapy with the anti-CD33-calicheamicin construct gemtuzumab ozogamicin has produced remissions in relapsed AML and appears promising when used in combination with standard chemotherapy for newly diagnosed AML. T-cell recognition of peptide antigens presented on the cell surface in combination with major histocompatibility complex antigen provides another potentially promising approach for the treatment of AML.     

VX-680体外诱导异基因干细胞移植后复发AML细胞凋亡的初步研究

目的:探讨Aurora激酶抑制剂VX-680在体外对异基因造血干细胞移植(Allo-HSCT)后复发的急性髓系白血病(AML)患者细胞增殖和凋亡的影响。方法:以正常人CD34+细胞为对照,体外用5nmol/L浓度VX-680分别处理3例Allo-HSCT后复发的AML患者白血病细胞,48h后用四甲基偶氮唑蓝(MTT)法观察细胞增殖活力,Hoechest33342方法观察细胞凋亡形态,流式细胞术检测细胞凋亡百分率,蛋白质印迹法检测Aurora-A磷酸化蛋白及Caspase-3凋亡蛋白的表达。结果:MTT法观察发现,体外VX-680均能抑制3例复发患者白血病细胞的增殖,增殖抑制率分别为(77.5±3.1)%、(76.8±4.7)%和(81.1±4.2)%,均明显高于正常对照的(11.2±1.6)%,P值均<0.001;Hoe-chest33342方法观察发现,3例患者白血病细胞在VX-680作用下出现了明显的细胞凋亡形态,流式细胞术检测到凋亡百分率分别为(88.8±4.6)%、(98.7±0.9)%和(99.3±0.4)%,也均高于正常对照的(13.6±3.5)%,P值均<0.001;蛋白质印迹法检测显示,VX-680处理后3例患者白血病细胞中Aurora-A磷酸化蛋白表达显著下降,而Caspase-3凋亡蛋白表达明显升高。结论:VX-680体外可通过诱导Allo-HSCT后AML复发患者的白血病细胞凋亡来抑制其增殖。     

Targeted therapy for chronic lymphocytic leukemia

The introduction of targeted agents such as the monoclonal antibodies rituximab (anti-CD20) and alemtuzumab (anti-CD52) has brought about a remarkable change in the therapy of chronic lymphocytic leukemia (CLL). Although it is unclear whether overall survival has been improved, the incorporation of these monoclonal antibodies into chemoimmunotherapy regimens has dramatically improved complete response rates and progression-free survival in patients with both newly-diagnosed and relapsed CLL. The success of rituximab and alemtuzumab has spurred the development of other monoclonal antibodies targeting distinct proteins and epitopes on the surface of CLL cells and an exciting array of novel immunotherapeutics. The judicious use of these agents provides the opportunity to develop risk-adapted therapeutic strategies to optimize responses and quality of life in patients with CLL.     

Monoclonal antibodies specific for oncofetal antigen – immature laminin receptor protein: Effects on tumor growth and spread in two murine models

The oncofetal antigen – immature laminin receptor protein (OFA/iLRP) has been linked to metastatic tumor spread for several years. The present study, in which 2 highly-specific, high-affinity OFA/iLRP-reactive mouse monoclonal antibodies were examined for ability to suppress tumor cell growth and metastatic spread in the A20 B-cell leukemia model and the B16 melanoma model, provides the first direct evidence that targeting OFA/iLRP with exogenous antibodies can have therapeutic benefit. While the antibodies were modestly effective at preventing tumor growth at the primary injection site, both antibodies strongly suppressed end-organ tumor formation following intravenous tumor cell injection. Capacity of anti-OFA/iLRP antibodies to suppress tumor spread through the blood in the leukemia model suggests their use as a therapy for individuals with leukemic disease (either for patients in remission or even as part of an induction therapy). The results also suggest use against metastatic spread with solid tumors.     

Arsenic trioxide induces apoptosis in leukemia/lymphoma cell lines via the CD95/CD95L system

Although arsenic trioxide (As2O3) has been shown to be an effective anticancer agent for acute promyelocytic leukemia (APL), its mechanisms of action as well as its effect on other leukemias than APL remain unclear. We studied in vitro effects of As2O3 at low concentrations (1.0-2.0 microM) on two human leukemia/lymphoma cell lines, HL-60, an acute myeloid leukemia cell line, and RL, a B-cell lymphoma cell line. As2O3 inhibited proliferation of HL-60 cells and RL cells to the similar degree to the reported inhibition by an APL cell line, NB4. As2O3-treated cell lines exhibited typical morphologic changes of apoptosis such as nuclear condensation and apoptotic bodies, and a cell cycle arrest at the subG1 phase. As2O3-treated cell lines also showed upregulation of CD95/CD95L expression and activation of caspases 8 and 3. Treatment of these cells with anti-CD95 antibodies capable of blocking the CD95 signaling pathway ameliorated As2O3-induced apoptosis. These data suggest that As2O3 can inhibit growth of leukemia/lymphoma cells by inducing the cell cycle arrest and apoptosis that is partially mediated by the CD95/CD95L system.     

Laboratory and clinical applications of monoclonal antibodies for leukemias and non-Hodgkin's lymphomas

Important insights into leukocyte differentiation and the cellular origins of leukemia and lymphoma have been gained through the use of monoclonal antibodies that define cell surface antigens and molecular probes that identify immunoglobulin and T-cell receptor genes. Results of these studies have been combined with markers such as surface membrane and cytoplasmic immunoglobulin on B lymphocytes, sheep erythrocyte receptors on T lymphocytes, and cytochemical stains. After using all of the aforementioned markers, it is now clear that acute lymphoblastic leukemia (ALL) is heterogeneous. Furthermore, monoclonal antibodies that identify B cells, such as the anti-CD20 and anti-CD19 antibodies in combination with studies of immunoglobulin gene rearrangement, have demonstrated that virtually all cases of non-T-ALL are malignancies of B-cell origin. At least six distinct subgroups of non-T-ALL can now be identified. T-ALL is subdivided by the anti-CD7, anti-CD5, and antibodies that separate T lymphocytes subsets into three primary subgroups. Monoclonal antibodies are also useful in the subclassification of non-Hodgkin's lymphoma, and certain distinct markers can be correlated with morphological classification. Although monoclonal antibodies are useful in distinguishing acute myeloid from acute lymphoid leukemias, they have less certain utility in the subclassification of acute myelogenous leukemia (AML). Attempts to subclassify AML by differentiation-associated antigens rather than by the French-American-British (FAB) classification are underway in order to document the potential prognostic utility of surface markers. Therapeutic trials using monoclonal antibodies in leukemia and lymphoma have been reported. Intravenous infusion of unlabeled antibodies is the most widely used method; transient responses have been demonstrated. Antibodies conjugated to radionuclides have been quite successful in localizing tumors of less than 1 cm in some studies. Therapy trials with antibodies conjugated to isotopes, toxins, and drugs have shown promise. Purging of autologous bone marrow with monoclonal antibodies and complement in vitro has been used in ALL and non-Hodgkin's lymphoma; preliminary data suggest that this approach may be an effective therapy and may circumvent many of the obstacles and toxicities associated with in vivo monoclonal antibody infusion.     

人端粒酶逆转录酶启动子在裸鼠中增强人喉癌对基因放射治疗的敏感性

目的 探索人端粒酶逆转录酶启动子(hTERTp)介导自杀基因辣根过氧化酶(HRP)-吲哚乙酸(IAA)系统联合射线,对相同来源而放射敏感性不同的人喉癌移植瘤模型的治疗作用.方法 建立相同来源而放射敏感性不同的人喉癌(Hep-2和Hep-2R细胞)移植瘤模型,并分为联合治疗组(A组和AR组)、基因治疗组(B组和BR组)、单纯放射组(C组和CR组)和对照组(D组和DR组).瘤内注射脂质体包裹的质粒phTERTp-HRP,腹腔内注射IAA从并联合放疗30 Gy,观察对移植瘤生长的抑制作用.应用原位末端转移酶标记技术(TUNEL)检测肿瘤细胞的凋亡情况;应用AP法检测瘤内HRP蛋白的表达.结果 裸鼠移植瘤生长以联合治疗组最慢,以对照组最快.A组的肿瘤抑制率为54.8%,B组为10.0%,C组为31.9%,AR组为52.7%,BR组为24.8%,CR组为17.0%.A组和AR组可见大量肿瘤细胞坏死和凋亡,凋亡指数分别为16.6%±1.3%和17.6%±1.3%,高于其他组(P<0.05).B组的HRP蛋白表达率(21.9%±5.7%)低于BR组和(33.3%±8.9%),辐射诱导后,A组和AR组的HRP蛋白表达率分别增加2.1和1.6倍(P<0.05).结论 在不同放射敏感性的喉癌移植瘤模型中,hTERTp能被射线诱导,并根据瘤内端粒酶活性增强HRP基因的表达.hTERTp·HRP-IAA系统通过诱导肿瘤细胞凋亡和引起细胞坏死,抑制裸鼠移植瘤生长,并与射线协同作用,起到放射增敏作用.     

Current uses of monoclonal antibodies in the treatment of acute leukemia

Advances in the treatment of acute leukemia have been limited by both disease resistance and toxicity. Monoclonal antibodies have been used as a means of targeting therapy to malignant cells in the form of antibody-mediated cellular toxicity, radiation, or other cytotoxic agents. Anti-CD33 and anti-CD45 antibodies have been most extensively studied. Antibodies conjugated with either radioisotopes or cytotoxic moieties have been used as part of stem cell transplant regimens or as induction therapy in patients with relapsed acute myelogenous leukemia (AML), and have demonstrated antileukemic activity with acceptable toxicities.     

hTERT脱氧核酶对白血病细胞HL-60凋亡相关基因的影响

[目的]探讨hTERT脱氧核酶对白血病细胞(HL-60)凋亡相关基因表达的影响。[方法]合成针对hTERTmRNA的"10～23"型脱氧核酶及其类似物,转染白血病细胞后,用PCR-ELISA法测定端粒酶活性;RT-PCR和荧光免疫测定Bcl-2和Bax的表达。[结果]脱氧核酶DzT转染白血病细胞后,能够显著降低白血病细胞端粒酶活性(P<0.01)和Bcl-2基因的表达(P<0.05),抑制白血病细胞的生长(P<0.05),上调Bax基因的表达(P<0.05)。[结论]脱氧核酶能降低白血病细胞的端粒酶活性,促进白血病细胞凋亡。     

Two hits are better than one: targeting both phosphatidylinositol 3-kinase and mammalian target of rapamycin as a therapeutic strategy for acute leukemia treatment

Phosphatidylinositol 3-kinase (PI3K) and mammalian target of rapamycin (mTOR) are two key components of the PI3K/Akt/mTOR signaling pathway. This signal transduction cascade regulates a wide range of physiological cell processes, that include differentiation, proliferation, apoptosis, autophagy, metabolism, motility, and exocytosis. However, constitutively active PI3K/Akt/mTOR signaling characterizes many types of tumors where it negatively influences response to therapeutic treatments. Hence, targeting PI3K/Akt/mTOR signaling with small molecule inhibitors may improve cancer patient outcome. The PI3K/Akt/mTOR signaling cascade is overactive in acute leukemias, where it correlates with enhanced drug-resistance and poor prognosis. The catalytic sites of PI3K and mTOR share a high degree of sequence homology. This feature has allowed the synthesis of ATP-competitive compounds targeting the catalytic site of both kinases. In preclinical models, dual PI3K/mTOR inhibitors displayed a much stronger cytotoxicity against acute leukemia cells than either PI3K inhibitors or allosteric mTOR inhibitors, such as rapamycin. At variance with rapamycin, dual PI3K/mTOR inhibitors targeted both mTOR complex 1 and mTOR complex 2, and inhibited the rapamycin-resistant phosphorylation of eukaryotic initiation factor 4E-binding protein 1, resulting in a marked inhibition of oncogenic protein translation. Therefore, they strongly reduced cell proliferation and induced an important apoptotic response. Here, we reviewed the evidence documenting that dual PI3K/mTOR inhibitors may represent a promising option for future targeted therapies of acute leukemia patients.