Emerging role of immunoPET in receptor targeted cancer therapy

ImmunoPET is a non-invasive imaging technology based on tracking and quantification of radiolabeled monoclonal antibodies, antibody fragments and peptides in vivo. The knowledge of distribution and expression levels of a given receptor is a key for successful receptor targeted cancer therapy. ImmunoPET performed with probes with high affinity and specificity to a given receptor aspires to be a method for obtaining comprehensive information about current in vivo status of the targeted receptor. This review describes methods for radiolabeling of peptides, monoclonal antibodies, and antibody fragments for immunoPET and highlights the recently reported pre-clinical and clinical applications of immunoPET in receptor targeted therapy.     

An update on the xenograft and mouse models suitable for investigating new therapeutic compounds for the treatment of B-cell malignancies

B-cell malignancies account for over the 90% of all lymphoid neoplasms. The clonal proliferations of B-cells show a high degree of variation in terms of clinical and presenting features, histopathology, immunophenotype, and genetics. Primary tumor samples are useful for examining the characteristics of a patient's own tumor, although both primary leukemic cells and cell lines provide an initial step for screening novel compounds for their activity in some hematological malignancies, they should be followed by models in intact animals. In this review, we try to summarize the animal models generated to study B-cell malignancies, in particular, B-cell lymphoma, B-cell CLL and MM that represent the major part of B-cell malignancies. Animals that spontaneously develop cancer are flawed to predict human disease. The development of human tumor xenograft models represented a big step towards more clinically relevant models. The major problems of these models are the requirement of immuno-compromised animals and the inability of these models to recapitulate the complex relationship between the tumor and the microenvironment. A number of strategies have been also applied to develop genetically engineered models of malignancies, in which the tumor arises "naturally" in the host. The disadvantages of these models include the differences between rodent and human stroma and that they can not be used to characterise anti-tumor activity of many immunotherapeutic drugs. These models can be used to study the molecular processes critical for the development, proliferation and survival of hematological malignancies and to characterise potential therapeutic targets.     

Vascular endothelial growth factor and its receptor as drug targets in hematological malignancies

Angiogenesis is defined as formation of new blood vessels from the preexisting vasculature, a process which is essential for malignant tumor growth. While this has been accepted for solid forms of cancer there is now emerging evidence that progression of hematological malignancies also requires the induction of new blood vessels. Vascular endothelial growth factor (VEGF) is known to be an essential regulator of physiological and pathological angiogenesis. Numerous preclinical and clinical studies have validated VEGF as target for antiangiogenesis and anticancer therapy. With regard to hematological malignancies a stimulating effect of VEGF for proliferation, survival and migration of leukemia cells could be demonstrated. Bone marrow of leukemia patients shows an increased microvessel density as well as VEGF expression. Complete remissions in acute myeloid leukemia (AML) have been reported by targeting the receptor tyrosine kinase system of VEGF. While the pathophysiology behind the contribution of VEGF to leukemia progression is not yet completely understood, VEGF and its receptors may provide promising targets not only in solid tumors but also hematological malignancies such as AML.     

Histone deacetylase inhibitors: potential targets responsible for their anti-cancer effect

The histone deacetylase inhibitors (HDACi) have demonstrated anticancer efficacy across a range of malignancies, most impressively in the hematological cancers. It is uncertain whether this clinical efficacy is attributable predominantly to their ability to induce apoptosis and differentiation in the cancer cell, or to their ability to prime the cell to other pro-death stimuli such as those from the immune system. HDACi-induced apoptosis occurs through altered expression of genes encoding proteins in both intrinsic and extrinsic apoptotic pathways; through effects on the proteasome/aggresome systems; through the production of reactive oxygen species, possibly by directly inducing DNA damage; and through alterations in the tumor microenvironment. In addition HDACi increase the immunogenicity of tumor cells and modulate cytokine signaling and potentially T-cell polarization in ways that may contribute the anti-cancer effect in vivo. Here, we provide an overview of current thinking on the mechanisms of HDACi activity, with attention given to the hematological malignancies as well as scientific observations arising from the clinical trials. We also focus on the immune effects of these agents.     

Ex vivo effects of the dual topoisomerase inhibitor tafluposide (F 11782) on cells isolated from fresh tumor samples taken from patients with cancer

Tafluposide (F 11782), a novel epipodophylloid with a unique mechanism of interaction with both topoisomerase I and II, has shown outstanding antitumor activity in vivo against a panel of experimental human tumor xenografts. The aim of this study was to evaluate its cytotoxicity against fresh tumor cells taken from patients. Cells derived from bone marrow, peripheral blood, malignant effusions or solid biopsies from 84 patients with either hematological or solid tumors were exposed continuously to 0.8-100 nuM tafluposide for 48 h, 96 h or 7 days. Cell survival was measured using an MTT assay or the ATP assay and LC(50) values (drug concentration required for 50% cell kill) were calculated. Tafluposide showed significant cytotoxicity against cells derived from either hematological or solid tumors, with a marked inter-patient variation. There was no significant difference between the effect of tafluposide in samples from untreated or previously treated patients (p>0.05 for all cancer types). Whilst tafluposide appeared to show weak (p<0.05) cross-resistance with the topoisomerase II inhibitor etoposide in acute myeloid leukemia (AML), there did not appear to be any correlation with the effect of the topoisomerase I inhibitor topotecan (p>0.05) in either hematological or solid malignancies. True synergism was identified when combining tafluposide with cisplatin in ovarian cancer [combination index (CI)=0.14, 0.79] and with etoposide in AML (CI=0.49, 0.63 and 0.78). Our results suggest that tafluposide is a strong candidate for inclusion in clinical trials, particularly in hematological malignancies.     

Exploring old drugs for the treatment of hematological malignancies

Drug discovery is costly and time-consuming, but it will become easier and simpler if a drug could be developed from an old one with well-documented investigations associated with pharmacology, pharmacokinetics, toxicology and clinical safety. In terms of hematological malignancies, several successful drugs have been discovered and developed from old ones such as arsenic trioxide for acute promyelocytic leukemia and thalidomide for multiple myeloma. In this review, we discussed the latest advancement in exploring old drugs for the treatment of hematological malignancies.     

Antiproliferative activity of an aqueous mistletoe extract in human tumor cell lines and xenografts in vitro

The in vitro antiproliferative activity of an aqueous mistletoe extract (AME) with a defined content of bioactive mistletoe lectin (ML) was tested in 25 human tumor cell lines, including 20 solid and 5 hematological malignancies and 47 human tumor xenografts. The antiproliferative activity of AME was compared to that of the standard cytotoxic agent doxorubicin (CAS 23214-92-8, adriamycin, ADR) using the sulforhodamin B, propidium iodide and soft agar colony forming assays, respectively. AME was highly cytotoxic in solid human tumors with mean IC70 values in the range of 0.17-1 ng ML/ml (2.8-17 pmol bioactive ML). On a molar basis, AME was 3 to 4 logs more potent than ADR and showed differential cytotoxicity towards tumors of the breast, small cell and non-small cell lung, prostate and renal cell cancers. AME was also highly active in hematological malignancies with steep dose response curves resulting in mean IC70 values of 0.12 ng ML/ml (2 pmol). The acute lymphoblastic leukemia cell line HL-60 was the most sensitive, the histiocytic lymphoma cell line U937 the most resistant hematological malignancy. It is important to stress that AME did not induce a biologically relevant increase of cell proliferation in any of the tumor cell lines tested. Our data suggest that AME has in vitro antitumor profiles similar to those of classical anticancer agents. Clear dose-response relationships were found in all of the performed experiments and interesting differential cytotoxicity patterns were observed. Experiments with sensitive tumor types identified in these in vitro studies are currently ongoing in order to demonstrate the anticancer activity of AME in different animal tumor models.     

恶性血液病患者血清Tpo水平与血小板关系的研究

目的探讨恶性血液病患者血清Tpo水平与血小板数量的关系及其临床意义。方法夹心酶联免疫法测定 4 0例恶性血液病人血清Tpo水平 ,同时用自动血细胞分析仪测定其血小板数。结果急慢性白血病病人血清Tpo水平均显著高于正常 (P <0 0 1) ,其它恶性血液病的水平低于正常(P <0 0 0 1) ;急性白血病及其它恶性血液病的PLT低于正常 (P <0 0 0 1) ,其Tpo水平与PLT数呈负相关 (r=- 0 .78,r =- 0 .6 2 ,P均 <0 0 0 5 ) ,慢性白血病组Tpo与血小板数不相关 (r=- 0 .2 3,P >0 0 5 )。结论恶性血液病人Tpo与PLT的关系呈异质性。除白血病外 ,其它恶性血液病人当血小板减少时 ,应用重组人Tpo治疗可能是有益的     

Targeted inhibition of human hematological cancers in vivo by doxorubicin encapsulated in smart lipoic acid-crosslinked hyaluronic acid nanoparticles

The chemotherapy of hematological cancers is challenged by its poor selectivity that leads to low therapeutic efficacy and pronounced adverse effects. Here, we report that doxorubicin encapsulated in lipoic acid-crosslinked hyaluronic acid nanoparticles (LACHA-DOX) mediate highly efficacious and targeted inhibition of human hematological cancers including LP-1 human multiple myeloma (MM) and AML-2 human acute myeloid leukemia xenografted in nude mice. LACHA-DOX had a size of ca. 183?nm and a DOX loading content of ca. 12.0?wt.%. MTT and flow cytometry assays showed that LACHA-DOX possessed a high targetability and antitumor activity toward CD44 receptor overexpressing LP-1 human MM cells and AML-2 human acute myeloid leukemia cells. The in vivo and ex vivo images revealed that LACHA-DOX achieved a significantly enhanced accumulation in LP-1 and AML-2 tumor xenografts. Notably, LACHA-DOX effectively suppressed LP-1 as well as AML-2 tumor growth and drastically increased mice survival rate as compared to control groups receiving free DOX or PBS. Histological analyses exhibited that LACHA-DOX caused little damage to the major organs like liver and heart. This study provides a proof-of-concept that lipoic acid-crosslinked hyaluronic acid nanoparticulate drugs may offer a more safe and effective treatment modality for CD44 positive hematological malignancies.     

Second generation proteasome inhibitors: carfilzomib and immunoproteasome-specific inhibitors (IPSIs)

The ubiquitin-proteasome pathway (UPP) is an attractive chemotherapeutic target due to its intrinsically stringent regulation of cell cycle, pro-survival, and anti-apoptotic regulators that disproportionately favor survival and proliferation in malignant cells. A reversible first-in-class proteasome inhibitor, bortezomib, is Food and Drug Administration approved for multiple myeloma and relapsed/refractory mantle cell lymphoma and has proven to be extremely effective, both as a single agent and in combination. An irreversible second generation proteasome inhibitor, carfilzomib, has shown preclinical effectiveness against hematological and solid malignancies both in vitro and in vivo. Carfilzomib, a peptidyl-epoxyketone functions similarly to bortezomib through primary inhibition of chymotrypsin-like (ChT-L) activity at the b5 subunits of the core 20S proteasome. Carfilzomib is also currently achieving successful response rates within the clinical setting. In addition to conventional proteasome inhibitors, a novel approach may be to specifically target the hematological-specific immunoproteasome, thereby increasing overall effectiveness and reducing negative off-target effects. The immunoproteasome-specific inhibitor, IPSI-001, was shown to have inhibitory preference over the constitutive proteasome, and display enhanced efficiency of apoptotic induction of tumor cells from a hematologic origin. Herein, we discuss the preclinical and clinical development of carfilzomib and explore the potential of immunoproteasome-specific inhibitors, like IPSI-001, as a rational approach to exclusively target hematological malignancies.     

Activity of CHS 828 in primary cultures of human hematological and solid tumors in vitro.

CHS 828 is a pyridyl cyanoguanidine that has shown promising preclinical anticancer activity against various experimental tumor models and is presently being tested in a phase II trial in man. In the present study the fluorometric microculture cytotoxicity assay was used for in vitro evaluation of CHS 828 activity in primary cell cultures from hematological and solid tumors. In total, 156 samples from various diagnoses were tested with 72-h continuous drug exposure. CHS 828 showed high relative in vitro activity against tumor cells from chronic lymphocytic leukemia as well as from acute leukemia and high-grade lymphoma. Activity was also observed in several solid tumor cell samples, although the group as a whole appeared less responsive. CHS 828 was significantly more active against hematological malignancies compared to normal lymphocytes. Correlation analysis with standard drugs revealed low to moderate correlation coefficients. The results show that CHS 828 has potent antitumor activity against primary cultures of human tumor cells from patients and might have a unique mechanism of action.     

Monoclonal antibodies in the management of solid tumors

Thorough understanding of the complex interactions between components of immunological response has led to the arousal of the concept of immune-mediated anti-cancer therapy. Although, the use of monoclonal antibodies (MAbs) in hematological malignancies met with success, therapy of solid tumors has been impeded by many obstacles. Some MAbs have increased the efficacy of treatment of certain tumors with acceptable adverse events. Trastuzumab, cetuximab and bevacizumab have become FDA approved for the treatment of breast and colorectal cancer, respectively. The dosing strategies, timing and schedule of antibody administration, duration of treatment are yet to be determined under specific circumstances. Combinations with other biologic agents, such as small-molecule inhibitors of the same pathway would be really useful. Multimodality approaches are based on synergistic effects observed with the combination of antibodies with chemotherapeutic drugs and/or radiotherapy. Immune-mediated effects may be further exploited with the use of bivalent (bispecific) molecules, while radioimmunotherapy via radiolabelling of the antibody is feasible. Modified recombinant antibodies could be applied for toxin delivery to tumor cells, while molecules fused with drug-activating enzymes can mediate prodrug therapy. Increased penetrability into tumors can also be achieved with novel antibody fragments. In the future, better selection of patient subpopulations with tumors overexpressing disease-related clinical biomarkers could result in an increase in both efficacy and specificity of antibody-based treatment.     

Emerging drugs for acute graft-versus-host disease

The number of allogeneic hematopoietic cell transplantations (HCT) continues to increase. More than 15,000 allogeneic transplantations are performed annually. The graft-versus-leukemia/tumor effect during allogeneic HCT effectively eradicates many hematological malignancies. The development of novel strategies that use donor leukocyte infusions, nonmyeloablative conditioning and umbilical cord blood transplantation have helped expand the indications for allogeneic HCT over the past several years, especially among older patients. Yet the major complication of allogeneic HCT, graft-versus-host disease, remains lethal and limits wider application of allogeneic HCT. In this article, we review current practice and recent advances made in prevention and treatment of graft-versus-host disease.     

Discovery of an orally bioavailable small molecule inhibitor of prosurvival B-cell lymphoma 2 proteins

Overexpression of prosurvival proteins such as Bcl-2 and Bcl-X L has been correlated with tumorigenesis and resistance to chemotherapy, and thus, the development of antagonists of these proteins may provide a novel means for the treatment of cancer. We recently described the discovery of 1 (ABT-737), which binds Bcl-2, Bcl-X L, and Bcl-w with high affinity, shows robust antitumor activity in murine tumor xenograft models, but is not orally bioavailable. Herein, we report that targeted modifications at three key positions of 1 resulted in a 20-fold improvement in the pharmacokinetic/pharmacodynamic relationship (PK/PD) between oral exposure (AUC) and in vitro efficacy in human tumor cell lines (EC 50). The resulting compound, 2 (ABT-263), is orally efficacious in an established xenograft model of human small cell lung cancer, inducing complete tumor regressions in all animals. Compound 2 is currently in multiple phase 1 clinical trials in patients with small cell lung cancer and hematological malignancies.     

Immunotherapeutic and immunoregulatory drugs in haematologic malignancies

A better understanding of the biology and pathogenesis of hematological malignancies has led to the development of immunotherapeutic and immunoregulatory drugs. Many of these agents have revolutionized the current treatment modalities, while others are under investigation. Rituximab (anti-CD20 antibody) has been established as the gold standard of treatment for aggressive B-cell lymphomas in combination with CHOP and has shown significant activity as monotherapy in the treatment of indolent B-cell lymphomas. In follicular lymphomas the combination of Rituximab with chemotherapy improves the outcome compared to chemotherapy alone. CD 20-based radioimmunotherapy, with the advantage of the bystander effect, represents an additional therapeutic alternative in B-cell lymphomas and may produce tumor regression in Rituximab resistant patients. The anti-CD52 monoclonal antibody, alemtuzumab, further expands the armamentarium against lymphoid malignancies producing high response rates in these entities. Antibody-targeted chemotherapy such as gemtuzumab ozogamicin, consisting of an anti-CD33 antibody combined to calicheamicin, has shown efficacy in the treatment of refractory acute myeloid leukemia; exact indications, timing and dosing schedule for optimized efficacy remain to be determined. Interferons have proven significant activity in cutaneous lymphomas, hairy cell leukemia and chronic myelogenous leukemia by mechanisms that are not fully elucidated. Thalidomide, by acting as an immunomodulatory and antiangiogenic agent can modulate neoplastic cells microenvironment and lead to disease control in multiple myeloma as well as in numerous other hematological malignancies. Bortezomib, a proteasome inhibitor, displays significant anti-tumor activity, especially in multiple myeloma and lymphoproliferative disorders. The addition of these agents in therapeutic regimens has improved considerably the treatment of hematological malignancies.     

CD70 as a therapeutic target in human malignancies

Background: Expression of CD70, a member of the tumor necrosis factor superfamily, is restricted to activated T and B lymphocytes and mature dendritic cells. CD70 has also been detected on hematological tumors and on carcinomas. The restricted expression pattern of CD70 in normal tissues and its widespread expression in various malignancies makes it an attractive target for antibody-based therapeutics. Investigations to exploit CD70 as a cancer target have lead to the identification of potential antibody-based clinical candidates. Anti-CD70 antibodies for therapeutic use have been developed and used to validate CD70 as a target for cancers. Antibodies are also used as a vehicle to deliver potent cytotoxic drugs to target CD70⁺malignant cells. Both unconjugated antibodies and antibody–drug conjugates targeting CD70 have been tested in animal models of human cancers. Objective: To describe the expression of CD70 in cancer cells and the development of antiboy-based therapies against CD70. Methods: A review of the available literature. Results/conclusions: Humanized anti-CD70 antibodies have shown significant antitumor activity in preclinical xenograft models of cancer. Additionally, anti-CD70 antibody-drug conjugates exhibit potent antitumor activity in solid tumor xenograft models, confirming increased therapeutic efficacy through cytotoxic drug delivery. Thus, preclinical animal models have provided strong evidence that targeting CD70 either with unconjugated antibodies or with antibody-drug conjugates represents a promising approach to treat human malignancies.     

New frontiers in cell-based immunotherapy of cancer

Background: Cancer remains one of the leading causes of death. Over the past decade, discovery of tumor antigens, as well as new findings in basic immunology, have led to novel opportunities for developing active immunotherapeutical approaches for prevention and treatment of cancer. Objective/methods: This is a review of the literature and patents on the therapeutic potential of immune-based cell cancer therapies. Results/conclusion: In this article, we discuss the different approaches at present used for immune-based cell cancer therapies, and the results obtained both in preclinical models and in clinical trials of hematological malignancies and solid tumors.     

PD-1/PD-L1抑制剂治疗血液恶性肿瘤综述

目的：程序性死亡受体-1（programmed death-1,PD-1）及其配体（programmed death-ligand 1,PD-L1）作为肿瘤免疫治疗的有效靶点之一,其抑制剂为血液恶性肿瘤的治愈带来了新的希望。本文旨在综述近年来PD-1/PD-L1抑制剂在血液恶性肿瘤,包括恶性淋巴瘤、白血病及多发性骨髓瘤（MM）方面的临床研究进展,并总结其对于血液恶性肿瘤的治疗效果。方法：在PubMed、Medline、The Cochrane Library、Embase、Elsevier、John Wiley等外文数据库及中国知网（CNKI）、万方、维普等中文数据库进行文献检索。结果：PD-1/PD-L1抑制剂多应用于恶性淋巴瘤的治疗,在各类白血病及MM的研究尚处于探索研究阶段。不同疾病获得的疗效存在差异,但整体较好,尤其是复发/难治经典霍奇金淋巴瘤（R/R cHL）。结论：PD-1/PD-L1抑制剂可显著提高缓解率,但仍有诸多争议有待进一步解决。     

Angiogenesis and hemostasis in hematological neoplasias

Angiogenesis is essential for tumor growth and metastasis. This is firmly established in solid tumors, but accumulating evidence suggests that this is also an important event in hematological neoplasias. Angiogenesis is therefore a putative target for therapy. The potential application of different angiogenesis inhibitors is currently under intense clinical investigation, and we will here review a number of these trials. The association between cancer and thromboembolic disease is even better documented, and again, this is not limited to solid tumors. It appears that many patients with hematological malignancies have a dysfunctional hemostatic system, with increased risk of thromboembolism. Furthermore, effective antithrombotic therapy seems to reduce the risk of cancer progression and even prolongs overall survival. In this review we will thus discuss the mechanisms involved in the regulation of angiogenesis and hemostasis and present evidence for a shared biology. A number of factors regulating the hemostatic system also have pro- or anti-angiogenic properties. Tissue factor (TF) and TF pathway inhibitor (TFPI) seem to play a central role, and there are several lines of evidence suggesting a close cooperation between TF/TFPI and pro-angiogenic factors like members of the vascular endothelial growth factor family. A better understanding of this shared biology may reveal new targets, and will probably increase the safety of targeting the blood supply.