Primary targeting of recombinant Fv-immunotoxin hscFv25-mTNFα against hepatocellular carcinoma

AIM: To obtain human recombinant Fv-immunotoxin hscFv25-mTNFα (mutant human TNFαfused to human scFv25) against hepatocellular carcinoma (HCC).METHODS: Two relevant sites of enzymatic digestion were added to mTNFα by PCR. mTNFα was linked to the 3‘ end of hscFv25 in pGEX4T-1 vector. This anti-HCC recombinant Fv-immunotoxin hscFv25-mTNFα was expressed in Escherichia coliand purified from inclusions. After purified by glutathione-S-transferase affinity chromatography and thrombin digestion, it was identified by electrophoresis and Western blot. And then, the purified recombinant Fvimmunotoxin was injected into nude mice with HCC xenografts through their tail veins, mTNFα protein and PBS were used as control at the same time. After treated for two weeks, nude mice were executed. The bulk and weight of tumors were observed. The tumor tissues were stained by immunohistochemical method with TNFα antibody.RESULTS: The expression ratio of recombinant Fv-immunotoxin hscFv25-mTNFα was 12% of bacterial protein. The result of tumor restraining trials of hscFv25-mTNFα showed 2/5 complete remission and 3/5 partial remission, mTNFα restraining trials showed 5/5 partial remission. The therapeutic result of hscFv25-mTNFα was better than that of mTNFα (F=8.70, P<O.05). The hscFv25-mTNFα remedial tumor tissues were positive for TNFα by immunohistochemical staining. The positive granules mainly existed in the cytoplasm of tumor cell.CONCLUSION: Recombinant Fv-immunotoxin hscFv25-mTNFα has better therapeutic effect than mTNFα. It can inhibit the cellular growth of HCC and has some potential of clinical application.     

抗肝癌单链免疫毒素的构建、表达及导向研究

目的 制备高效、低毒的抗肝癌单链免疫毒素。 方法 将人突变型肿瘤坏死因子α(mTNF α)与人源化抗肝癌单链抗体hscFv25基因连接,构建pGEx4T-1/hscFv25-mTNF α融合蛋白原核表达载体,在大肠杆菌中表达并纯化目的蛋白,经western blot鉴定之后,进行荷肝癌(SMMC-7721)裸鼠体内初步抑瘤实验,并对治疗后裸鼠肿瘤组织进行抗TNF α的免疫组织化学染色。 结果 原核表达载体pGEX4T-1/hscFv25 mTNF α融合蛋白的表达量占细菌总蛋白的12％,hscFv25-mTNFα治疗组对荷肝癌裸鼠的有效率为5/5,其中2/5为完全缓解,3/5为部分缓解,疗效明显高于mTNFα对照组(F=8.70,P<0.05),治疗组裸鼠的肝、肺等组织中未见转移性病灶,经hscFv25-mTNFα治疗后的肿瘤组织,呈TNFα弥漫阳性反应,阳性颗粒主要位于瘤细胞的胞质中。 结论 hscFv25-mTNFα是高效、低毒的抗肝癌单链免疫毒素。     

Enhancement of the antitumor properties of interleukin-2 by its targeted delivery to the tumor blood vessel extracellular matrix

Angiogenic processes depend on the precise coordination of different cell types and a complex exchange of signals, many of which derive from new specific components of the provisional, angiogenesis-related, extracellular matrix (ECM). Angiogenesis-associated ECM components thus represent appealing targets for the selective delivery of therapeutic molecules to newly forming tumor vessels. Results of a previous study indicated that a high affinity recombinant antibody (L19) to ED-B, a domain contained in the angiogenesis-associated isoform of fibronectin (B-FN), selectively and efficiently targets tumor vessels. The present study shows that a fusion protein between L19 and interleukin 2 (L19-IL-2) mediates the selective delivery and concentration of IL-2 to tumor vasculature, thereby leading to a dramatic enhancement of the therapeutic properties of the cytokine. By contrast, IL-2 fused to an irrelevant recombinant antibody used as a control fusion protein showed neither accumulation in tumors nor therapeutic efficacy. Tumors in mice treated with L19-IL-2 were significantly smaller compared to those in animals treated with saline, the control fusion protein, or IL-2 alone (P =.003,.003, and.002, respectively). Moreover, no significant differences in size were observed among the tumors from the different control groups (using the control fusion protein, a mixture of IL-2 and L19, or saline alone). Immunohistochemical analysis of tumor infiltrates demonstrated a significantly higher number of T lymphocytes, natural killer cells, and macrophages, as well as increased interferon-gamma (IFN-gamma) accumulation, in tumors from animals treated with L19-IL-2 compared to tumors from control groups. The fact that ED-B is 100% homologous in human and mouse, thus ensuring that L19 reacts equally well with human and murine antigen, should ultimately expedite transfer of this reagent to clinical trials.     

Human microtubule‐associated protein tau mediates targeted killing of CD30+ lymphoma cells in vitro and inhibits tumour growth in vivo

Hodgkin lymphoma (HL) and systemic anaplastic large cell lymphoma (sALCL) are rare lymphoproliferative cancer types. Although most HL patients can be cured by chemo‐ and radio‐therapy, 4–50% of patients relapse and have a poor prognosis. The need for improved therapeutic options for patients with relapsed or refractory disease has been addressed by CD30‐specific antibody‐based immunotherapeutics. However, available CD30‐specific monoclonal antibodies (mAbs), antibody drug conjugates (ADCs) or chimeric immunotoxins suffer from the requirement of a functional host immunity, undesirable immune reactions or heterogeneity and instability, respectively. Here, we present a new fusion protein comprised of the CD30‐specific antibody single‐chain fragment Ki4(scFv) and the human pro‐apoptotic effector protein, microtubule‐associated protein tau (MAPT). Ki4(scFv)‐MAP selectively induced apoptosis in rapidly proliferating L540cy, L428, and Karpas 299 cells in a dose‐dependent manner. Tubulin polymerization assays confirmed that Ki4(scFv)‐MAP stabilizes microtubules, suggesting a mechanism for its pro‐apoptotic action. Dose‐finding experiments proved that Ki4(scFv)‐MAP is well tolerated in mice compared to the previously reported Ki4(scFv)‐ETA'. Ki4(scFv)‐MAP significantly inhibited growth of subcutaneous L540cy xenograft tumours in mice. Our data present a novel approach for the treatment of CD30⁺ lymphomas, combining the binding specificity of a target‐specific antibody fragment with the selective cytotoxicity of MAPT towards proliferating lymphoma cells.     

Synthesis of site-specific antibody-drug conjugates using unnatural amino acids

Antibody-drug conjugates (ADCs) allow selective targeting of cytotoxic drugs to cancer cells presenting tumor-associated surface markers, thereby minimizing systemic toxicity. Traditionally, the drug is conjugated nonselectively to cysteine or lysine residues in the antibody. However, these strategies often lead to heterogeneous products, which make optimization of the biological, physical, and pharmacological properties of an ADC challenging. Here we demonstrate the use of genetically encoded unnatural amino acids with orthogonal chemical reactivity to synthesize homogeneous ADCs with precise control of conjugation site and stoichiometry. p-Acetylphenylalanine was site-specifically incorporated into an anti-Her2 antibody Fab fragment and full-length IgG in Escherichia coli and mammalian cells, respectively. The mutant protein was selectively and efficiently conjugated to an auristatin derivative through a stable oxime linkage. The resulting conjugates demonstrated excellent pharmacokinetics, potent in vitro cytotoxic activity against Her2⁺ cancer cells, and complete tumor regression in rodent xenograft treatment models. The synthesis and characterization of homogeneous ADCs with medicinal chemistry-like control over macromolecular structure should facilitate the optimization of ADCs for a host of therapeutic uses.     

A high-affinity human antibody that targets tumoral blood vessels.

Angiogenesis is a characteristic feature of many aggressive tumors and of other relevant disorders. Molecules capable of specifically binding to new-forming blood vessels, but not to mature vessels, could be used as selective vehicles and would, therefore, open diagnostic and therapeutic opportunities. We have studied the distribution of the ED-B oncofetal domain of fibronectin, a marker of angiogenesis, in four different tumor animal models: the F9 murine teratocarcinoma, SKMEL-28 human melanoma, N592 human small cell lung carcinoma, and C51 human colon carcinoma. In all of these experimental models we observed accumulation of the fibronectin isoform containing the ED-B domain around neovascular structures when the tumors were in the exponentially growing phase, but not in the slow-growing phase. Then we performed biodistribution studies in mice bearing a subcutaneously implanted F9 murine teratocarcinoma, using a high-affinity human antibody fragment (L19) directed against the ED-B domain of fibronectin. Radiolabeled L19, but not an irrelevant anti-lysozyme antibody fragment (D1.3), efficiently localizes in the tumoral vessels. The maximal dose of L19 accumulated in the tumor was observed 3 hours after injection (8.2% injected dose per gram). By virtue of the rapid clearance of the antibody fragment from the circulation, tumor-to-blood ratios of 1.9, 3.7, and 11.8 were obtained at 3, 5, and 24 hours, respectively. The tumor-targeting performance of L19 was not dose-dependent in the 0.7 to 10 microg range of injected antibody. The integral of the radioactivity localized in tumoral vessels over 24 hours was greater than 70-fold higher than the integral of the radioactivity in blood over the same time period, normalized per gram of tissue or fluid. These findings quantitatively show that new-forming blood vessels can selectively be targeted in vivo using specific antibodies, and suggest that L19 may be of clinical utility for the immunoscintigraphic detection of angiogenesis in patients.     

High efficient mammalian expression and secretion of a functional humanized single-chain Fv/human interleukin-2 molecules

AIM: To construct and produce a recombinant bispecific humanized single-chain Fv (sFv) /Interleukin-2 (IL-2) fusion protein by using mammalian cells. METHODS: The sFv/IL-2 protein was genetically engineered, and transfected to mammalian cells to determine whether the mammalian protein folding machinery can produce and secrete active sFv/IL-2 with high efficiency. RESULTS: The fusion protein was constructed and high efficiently expressed with yields up to 102±4.2 mg/L in culture supernatant of the stably transfected 293 cell line. This recombinant fusion protein consisted of humanized variable heavy (Vh) and light (Vl) domains of monoclonal antibody (mAb) 520C9 directed against the human HER-2/neu (c-erbB2) proto-oncogene product pl85, and human IL-2 connected by polypeptide linker. The fusion protein was shown to retain the immunostimulatory activities of IL-2 as measured by IL-2-dependent cell proliferation and cytotoxicity assays. In addition to its IL-2 activities, this fusion protein also possessed antigen-binding specificity against pl85, as determined by indirect ELISA using pl85 positive SKOV 3ipl cells. CONCLUSION: The large-scale preparation of the recombinant humanized sFv antibody/IL-2 fusion protein is performed with 293 cells. The recombinant humanized sFv antibody/IL-2 fusion protein may provide an effective means of targeting therapeutic doses of IL-2 to p185 positive tumors without increasing systemic toxicity or immunogenicity.     

Antitumor necrosis factor therapy for inflammatory bowel disease: a review of agents, pharmacology, clinical results, and safety.

Tumor necrosis factor-alpha (TNFalpha), a proinflammatory cytokine, plays an important role in the pathogenesis of inflammatory bowel disease (IBD). Biotechnology agents including a chimeric monoclonal anti-TNF antibody (infliximab), a humanized monoclonal anti-TNF antibody (CDP571), and a recombinant TNF receptor fusion protein (etanercept) have been used to inhibit TNFalpha activity. Controlled trials have demonstrated efficacy for infliximab in moderately to severely active Crohn's disease (CD) and fistulizing CD sufficient to justify recent U.S. Food and Drug Administration (FDA) approval. Additional trials have been completed in rheumatoid arthritis (RA). Similarly, preliminary controlled trials have suggested efficacy for CDP571 in active CD and RA. Larger controlled trials have demonstrated efficacy for etanercept in RA patients who have failed disease modifying antirheumatic drug (DMARD) therapy leading to FDA approval for RA. Toxicities observed with anti-TNF therapies have included formation of human antichimeric antibodies (HACA) with associated acute and delayed hypersensitivity infusion reactions, human antihuman antibodies (HAHAs), and formation of autoantibodies with rare instances of drug-induced lupus. Several cases of non-Hodgkin's lymphoma also has been described. Future studies should evaluate optimal timing and duration of anti-TNF therapy, the utility of adjuvant medical treatments during anti-TNF therapy, and evaluate long-term safety and efficacy of the various anti-TNF agents.     

抗肝癌人源化单链抗体融合肿瘤坏死因子a的导向作用

目的 获得有临床应用潜力的人源化抗肝癌基因工程双功能抗体。方法 将鼠源性抗肝癌单克隆抗体HAb25的人源化单链抗体（hscFv25）基因与人TNF（基因偶连构建抗肝癌双功能抗体（hscFv25-TNF a）,亚克隆入原核GST融合表达载体pGEX 4T-1中,在大肠杆菌中进行表达并纯化目的蛋白。对肝癌SMMC-7721细胞涂片进行间接免疫荧光染色测定纯化后的基因重组双功能抗体蛋白活性。MTT实验测定hscFv25-TNF a对靶细胞SMMC-7721杀伤活性。荷肝癌（SMMC-7721）裸鼠体内的初步抑瘤实验检测hscFv25-TNF a的导向治疗效果。结果 hscFv25-TNF a具有与亲本抗体HAb25相同的抗原结合特异性。1h预处理的MTT实验显示,hscFv25-TNF a对靶细胞SMMC-7721具有明确的杀伤作用,其IC50值为7.1mg/L。且该杀伤作用可被亲本抗体HAb25所封闭,表明hscFv25-TNF a对靶细胞的杀伤作用是抗体hscFv25介导的选择性杀伤作用。hscFv25-TNF a对荷肝癌裸鼠体内直径3.0mm左右的肿瘤具有明确的导向杀伤作用,有效率达到3/3,1/3完全缓解,强于TNF a对照组,该组有效者只有2/3,同时无完全缓解。结论 hscFv25-TNF a是具有一定临床应用潜力的抗肝癌双功能抗体。     

Boosting antibody therapy with complement

In this issue of Blood, Elvington et al present a method to enhance complement activation during antibody therapy of cancer. Using a fusion protein of a complement receptor and an IgG Fc fragment, therapeutic outcome was improved in vivo.     

Antibody-enzyme fusion proteins for cancer therapy

Advances in biomolecular technology have allowed the development of genetically fused antibody-enzymes. Antibody-enzyme fusion proteins have been used to target tumors for cancer therapy in two ways. In one system, an antibody-enzyme is pretargeted to the tumor followed by administration of an inactive prodrug that is converted to its active form by the pretargeted enzyme. This system has been described as antibody-directed enzyme prodrug therapy. The other system uses antibody-enzyme fusion proteins as direct therapeutics, where the enzyme is toxic in its own right. The key feature in this approach is that the antibody is used to internalize the toxic enzyme into the tumor cell, which activates cell-death processes. This antibody-enzyme system has been largely applied to deliver ribonucleases. This article addresses these two antibody-enzyme targeting strategies for cancer therapy from concept to (pre)clinical trials.     

Update on gene therapy approaches for cancer

The goal of cancer gene therapy is the selective and efficient eradication of tumor cells without significant systemic toxicity. Although several different gene therapy approaches have been developed and tested both in preclinical and clinical trials, none of these methods are suitable for the safe and efficient treatment of cancer. Recent advances in tumor cell biology have accelerated the identification of novel proteins as targets for gene transfer strategies. However, the development of vectors and delivery systems for specific and efficient gene therapy has not kept pace with these discoveries. Below, we describe the most widely used gene therapy approaches and discuss the caveats of using these techniques in the clinic.     

CD7-restricted activation of Fas-mediated apoptosis: a novel therapeutic approach for acute T-cell leukemia

Agonistic anti-Fas antibodies and multimeric recombinant Fas ligand (FasL) preparations show high tumoricidal activity against leukemic cells, but are unsuitable for clinical application due to unacceptable systemic toxicity. Consequently, new antileukemia strategies based on Fas activation have to meet the criterion of strictly localized action at the tumor-cell surface. Recent insight into the FasL/Fas system has revealed that soluble homotrimeric FasL (sFasL) is in fact nontoxic to normal cells, but also lacks tumoricidal activity. We report on a novel fusion protein, designated scFvCD7:sFasL, that is designed to have leukemia-restricted activity. ScFvCD7:sFasL consists of sFasL genetically linked to a high-affinity single-chain fragment of variable regions (scFv) antibody fragment specific for the T-cell leukemia-associated antigen CD7. Soluble homotrimeric scFvCD7:sFasL is inactive and acquires tumoricidal activity only after specific binding to tumor cell-surface-expressed CD7. Treatment of T-cell acute lymphoblastic leukemia (T-ALL) cell lines and patient-derived T-ALL, peripheral T-cell lymphoma (PTCL), and CD7-positive acute myeloid leukemia (AML) cells with homotrimeric scFvCD7:sFasL revealed potent CD7-restricted induction of apoptosis that was augmented by conventional drugs, farnesyl transferase inhibitor L-744832, and the proteasome inhibitor bortezomib (Velcade; Millenium, Cambridge, MA). Importantly, identical treatment did not affect normal human peripheral-blood lymphocytes (PBLs) and endothelial cells, with only moderate apoptosis in interleukin-2 (IL-2)/CD3-activated T cells. CD7-restricted activation of Fas in T-cell leukemic cells by scFvCD7:sFasL revitalizes interest in the applicability of Fas signaling in leukemia therapy.     

Discovery of an orally active small-molecule irreversible inhibitor of protein disulfide isomerase for ovarian cancer treatment

Protein disulfide isomerase (PDI), an endoplasmic reticulum chaperone protein, catalyzes disulfide bond breakage, formation, and rearrangement. The effect of PDI inhibition on ovarian cancer progression is not yet clear, and there is a need for potent, selective, and safe small-molecule inhibitors of PDI. Here, we report a class of propynoic acid carbamoyl methyl amides (PACMAs) that are active against a panel of human ovarian cancer cell lines. Using fluorescent derivatives, 2D gel electrophoresis, and MS, we established that PACMA 31, one of the most active analogs, acts as an irreversible small-molecule inhibitor of PDI, forming a covalent bond with the active site cysteines of PDI. We also showed that PDI activity is essential for the survival and proliferation of human ovarian cancer cells. In vivo, PACMA 31 showed tumor targeting ability and significantly suppressed ovarian tumor growth without causing toxicity to normal tissues. These irreversible small-molecule PDI inhibitors represent an important approach for the development of targeted anticancer agents for ovarian cancer therapy, and they can also serve as useful probes for investigating the biology of PDI-implicated pathways.     

Cloning of α-β fusion gene from Clostridium perfringens and its expression

AIM: To study the cloning of alpha-beta fusion gene from Clostridium perfringens and the immunogenicity of alpha-beta fusion expression. METHODS: Cloning was accomplished after PCR amplification from strains NCTC64609 and C58-1 of the protective antigen genes of alpha-toxin and beta-toxin. The fragment of the gene was cloned using plasmid pZCPAB. This fragment coded for the gene with the stable expression of alpha-beta fusion gene binding. In order to verify the exact location of the alpha-beta fusion gene, domain plasmids were constructed. The two genes were fused into expression vector pBV221. The expressed alpha-beta fusion protein was identified by ELISA, SDS-PAGE, Western blotting and neutralization assay. RESULTS: The protective alpha-toxin gene (cpa906) and the beta-toxin gene (cpb930) were obtained. The recombinant plasmid pZCPAB carrying alpha-beta fusion gene was constructed and transformed into BL21(DE3). The recombinant strain BL21(DE3)(pZCPAB) was obtained. After the recombinant strain BL21(DE3)(pZCPAB) was induced by 42 degC, its expressed product was about 22.14% of total cellular protein at SDS-PAGE and thin-layer gel scanning analysis. Neutralization assay indicated that the antibody induced by immunization with alpha-beta fusion protein could neutralize the toxicity of alpha-toxin and beta-toxin. CONCLUSION: The obtained alpha-toxin and beta-toxin genes are correct. The recombinant strain BL21(DE3)(pZCPAB) could produce alpha-beta fusion protein. This protein can be used for immunization and is immunogenic. The antibody induced by immunization with alpha-beta fusion protein could neutralize the toxicity of alpha-toxin and beta-toxin.     

Phase I/II study of the tumour-targeting human monoclonal antibody–cytokine fusion protein L19-TNF in patients with advanced solid tumours

Purpose

L19-TNF is an armed antibody that selectively targets human TNF to extra domain B-fibronectin on tumour blood vessels. We performed a phase I/II first-in-man trial with L19-TNF monotherapy in metastatic solid cancer patients to study safety and signs of clinical activity.

Methods

Six cohorts of patients were treated with increasing (1.3–13 μg/kg) doses of intravenous L19-TNF on day 1, 3, and 5 of repeated 3-weekly cycles, and 12 colorectal cancer patients were treated at 13 μg/kg. PK, antibody formation, changes in lymphocyte subsets, 5-HIAA plasma levels as well as safety and clinical activity were analysed.

Results

Thirty-four patients received at least one L19-TNF dose. The serum half-life of L19-TNF at 13 μg/kg was 33.6 min, and maximum peak serum concentration was 73.14 μg/L. Mild chills, nausea and vomiting but no haemato- or unexpected toxicity were observed. Grade 3 lumbar pain in bone metastasis was the only dose-limiting toxicity found in one patient. Objective tumour responses were not detected. Transient stable disease occurred in 19 of 31 evaluable patients.

Conclusions

Intravenous L19-TNF on day 1, 3, and 5 of a 3-weekly schedule was safe up to 13 μg/kg, but did not result in objective tumour responses. The maximally tolerated dose (MTD) was not reached, allowing for further dose escalation of L19-TNF possibly in combination with chemotherapy.     

Monoclonal antibody-superantigen fusion proteins: tumor-specific agents for T-cell-based tumor therapy.

The bacterial superantigen staphylococcal enterotoxin A (SEA) is an extremely potent activator of T lymphocytes when presented on major histocompatibility complex (MHC) class II molecules. To develop a tumor-specific superantigen for cancer therapy, we have made a recombinant fusion protein of SEA and the Fab region of the C215 monoclonal antibody specific for human colon carcinoma cells. SEA as part of a fusion protein showed a > 10-fold reduction in MHC class II binding compared to native SEA, and accordingly, the affinity of the FabC215-SEA fusion protein for the C215 tumor antigen was approximately 100-fold stronger than to MHC class II molecules. The FabC215-SEA fusion protein efficiently targeted T cells to lyse C215+ MHC class II- human colon carcinoma cells, which demonstrates functional substitution of the MHC class II-dependent presentation of SEA with tumor specificity. Treatment of mice carrying B16 melanoma cells expressing a transfected C215 antigen resulted in 85-99% inhibition of tumor growth and allowed long-term survival of animals. The therapeutic effect was dependent on antigen-specific targeting of the FabC215-SEA fusion protein, since native SEA and an antigen-irrelevant FabC242-SEA fusion protein did not influence tumor growth. The results suggest that Fab-SEA fusion proteins convey superantigenicity on tumor cells, which evokes T cells to suppress tumor growth.     

Cloning of α-β fusion gene from Clostridium perfringens and its expression

AIM: To study the cloning of α-β fusion gene from Clostridium perfringens and the immunogenicity of α-β fusion expression.METHODS: Cloning was accomplished after PCR amplification from strains NCTC64609 and C58-1 of the protective antigen genes of α-toxin and β-toxin. The fragment of the gene was cloned using plasmid pZCPAB. This fragment coded for the gene with the stable expression of α-β fusion gene binding. In order to verify the exact location of the α-β fusion gene, domain plasmids were constructed. The two genes were fused into expression vector pBV221. The expressed α-β fusion protein was identified by ELISA, SDS-PAGE, Western blotting and neutralization assay.RESULTS: The protective α-toxin gene (cpa906) and the β-toxin gene (cpb930) were obtained. The recombinant plasmid pZCPAB carrying α-β fusion gene was constructed and transformed into BL21(DE3). The recombinant strain BL21(DE3)(pZCPAB) was obtained. After the recombinant strain BL21(DE3)(pZCPAB) was induced by 42℃, its expressed product was about 22.14% of total cellular protein at SDS-PAGE and thin-layer gel scanning analysis. Neutralization assay indicated that the antibody induced by immunization with α-β fusion protein could neutralize the toxicity of α-toxin and β-toxin.CONCLUSION: The obtained α-toxin and β-toxin genes are correct. The recombinant strain BL21(DE3)(pZCPAB)could produce α-β fusion protein. This protein can be used for immunization and is immunogenic. The antibody induced by immunization with α-β fusion protein could neutralize the toxicity of α-toxin and β-toxin.