Horizontal transmission of malignancy by cell-cell fusion.

Introduction: The crosstalk between tumor and stromal cells has become an increasing important subject of the biology of oncogenesis, also involving new therapy paradigms for treating tumor-reactive host cells and vasculature.

Areas Covered: This article describes the long-term propagation in hamsters of a human glioblastoma which was derived from the in-vivo fusion of the human tumor cells with hamster stromal cells. The hybrid tumor cells retained at least seven human genes, of which three were able to translate their protein products during serial passages in vitro and in vivo, as well as features of the original tumor's histological appearance.

Pretargeting: taking an alternate route for localizing radionuclides.

Bispecific antibody pretargeting is a two-step procedure for selectively delivering radionuclides to tumors. The procedure was developed to solve a number of problems encountered when radionuclides are directly coupled to an IgG, such as slow blood clearance and delayed tumor accretion. While various forms of antibody fragments can reduce blood pool activity and provide faster tumor localization, tumor uptake is reduced considerably.

Epratuzumab-SN-38: a new antibody-drug conjugate for the therapy of hematologic malignancies.

We previously found that slowly internalizing antibodies conjugated with SN-38 could be used successfully when prepared with a linker that allows approximately 50% of the IgG-bound SN-38 to dissociate in serum every 24 hours. In this study, the efficacy of SN-38 conjugates prepared with epratuzumab (rapidly internalizing) and veltuzumab (slowly internalizing), humanized anti-CD22 and anti-CD20 IgG, respectively, was examined for the treatment of B-cell malignancies. Both antibody-drug conjugates had similar nanomolar activity against a variety of human lymphoma/leukemia cell lines, but slow release of SN-38 compromised potency discrimination in vitro even against an irrelevant conjugate.

The humanized anti-HLA-DR moAb, IMMU-114, depletes APCs and reduces alloreactive T cells: implications for preventing GVHD.

In contrast to the conventional immunosuppressive agents and nonselective T-cell-depleting antibodies, selective depletion of donor alloreactive T cells and/or host APCs, particularly DCs, represents a novel approach that can effectively control GVHD with less or no impairment of T-cell-mediated antiviral and GVL immunity. Here we report that IMMU-114, a humanized anti-human leukocyte antigen-DR (HLA-DR) moAb, efficiently depleted human PBMCs of all APCs, including B cells, monocytes, myeloid DC type-1 (mDC1), mDC2 and plasmacytoid DCs (pDCs). Early and late apoptosis of mDC1, mDC2 and pDCs, and late apoptosis of all APC subsets, were increased by IMMU-114 treatment.

Horizontal transmission and retention of malignancy, as well as functional human genes, after spontaneous fusion of human glioblastoma and hamster host cells in vivo.

Cell fusion in vitro has been used to study cancer, gene mapping and regulation, and the production of antibodies via hybridomas. However, in-vivo heterosynkaryon formation by cell-cell fusion has received less attention. This investigation describes the spontaneous fusion of a human glioblastoma with normal hamster cells after xenogeneic transplantation, resulting in malignant cells that express both human and hamster genes and gene products, and retention of glioblastoma traits with an enhanced ability to metastasize.

Combination radioimmunotherapy and chemoimmunotherapy involving different or the same targets improves therapy of human pancreatic carcinoma xenograft models.

Chemoimmunotherapy with antibody-drug conjugates (ADC) is emerging as a promising therapy for solid tumors, whereas radioimmunotherapy (RAIT) of solid tumors has been relatively ineffective because of their resistance to radiation. We developed antibody-SN-38 conjugates that have significant antitumor activity in xenograft models at nontoxic doses. The goal of this study was to determine if an ADC could be combined with RAIT to enhance efficacy without a commensurate increase in host toxicity.

Optimization of hapten-peptide labeling for pretargeted immunoPET of bispecific antibody using generator-produced 68Ga.

Unlabelled: Bispecific antibody pretargeting is highly sensitive and specific for cancer detection by PET. In this study, the preparation of a high-specific-activity (68)Ga-labeled hapten-peptide, IMP288, was evaluated.

Methods: IMP288 (DOTA-D-Tyr-D-Lys(histamine-succinyl-glycine [HSG])-D-glu-D-Lys(HSG)-NH(2)) was added to buffered (68)Ga and then heated in boiling water and purified on a reversed-phase cartridge.

Cancer radioimmunotherapy.

Targeting of radionuclides with antibodies, or radioimmunotherapy, has been an active field of research spanning nearly 50 years, evolving with advancing technologies in molecular biology and chemistry, and with many important preclinical and clinical studies illustrating the benefits, but also the challenges, which all forms of targeted therapies face. There are currently two radiolabeled antibodies approved for the treatment of non-Hodgkin lymphoma, but radioimmunotherapy of solid tumors remains a challenge. Novel antibody constructs, focusing on treatment of localized and minimal disease, and pretargeting are all promising new approaches that are currently under investigation.

Enhanced expression of CD74 in gastrointestinal cancers and benign tissues.

CD74, a transmembrane glycoprotein that associates with MHC II, is an important chaperone that regulates antigen presentation for immune response. In addition, CD74 is the receptor for macrophage migration-inhibitory factor which, when bound to CD74, initiates survival pathways and cell proliferation. Formalin fixed, paraffin embedded clinical specimens were evaluated by immunohistochemical procedures for expression of CD74.

Evaluation of anti-human leukocyte antigen-DR monoclonal antibody therapy in spontaneous canine lymphoma.

A pilot study of anti-human leukocyte antigen (HLA)-DR monoclonal antibody (mAb) in dogs with lymphoma was undertaken to verify the suitability of a canine model to address therapeutically relevant endpoints prior to a full trial in dogs, and ultimately human investigation. In vitro studies demonstrated that L243, a murine IgG1 anti-HLA-DR, binds to normal and malignant canine lymphocytes and induces apoptosis in canine lymphoma cells. Moreover, L243 was administered safely to normal dogs and dogs with lymphoma, and bound to malignant cells in nodal tissue.

Radioactive antibodies: a historical review of selective targeting and treatment of cancer.

Radioactive antibodies have served as imaging and therapeutic agents for several decades, but recent developments raise enthusiasm that a new generation of cancer therapeutics and diverse molecular imaging agents for various cancers are more likely than ever before. This article traces the development of tumor-targeting antibodies labeled with diagnostic or therapeutic radionuclides, and describes the problems encountered and the clinical advances made. We also emphasize recent attempts to improve both molecular imaging and radioimmunotherapy with multistep pretargeting methods that separate the delivery of the tumor-binding, bispecific antibody given in the first step from the radionuclide carrier, which, in the second step, will localize to the "anti-carrier" binding arm of the pretargeted bispecific antibody.

Detection of early-stage pancreatic adenocarcinoma.

Background: Pancreatic adenocarcinoma is an almost universally lethal disease, in large part, due to our inability to detect early-stage disease. Monoclonal antibody PAM4 is reactive with a unique biomarker expressed by >85% of pancreatic adenocarcinomas. In this report, we examined the ability of a PAM4-based immunoassay to detect early-stage disease.

Placental growth factor (PlGF) enhances breast cancer cell motility by mobilising ERK1/2 phosphorylation and cytoskeletal rearrangement.

Background: During metastasis, cancer cells migrate away from the primary tumour and invade the circulatory system and distal tissues. The stimulatory effect of growth factors has been implicated in the migration process. Placental growth factor (PlGF), expressed by 30-50% of primary breast cancers, stimulates measurable breast cancer cell motility in vitro within 3 h.

Recombinant bispecific monoclonal antibodies prepared by the dock-and-lock strategy for pretargeted radioimmunotherapy.

The selective delivery of therapeutic radionuclides is a promising approach for treating cancer. Antibody-targeted radionuclides are of particular interest, with 2 products approved for the treatment of certain forms of non-Hodgkin lymphoma. However, for many other cancers, radioimmunotherapy has been ineffective, being limited by prolonged exposure to the highly radiosensitive bone marrow.

Veltuzumab (humanized anti-CD20 monoclonal antibody): characterization, current clinical results, and future prospects.

Veltuzumab is a humanized, anti-CD20 monoclonal IgG(1) antibody (MAb), constructed recombinantly on the framework regions of epratuzumab, with complementarity-determining regions (CDRs) identical to rituximab, except for a single amino acid in CDR3 of the variable heavy chain. Veltuzumab showed anti-proliferative, apoptotic, and antibody-dependent cellular cytotoxicity effects in vitro similar to rituximab, but with significantly slower off-rates and increased complement-dependent cytotoxicity in several human lymphoma cell lines. In addition, very low doses of veltuzumab, given either intravenously or subcutaneously, depleted B cells in normal cynomolgus monkeys, and controlled tumor growth in mice bearing human lymphomas.

Improving the treatment of non-Hodgkin lymphoma with antibody-targeted radionuclides.

Radioimmunotherapy of non-Hodgkin lymphoma comprises a (90)Y- or (131)I-labeled murine anti-CD20 IgG, but both agents also include a substantial dose of unlabeled anti-CD20 IgG given immediately before the radioconjugate to reduce its uptake in the spleen (primary normal B-cell antigen sink); this extends its plasma half-life and improves tumor visualization. Thus, these treatments combine an effective anti-CD20 radioconjugate with an unconjugated anti-CD20 antibody that is also therapeutically active, but the large anti-CD20 IgG predose ( approximately 900 mg) may diminish the tumor localization of the radioimmunoconjugate (eg, 10-35 mg). We have examined alternative approaches that enhance radionuclide targeting and improve antitumor responses.

Therapy of B-cell malignancies by anti-HLA-DR humanized monoclonal antibody, IMMU-114, is mediated through hyperactivation of ERK and JNK MAP kinase signaling pathways.

A humanized IgG4 anti-HLA-DR monoclonal antibody (IMMU-114), engineered to avoid side effects associated with complement activation, was examined for binding and cytotoxicity on leukemia, lymphoma, and multiple myeloma cell lines and chronic lymphocytic leukemia (CLL) patient specimens, followed by evaluation of the effects of IMMU-114 on extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) signaling pathways. HLA-DR was expressed on the majority of these cells at markedly higher levels than CD20, CD22, and CD74. IMMU-114 was toxic to mantle cell lymphoma, CLL, acute lymphoblastic leukemia, hairy cell leukemia, non-Hodgkin lymphoma (including rituximab-resistant), and multiple myeloma cell lines, and also patient CLL cells.

Ceramide regulates gemcitabine-induced senescence and apoptosis in human pancreatic cancer cell lines.

Bioactive sphingolipids are potent intracellular signaling molecules having profound effects on cell death, growth, and differentiation. Pharmacologic manipulation of sphingolipid levels could have a significant effect on the induction of apoptosis by anticancer agents, and thus, improve treatment efficacy. We observed that gemcitabine cannot completely kill AsPc1 and Panc1 human pancreatic cancer cells in culture; even at high concentrations of gemcitabine, 30% to 40% of the cells remain viable.

Induction of apoptosis by cross-linking antibodies bound to human B-lymphoma cells: expression of Annexin V binding sites on the antibody cap.

Unlabelled: There are many reports that cross-linking antibodies (Abs) bound to the surface of B-lymphoma cells can induce apoptosis and/or cell death, especially with anti-CD20 Abs. This study was intended to extend our understanding of these effects. To determine if CD20 is a unique target in this respect, or whether Abs to other antigens would have similar effects, six Abs were tested, with and without cross-linking with a secondary Ab, on three target cell lines.

Novel strategies for improved cancer vaccines.

Therapeutic vaccination against cancer is an important modality complementing current standard therapies and may lead to long-term control of cancer. Numerous strategies are in development in an attempt to achieve better effectiveness but, except for the recent advent of vaccines against human papillomavirus, the long effort to produce a cancer vaccine has not succeeded. Nevertheless, a number of novel approaches can be pursued that, in our view, include optimized antigen design, in vivo-targeted dendritic cell vaccination and cancer vaccines used in combination with chemotherapy, monoclonal antibodies, adoptive T-cell transfer or stem cell transplantation.

Combining milatuzumab with bortezomib, doxorubicin, or dexamethasone improves responses in multiple myeloma cell lines.

Purpose: The humanized anti-CD74 monoclonal antibody, milatuzumab, is in clinical evaluation for the therapy of multiple myeloma (MM). The ability of milatuzumab to increase the efficacy of bortezomib, doxorubicin, and dexamethasone was examined in three human CD74+ MM cell lines, CAG, KMS11, KMS12-PE, and one CD74-MM cell line, OPM-2.

Experimental Design: Activity of milatuzumab as a monotherapy and combined with the drugs was evaluated by studying in vitro cytotoxicity, signaling and apoptotic pathways, and in vivo therapeutic activity in severe combined immunodeficient (SCID) mouse models of MM.

Pretargeted versus directly targeted radioimmunotherapy combined with anti-CD20 antibody consolidation therapy of non-Hodgkin lymphoma.

Unlabelled: We determined whether therapeutic responses using a bispecific antibody that pretargeted (90)Y-hapten-peptide radioimmunotherapy or a directly radiolabeled, humanized, (90)Y-anti-CD20 IgG (veltuzumab) could be improved by combining these treatments with unlabeled humanized antibodies against CD22 (epratuzumab), CD74 (milatuzumab), or veltuzumab.

Methods: Nude mice bearing established subcutaneous Ramos human Burkitt lymphoma were treated with antibodies alone or in combination with pretargeted radioimmunotherapy (PT-RAIT) or radioimmunotherapy, and tumor growth was monitored. Biodistribution studies examined the effect that predosing with unlabeled veltuzumab had on radioimmunotherapy and PT-RAIT targeting.

A re-examination of radioimmunotherapy in the treatment of non-Hodgkin lymphoma: prospects for dual-targeted antibody/radioantibody therapy.

Antibody-based therapies, both unconjugated antibodies and radioimmunotherapy, have had a significant impact on the treatment of non-Hodgkin lymphoma. Single-agent rituximab is an effective therapy, but it is being increasingly used with combination chemotherapy to improve the objective response and its duration. The approved anti-CD20 radioimmunoconjugates ((90)Y-ibritumomab tiuxetan or (131)I-tositumomab) have had encouraging results, with trials now seeking to incorporate a radioimmunoconjugate in various settings.