Hormone conjugated with antibody to CD3 mediates cytotoxic T cell lysis of human melanoma cells

DNA and mRNA Vaccines for Chronic Viral Infections and Cancer: Rationale, Mechanisms, and Progress

Interest in the capabilities of nucleic acid vaccines, (DNA and mRNA vaccines) for both prophylactic and therapeutic uses have greatly increased following the successful deployment of two mRNA and, on a more limited scale, one DNA vaccine for COVID-19. In addition to targeting other pathogens for prophylactic vaccines, efforts are also being made towards using them for therapies for chronic infections and cancer. An examination of past and current successes for such therapies using other technologies with an emphasis on the immunological mechanisms will be provided followed by an assessment of the relevant characteristics of DNA and mRNA vaccines to predict their utility for therapies for chronic viral infections and cancer. Efforts and progress for these targets will be described.

Path to Success and Future Impact of Nucleic Acid Vaccines: DNA and mRNA

The rapid development of mRNA vaccines for COVID-19 has both astonished the world and raised concerns about their safety, perhaps because many people do not realize the decades’ long efforts for nucleic acid vaccines, both mRNA and DNA vaccines, including the licensure of several veterinary DNA vaccines. This manuscript traces the milestones for nucleic acid vaccine research and development (R&D), with a focus on the immune and safety issues they both raised and answered. The characteristics of the two entities are compared, demonstrating the similarities and differences between them, the advantages and disadvantages, which might lead toward using one or the other technology for different indications. In addition, as the SARS-CoV-2 pandemic has once again highlighted the importance of One Health, that is, the interactions between animal and human pathogens, focus will also be given to how DNA vaccine utilization and studies both in large domestic animals and in wildlife pave the way for more integrated approaches for vaccines to respond quickly to, and prevent, the global impacts of emerging diseases.

Redirecting cytotoxic T cells with chemically programmed antibodies

T-cell engaging bispecific antibodies (T-biAbs) mediate potent and selective cytotoxicity by combining specificities for target and effector cells in one molecule. Chemically programmed T-biAbs (cp-T-biAbs) are precisely assembled compositions of (i) small molecules that govern cancer cell surface targeting with high affinity and specificity and (ii) antibodies that recruit and activate T cells and equip the small molecule with confined biodistribution and longer circulatory half-life. Conceptually similar to cp-T-biAbs, switchable chimeric antigen receptor T cells (sCAR-Ts) can also be put under the control of small molecules by using a chemically programmed antibody as a bispecific adaptor molecule. As such, cp-T-biAbs and cp-sCAR-Ts can endow small molecules with the power of cancer immunotherapy. We here review the concept of chemically programmed antibodies for recruiting and activating T cells as a promising strategy for broadening the utility of small molecules in cancer therapy.

PSMA-targeted bispecific Fab conjugates that engage T cells

Bioconjugate formats provide alternative strategies for antigen targeting with bispecific antibodies. Here, PSMA-targeted Fab conjugates were generated using different bispecific formats. Interchain disulfide bridging of an αCD3 Fab enabled installation of either the PSMA-targeting small molecule DUPA (SynFab) or the attachment of an αPSMA Fab (BisFab) by covalent linkage. Optimization of the reducing conditions was critical for selective interchain disulfide reduction and good bioconjugate yield. Activity of αPSMA/CD3 Fab conjugates was tested by in vitro cytotoxicity assays using prostate cancer cell lines. Both bispecific formats demonstrated excellent potency and antigen selectivity.

Chemically programmed bispecific antibodies that recruit and activate T cells

Bispecific antibodies (biAbs) that mediate cytotoxicity by recruiting and activating endogenous immune cells are an emerging class of next-generation antibody therapeutics. Of particular interest are biAbs of relatively small size (∼50 kDa) that can redirect cytotoxic T cells through simultaneous binding of tumor cells. Here we describe a conceptually unique class of biAbs in which the tumor cell specificity of a humanized antibody fragment that recognizes CD3 on T cells is chemically programmed through a C-terminal selenocysteine (Sec) residue. We demonstrate that through chemically programmed specificity for integrin α(4)β(1) or folate receptor 1 (FOLR1), and common specificity for CD3, these hybrid molecules exert potent and specific in vitro and ex vivo cytotoxicity toward tumor cell lines and primary tumor cells in the presence of primary T cells. Importantly, the generic nature of chemical programming allows one to apply our approach to virtually any specificity, promising a broad utility of chemically programmed biAbs in cancer therapy.

Targeting of drugs to cell surface receptors

The new approach to the treatment of cancer or to immunomodulation is drug targeting. The effort to achieve either an absolute or a relative amplification of the tumoricidal effect of anticancer drugs through increased generation or acquisition of reactive molecules at the tumor site or a reduction of the toxic molecules available to the periphery has led to a number of strategies. Among them are (1) targeting using antibodies to their fragments, hormones, carbohydrates, and growth factors; (2) retargeting using bispecific antibodies; (3) construction of chimeric genes; (4) streptavidin-biotin based immunotherapy; (5) prodrug activation strategies (ADEPT); (6) antibody-targeted superantigens; and (7) gene delivery for the purpose of gene therapy.

Conjugates of folate and anti-T-cell-receptor antibodies specifically target folate-receptor-positive tumor cells for lysis

High-affinity folate receptors (FRs) are expressed at elevated levels on many human tumors. Bispecific antibodies that bind the FR and the T-cell receptor (TCR) mediate lysis of these tumor cells by cytotoxic T lymphocytes. In this report, conjugates that consist of folate covalently linked to anti-TCR antibodies are shown to be potent in mediating lysis of tumor cells that express either the alpha or beta isoform of the FR. Intact antibodies with an average of five folate per molecule exhibited high affinity for FR+ tumor cells but did not bind to FR- tumor cells. Lysis of FR+ cell lines could be detected at concentrations as low as 1 pM (approximately 0.1 ng/ml), which was 1/1000th the concentration required to detect binding to the FR+ cells. Various FR+ mouse tumor cell lines could be targeted with each of three different anti-TCR antibodies that were tested as conjugates. The antibodies included 1B2, a clonotypic antibody specific for the cytotoxic T cell clone 2C; KJ16, an anti-V beta 8 antibody; and 2C11, an anti-CD3 antibody. These antibodies differ in affinities by up to 100-fold, yet the cytolytic capabilities of the folate/antibody conjugates differed by no more than 10-fold. The reduced size (in comparison with bispecific antibodies) and high affinity of folate conjugates suggest that they may be useful as immunotherapeutic agents in targeting tumors that express folate receptors.

Melanocortins and their implication in melanoma

The melanocortins (MCs), that is, the melanocyte-stimulating hormones (MSHs) and ACTH, are a group of related peptides containing the typical melanotropin core sequence, His-Phe-Arg-Trp, and are derived from a common precursor, pro-opiomelanocortin. They are pleiotropic molecules that occur in the pituitary, some brain regions, and also in several peripheral tissues, and they exert a variety of physiologic functions. Their effect on melanogenesis in the skin is well established, but their role in melanocyte and melanoma cell proliferation and metastasis is less clear. The recent cloning of five types of MC receptors (MC1-5), new studies on the regulation of these receptors, the discovery of a naturally occurring MSH antagonist, the agouti protein, and the finding that melanocytes and melanoma cells exclusively express MC1 receptors have laid the basis for the future development of specific MC ligands, which may become useful for melanoma diagnosis and eventually therapy.

Specific incorporation of 2-thiouracil into biological melanins

2-Thiouracil (TU), an antithyroid drug, is generally recognized as a highly specific melanoma seeker owing to its capability of being selectively accumulated into active melanin-producing tissues. We recently reported evidence that in vitro TU is capable of reacting with dopaquinone (DQ), an early intermediate in melanin biosynthesis, to give an addition product characterized as 6-S-thiouracildopa (TD). However, several aspects of the mechanism of the uptake of TU into melanin in vivo still need to be clarified. We report here the extremely rapid incorporation of [2-14C]thiouracil into melanoma tumors growing subcutaneously in mice and show its selective accumulation into melanin by isolation and purification of the pigment fraction. Formation of the TD adduct in the tumor was examined by HPLC analysis of the soluble fractions of the tissue homogenates: however, no trace of TD could be detected on account of its rapid oxidation by the melanogenic enzyme tyrosinase, as evidenced by in vitro kinetic measurements. Monitoring the course of the tyrosinase-catalyzed oxidation of 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA) in the presence of TU, at various molar ratios, provided evidence for the ability of the drug to affect melanogenesis by interaction with biosynthetic intermediates beyond the DQ stage, suggesting other possible modes for its chemical binding to the growing pigment.

Molecular cloning and expression of the human melanocyte stimulating hormone receptor cDNA

Melanocytes and melanoma cells are known to possess receptors for melanocyte stimulating hormone (MSH). A cDNA clone, designated 11D, has been isolated from human melanoma cells and encodes a MSH receptor. The cloned cDNA encodes a 317 amino acid protein with transmembrane topography characteristics of a G-protein-coupled receptor, but it does not show striking similarity to already published sequences of other G-protein-coupled receptors. When 11D cDNA is expressed in COS-7 cells, it binds an 125I-labelled MSH analogue (NDP-MSH) in a specific manner. The bound ligand could be displaced by melanotropic peptides, alpha-MSH, beta-MSH, gamma-MSH and ACTH (adrenocorticotropic hormone), but not by the non-melanotropic peptide, beta-endorphin. This is the first report of the cloning of the receptor gene of the melanotropin receptor family.

Novel antibody drug products

Recent developments in protein and genetic engineering methods have allowed the production of antibody-derived molecules that have important potential as therapeutic agents. Although monoclonal antibodies of murine origin have been used for therapeutic purposes, limitations due to anti-antibody responses and suboptimal effectiveness for some indications, such as tumor cell killing, have led to the development of human monoclonal antibodies, chimeric and complementarity determining-region grafted antibodies, immunotoxins, and other engineered products. These novel antibodies are being tested for the treatment and prevention of infectious diseases and for the diagnosis and treatment of cancers, as well as for indications considered nontraditional for antibodies (e.g., as antithrombotics or inhibitors of neutrophil adherence). The availability of antibody drug products raises a number of issues for clinicians. Among these are new patterns of adverse effects, immunogenicity (development of anti-antibody response), important questions regarding administration and dosage, and substantial cost implications.

Effects of HC antibody in autologous tumor-specific cytotoxicity by human melanoma tumor-infiltrating lymphocytes

Heteroconjugate (HC) antibody has a potential use in cancer biotherapy because of its ability to mimic antigenic specificity and induce cytotoxicity in the activated lymphocytes against various tumor cells. This study investigated the effects of HC antibody (anti-CD3 MAb x anti-p97 melanoma cell MAb) in autologous tumor-specific cytotoxicity by interleukin-2 (IL-2)-activated melanoma tumor-infiltrating lymphocytes (TILs). HC antibody significantly augmented p97pos uncultured autologous tumor cell lysis mediated by effector TILs or cytotoxic T lymphocyte (CTL) clones derived from TIL. It did not significantly increase p97mix autologous tumor-cell lysis and slightly inhibited the lysis only at higher E:T ratios and higher concentrations (greater than or equal to 100 ng/ml). It inhibited p97neg autologous tumor-cell lysis. HC antibody respectively induced potent lysis of p97pos or modest lysis of p97mix tumor cells by allogeneic effector TILs as well as PBMC. In contrast, parental anti-CD3 MAb primarily suppressed the autologous tumor-specific cytotoxicity, and did not induce lysis of uncultured melanoma cells, regardless of differences in expression of p97 antigens on tumor cells. Although parental anti-p97 MAb did not augment or suppress the autologous tumor-specific cytotoxicity, it completely abrogated HC antibody-mediated augmentation of p97pos autologous tumor cell lysis by effector TILs. Anti-class-I MAb, but not anti-DR MAb, suppressed the autologous tumor-specific cytotoxicity, but failed to block HC antibody-mediated augmentation of p97pos autologous tumor-cell lysis. These results suggest that the levels of p97 antigen expression largely influenced HC antibody-mediated modulation of TIL cytotoxicity against uncultured autologous tumor cells.

Mechanisms of rejection during OKT3 therapy: propagation and characterization of CD3 resistant allospecific cytotoxic T cells from a rejecting liver allograft

Allograft rejection remains the single largest impediment to success in the field of transplantation. While OKT3 therapy has proven to be a significant advancement, many grafts are still lost. Late treatment, subtherapeutic OKT3 levels, anti-OKT3 antibodies, and OKT3-induced class II antigen expression are possible explanations. To determine the mechanism of OKT3 resistant rejection we propagated and characterized infiltrating T cells from the biopsy of a liver transplant patient who was rejecting while on prophylactic OKT3. The T lymphocytes demonstrated allospecific proliferation and interleukin 2 (IL2) production and showed a high degree of cytolysis of donor splenocytes. CD3 epsilon monoclonal antibodies (Mab) in concentrations up to 100 micrograms/ml did not inhibit lysis. In contrast, T lymphocytes derived from rejecting allografts of patients receiving cyclosporine and prednisone were readily inhibited from killing by CD3 epsilon Mab at doses of 1 microgram/ml. Furthermore, allospecific proliferation and IL2 production were not inhibited in the OKT3-treated patient by the addition of CD3 epsilon MaB. Incomplete modulation of the CD3-TCR complex was noted after a 72-hr incubation with CD3 epsilon Mab. The T cells did demonstrate other intact CD3-mediated functions such as a rise in intracellular calcium and CD3-dependent cytotoxicity. These results should alert clinicians that CD3 resistant cytotoxic T cells can emerge during OKT3 therapy and may cause rejection. Immunotherapy that targets additional cell surface structures may be of benefit.

Human autologous tumor-specific T cells in malignant melanoma

T cell lines and clones with autologous tumor-specific activity have been developed in malignant melanoma by stimulating peripheral blood lymphocytes (PBL), lymph node lymphocytes or tumor-infiltrating lymphocytes (TIL) with autologous melanoma cells in the presence of recombinant interleukin 2 (rIL2). T-cell lines and clones have been developed with specific cytotoxicity and/or proliferative responses for autologous melanoma targets but not for allogeneic melanoma tumor cells, autologous normal cells or natural killer (NK)-sensitive targets. The concentration of rIL2 is critical for the generation of autologous tumor-specific T-cell lines, with low rIL2 concentrations (up to 800 IU/ml) facilitating the growth of T-cell lines with tumor-specific activity. The alpha beta T-cell receptor (TCR) and the CD3 antigen are involved in specific cytotoxicity and/or proliferative responses of these T-cell lines and clones. An oligoclonal pattern of beta-chain TCR gene rearrangements was observed on T-cell lines and clones with autologous tumor-specific cytotoxicity, suggesting that they are comprised of T cells that have undergone a clonal expansion in response to particular antigen. Autologous tumor-specific cytotoxic T cells are HLA-restricted and recognize on the melanoma tumor cells HLA Class I or possibly Class II antigens plus a tumor-specific determinant. TIL from patients with metastatic melanoma have unique characteristics in comparison with PBL and lymph node lymphocytes and they appear to contain substantial proportions of T cells that have been locally sensitized to autologous tumor cells. Single stimulation of TIL with autologous tumor cells in the presence of rIL2 is sufficient for the generation of T cell lines with autologous tumor-specific activity, whereas, multiple stimulation of PBL and lymph node lymphocytes was required to achieve the same purpose. TIL-derived T cell lines have been expanded in rIL2 in vitro by at least 1,500-fold without losing their activity. Approximately, 40% of the patients exhibited complete or partial responses to adoptive immunotherapy with melanoma TIL and rIL2.

Augmentation of interleukin-2-induced activation of human melanoma tumor-infiltrating lymphocytes by heteroconjugate antibody

Heteroconjugate (HC) antibody (anti-CD3 mAb x anti-p97 melanoma mAb) or monomeric anti-CD3 mAb by itself did not induce proliferation of uncultured melanoma tumor-infiltrating lymphocytes (TILs). They also failed to induce IL-2 production in uncultured TILs, although anti-CD3 mAb, but not HC antibody, stimulated IL-2 production in peripheral blood mononuclear cells (PBMCs). Sequential treatment of uncultured TILs from p97-antigen-positive (p97+) melanomas with HC antibody, followed by washing and incubation with interleukin-2 (IL-2), induced significantly higher proliferation than incubation with IL-2 alone. HC antibody pretreatment led to significantly greater results than with anti-CD3 mAb at a 1 ng/ml level in IL-2-induced proliferation of TILs from p97+ melanomas, similar to those with anti-CD3 mAb at a level of 100 ng/ml. HC antibody (1 ng/ml) pretreatment did not enhance IL-2-induced proliferation of either TILs from p97- melanomas or PBMCs, while anti-CD3 mAb enhanced the proliferation of TILs from some p97- melanomas and PBMCs. Regardless of the pretreatment of uncultured TILs with HC antibody or anti-CD3 mAb, IL-2-activated TILs were cytotoxic primarily only to autologous tumor cells, and their phenotypes remained the same. Thus, HC antibody can augment IL-2-induced activation of TILs only from p97+ melanomas, without altering their pattern of cytotoxicity or phenotype. The findings were consistent with observations at the clonal level. In contrast to anti-CD3 mAb, HC pretreatment of uncultured TILs from only p97+ melanoma prior to limiting-dilution analysis increased the number of proliferating TIL clones, including autologous tumor-specific cytotoxic T lymphocyte clones. These results suggest that use of HC antibody in vivo would be more advantageous than anti-CD3 mAb, with regard to augmentation of IL-2-induced TIL activation.

A chelating derivative of alpha-melanocyte stimulating hormone as a potential imaging agent for malignant melanoma

A chelating derivative of alpha-melanocyte stimulating hormone (MSH) has been synthesised, in which two molecules of the hormone are cross-linked by diethylenetriamine pentaacetic acid (DTPA). This compound, bisMSH-DTPA, was equipotent with MSH in an in vitro tyrosinase assay with Cloudman S91 melanoma cells. When DBA/2 mice bearing the same tumour were injected with bisMSH-DTPA labelled with the gamma-emitting isotope indium-111 (111In), the radioactivity became rapidly associated with the melanoma tissue. By 24 h post-injection, radioactivity in tumour tissue was significantly higher (P less than 0.001) than in spleen, lung, brain, eye and skin. Uptake of radioactivity by the tumours was inhibited by a 200-fold molar excess of MSH, whereas uptake by liver, kidney, spleen, lung, brain, eye and skin was unaffected. We conclude that bisMSH-DTPA may offer an alternative to antibody targeting in the imaging of malignant melanoma.

Toward regulation of gonadal function by a synthetic hybrid molecule composed of gonadotropin and Fc fragment of immunoglobulin G

A conjugate of human chorionic gonadotropin (HCG) and Fc fragment of immunoglobulin G was prepared by covalent cross-linking using the heterobifunctional reagent, N-succinimidyl 3-(2-pyridyldithio) propionate. Mouse Leydig tumor cells expressing receptors for luteinizing hormone were specifically lysed in vitro as a consequence of complement fixation via the Fc component of the hybrid molecule. Furthermore, administration of HCG-Fc to rams caused an acute depression in circulatory testosterone. This novel concept of targeted inhibition of gonadal function could prove to have future applications in control of reproductive processes.

Induction of cytotoxicity in human T cells coated with anti-glioma x anti-CD3 bispecific antibody against human glioma cells

A bifunctional hetero-F(ab')2 antibody fragment was developed that contained the Fab portions from anti-CD3 and anti-glioma monoclonal antibodies. The antibody simultaneously recognized two different molecules, the CD3 complex on effector T cells and a human glioma-associated antigen; thus, it could cross-link effector and target cells. This bispecific F(ab')2 fragment induced peripheral blood mononuclear cells (PBMC's) from healthy donors to lyse cells of the human glioma cell line, U251MG, which are resistant to natural killer cell-mediated cytolysis. The effect of the bispecific antibody on lymphokine-activated killer (LAK) cell activity was tested in patients suffering from malignant glioma. For this study, PBMC's from these patients were preactivated with recombinant interleukin-2 and their killer activity against U251MG cells was investigated in vitro with and without the bispecific antibody. The LAK cell activity of the PBMC's from patients with malignant gliomas was found to be suppressed compared with those of healthy donors. However, after preincubation with bispecific antibody, the patients' LAK cells exhibited marked cytolytic activity against U251MG cells. These findings suggest that this bispecific antibody may be a useful addition to anti-glioma immunotherapy.

Therapy for cutaneous melanoma: an update

This article reviews the current therapy for cutaneous melanoma. Diagnosis, staging, and prognostic evaluation, which are crucial to proper management, are discussed. Surgical excision is the treatment of choice for primary melanoma. The resection margins should be tailored to tumor thickness. Guidelines for surgery are presented. The controversy about elective regional lymph node dissections is discussed. Limb perfusion, chemotherapy, immunotherapy, radiotherapy, and hormonal therapy as adjuvant treatments of primary melanomas as well as the treatment of disseminated melanomas are reviewed and new developments are highlighted. Guidelines for the management of metastatic melanoma at various sites are given. Special issues such as "pregnancy/estrogen and melanoma" and "borderline melanoma" are discussed and approaches to these problems are suggested. Recommendations are given for the follow-up and counseling of patients with melanoma.

Antibody mediated targeting of radioisotopes, drugs and toxins in diagnosis and treatment

The recent resurgence of interest in site specific delivery of radioisotopes, chemotherapeutic drugs and toxins for the diagnosis and treatment of cancer, and for the selective manipulation of the immune system, can be directly related to the need for improved diagnosis and the fact that for many cancers, for example lung, colon and gastric, the conventional treatments of surgery, radiotherapy and chemotherapy have reached a plateau in terms of the number of patients cured. To date, because of their specificity, the major emphasis has been on the use of antibodies as carriers and extensive in vitro, in vivo preclinical and clinical evaluation is underway. The aim of this article is to review recent progress, highlight avenues being explored to overcome limitations and to indicate new approaches that are evolving in antibody mediated targeting.

Murine anti-CD3 monoclonal antibody induces potent cytolytic activity in both T and NK cell populations

Antibodies specific for the CD3 complex have the capacity to both stimulate and inhibit a variety of T cell functions. We show here that a monoclonal antibody to the epsilon chain of CD3 can induce efficient non-MHC-restricted cytolytic activity in murine lymphocytes with peak activity occurring after 48 hr of incubation. In a panel of targets, the anti-CD3-activated effectors lysed tumor cells but not normal lymphoblasts. Cytolysis was not dependent on the presence of the antibody in the cytolytic assay. Moderate to high cytolytic activity was elicited from lymph nodes, spleen, and thymus by anti-CD3 treatment in vitro, whereas only low activity was apparent in bone marrow. The precursors of anti-CD3-activated cells consisted largely of mature T cells, although a smaller component of immature T cells was also involved. Thus, separation of thymocytes based on adhesion to peanut agglutinin revealed that both positive (immature) and negative (mature) fractions could be activated, while cytotoxic pretreatment of spleen cells with an antibody (J11d) to immature T cells before anti-CD3 activation significantly decreased the resulting cytotoxicity. The majority of precursors in spleen were Thy 1+ and CD8+ and/or AGM1+. Antibody depletion studies showed that the effector cells have both a T and a NK component consisting of Thy 1+, CD5+, CD8+, CD4-, and AGM1- cells and Thy 1-, CD5-, CD8-, CD4-, and AGM1+ cells, respectively. The production of significant amounts of IL-2 and TNF in culture following anti-CD3 treatment, along with the synergistic effect of exogenously added IL-2, suggests that one or both of the effector cell types could be induced by lymphokines. The intraperitoneal administration of the anti-CD3 antibody induces cytolytic activity in vivo. Therefore, the direct activation of cytolysis by anti-CD3 antibody and the additional effects, both direct and synergistic, of lymphokines produced by the activated lymphocytes could conceivably provide a potent anti-tumor therapy.

Cytotoxicity mediated by human Fc receptors for IgG

The Fc receptors for IgG(Fc gamma R) play a major role in the removal of antibody-coated infectious agents and may be important molecules for triggering cytotoxicity of tumor cells; they may also serve as an entry for infection of Fc gamma R-bearing cells by viral (including HIV and Dengue), and perhaps other infectious agents. Although central to immune defense, an understanding of the role of these Fc gamma R in cytotoxicity has been complicated in part by the presence of several biochemically distinct types of receptor that have different distributions, specificities, affinities and modes of activation for killing. The development of monoclonal antibodies specific for Fc gamma R on human leukocytes has established the existence of three distinct Fc gamma R and furthermore has helped clarify the function of each of these receptors. In this review, Michael Fanger and colleagues discuss the use of Fc gamma R-specific mAb and the hybridoma cell lines that produce them in examining the ability of each of these unique receptors to mediate killing of tumor and red cell targets. In particular, the use of self-directed hybridoma cells as a model of tumor-cell killing and of bi-specific antibodies to link target cells to effector cells through the different Fc gamma R is discussed. The results of these studies suggest that the ability of a given Fc gamma R to trigger killing is sometimes dependent on the type of Fc gamma R, but is also markedly influenced by the type of target cell and by the nature and state of activation of the effector cell.

Malignant cell glycoproteins and glycolipids

The cell surface is involved in cell growth and division, cell-cell interaction, communication, differentiation and migration, and other processes likely to be involved in malignant transformation and/or the metastatic spread of cancer. Although there are many alterations of glycoproteins and glycolipids on the malignant cell surface, it is unclear whether these alterations are epiphenomena or an integral part of the malignancy process. This article reviews the recent literature and some earlier studies relevant for understanding emerging concepts and trends with respect to malignant cell glycoconjugates. Emphasis is on structural alterations of the carbohydrate portions of malignant cell glycoproteins and glycolipids and on the enzymes (glycosyltransferases and glycosidases) involved in their metabolism. Practical applications derived from malignant cell glycoconjugate studies are discussed briefly with respect to the diagnosis, staging, monitoring, and treatment of malignant disease. The review concludes by indicating which research areas on malignant cell glycoconjugates are likely to be fruitful in increasing our basic understanding of, and ability to deal effectively with, malignant disease.

The cellular immunotherapy of cancer: current and potential uses of interleukin-2

The potential for immune-mediated destruction of neoplasms was suggested nearly one century ago. Despite this, no "magic bullet" has yet been identified. Nevertheless, the physiology of cell-mediated immune reactions has been well characterized in molecular, cellular, and clinical studies of allograft and microbial immunity. Extensive studies performed in laboratory animal models have documented the in vitro and in vivo destruction of various neoplastic tissues by immune cells. This destruction can be directed against autologous, syngeneic, or allogeneic tumors in several systems with varying degrees of "tumor specificity". Two approaches exist towards utilizing these immune reaction in vivo. The first involves providing the tumor bearer with immunostimulatory agents, either specific or nonspecific, designed to activate and amplify the destructive potential of the individual's endogenous immune cells able to recognize and destroy autologous tumor. The second approach provides immune cells with antitumor capacity to a tumor-bearing individual, these cells having been activated exogenously. A number of successful regimens involving these two approaches, and combinations of them, have been delineated in animal tumor models. These experimental studies lay a strong foundation for initiating clinical trials of these concepts for patients with cancer. This review summarizes the diverse experimental studies in animals leading to clinical trials, presents recent data from ongoing clinical trials directly testing the potential for cellular immunotherapy, and then presents some of the major challenges facing further development and application of this potential therapeutic approach.

Prospects for clinical cancer treatment using interleukin-2

Even if many of these immunologic approaches to anticancer therapy show the desired effect, with a greater percentage of patients having antitumor responses (hopefully without need for ICU level toxicity), it may be unrealistic to hope that these biological treatments will significantly prolong the survival of most patients with large progressively growing tumors. It is possible that the large, yet finite, number of cells with LAK activity that can be activated endogenously, or infused into a patient, may only be able to destroy a finite number of neoplastic cells. If so, the smaller the number of neoplastic cells at the time of in vivo LAK induction therapy, the more likely the chance for effective eradication of all tumor cells. Experimental animal studies support this postulate (46). Clinical regimens utilizing IL-2 therapy, alone or combined with other agents, with documented immunologic and antitumor activity, will need to be tested in a large number of patients in randomized adjuvant trials. This testing will probably require the involvement of large cooperative oncology trials groups, in order to determine the potential prolongation of survival by any adjuvant IL-2 approach. A vast number of regimens could presently be suggested for combining these separate approaches in groupwide trials (especially when issues of dose, route, and scheduling are considered). Trials in murine models must continue rapidly and be interpreted with caution in generating regimens to be tested clinically. Further treatment improvements, to be identified in Phase I and Phase II clinical trials, are still required to allow large groupwide randomized Phase III trials to test tolerable and effective IL-2-containing regimens likely to significantly prolong survival.

Homologous recombination between transferred and chromosomal immunoglobulin kappa genes

Homologous recombination between transferred and chromosomal DNAs provides a means of introducing well-defined, predetermined changes in the chromosomal genes. Here we report that this approach can be used to specifically modify the immunoglobulin genes in mouse hybridoma cells. The test system is based on the Sp6 hybridoma, which synthesizes immunoglobulin M (kappa) specific for the hapten 2,4,6-trinitrophenyl (TNP). As recipient cells, we used the Sp6-derived mutant hybridoma igk14, which has a deletion of the kappa TNP gene and consequently does not synthesize TNP-specific immunoglobulin M. igk14 retains the mu TNP gene and two additional rearranged kappa genes, denoted kappa M21B1 and kappa M21G. As a transfer vector, we used pSV2neo bearing the functionally rearranged TNP-specific V kappa segment. Following DNA transfer by electroporation, we isolated rare transformants which produced normal amounts of the functional kappa TNP chain. Analysis of the DNA of these transformants indicated that in all cases, a functional kappa TNP gene had been formed as the result of a homologous integrative recombination event with the igk14 kappa M21B1 gene. These results suggest that homologous recombination might be used for mapping and introducing immunoglobulin gene mutations and for more conveniently engineering specifically altered immunoglobulins.

Homologous recombination between transferred and chromosomal immunoglobulin kappa genes

Homologous recombination between transferred and chromosomal DNAs provides a means of introducing well-defined, predetermined changes in the chromosomal genes. Here we report that this approach can be used to specifically modify the immunoglobulin genes in mouse hybridoma cells. The test system is based on the Sp6 hybridoma, which synthesizes immunoglobulin M (kappa) specific for the hapten 2,4,6-trinitrophenyl (TNP). As recipient cells, we used the Sp6-derived mutant hybridoma igk14, which has a deletion of the kappa TNP gene and consequently does not synthesize TNP-specific immunoglobulin M. igk14 retains the mu TNP gene and two additional rearranged kappa genes, denoted kappa M21B1 and kappa M21G. As a transfer vector, we used pSV2neo bearing the functionally rearranged TNP-specific V kappa segment. Following DNA transfer by electroporation, we isolated rare transformants which produced normal amounts of the functional kappa TNP chain. Analysis of the DNA of these transformants indicated that in all cases, a functional kappa TNP gene had been formed as the result of a homologous integrative recombination event with the igk14 kappa M21B1 gene. These results suggest that homologous recombination might be used for mapping and introducing immunoglobulin gene mutations and for more conveniently engineering specifically altered immunoglobulins.

Murine, Not Human, Cell Line

In the Research News article "Solutions to Euler equation" by Barry A. Cipra (29 Jan., p. 464), the equation in the first line of the fourth paragraph was incorrectly printed. It should have been "x(4) + y(4) + z(4) = u(2)."