Search

TP53 is a tumor suppressor gene that is mutated in 50% of cancers, and its function is tightly regulated by the E3 ligase, Mdm2. Both p53 and Mdm2 are localized in the cell nucleus, a site that is impervious to therapeutic regulation by most antibodies. We identified a cell-penetrating lupus monoclonal anti-DNA antibody, mAb 3E10, that targets the nucleus, and we engineered mAb 3E10 to function as an intranuclear transport system to deliver therapeutic antibodies into the nucleus as bispecific single chain Fv (scFv) fragments. Bispecific scFvs composed of 3E10 include PAb421 (3E10-PAb421) that binds p53 and restores the function of mutated p53, and 3G5 (3E10-3G5) that binds Mdm2 and prevents destruction of p53 by Mdm2. We documented the therapeutic efficacy of these bispecific scFvs separately in previous studies. In this study, we show that combination therapy with 3E10-PAb421 and 3E10-3G5 augments growth inhibition of cells with p53 mutations compared to the effect of either antibody alone. By contrast, no enhanced response was observed in cells with wild-type p53 or in cells homozygous null for p53.

Castration-resistant prostate cancer cells exhibit continued androgen receptor signaling in spite of low levels of ligand. Current therapies to block androgen receptor signaling act by inhibiting ligand production or binding. We developed bispecific antibodies capable of penetrating cells and binding androgen receptor outside of the ligand-binding domain. Half of the bispecific antibody molecule consists of a single-chain variable fragment of 3E10, an anti-DNA antibody that enters cells. The other half is a single-chain variable fragment version of AR441, an anti-AR antibody. The resulting 3E10-AR441 bispecific antibody enters human LNCaP prostate cells and accumulates in the nucleus. The antibody binds to wild-type, mutant and splice variant androgen receptor. Binding affinity of 3E10-AR441 to androgen receptor (284 nM) was lower than that of the parental AR441 mAb (4.6 nM), but could be improved (45 nM) through alternative placement of the affinity tags, and ordering of the VH and VK domains. The 3E10-AR441 bispecific antibody blocked genomic signaling by wild-type or splice variant androgen receptor in LNCaP cells. It also blocked non-genomic signaling by the wild-type receptor. Furthermore, bispecific antibody inhibited the growth of C4-2 prostate cancer cells under androgen-stimulated conditions. The 3E10-AR441 biAb can enter prostate cancer cells and inhibits androgen receptor function in a ligand-independent manner. It may be an attractive prototype agent for prostate cancer therapy.

Background Although early reperfusion is the most desirable intervention after ischemic myocardial insult, it may add to damage through oxidative stress. Objectives This study investigated the cardioprotective effects of a single intravenous dose of heat shock protein-72 (HSP72) coupled to a single-chain variable fragment (Fv) of monoclonal antibody 3E10 (3E10Fv) in a rabbit ischemia-reperfusion model. The Fv facilitates rapid transport of HSP72 into cells, even with intact membranes. Methods A left coronary artery occlusion (40 min) reperfusion (3 h) model was used in 31 rabbits. Of these, 12 rabbits received the fusion protein (Fv-HSP72) intravenously. The remaining 19 control rabbits received a molar equivalent of 3E10Fv alone (n = 6), HSP72 alone (n = 6), or phosphate-buffered saline (n = 7). Serial echocardiographic examinations were performed to assess left ventricular function before and after reperfusion. Micro–single-photon emission computed tomography imaging of 99mTc-labeled annexin-V was performed with micro–computed tomography scanning to characterize apoptotic damage in vivo, followed by gamma counting of the excised myocardial specimens to quantify cell death. Histopathological characterization of the myocardial tissue and sequential cardiac troponin I measurements were also undertaken. Results Myocardial annexin-V uptake was 43% lower in the area at risk (p = 0.0003) in Fv-HSP72–treated rabbits compared with control animals receiving HSP72 or 3E10Fv alone. During reperfusion, troponin I release was 42% lower and the echocardiographic left ventricular ejection fraction 27% higher in the Fv-HSP72–treated group compared with control animals. Histopathological analyses confirmed penetration of 3E10Fv-containing molecules into cardiomyocytes in vivo, and treatment with Fv-HSP72 showed fewer apoptotic nuclei compared with control rabbits. Conclusions Single-dose administration of Fv-HSP72 fusion protein at the time of reperfusion reduced myocardial apoptosis by almost one-half and improved left ventricular functional recovery after myocardial ischemia-reperfusion injury in rabbits. It might have potential to serve as an adjunct to early reperfusion in the management of myocardial infarction.

The therapeutic use of antibodies is restricted by the limited access of antibodies to intracellular compartments. To overcome this limitation, we developed a cell-penetrating monoclonal antibody, mAb 3E10, as an intracellular delivery vehicle for the intracellular and intranuclear delivery of antibodies constructed as bispecific single-chain Fv fragments. Because MDM2 is an important target in cancer therapy, we selected monoclonal antibody (mAb) 3G5 for intracellular transport. mAb 3G5 binds MDM2 and blocks binding of MDM2 to p53. Here, we show that the resulting 3E10-3G5 bispecific antibody retains cell-penetrating and MDM2-binding activity, increases tumor p53 levels, and inhibits growth of MDM2-addicted tumors. The use of cell-penetrating bispecific antibodies in targeted molecular therapy will significantly broaden the spectrum of accessible intracellular targets and may have a profound impact in cancer therapy. Mol Cancer Ther; 11(10); 2169–73. ©2012 AACR.

Foxp3 is a nuclear transcription factor that is both a tumor suppressor factor and regulator of T-regulatory cell (Treg) function, and is a potential therapeutic target in both autoimmunity and cancer. In order to distinguish molecular pathways responsible for these separate Foxp3 functions, deletion mutants of Foxp3 proteins were transduced and analyzed for cytotoxic activity in human cancer cell lines Skov3, MDA-MB-231, MCF-7 and Jurkat. Human Foxp3 cDNA mutants were amplified and ligated to produce plasmids for direct cell transfection. Constructs were produced and confirmed by DNA sequencing. Lipofectamine 2000 was used for plasmid transfection. Foxp3 cells were then examined. The results of our experiments reveal retention of tumor suppressor function in the absence of NFAT binding and transcriptional activation required for Treg function. Our results have significant implications for the design of autoimmune and cancer therapies that target Foxp3 and Treg cells.

Background and Purpose— This study investigated the effects of intravenous recombinant Fv-Hsp70 protein on infarction volume and behavior after experimental ischemic stroke. Methods— Focal cerebral ischemia was produced by occluding the middle cerebral artery using the intraluminal suture technique. Rats subjected to 2 hours of focal ischemia were allowed to survive 24 hours. At 2¼ hours and 3 hours after onset of ischemia, Fv-Hsp70 recombinant protein (0.5 mg/kg) or saline was injected through the tail vein. Sensorimotor function and infarction volume were assessed at 24 hours after ischemia. Results— Administration of Fv-Hsp70 after focal cerebral ischemia significantly decreased infarct volume by 68% and significantly improved sensorimotor function compared with the saline-treated control group. Western blots showed Fv-Hsp70 in ischemic but not in control brain; and Fv-Hsp70 suppressed endogenous Hsp70. Conclusion— Fv-Hsp70 protected the ischemic brain in this experimental stroke model.

Defects in dendritic spines and synapses contribute to cognitive deficits in mental retardation syndromes and, potentially, Alzheimer disease. p21-activated kinases (PAKs) regulate actin filaments and morphogenesis of dendritic spines regulated by the Rho family GTPases Rac and Cdc42. We previously reported that active PAK was markedly reduced in Alzheimer disease cytosol, accompanied by downstream loss of the spine actin-regulatory protein Drebrin. beta-Amyloid (Abeta) oligomer was implicated in PAK defects. Here we demonstrate that PAK is aberrantly activated and translocated from cytosol to membrane in Alzheimer disease brain and in 22-month-old Tg2576 transgenic mice with Alzheimer disease. This active PAK coimmunoprecipitated with the small GTPase Rac and both translocated to granules. Abeta42 oligomer treatment of cultured hippocampal neurons induced similar effects, accompanied by reduction of dendrites that were protected by kinase-active but not kinase-dead PAK. Abeta42 oligomer treatment also significantly reduced N-methyl-d-aspartic acid receptor subunit NR2B phosphotyrosine labeling. The Src family tyrosine kinase inhibitor PP2 significantly blocked the PAK/Rac translocation but not the loss of p-NR2B in Abeta42 oligomer-treated neurons. Src family kinases are known to phosphorylate the Rac activator Tiam1, which has recently been shown to be Abeta-responsive. In addition, anti-oligomer curcumin comparatively suppressed PAK translocation in aged Tg2576 transgenic mice with Alzheimer amyloid pathology and in Abeta42 oligomer-treated cultured hippocampal neurons. Our results implicate aberrant PAK in Abeta oligomer-induced signaling and synaptic deficits in Alzheimer disease.

A nuclear-penetrating lupus anti-DNA autoantibody, 3E10, has been found to inhibit DNA repair and selectively kill certain cancer cells that are highly vulnerable to DNA damage. In addition, a 3E10 single chain variable fragment (scFv) has been developed for use as a delivery vehicle to carry therapeutic cargo proteins into cell nuclei. A greater understanding of the mechanism by which 3E10 penetrates cell nuclei is needed to help determine the scope of its potential therapeutic applications. Here we show that the presence of extracellular DNA significantly enhances the nuclear uptake of 3E10 scFv. In addition, we find that 3E10 scFv preferentially localizes into tumor cell nuclei in vivo, likely due to increased DNA in the local environment released from ischemic and necrotic regions of tumor. These data provide insight into the mechanism of nuclear penetration by 3E10 and demonstrate the potential for use of 3E10 in therapeutic approaches to diseases ranging from malignancy to ischemic conditions such as stroke.

Protein therapy refers to the direct delivery of therapeutic proteins to cells and tissues with the goal of ameliorating or modifying a disease process. Current techniques for delivering proteins across cell membranes include taking advantage of receptor-mediated endocytosis or using protein transduction domains that penetrate directly into cells. The most commonly used protein transduction domains are small cell-penetrating peptides derived from such proteins as the HIV-1 Tat protein. A novel protein transduction domain developed as the single chain fragment (Fv) of a murine anti-DNA autoantibody, mAb 3E10, has recently been developed and used to deliver biologically active proteins to living cellsin vitro. This review will provide a brief overview of the development of the Fv fragment and provide a summary of recent studies using Fv to deliver therapeutic peptides and proteins (such as a C-terminal p53 peptide, C-terminal p53 antibody fragment, full-length p53, and micro-dystrophin) to cells.

Methods for cell type specific targeted intracellular delivery of proteins in vivo remain limited. A murine monoclonal anti-dsDNA antibody, mAb 3E10, was selectively transported into skeletal muscle cells in vivo. The antibody bound a 200 kDa protein only found in lysates of skeletal muscle by Western blotting. The 200 kDa protein was purified from muscle lysate by antibody affinity chromatography and identified as the skeletal muscle specific heavy chain of myosin IIb by electrospray mass spectrometry. Antibody binding specificity for myosin IIb was demonstrated in Western blots by binding myosin in skeletal muscle lysates from mice null for myosin IId but not in mice null for myosin IIb. Myosin IIb is implicated in the specific targeting of mAb 3E10 to skeletal muscle.

Cancer cells with defects in DNA repair are highly susceptible to DNA-damaging agents, but delivery of therapeutic agents into cell nuclei can be challenging. A subset of lupus autoantibodies is associated with nucleolytic activity, and some of these antibodies are capable of nuclear penetration. We hypothesized that such antibodies might have potential as therapeutic agents targeted towards DNA repair-deficient malignancies. We identified the lupus autoantibody 5C6 as a cell-penetrating nucleolytic antibody and found that 5C6 has a differential effect on a matched pair of BRCA2-proficient and deficient DLD1 colon cancer cells. 5C6 selectively induced γH2AX in, and suppressed the growth of, the BRCA2-deficient cells. These findings demonstrate the potential utility of 5C6 in targeted therapy for DNA repair-deficient malignancies and strengthen the rationale for studies of additional lupus autoantibodies in order to identify the best candidates for development as therapeutic agents. In addition, the toxic effect of 5C6 on BRCA2-deficient cells provides further support for the hypothesis that some lupus autoantibodies contribute to the lower risk of specific cancers associated with systemic lupus erythematosus.

The specificity of binding by antibodies to target antigens is a compelling advantage to antibody-based cancer therapy, but most antibodies cannot penetrate cells to affect intracellular processes. Select lupus autoantibodies penetrate into cell nuclei, and the potential for application of these antibodies in cancer therapy is an emerging concept. Here, we show that a divalent lupus anti-DNA autoantibody fragment with enhancing mutations that increase its ability to penetrate cell nuclei and bind DNA causes accumulation of DNA double-strand breaks in and is highly and selectively toxic to cancer cells and tumors with defective homology-directed repair of DNA double-strand breaks. These findings provide proof of principle for the use of optimized lupus autoantibodies in targeted cancer therapy. Cancer Res; 75(11); 2285–91. ©2015 AACR.

A murine monoclonal anti-dsDNA antibody was found to penetrate living cells and localize in the nucleus without pathologic effects. A single mutation in VHmarkedly enhanced cellular penetration. The mutant antibody was produced as recombinant Fab and single chain antibody fragments to investigate its use as a delivery system to target the cell nucleus. Complexes were made containing Fab fragments and alkaline phosphatase conjugated goat antibodies to mouse |gk chains. Fab fragments transported 305 kDa goat antibody–enzyme complexes into the nucleus in COS-7 and CHO cells. A single chain antibody cDNA was constructed by splice overlap extension PCR and expressed in COS-7 cells. Binding of the single chain antibody to dsDNA was shown by ELISA, and cellular penetration and nuclear localization were demonstrated in COS-7 and CHO cells. The single chain antibody cDNA was ligated into the expression vector, pEGFP, to produce a fusion protein with green fluorescent protein. The fusion protein penetrated COS-7 cells and localized in the cell nucleus. The single chain antibody produced during sustained expression in CHO cells re-entered antibody-producing cells and localized in the nucleus without affecting cell viability. Our results demonstrate the potential use of a modified autoantibody as a delivery system to target the cell nucleus.

Rheumatoid arthritis (RA) is a destructive polyarthritis in which synovial-like fibroblasts (SFs) invade and erode cartilage by expressing membrane-anchored type 1 matrix metalloproteinase (MT1-MMP). The mitogen activated protein kinase (MAPK) pathway is activated in RA SFs, but the mechanism of activation is unknown. Here we identify aberrant BRAF splice variants with deletions in both the kinase domain and RAS-binding domain (RBD) in SFs from the majority of RA patients and show that these BRAF splice variants constitutively activate MAPK through CRAF, increase expression of MT1-MMP, and enhance fibroblast invasion of collagen.

Systemic lupus erythematosus (SLE) is distinct among autoimmune diseases due to its association with circulating autoantibodies reactive against host DNA. The precise role that anti-DNA antibodies play in SLE pathophysiology remains to be elucidated, and potential applications of lupus autoantibodies in cancer therapy have not previously been explored. Here we report the unexpected finding that a cell-penetrating lupus autoantibody, 3E10, has potential as a targeted therapy for DNA-repair deficient malignancies. We find that 3E10 preferentially binds DNA single-strand tails, inhibits key steps in DNA single-strand and double-strand break repair, and sensitizes cultured tumor cells and human tumor xenografts to DNA-damaging therapy, including doxorubicin and radiation. Moreover, we demonstrate that 3E10 alone is synthetically lethal to BRCA2-deficient human cancer cells and selectively sensitizes such cells to low dose doxorubicin. Our results establish an approach to cancer therapy that we expect will be particularly applicable to BRCA2-related malignancies such as breast, ovarian, and prostate cancers. In addition, our findings raise the possibility that lupus autoantibodies may be partly responsible for the intrinsic deficiencies in DNA repair and the unexpectedly low rates of breast, ovarian, and prostate cancers observed in SLE patients. In summary, this study provides the basis for the potential use of a lupus anti-DNA antibody in cancer therapy and identifies lupus autoantibodies as a potentially rich source of therapeutic agents.

Synovial fibroblasts destroy articular cartilage and bone in rheumatoid arthritis, but the mechanism of fibroblast transformation remains elusive. Because gain-of-function mutations of BRAF can transform fibroblasts, we examined BRAF in rheumatoid synovial fibroblasts. The strong gain-of-function mutation, V600R, of BRAF found in melanomas and other cancers was identified in first passage synovial fibroblasts from two of nine rheumatoid arthritis patients and confirmed by restriction site mapping. BRAF-specific siRNA inhibited proliferation of synovial fibroblasts with V600R mutations. A BRAF aberrant splice variant with an intact kinase domain and partial loss of the N-terminal autoinhibitory domain was identified in fibroblasts from an additional patient, and fibroblast proliferation was inhibited by BRAF-specific siRNA. Our finding is the first to establish mechanisms for fibroblast transformation responsible for destruction of articular cartilage and bone in rheumatoid arthritis and establishes a new target for therapeutic intervention.

OBJECTIVE Human T-cell leukemia virus types I (HTLV-I) and II (HTLV-II) are closely related human retroviruses. HTLV-I has been implicated in a chronic progressive myelopathy, known as tropical spastic paraparesis (TSP) or HTLV-I-associated myelopathy (HAM). We sought to determine whether autoantibodies to brain antigens were present in the cerebrospinal fluid (CSF) of a patient with chronic progressive spastic myelopathy with evidence of both HIV-1 infection and HTLV-I/II seropositivity. DESIGN A 54-year-old bisexual man with clinical features of HAM/TSP of over 20 years' duration was followed. METHODS We applied discriminatory DNA amplification (polymerase chain reaction) to distinguish HTLV-I from HTLV-II and to verify co-infection with HIV-1. The patient's CSF was used to screen a human brain cDNA expression library to identify antibodies directed against brain antigens. Autoreactive bacteriophage clones were isolated and sequenced. RESULTS The patient was found to be co-infected with both HIV-1 and HTLV-II, but not with HTLV-I. HTLV-II proviral levels in the peripheral blood remained relatively constant, despite therapy with zidovudine. Prominent oligoclonal banding of immunoglobulins was present in the patient's CSF. A single repeatedly reactive cDNA clone was identified, by screening with CSF antibody, sequenced, and found to be the human homologue of the rat insulinoma gene, rig. CONCLUSIONS HTLV-II infection may predispose to development of a HAM/TSP-like illness. Autoimmune mechanisms, such as autoantibody formation, may play a role in pathogenesis.

In addition to its immune suppressive function in T-regulatory cells, the nuclear transcription factor, FOXP3, has been identified as a tumor suppressor. To evaluate the clinical efficacy of monoclonal antibody (mAb) 3E10 Fv antibody-mediated FOXP3 protein therapy of cancer, the Fv-FOXP3 fusion protein produced in Pichia pastoris was tested on breast, ovarian, and colon cancer cells in vitro, and with colon cancer cells in vivo in a mouse model of colon cancer metastasis to liver. Treatment with Fv-FOXP3 resulted in dose-dependent cell death of cancer cells in vitro. Apoptosis was established as a mechanism of cell death by demonstrating increased production of the p17 activated fragment of caspase-3 by cancer cells in response to Fv-FOXP3 and inhibition of cell killing by the caspase inhibitor, Z-VAD-FMK. Fv-FOXP3 treatment resulted in clinically significant reduction in tumor burden in a syngeneic model of colon cancer metastasis to liver in Balb/c mice. These results represent the first demonstration of effective full-length FOXP3 protein therapy and emphasize the clinical potential of mAb 3E10 as an intracellular and intranuclear delivery vehicle of FOXP3 for prevention and treatment of cancer metastasis.

To measure rheumatoid factors specific for patients with rheumatoid arthritis an enzyme linked immunosorbent assay (ELISA) was developed to measure rheumatoid factors in human serum that bind a cross-reactive determinant shared on human and other mammalian IgG. Rheumatoid factors that cross link human IgG and sheep IgG in a double binding ELISA were almost completely specific (greater than 99%) for rheumatoid arthritis in assays of 108 sera from patients with rheumatoid arthritis compared with 231 sera from patients with other connective tissue diseases and 365 sera from healthy subjects and patients without these diseases. Moreover, positive tests occurred primarily in patients with active arthritis (r = 0.68). In contrast, these rheumatoid factor autoantibodies were not detected in sera from most of the patients with other autoimmune diseases, including patients with systemic lupus erythematosus. These results show that rheumatoid factors identified in human sera by the double binding test are specific for active rheumatoid arthritis.

Human granulocyte colony-stimulating factor (G-CSF) is a regulatory glycoprotein that stimulates the production of neutrophilic granulocytes from committed hematopoietic progenitor cells both in vitro and in vivo. In this report, we show that biosynthetic (recombinant) human G-CSF enhances colony formation by normal human bone marrow and the human myeloid leukemic cell lines, HL-60 and KG-1, as well as nonhematopoietic small cell lung cancer lines, H128 and H69. G-CSF also modulates multiple differentiated functions of human neutrophils, including enhanced oxidative metabolism in response to f- Met-Leu-Phe (f-MLP), increased antibody-dependent cell-mediated cytotoxicity (ADCC), and augmented arachidonic acid release in response to ionophore and chemotactic agents. These effects are all maximal at a concentration of 100 to 500 pmol/L. Using 125I-labeled recombinant human G-CSF, high affinity binding sites were identified on human neutrophils, the myeloid leukemia cell lines KG-1 and HL-60, and the small cell carcinoma cell lines, H128 and H69. G-CSF receptor numbers ranged between 138 and 285 sites per cell with a kd of 77 to 140 pmol/L, consistent with the concentrations of G-CSF that elicit biologic responses in vitro. Decreased specific binding of 125l-G-CSF by human neutrophils was consistently observed in the presence of excess unlabeled human granulocyte-macrophage colony-stimulating factor (GM-CSF), suggesting competition or down modulation by GM-CSF of the G- CSF receptor.

Colony-stimulating factors (CSFs) have important effects on mature myeloid cells in addition to their regulatory role in haemopoiesis. Exposure of neutrophils to granulocyte macrophage-CSF (GM-CSF) increases chemotaxis, phagocytosis and cytotoxicity and primes the cells for enhanced oxidative metabolism in response to stimuli, such as formylated oligopeptides derived from bacteria (f-Met-Leu-Phe) and endogenous activated complement components (C5a). GM-CSF induces time-dependent changes in neutrophil f-Met-Leu-Phe receptor number and affinity that correspond to changes in functional activity. The neutrophil IgA Fc receptor is also modulated by GM-CSF such that it develops a high affinity state and transduces a phagocytic signal. The ability to regulate the number and activity of mature myeloid effector cells in vivo establishes unique therapeutic opportunities in the area of infectious disease, cancer treatment, bone marrow transplantation and augmentation of host defence in immunodeficient patients.

To evaluate the clinical efficacy of monoclonal antibody (mAb) 3E10 Fv antibody-mediated p53 protein therapy, an Fv-p53 fusion protein produced in Pichia pastoris was tested on CT26.CL25 colon cancer cells in vitro and in vivo in a mouse model of colon cancer metastasis to the liver. In vitro experiments showed killing of CT26.CL25 cells by Fv-p53 but not Fv or p53 alone, and immunohistochemical staining confirmed that Fv was required for transport of p53 into cells. Prevention of liver metastasis in vivo was tested by splenic injection of 100 nmol/L Fv-p53 10 min and 1 week after injection of CT26.CL25 cancer cells into the portal vein of BALB/c mice. Mice were sacrificed 1 week after the second injection of Fv-p53 and assigned a quantitative metastasis score. Control mice had an average metastasis score of 3.3 ± 1.3, whereas mice treated with Fv-p53 had an average metastasis score of 0.8 ± 0.4 (P = 0.004). These results indicate that Fv-p53 treatment had a profound effect on liver metastasis and represent the first demonstration of effective full-length p53 protein therapy in vivo. mAb 3E10 Fv has significant clinical potential as a mediator of intracellular and intranuclear delivery of p53 for prevention and treatment of cancer metastasis. [Cancer Res 2007;67(4):1769–74]

Androgen receptor (AR) plays a critical role in the development and progression of prostate cancer (PCa). Current therapies target the ligand-binding domain (LBD) of AR by inhibiting production or binding of ligand. In castration-resistant PCa (CRPC), AR isoforms lacking the LBD are highly expressed, resulting in constitutive, ligand-independent AR signaling. Therapies to block ligand-independent AR signaling have not been introduced into clinical use. We have developed bispecific antibodies (bsAbs) that penetrate PCa cells and bind to the N-terminal domain of the AR, inhibiting AR signaling. The 3E10-AR441 bsAb was engineered by connecting two single-chain variable fragments (scFv) with a linker. One half of the bsAb molecule is scFv 3E10, derived from a lupus anti-DNA antibody. This module enters cells through the ENT2 nucleoside salvage receptor and locates in the nucleus. The other half is an scFv based on the anti-AR monoclonal antibody AR441. The 3E10-AR441 bsAb is expressed in yeast as a single recombinant protein. Treatment of LNCaP with bsAb resulted in nuclear accumulation of the antibody, visualized by confocal microscopy. The 3E10-AR441 bsAb also engaged its target under denaturing and non-denaturing conditions. The bsAb could detect AR when used to probe an AR immunoblot. It could also immunoprecipitate WT AR, as well as mutant/variant AR lacking the LBD (AR(Q640X), Arv7). The scFv 3E10 alone did not bind to AR. BsAb binding affinity to AR was assessed using a competitive sandwich-type ELISA. An anti-AR antibody-coated microtiter plate was used to capture WT AR or mutant\variant AR from cell lysates. AR441-HRP antibody conjugate was mixed with increasing concentrations of 3E10-AR441 or AR441 as competitors. Binding affinity of 3E10-AR441 to WT AR (180nM) was higher than that of the parental AR441 MoAb (7nM). Affinity of bsAb was 3 fold higher to WT AR than to an AR(Q640X) mutant. The bsAb blocked genomic AR signaling in LNCaP cells, as measured by dihydrotestosterone (DHT) activation of both artificial (ARE-luciferase) and endogenous (PSA) reporters. The magnitude of inhibition was similar to that seen with enzalutamide at 5 μM. The 3E10 scFv alone had minimal effect on reporter gene expression. Non-genomic AR signaling was measured by calcium release upon DHT treatment. Calcium5 dye was added to LNCap treated with variable doses of bsAb or 3E10. The fluorescence intensity is proportional to the amount of calcium released. 3E10-AR441 blocked DHT-induced release of calcium while 3E10 did not. Current work is focused on the design of 3E10-AR441 derivatives with enhanced binding affinity towards AR mutants lacking the LBD. 3E10-AR441 bsAb is an attractive therapeutic agent due to its ability to inhibit AR function in a ligand-independent manner. Citation Format: Nancy L. Goicochea, Maria Garnovskaya, Mary Blanton, Grace Chan, Richard Weisbart, Michael Lilly. Cell-penetrating bispecific antibodies for targeting androgen receptor signaling in advanced prostate cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 642. doi:10.1158/1538-7445.AM2015-642

Defects in dendritic spines are common to several forms of cognitive deficits, including mental retardation and Alzheimer disease. Because mutation of p21-activated kinase (PAK) can lead to mental retardation and because PAK-cofilin signaling is critical in dendritic spine morphogenesis and actin dynamics, we hypothesized that the PAK pathway is involved in synaptic and cognitive deficits in Alzheimer disease. Here, we show that PAK and its activity are markedly reduced in Alzheimer disease and that this is accompanied by reduced and redistributed phosphoPAK, prominent cofilin pathology and downstream loss of the spine actin-regulatory protein drebrin, which cofilin removes from actin. We found that beta-amyloid (Abeta) was directly involved in PAK signaling deficits and drebrin loss in Abeta oligomer-treated hippocampal neurons and in the Appswe transgenic mouse model bearing a double mutation leading to higher Abeta production. In addition, pharmacological PAK inhibition in adult mice was sufficient to cause similar cofilin pathology, drebrin loss and memory impairment, consistent with a potential causal role of PAK defects in cognitive deficits in Alzheimer disease.

The Fv fragment of an antibody that selectively targets and penetrates skeletal muscle in vivo was produced as a fusion protein with a micro-dystrophin for use as a delivery vehicle to transport micro-dystrophin into muscle cells. Fv-micro-dystrophin was produced as a secreted protein by transient transfection of Fv-micro-dystrophin cDNA in COS-7 cells and as a non-secreted protein by permanent transfection in Pichia pastoris. Isolated Fv-micro-dystrophin was shown to be full-length by Western blot analysis. Fv-micro-dystrophin penetrated multiple cell lines in vitro, and it localized to the plasma membrane of a cell line with membrane beta-dystroglycan. In the absence of membrane beta-dystroglycan, it localized to the cytoplasm. Antibody-mediated transduction of micro-dystrophin into muscle cells is a potential therapy for dystrophin-deficient muscular dystrophies.

Some human cancers are caused by functional defects in p53 that are restored by gene therapy with wild-type p53. To circumvent the use of viral vectors, we reconstituted cancer cell lines with p53 by protein transduction. A fusion protein was produced from cDNA constructed from the Fv fragment of an antibody that penetrates living cells and wild-type p53 (Fv-p53). Fv-p53 penetrated and killed cancer cells that do not express p53. Additionally, Fv-p53 killed cancer cells that were malignant as a result of mutations within p53, nuclear exclusion of p53 and over-expression of MDM2. Non-specific toxicity was excluded by showing that Fv-p53 penetrated but did not kill primary cells and cancer cells unresponsive to p53. Fv fragments alone were not cytotoxic, indicating that killing was due to transduction of p53. Fv-p53 was shown to penetrate cancer cells engrafted in vivo. These results support continued efforts to evaluate the potential efficacy of Fv-p53 for the treatment of certain cancers in vivo.

scFv fragments of a monoclonal antibody that penetrates living cells and localizes in nuclei were designed as fusion proteins with C-terminal p53 peptides and tested for restoring p53 function in p53 mutant cancer cells. scFv fragments transported a 30-mer C-terminal peptide of p53 into cancer cells and induced cellular cytotoxicity in contrast to scFv fragments alone and other scFv-p53 fusion peptides. Cellular toxicity was not observed with scFv fragments containing a single mutation in VH that prevented antibody penetration. Our results demonstrate the potential efficacy of antibody scFv fragments as a nuclear delivery system in cancer cells.

Aberrant G-protein signaling due to mutations in genes encoding the Ras family of small GTPases is associated with approximately 30% of human cancers, and K-ras is one of the most commonly mutated Ras proteins. Development of targeted therapies that are preferentially toxic to cancer cells harboring K-ras mutations is therefore an important goal in cancer research. We have identified an unusual cell-penetrating lupus autoantibody, 4H2, as a potential candidate for development as a targeted therapy for tumors with activating K-ras mutations. 4H2 is an anti-guanosine antibody that has previously been shown to penetrate living cells and inhibit cAMP formation. Taken together, the ability of 4H2 to bind guanosine (a component of GDP/GTP) and to inhibit cAMP formation suggests that 4H2 perturbs G-protein signaling. We therefore hypothesized that 4H2 would be selectively toxic to cancer cells with aberrant G-protein signaling due to activating K-ras mutations compared to cells without mutations in K-ras. To test this hypothesis, we evaluated the effects of 4H2 on a panel of isogenic pairs of cells with and without activating K-ras mutations, including Cal12T lung cancer cells (with and without a G12C activating K-ras mutation), NCI-H1975 lung cancer cells (with and without a G12D activating K-ras mutation), and SW48 colon cancer cells (with and without a G12A activating K-ras mutation). Immunofluorescence experiments confirmed that 4H2 penetrates into and localizes to the cytoplasm of cells with and without an activating K-ras mutation. In cell proliferation assays the matched pairs of cells were treated with 4H2 while growing as subconfluent monolayers, and 4H2 was observed to significantly inhibit the proliferation of the cells with activating K-ras mutations but not the cells without K-ras mutations. Next, colony formation assays confirmed that treatment with 4H2 was significantly more toxic to cells with activating K-ras mutations compared to cells without K-ras mutations. Mechanistically, Western blot analyses suggest a differential effect of 4H2 on the MAP kinase and Akt signaling pathways in K-ras mutant and wild type cells, consistent with the hypothesis that 4H2 interferes with G-protein associated intracellular signaling pathways. In summary, this work has demonstrated that 4H2 is an intriguing candidate for further study and development as a potential targeted therapy for tumors with activating mutations in K-ras. Citation Format: Melissa R. Young, Philip W. Noble, Richard H. Weisbart, James E. Hansen. Targeting K-ras mutant cancer cells with a lupus anti-guanosine antibody. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 654. doi:10.1158/1538-7445.AM2014-654

Identification of therapeutic agents that are more toxic to malignant cells than normal cells is a key goal in cancer research. Many tumor cells harbor genetic defects that distinguish them from normal cells, and some of these defects have the potential to be exploited in the development of targeted therapies for cancer. Cancer cells with defects in DNA repair are highly susceptible to DNA-damaging agents, but delivery of therapeutic agents into cell nuclei can be challenging. A subset of lupus autoantibodies is associated with nucleolytic activity, and some of these antibodies are capable of nuclear penetration. We hypothesized that such antibodies might be capable of damaging DNA in cell nuclei and therefore have potential as therapeutic agents targeted towards DNA repair-deficient malignancies, such as tumors that are BRCA2-deficient. To test this hypothesis we screened a panel of cell-penetrating lupus autoantibodies for nucleolytic activity, and we identified 5C6 as an antibody of interest. 5C6 catalyzes degradation of single and double-stranded DNA in vitro and induces phospho-H2AX formation in BRCA2-deficient cells. When tested on a matched pair of BRCA2-proficient and deficient cancer cells, 5C6 selectively suppressed the growth of and was significantly more toxic to the BRCA2-deficient cells. These findings demonstrate the potential utility of 5C6 in targeted therapy for DNA repair-deficient malignancies and strengthen the rationale for studies of additional lupus autoantibodies in order to identify the best candidates for development as therapeutic agents. In addition, the toxicity of 5C6 for BRCA2-deficient cells provides further support for the hypothesis that some lupus autoantibodies contribute to the unusual cancer risk profile associated with systemic lupus erythematosus. Citation Format: Philip W. Noble, Melissa R. Young, Richard H. Weisbart, James E. Hansen. A cell-penetrating nucleolytic lupus autoantibody damages DNA and is toxic to BRCA2-deficient cancer cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4220. doi:10.1158/1538-7445.AM2014-4220

An Ab-based system to deliver functional proteins into neurons was developed using the murine mAb, mAb 3E10. This was achieved by covalently conjugating catalase to the Ab so that the conjugate retained high activity for the degradation of hydrogen peroxide. Three-dimensional fluorescence microscopy was used to demonstrate penetration of the Ab into the nucleus of living primary cortical neurons. The Ab conjugate localized in both the cytoplasm and nucleus. Retention of catalase activity after penetration and distribution of conjugate was demonstrated by reduction in cell death following exposure of treated neurons to hydrogen peroxide. These studies illustrate the potential of this method for the intracellular delivery of therapeutic proteins.

The idea that some antibodies possess the ability to penetrate both the cell and nuclear membranes of a living cell is still considered to be a controversial, if not heretical, notion. However, there is a considerable body of literature to support the idea that penetration of cells by certain antibodies can and does occur. The first reports observing the presence of immunoglobulin in the nuclei of cells were published over 30 yr ago. In these studies, skin (1) and renal (2) biopsy specimens from patients with systemic lupus erythematosus (SLE) were examined for the presence or absence of immunoglobulin by immunofluores-cence staining with anti-IgG antisera. SLE is an autoimmune disease characterized by the production of a wide variety of autoantibodies. Within each tissue type, several different patterns of immunoglobulin deposition were seen. One recurrent pattern was the finding of nuclear deposits of immunoglobulin in either a homogenous or a speckled distribution. Implicit in this observation is the notion that the antibody deposition had occurred in vivo prior to the collection of the specimen, and by extension, that the deposits might somehow be involved in the pathogenesis of the skin findings. Only some individuals with the disease demonstrated the presence of penetrating antibodies and there was some suggestion that the penetrating antibodies showed tissue specificity (1).

A subset of autoantibodies produced by patients with systemic lupus erythematosus (SLE) penetrates into cell nuclei and binds DNA, and we believe that such antibodies may have applications in cancer therapy. We have discovered that the cell-penetrating, nuclear-localizing anti-DNA lupus antibody 3E10 inhibits key steps in DNA single- and double-strand break repair and has potential for development as a targeted therapy for tumors harboring deficiencies in DNA repair. 3E10 preferentially binds DNA substrates with free single-strand tails and interferes with both base excision repair and homology-directed repair (HDR) in vitro, and HDR efficiency is reduced in cells treated with 3E10 as measured in the chromosome-based DR-GFP fluorescent reporter assay. The binding of 3E10 to DNA can be directly visualized under electron microscopy (EM), and EM studies confirmed that 3E10 interferes with RAD51 filament formation, which is a critical step in HDR. The 3E10 single chain variable fragment penetrates into human tumor xenografts in nude mice, and 3E10 sensitizes cancer cells and tumors to DNA-damaging therapy. In addition, 3E10, by itself, is toxic to BRCA2-deficient cancer cells but not to repair-proficient cells, and when combined with a DNA-damaging agent, 3E10 has a very large cytotoxic effect on BRCA2-deficient cancer cells. The synthetically lethal effect of 3E10 on BRCA2-deficient cancer cells is consistent with our finding that 3E10 inhibits DNA repair, and it suggests that 3E10 has potential as a targeted therapy for tumors harboring deficiencies in DNA repair, such as certain breast, ovarian, and prostate cancers. Of note, patients with SLE have lower than expected incidence rates of breast, ovarian, and prostate cancers, and it is tempting to speculate that the circulating cell-penetrating anti-DNA autoantibodies provide patients with SLE some protection against the development of DNA repair-deficient tumors. In summary, our work with the 3E10 antibody has provided proof of principle for the development of a lupus antibody as a cancer therapy and opened up new avenues for exploration into the biology of lupus antibodies. Citation Format: James E. Hansen, Grace Chan, Yanfeng Liu, Denise C. Hegan, Shibani Dalal, Eloise Dray, Youngho Kwon, Yuanyuan Xu, Xiaohua Xu, Elizabeth Peterson-Roth, Erik Geiger, Yilun Liu, Joseph Gera, Joann B. Sweasy, Patrick Sung, Sara Rockwell, Robert N. Nishimura, Richard H. Weisbart, Peter M. Glazer. Lupus antibody-based cancer therapy. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4319. doi:10.1158/1538-7445.AM2013-4319

The stimulus for the production of anti-DNA autoantibodies in lupus remains unknown. Since double-stranded DNA (dsDNA) is a weak immunogen, other stimuli such as B cell superantigens or anti-idiotypic antibodies may provide an alternative mechanism for their production. The presence of regulatory determinants on autoantibodies might be revealed through their structural characterization, but they have eluded detection, perhaps because they may be three-dimensional and require closer analysis. In this report we cloned and sequenced the heavy chain variable region (VH) of a monoclonal anti-dsDNA antibody, mAb 3E10, derived from MRL/lpr mice with lupus nephritis previously shown to express an idiotype associated with nephritis in murine and human lupus. We now show that mAb 3E10 VH contains novel structural features unrelated to DNA binding which are shared only by a subset of autoantibodies expressed in murine lupus. These lupus autoantibodies can be distinguished from antibodies of non-autoimmune strains by the presence of a specific sequence at the junction of the diversity and joining genes combined with the use of variable region genes with conserved sequences in framework 1 (FR1) and FR3. The location of the novel sequences indicates the possibility of a three-dimensional solvent-exposed determinant located distant from the classical antigen binding site that could regulate their production, possibly through binding B cell superantigens or other infectious agents.

Neutrophil migration inhibition factor from T lymphocytes (NIF-T) is a lymphokine that acts to localize granulocytes. Medium conditioned by the Mo human T-lymphoblast cell line was used to purify NIF-T, a glycoprotein with a molecular weight of 22,000. The NIF-T was found to potently stimulate the growth of granulocyte and macrophage colonies from human bone marrow and colony formation by the KG-1 myeloid leukemia cell line. Thus a human lymphokine (NIF-T) that modulates the activities of mature neutrophilic granulocytes is also a colony-stimulating factor acting on precursors to induce growth and differentiation of new effector cells.

A reliable microassay for human leukocyte migration is described by which 50 to 100 assays can be performed each day in quadruplicate with the number of indicator cells obtainable from 10 to 20 ml of peripheral blood. The reproducibility of this method is demonstrated with respect to the variability among replicate test wells (including reading), the variability among different test readers, the variability among replicate cultures, and the variability of using indicator cells from different subjects. A microculture system is described that requires only 75,000 mononuclear cells to consistently produce detectable polymorphonuclear leukocyte migration inhibition factor in response to PPD. The reproducibility of this culture system is demonstrated with respect to the variability of lymphocyte responsiveness on repetitive testing in the same individuals.

Production of human migration inhibitory factor by lymphocytes exposed to antigen was studied at intervals over a 7-day period. Migration inhibitory factor was measured by an agarose gel method, with buffycoat leukocytes as indicator cells. Lymphocyte supernatants from 7-day cultures consistently showed migration inhibitory factor activity; by contrast, enhancement of migration was frequently noted when effector cells were exposed to supernatants from 2- to 5-day cultures. Enhancement activity was manifested either by enhanced migration or by a sequential reduction in inhibitory activity consistent with a factor opposing the action of migration inhibitory factor. When supernatants were subjected to polyacrylamide gel electrophoresis, enhancement activity was regularly found in the beta-globulin region and migration inhibitory factor in the albumin fraction of the gel. The enhancement activity was heat-stable and nondialyzable. These findings characterize a hitherto unreported lymphokine, migration enhancement factor.

We conducted a clinical trial of human recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF) in leukopenic patients with acquired immunodeficiency syndrome (AIDS) and analyzed neutrophil function before, during, and after in vivo administration of rGM-CSF. Prior to GM-CSF infusion, AIDS patients' neutrophil superoxide generation and neutrophil antibody-dependent cell-mediated cytotoxicity were enhanced normally by in vitro exposure to GM-CSF. Neutrophil phagocytosis and intracellular killing of Staphylococcus aureus were also normal in the majority of these patients. Two patients, however, had discrete neutrophil functional defects: one in phagocytosis and one in intracellular killing. During the period of GM-CSF infusion, these abnormalities were corrected. The number of circulating neutrophils increased in all patients treated with GM-CSF in a dose-dependent manner. Neutrophils produced in vivo in response to GM-CSF administration functioned normally and there was evidence for neutrophil priming and activation in vivo. We conclude that GM-CSF treatment of AIDS patients leads to the production of functionally active neutrophils, suggesting therapeutic potential for GM-CSF in the treatment of patients with impaired host defense.

Plasma catecholamine (norepinephrine) concentration during upright posture and lymphocyte adenylate cyclase response to the β-adrenergic catecholamine isoproterenol were compared in two age groups of healthy subjects. Compared to subjects between the ages of 19-38 yr, those between 65-88 yr had higher plasma norepinephrine concentrations (353 ± 42 vs. 577 ± 65 pg⁄ml) and reduced lymphocyte adenylate cyclase responsiveness to NaF, isoproterenol, guanyl nucleotide, and isoproterenol in the presence of guanylyl nucleotide. There were important differences between the properties of adenylate cyclase in cells from the aged subjects and those from younger subjects pretreated with norepinephrine in vitro. Pretreated cells had diminished responsiveness to isoproterenol (desensitization), but not to guanylyl nucleotide. Moreover, guanylyl nucleotide restored isoproterenol responsiveness to the desensitized enzyme. Thus, reduced responsiveness of lymphocyte adenylate cyclase from aged subjects was not attributable ...

The effect of prednisone on serum levels of IgG antibodies to viral and bacterial antigens was measured and compared to its effect on IgG antibodies to nuclear antigens in 8 patients with systemic lupus erythematosus. Prednisone at 15-80 mg/day (mean 55 mg/day) for 14-30 days (mean 19 days) lowered the serum IgG by an average of 22% (p less than 0.005). An even greater reduction in IgG antinuclear antibodies occurred (mean 43%, p less than 0.001) including responses to double stranded DNA, single stranded DNA, and the nucleosides, adenosine, guanosine, cytidine and thymine riboside. In contrast, there was no alteration in serum IgG antibody levels to influenza virus vaccine and pneumococcal vaccine antigens. These results suggest that prednisone has a selective effect on the expression of autoimmunity which may, in part, be responsible for its clinical efficacy in systemic lupus erythematosus.

The antigen specificity, isotype, and subclass of antinuclear antibodies may be related to their pathogenicity in systemic lupus erythematosus (SLE). Our laboratory found that IgG antibodies that bound the nucleoside, guanosine, occurred frequently in SLE patients. In contrast, sera from healthy subjects contained IgM but not IgG antiguanosine antibodies. The present studies were designed to characterize the fine specificity of IgG antiguanosine antibodies in SLE and compare them with IgM antiguanosine antibodies in normal sera. Serum antinuclear antibodies from six healthy subjects and six SLE patients were isolated by affinity binding to guanosine and measured by an enzyme-linked immunosorbent assay (ELISA). IgM in normal sera, and both IgM and IgG in SLE sera bound guanosine. IgM antiguanosine antibodies in normal sera were polyspecific and bound other nucleosides and 1-methylguanosine but not denatured DNA (ssDNA). In contrast, IgG antiguanosine antibodies from the SLE patients bound guanosine and ssDNA but not other nucleosides or 1-methylguanosine. SLE IgM antiguanosine antibodies had the same fine specificity and bound guanosine and ssDNA but not any of the other nucleosides. These results suggest that SLE IgG and IgM antiguanosine antibodies have fine specificity in contrast to the polyspecific IgM antibodies in normal sera. In addition, subclass analysis indicated that all SLE patients had either IgG1 or IgG3 subclass of antiguanosine antibodies that bind complement. Characterizing the isotype, subclass, and fine antigen specificity of antiguanosine antibodies should assist in evaluating their potential pathogenicity in SLE.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a T cell- derived lymphokine which induces hematopoietic precursor cells to proliferate in vitro and differentiate to neutrophils and macrophages. GM-CSF also inhibits the motility of mature neutrophils (NIF-T activity), and primes neutrophils to enhance oxidative metabolism in response to the bacterial chemoattractant, N-formyl-methionyl-leucyl- phenylalanine (f-MLP). The present study was designed to determine whether this lymphokine also enhances neutrophil oxidative metabolism in response to the other major physiological chemoattractants which include complement-derived C5a, and the 5-lipoxygenation product of arachidonic acid, leukotriene B4 (LTB4). Superoxide anion production was measured as superoxide dismutase-inhibitable cytochrome C reduction. Purified biosynthetic GM-CSF enhanced superoxide anion production by neutrophils in response to f-MLP, C5a desArg, and LTB4. In contrast to several other factors which prime neutrophils, GM-CSF did not prime for an enhanced oxidative response to phorbol myristate acetate (PMA). These results suggest that GM-CSF may be an endogenous regulator of neutrophil inflammatory responses induced by the major physiological chemoattractants.

The colony-stimulating factors (CSF) are a family of glycoprotein hormones that regulate the proliferation and maturation of hematopoietic progenitor cells. In addition to their effects on hematopoiesis, CSFs modulate the function of fully mature cells and, therefore, play an important role in regulating inflammatory responses vital to host defense. Here we review recent information that describes the biological activity of the CSFs on mature cell function, including chemotaxis, adherence, motility, phagocytosis, oxidative metabolism, and cytotoxicity.

In order to determine whether human granulocyte-macrophage colony- stimulating factor (GM-CSF) can enhance phagocytosis, neutrophils were combined with Staphylococcus aureus (S aureus), and both the number of bacteria per neutrophil and the percent of neutrophils phagocytizing were assessed in the absence and presence of GM-CSF. Exposure to GM-CSF did not enable neutrophils to ingest unopsonized bacteria. When bacteria were opsonized with serum, both the number of bacteria per neutrophil and the percent of cells phagocytizing were increased by treatment with GM-CSF. Digestion of extracellular organisms by lysostaphin was used to substantiate phagocytosis. These results indicate that another effect of GM-CSF on the mature neutrophil is the enhancement of phagocytosis.

Purified natural and biosynthetic (recombinant) human granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulate colony formation by myeloid progenitor cells and enhance the function of mature neutrophils. Both of these actions occur at concentrations between 1 and 100 pM, with half-maximal stimulation at 10-20 pM. We have examined specific binding of 125I-labeled GM-CSF to responsive target cells in this range of concentrations. The results show a low number (50-250) of high-affinity (15-30 pM) binding sites on GM-CSF-responsive leukemic cells (KG-1, HL-60), as well as on peripheral blood neutrophils from normal donors. This high-affinity binding component was absent from unresponsive cell lines (KG-1a, K562). These results suggest that this binding site mediates the biological activities of GM-CSF on both proliferation and function of myeloid cells.

Wegener's granulomatosis is a systemic necrotizing granulomatous vasculitis in which the average age at onset is in the forties. The disease has an excellent response to treatment with cyclophosphamide. We proposed that the tendency to accept multisystem disease in elderly patients (greater than or equal to 60 years old) and a reluctance to administer aggressive therapy would be reflected in the diagnosis and treatment of Wegener's granulomatosis in the elderly, and that as a consequence, the delay in diagnosis and implementation of therapy could result in a needlessly higher morbidity and mortality rate for this population of patients.

Antinuclear antibodies are present in most patients receiving procainamide. To ascertain whether IgG antiguanosine antibodies are associated with the development of the symptoms of systemic lupus erythematosus, we compared the levels of these antibodies in the sera of 65 patients receiving procainamide: 18 with procainamide-induced symptoms and 47 asymptomatic patients. Antinuclear antibodies measured by immunofluorescence were present in the 18 patients with drug-induced symptoms but also in 24 asymptomatic patients. Similarly, elevated serum levels of antibodies to single-stranded DNA were found in 15 patients with symptoms and in 20 asymptomatic patients. In contrast, levels of IgG antiguanosine antibodies were elevated in 15 patients with drug-induced symptoms, but in only 3 asymptomatic patients. Antiguanosine antibodies binding to single-stranded DNA were found primarily in patients with arthritis, pleuritis, and pericarditis. These results suggest a strong association between IgG antiguanosine antibodies and major manifestations of procainamide-induced systemic lupus erythematosus.