Penetration of anti-DNA antibodies into immature live cells

KRAS-specific antibody binds to KRAS protein inside colorectal adenocarcinoma cells and inhibits its localization to the plasma membrane

Colorectal cancer (CRC) is the third highest incidence cancer and a leading cause of cancer mortality worldwide. To date, chemotherapeutic treatment of advanced CRC that has metastasized has a dismayed success rate of less than 30%. Further, most (80%) sporadic CRCs are microsatellite-stable and are refractory to immune checkpoint blockade therapy. KRAS is a gatekeeper gene in colorectal tumorigenesis. Nevertheless, KRAS is ‘undruggable’ due to its structure. Thus, focus has been diverted to develop small molecule inhibitors for its downstream effector such as ERK/MAPK. Despite intense research efforts for the past few decades, no small molecule inhibitor has been in clinical use for CRC. Antibody targeting KRAS itself is an attractive alternative. We developed a transient ex vivo patient-derived matched mucosa-tumor primary culture to assess whether anti-KRAS antibody can be internalized to bind and inactivate KRAS. We showed that anti-KRAS antibody can enter live mucosa-tumor cells and specifically aggregate KRAS in the cytoplasm, thus hindering its translocation to the inner plasma membrane. The mis-localization of KRAS reduces KRAS dwelling time at the site where it tethers to activate downstream effectors. We previously showed that expression of SOX9 was KRAS-mutation-dependent and possibly a better effector than ERK in CRC. Herein, we showed that anti-KRAS antibody treated tumor cells have less intense SOX9 cytoplasmic and nuclear staining compared to untreated cells. Our results demonstrated that internalized anti-KRAS antibody inhibits KRAS function in tumor. With an efficient intracellular antibody delivery system, this can be further developed as combinatorial therapeutics for CRC and other KRAS-driven cancers.

Peptide Sharing Between Viruses and DLX Proteins: A Potential Cross-Reactivity Pathway to Neuropsychiatric Disorders

The present study seeks to determine potential associations between viral infections and neuropsychiatric diseases. To address this issue, we investigated the peptide commonalities between viruses that have been related to psychiatric and neurological disorders—such as rubella, human immunodeficiency virus, and herpesviruses—and human distal-less homeobox (DLX) proteins expressed in developing brain—namely, DLX1, DLX2, DLX5, and DLX6. Peptide matching analyses revealed a high degree of pentapeptide sharing. From an immunological perspective, this overlap is relevant because pentapeptides are endowed with immunogenicity and antigenicity—that is, they are immune determinants. Moreover, infection-induced immune cross-reactions might have functional, spatial, and temporal implications related to the functions and expression patterns of DLX1 and DLX5 in the fetal and adult human brain. In sum, our data support the hypothesis that viral infections may be linked to neuropsychiatric diseases through autoimmune cross-reactions caused by molecular mimicry between viral proteins and brain-specific DLX self-antigens.

Immunophenotypic characterization of lymphoid cell infiltrates in vitiligo

The pathogenesis of vitiligo is still controversial. The purpose of this study was to gain insight into the nature of lymphoid cells infiltrating depigmented areas of skin in vitiligo. Immunochemical procedures were carried out in biopsies from 20 patients with active lesions to search for cells expressing CD1a, CD2, CD3, CD4, CD5, CD8, CD20, CD25, CD30, CD56, CD68 and CD79a. Results indicate that early lesions are infiltrated mainly by dendritic cells, whereas older lesions display significantly lower proportions of these cells and increased percentages of mature T cells. This finding might suggest that the autoimmune reactivity towards melanocyte antigens might be T cell-dependent and antigen-driven. It is possible that a non-immune offence of melanocytes is responsible for the exposure of intracellular antigens, while autoreactivity might be a secondary, self-perpetuating mechanism.

Linking complement and anti-dsDNA antibodies in the pathogenesis of systemic lupus erythematosus

Systemic lupus erythematosus is a severe autoimmune disease that affects multiple organ systems resulting in diverse symptoms and outcomes. It is characterized by antibody production to a variety of self-antigens, but it is specifically associated with those against anti-dsDNA. Anti-dsDNA antibodies are present before the onset of clinical disease and are associated with severe manifestations of lupus such as glomerulonephritis. Their levels fluctuate with changes in disease activity and, in combination with the levels of complement proteins C3 and C4, are strong indicators of disease flare and treatment response in patients with lupus. The decreased complement levels that are noted during flares of lupus activity are believed to be secondary to increased autoantibody production and immune complex formation that results in tissue damage; however, recent data suggest that complement activation can also drive development of these pathogenic autoantibodies. This review will explore the various roles of complement in the development and pathogenesis of anti-dsDNA antibodies.

Anti-CENP-B antibodies are associated with prolonged survival in breast cancer

AIMS

Presence of a relationship between autoimmunity and malignant diseases has been investigated for a long time. Anti-SS-B and anti-centromere protein (CENP)-B antibodies are used as serologic markers for autoimmune diseases. In this study, these autoantibodies were studied in breast cancer patients, and their effect on survival was evaluated.

PATIENTS & METHODS

Breast cancer patients treated between January and June 2003 were prospectively included in this study. Antibodies were studied by ELISA, and serum values of greater than 10 U/ml were accepted as positive.

RESULTS

In total, 55 patients with breast cancer were prospectively included in the study. Median follow-up time was 62 months. In univariate analysis, estrogen receptor status, anti-CENP-B antibody status and tumor size significantly affected disease-free survival, whereas overall survival was significantly dependent on tumor size and anti-CENP-B antibody status. In multivariate analysis, anti-CENP-B status was the independent prognostic factor for disease-free survival, whereas tumor size and anti-CENP-B status were independent prognostic factors for overall survival.

CONCLUSION

Anti-CENP-B autoantibodies in breast cancer patients prolong disease-free and overall survival.

A common repertoire of autoantibodies is shared by cancer and autoimmune disease patients: Inflammation in their induction and impact on tumor growth

The repertoire of autoantibodies found in cancer patients partly overlaps with that typical of patients with autoimmune diseases. Beside the biochemical and immunological properties of the target antigens and their altered expression in tumor tissues, the intratumoral inflammatory context can play a key role in the induction of autoimmune disease-associated autoantibodies in cancer patients. Furthermore, the impact of such antibodies on cancer growth and progression can be deeply influenced by the interplay with inflammation. The characterization of the spontaneous humoral responses occurring in cancer patients, of the mechanisms that trigger and sustain the autoantibody response and of the biological effects of such autoantibodies may help the rational design of anti-cancer immunotherapeutic protocols.

Autoantibodies from Sjögren's syndrome trigger apoptosis in salivary gland cell line

The presence of serum autoantibodies has been associated with Sjögren's syndrome (SS), an autoimmune rheumatic disease that targets salivary and lachrymal glands. The association of apoptosis with autoantibodies production seems to play a role in the pathogenesis of glandular damage. The best-defined antibodies in SS are those reacting with the ribonucleoprotein antigens SS-A (Ro) and SS-B (La). Anti-Ro antibodies are found in about 70-90%, and anti-La in approximately the same frequency, of patients with primary SS. The objective of this work was to explore whether anti-Ro and anti-La autoantibodies purified from Sjögren IgG fractions are able to trigger apoptotic process in the human salivary gland cell line A-253. Anti-Ro and anti-La autoantibodies were purified on protein G Sepharose affinity column and used for the A-253 cell treatment. Apoptosis induced by autoantibodies was revealed by FACS analysis, and the active caspase-3 and the cleaved caspase-3 substrate poly (ADP-ribose) polymerase (PARP) was demonstrated by colorimetric assay and Western blot. This report shows that anti-Ro and anti-La autoantibodies, but not healthy IgG, activate the caspase-3 and determine the cleavage of PARP in A-253 cells. Apoptosis triggered by Sjögren autoantibodies could be responsible for the impairment of the secretory function in the salivary glands.

Apoptosis of melanocytes in vitiligo results from antibody penetration

Vitiligo is a rather common disease characterized by depigmentation of skin and mucosae due to the loss of melanocytes, most likely as a result of autoimmune phenomena. In this study we demonstrated apoptotic markers in residual melanocytes in skin biopsies of patients with vitiligo, as well as the presence of serum antibodies to melanocyte-specific antigens in the vast majority of patients. Moreover, we were able to prove that serum IgG antibodies from vitiligo patients, but not from healthy controls, were capable to penetrate into cultured melanocytes in vitro, and trigger them to engage in apoptosis. Our results are consonant with the theory that melanocyte-specific antibodies are responsible for the deletion of melanocytes through antibody penetration and apoptosis.

The clinical significance of autoantibodies in gastrointestinal malignancies: an overview

Autoimmunity can be associated with cancer and one of the forms of its expression is the development of antibodies to autologous cellular antigens. The types of cellular proteins which induce autoantibody responses in gastrointestinal malignancies are quite varied and include cellular proteins encoded by mutated normal genes (p53), cellular proteins that are overexpressed and/or aberrantly expressed in malignant tissues (carcinoembryonic antigen), inhibitors of apoptosis (survivin and livin), major components of mucus (mucins), surface receptors of apoptosis (Fas) and nuclear-restricted proteins (double-stranded DNA, single-stranded DNA and Sm family proteins). In the past few years, due to the great clinical interest and the advancement in detection techniques, the above list has grown significantly and a large number of cancer-related antigens, which trigger a specific humoral immune response to the host, have also been identified. The authors review the autoantibodies associated with gastrointestinal malignancies and their clinical implications.

Autoantibodies from Sjögren's syndrome induce activation of both the intrinsic and extrinsic apoptotic pathways in human salivary gland cell line A-253

Sjögren's syndrome (SS) is an autoimmune rheumatic disease that targets salivary and lachrymal glands, characterized by a high concentration of serum autoantibodies directed against nuclear and cytoplasmic antigens. It is known that autoantibodies can enter viable cells and this phenomenon has functional consequences including activation of apoptotic process. The objective of this work was to explore whether autoantibodies contained in IgG purified from Sjögren sera trigger apoptotic process in an experimental model represented by the human salivary gland cell line A-253. To define if the intrinsic or extrinsic pathways are activated, we examined which caspases are critical for inducing cell death. The results have demonstrated that morphological changes and DNA laddering, consistent with apoptotic cell death, occurred in A-253 cells treated with IgG from Sjögren sera. Sjögren IgG induced cleavage and activation of the effector caspase-3 and degradation of the caspase-3 substrate poly(ADP-ribose)polymerase. Both the intrinsic and extrinsic apoptotic pathways were activated, since both caspase-8 and caspase-9 cleavages occurred. In conclusion, autoantibodies contained in IgG purified from Sjögren sera mediate apoptosis of the A-253 cell line in a caspase-dependent manner.

Cell-penetrating anti-native DNA antibodies trigger apoptosis through both the neglect and programmed pathways

It has been previously shown that certain antibodies to double stranded-DNA are capable to transgress the cell membrane, translocate to the cell nucleus and react with their antigens. When so doing, they signal the penetrated cells to undergo apoptosis. In this study we dissected the two main-streams of apoptotic triggering and found that the neglect, mitochondrial pathway, is definitely involved, but activation of caspases 2 and 8, classically known to be associated to the membrane pathway, also occurs in a small proportion of cells. Our results suggest that penetrating anti-dsDNA antibodies, besides activating neglect apoptosis, may also trigger programmed cell death, perhaps initiated at the cell membrane level.

Origin and anti-tumor effects of anti-dsDNA autoantibodies in cancer patients and tumor-bearing mice

In the present investigation, we detected anti-dsDNA autoantibodies in cancer patients and modeled the production of anti-dsDNA autoantibodies by inoculating tumors in BALB/c mice. Moreover, induction of anti-dsDNA autoantibodies by immunization with inactivated tumor cells and their DNA indicated that DNA of tumor cells was probably the primary antigen, which was supported by the significantly increasing levels of sera free DNA in cancer patients and tumor-bearing mice. cELISA and indirect immunofluorescence assay showed that the anti-dsDNA autoantibodies could bind to the surface components of tumor cells. In vitro assay showed that immunosera at week 6 from immunized mice displayed significant cytotoxicity to tumor cells compared to that of negative control, but no cytotoxicity mediated by immunosera at week 22 was observed. In addition, by flow cytometry and electrophoresis of fragmented DNA, the cytotoxicity might probably be mediated by apoptosis. Our data also showed that the ability of the anti-dsDNA autoantibodies to induce apoptosis of SP2/0 and Wehi 164 cells was significantly correlated (r = 0.990, p < 0.01 and r = 0.901, p < 0.05) with their functional affinity. In vivo, the growth of solid tumors was significantly inhibited in the immunized mice inoculated directly with SP2/0 and Wehi 164 cells, or in the naïve mice which were inoculated with SP2/0 cells preincubated with immunosera containing anti-dsDNA autoantibodies. In conclusion, we demonstrated the origin of anti-dsDNA autoantibodies in cancer patients and tumor-bearing mice. And our data also showed that these autoantibodies revealed anti-tumor effect by inducing apoptosis.

Nuclear-targeting autoantibodies induced nuclear PARP cleavage accompanied by more pronounced decrease of peripheral white blood cells than Ro/SSA and La/SSB antigen-targeting autoantibodies

Autoantibody production and leukocytopenia may be linked in patients with lupus erythematosus (LE). Unclear is the ability of different autoantibody species to induce apoptosis and cell loss. Laboratory routine analyses (white blood cell counts, autoantibody detection), and flow cytometry (annexin V, CD3, CD4, CD8) have been performed in 126 consecutive LE-patients. Nuclei of PBMC were investigated flow cytometrically for the presence of the 85 kDa poly-(ADP-ribose)-polymerase (PARP) fragment. Peripheral total white blood cells (WBC), lymphocytes, T-cells, CD3+ CD4+, and CD3+ CD8+ cells were significantly decreased in patients with LE (P from 1.2 x 10(-14) to P < .0008). In the presence of either antinuclear (P from 1.2 x 10(-14) to P < .0008) or anti-dsDNA antibodies (P from 2.9 x 10(-12) to P < .007) were significantly diminished. Differences in cell numbers in LE patients with versus without anti-Ro/SSA were less pronounced: significant differences could be only obtained in lymphocytes and T-cells (P < .02). Anti-La/SSB antibodies were accompanied by significant increased leukocytes (P < .02). PARP cleavage (85 kDa) in nuclei was preferentially observed in cases with nuclear targeting autoantibodies. These results indicate that nuclear targeting autoantibodies are associated to lower peripheral blood cells counts than Ro/SSA, and La/SSB cytoplasmic targeting autoantibodies. This provides an explanation for the pathogenesis of cytopenias associated with SLE.

Experimental bullous pemphigoid generated in mice with an antigenic epitope of the human hemidesmosomal protein BP230

Bullous pemphigoid (BP) is an IgG-mediated autoimmune blistering disease that targets the hemidesmosomal proteins BP230 and BP180. To investigate the pathogenic role of anti-BP230 antibodies, rabbit polyclonal antibodies were generated against an antigenic sequence of the human BP230 antigen (BPAG 1, 2479-2499), which shows 67% homology in the human and the mouse BP230. Purified IgG from the rabbit anti-serum was transferred subcutaneously into the dorsal skin of neonatal isogeneic CBA/Ca (CBA) mice in a dose of 5 mg (n=7) or 1.2 mg IgG/50 microl (n=16). After 24 h, 1 of the mice injected with 5 mg IgG exhibited blisters, but the dorsal skin of all 7 of them was erythematous, and gentle friction produced a fine persistent wrinkling of the epidermis in 4 mice. The mice injected with 1.2 mg IgG developed less severe symptoms. Immunohistological examinations revealed linear rabbit IgG and mouse C3 depositions along the basement membrane of the perilesional skin and subepidermal blister formation. An intradermal inflammatory reaction (granulocyte infiltration) was also detected. None of these symptoms was seen in mice injected with IgG from a control rabbit anti-serum. These findings demonstrate that antibodies against BP230 can elicit the clinical and immunopathological features of BP in neonatal mice, suggesting that anti-BP230 antibodies may possibly play a pathogenic role in this disease.

Characterization of the antigenicity of the formiminotransferase-cyclodeaminase in type 2 autoimmune hepatitis

Human formiminotransferase-cyclodeaminase (hFTCD) is the autoantigen recognized by anti-liver cytosol type 1 (LC1) autoantibodies in type 2 autoimmune hepatitis (AIH) patients. In rats, this octameric protein is localized on the Golgi apparatus and binds brain microtubules (MTs) and vimentin. Subcellular localization of human formiminotransferase-cyclodeaminase and its implication in the pathogenesis of autoimmune hepatitis are unknown. Localization of the human formiminotransferase-cyclodeaminase in human hepatocytes was done using indirect immunofluorescence and subcellular fractionations followed by in vitro binding techniques. The formiminotransferase-cyclodeaminase antigen at two distinct locations in hepatocytes, free in the cytosol and associated with the Golgi membranes are recognized by anti-liver cytosol type 1 autoantibodies. The human formiminotransferase-cyclodeaminase binds reversibly to the Golgi membranes and this complex formation is increased by anti-liver cytosol type 1 autoantibodies. Finally, human formiminotransferase-cyclodeaminase does not interact with liver-specific cytoskeleton proteins. Anti-liver cytosol type 1 autoantibodies are directed against the mature high molecular form of human formiminotransferase-cyclodeaminase. Therefore, the subcellular location of the protein may influence the production of autoantibodies and their role in the pathogenesis of type 2 autoimmune hepatitis. This antigen-driven response does not appear to be facilitated or enhanced by a possible interaction between human formiminotransferase-cyclodeaminase and hepatocyte cytoskeleton proteins.

Novel facts about an old marker: the LE cell

For more than fifty years, lupus erythematosus (LE) cells were believed to result from in vitro opsonization of bare nuclei by serum antinuclear antibodies and their ultimate phagocytosis by neutrophils. Twenty years ago, we described that certain antinuclear antibodies could enter into viable cells, and later on, it was proved that penetration of anti-DNA antibodies into cells results in protracted active cell death. Recent findings indicate that the material engulfed by LE cells are apoptotic blebs as residuals of cells dying after penetration of anti-DNA antibodies. These observations not only change the interpretation of the presence of the LE cell phenomenon, but also stress the potential pathophysiological role of antibodies to intracellular antigens in autoimmune diseases.

The majority of lamina propria CD4(+) T-cells from scid mice with colitis undergo Fas-mediated apoptosis in vivo

We have previously shown that adoptively transferred CD4(+) T-cells mediate an chronic colitis in severe combined immune deficient (scid) mice. Colitis is accompanied by activation and apoptosis of Fas ligand and TNF-alpha expressing CD4(+) T-cells in the diseased colonic lamina propria (Eur. J. Immunol. 28:3655 (1998)). Here we investigate the apoptosis-inducing mechanism in these lamina propria infiltrating CD4(+) T-cells. We observe that freshly isolated lamina propria CD4(+) T-cells can kill Fas transfected P815 mastocytoma cells in a TCR/CD3 redirected chromium-release assay, but do not express TNF-alpha mediated cytotoxicity. Pre-incubation of the isolated lamina propria CD4(+) T-cells with an anti-FasL antiserum partially blocked killing of the Fas transfected target cells, indicating a role for the Fas-FasL system in the killing process. Treatment of scid mice with colitis with anti-FasL antiserum for 12 h blocked the apoptotic process in lamina propria CD4(+) T-cells by more than 65% compared to mice treated with control antiserum. Together, these results point towards the Fas-FasL and not the TNF-alpha-TNF-alpha receptor system as the primary apoptosis-inducing mechanism of lamina propria CD4(+) T-cells in this model of murine chronic colitis, and suggest an important role for the Fas-FasL system in the maintenance of homeostasis of locally proliferating T-cells.

'LE cells' result from phagocytosis of apoptotic bodies induced by antinuclear antibodies

Lupus erythematosus (LE) cells are believed to represent phagocytosis by granulocytes of cell nuclei whose DNA has been 'depolymerized' and opsonized by serum factors, most likely antinuclear antibodies and C3b. Since it is known that certain antinuclear antibodies are capable of inducing apoptosis after intracellular penetration; and that the resulting apoptotic bodies can be ingested by non-professional phagocytes, we decided to investigate the possibility that LE cells could result from the phagocytosis of apoptotic bodies induced by antinuclear antibodies. We demonstrate herein, through different methodological approaches, that the ingested material within LE cells corresponds to apoptotic bodies, and that the LE cell phenomenon can be reproduced, in the absence of other serum factors, by penetrating murine monoclonal anti DNA antibodies.