Search PubMed⌕ Search

Biomedical subjects

Luis A Diaz

Publications and source records attributed to Luis A Diaz.

36 records · Page 2Linked to original sources
PubMed2005

Mutant PIK3CA promotes cell growth and invasion of human cancer cells.

PIK3CA is mutated in diverse human cancers, but the functional effects of these mutations have not been defined. To evaluate the consequences of PIK3CA alterations, the two most common mutations were inactivated by gene targeting in colorectal cancer (CRC) cells. Biochemical analyses of these cells showed that mutant PIK3CA selectively regulated the phosphorylation of AKT and the forkhead transcription factors FKHR and FKHRL1. PIK3CA mutations had little effect on growth under standard conditions, but reduced cellular dependence on growth factors. PIK3CA mutations resulted in attenuation of apoptosis and facilitated tumor invasion. Treatment with the PI3K inhibitor LY294002 abrogated PIK3CA signaling and preferentially inhibited growth of PIK3CA mutant cells. These data have important implications for therapy of cancers harboring PIK3CA alterations.

Amino Acid Substitution↗
PubMed2005

Cancer drug discovery through collaboration.

It has been two decades since cancer was first described as a genetic disease and researchers offered the promise of early diagnosis and targeted therapies. Today, most cancer patients still await life-saving treatments. Genomics and other '-omics' technologies have revealed a complexity among cancers that makes almost any tumour genetically unique; as a consequence, effective targeted therapies might be suitable only for small subgroups of patients. We suggest that by merging and organizing their core competencies, academia, biotechnology companies and the pharmaceutical industry can address existing bottlenecks in anticancer drug discovery and development.

Antineoplastic Agents↗
PubMed2005

Synergy between a plasminogen cascade and MMP-9 in autoimmune disease.

Extracellular proteolysis by the plasminogen/plasmin (Plg/plasmin) system and MMPs is required for tissue injury in autoimmune and inflammatory diseases. We demonstrate that a Plg cascade synergizes with MMP-9/gelatinase B in vivo during dermal-epidermal separation in an experimental model of bullous pemphigoid (BP), an autoimmune disease. BP was induced in mice by antibodies to the hemidesmosomal antigen BP180. Mice deficient in MMP-9 were resistant to experimental BP, while mice deficient in Plg and both tissue Plg activator (tPA) and urokinase Plg activator (uPA) showed delayed and less intense blister formation induced by antibodies to BP180. Plg-deficient mice reconstituted locally with Plg or the active form of MMP-9 (actMMP-9), but not the proenzyme form of MMP-9 (proMMP-9), developed BP. In contrast, proMMP-9 or actMMP-9, but not Plg, reconstituted susceptibility of MMP-9-deficient mice to the skin disease. In addition, MMP-3-deficient mice injected with pathogenic IgG developed the same degree of BP and expressed levels of actMMP-9 in the skin similar to those of WT controls. Thus, the Plg/plasmin system is epistatic to MMP-9 activation and subsequent dermal-epidermal separation in BP.

Animals↗
PubMed2004

The current clinical value of genomic instability.

Clinical Oncologists have largely ignored the debate over genetic instability in human cancers. It is clear that genetic lesions themselves provide valuable information in the treatment of patients with cancer and those genetic lesions can be exploited successfully as therapeutic targets. Whether the mechanisms resulting in the accumulation of genetic lesions can be translated and used clinically remains to be seen.

Chromosome Aberrations↗
PubMed2004

Bacteriolytic therapy can generate a potent immune response against experimental tumors.

When spores of the anaerobic bacterium Clostridium novyi-NT are systemically injected into animals, they germinate exclusively within the hypoxic regions of cancers. The germinated bacteria destroy adjacent tumor cells but spare a rim of well oxygenated tumor cells that subsequently expand. Surprisingly, we found that approximately 30% of mice treated with such spores were cured of their cancers despite the viable tumor rim initially remaining after spore germination. The mechanism underlying this effect was shown to be immune-mediated, because cured animals rejected a subsequent challenge of the same tumor. Similar effects were observed in rabbits with intrahepatic tumors. It was particularly notable that the induced immune response, when combined with the bacteriolytic effects of C. novyi-NT, could eradicate large established tumors.

Adoptive Transfer↗
PubMed2004

Digital karyotyping identifies thymidylate synthase amplification as a mechanism of resistance to 5-fluorouracil in metastatic colorectal cancer patients.

Resistance to chemotherapy is a major cause of mortality in advanced cancer patients. In this study, digital karyotyping was used to search for genomic alterations in liver metastases that were clinically resistant to 5-fluorouracil (5-FU). In two of four patients, we identified amplification of an approximately 100-kb region on 18p11.32 that was of particular interest because it contained the gene encoding thymidylate synthase (TYMS), a molecular target of 5-FU. Analysis of TYMS by fluorescence in situ hybridization identified TYMS gene amplification in 23% of 31 5-FU-treated cancers, whereas no amplification was observed in metastases of patients that had not been treated with 5-FU. Patients with metastases containing TYMS amplification had a substantially shorter median survival (329 days) than those without amplification (1,021 days, P <0.01). These data suggest that genetic amplification of TYMS is a major mechanism of 5-FU resistance in vivo and have important implications for the management of colorectal cancer patients with recurrent disease.

Chromosomes, Human, Pair 18↗
PubMed2004

Pemphigus foliaceus with neutrophilic spongiosis evolving to an atypical pemphigus phenotype.

A 46-year-old Brazilian man, with initial pustular lesions, neutrophilic spongiosis and subcorneal cleavage evolved to an atypical pemphigus phenotype, with suprabasal acantholysis. Interestingly, his autoantibody profile, tested by immunofluorescence, immunoblotting, enzyme-linked immunosorbent assay, and immunoprecipitation revealed exclusive IgG anti-desmoglein 1 antibodies in all phases of the disease.

Acantholysis↗
PubMed2004

Anti-desmoglein-1 antibodies in onchocerciasis, leishmaniasis and Chagas disease suggest a possible etiological link to Fogo selvagem.

Pemphigus foliaceus (PF) and the endemic form Fogo Selvagem (FS) are mediated by pathogenic antibodies to the EC1-2 domains of desmoglein-1. There is a preclinical phase with antibodies to only EC5. Based on geographic clustering of cases, FS is thought to have an, as yet unidentified, environmental trigger. In this study we have searched for anti-desmoglein-1 antibodies in sera from parasitic (leishmaniasis, Chagas, and onchocerciasis), and infectious diseases (leprosy and South American (SA) blastomycosis), which are prevalent in the same geographic regions of Brazil as FS. A specific and sensitive desmoglein-1 ELISA detected antibodies in 34 of 41 onchocerciasis (83%), 38 of 88 leishmaniasis (43%), 18 of 31 Chagas disease (58%), 7 of 28 SA blastomycosis (25%), and 14 of 83 leprosy sera (17%). These sera recognized epitopes restricted to the EC5 domain. These findings identify several etiological factors for FS. It is hypothesized that a component of insect vector saliva, rather than the parasite itself may trigger an antibody response to EC-5. In persons with the known HLA susceptibility alleles and living in endemic areas, a response to the EC1-2 domains may subsequently develop by epitope spreading with associated clinical signs of FS.

Antigens, Protozoan↗
PubMed2004

Environmental risk factors in endemic pemphigus foliaceus (fogo selvagem).

An ongoing sero-epidemiological study of the Terena reservation of Limao Verde, known to have a high prevalence and incidence of FS, has revealed important information about this autoimmune disease. During surveillance of this population of approximately 1,200, which began in 1994, we documented 43 FS cases and studied the transition from the normal state to the disease state in several of these individuals. Furthermore, we established that FS patients as well as a large number of normal individuals on the reservation possess anti-dsg1 autoantibodies. The following interesting observations were made: (1) the ectodomain of dsg1 contains epitopes recognized by both autoantibodies and T cells from FS patients; (2) pathogenic anti-dsg1 autoantibodies in FS belong to the IgG4 subclass; (3) nonpathogenic anti-dsg1 autoantibodies of the IgG1 subclass were detected in normal individuals from Limao Verde and in patients in the preclinical stage of the disease; (4) anti-dsg1 autoantibodies from normal individuals and patients in the preclinical stage of FS recognize the EC5 domain of dsg1, whereas pathogenic anti-dsg1 autoantibodies bind the EC1/EC2 domains; (5) houses of FS patients are rustic, with thatched roofs and walls and dirt floors; (6) there was a high frequency of hematophagous insects (bedbugs and kissing bugs) in the houses of FS patients; (7) previous studies revealed that the predominant black fly on this reservation belongs to the species Simunlium nigrimanum. These findings suggest that the environmental antigen(s) triggering the autoimmune response in FS may be linked to exposure to hematophagous insects.

Brazil↗
PubMed2003

The role of intramolecular epitope spreading in the pathogenesis of endemic pemphigus foliaceus (fogo selvagem).

We report here a relationship between intramolecular epitope spreading and the clinical onset of the endemic form of pemphigus foliaceus in a Brazilian community with a high prevalence and incidence of the disease. Also known as Fogo Selvagem (FS), this disease is characterized by severe skin blistering and pathogenic anti-desmoglein-1 (Dsg1) autoantibodies. These autoantibodies bind the Dsg1 ectodomain and trigger keratinocyte cell detachment, the hallmark of FS. We show that (a) sera from FS patients in the preclinical stage recognized epitopes on the COOH-terminal EC5 domain of Dsg1, (b) disease onset was associated with the emergence of antibodies specific for epitopes on the NH2-terminal EC1 and EC2 domains, (c) all sera from FS patients with active disease recognized the EC1 and/or EC2 domains, and (d) sera from FS patients in remission showed reactivity restricted to EC5. These results suggest that anti-Dsg1 autoantibodies in FS are initially raised against the COOH-terminal EC5 domain of Dsg1 in individuals without skin disease; in genetically predisposed subjects the autoimmune response may then undergo intramolecular epitope spreading toward epitopes on the NH2-terminal EC1 and EC2 domains of Dsg1 leading to disease onset. Moreover, intramolecular epitope spreading may also modulate remissions and relapses of FS.

Antibody Specificity↗
PubMed2003

Xenogeneic cells and superantigen induce human T-cell activation in the absence of T-cell recognition of xenoantigen.

The extent of interaction between human T-lymphocytes and xenogeneic antigen-presenting cells (APCs) is species-dependent. A successful interaction requires high-affinity receptor-ligand pairing across species and recognition of antigens presented by foreign major histocompatibility complex (MHC). A deficient human T-lymphocyte response to xenogeneic cells is likely the result of a defect in these interactions. However, the requirements for a T-cell response to superantigen (SAg) may differ from those of other T-cell responses. Using irradiated murine splenocytes, which are believed to be incapable of eliciting human T-cell responses, and porcine aortic endothelial cells (PAECs) as the APC populations, we studied the human T-lymphocyte response to antigens presented by these cells. Direct proliferation of human T-lymphocytes to SAg presented by murine APCs was demonstrated; it was blocked by anti-human LFA-1 and anti-murine MHC class II but not by anti-human MHC class II. PAECs also presented SAg to human T-cells, generating a proliferative response greater than the primary response to porcine xenoantigen. Culture of human T-cells with murine splenocytes or PAECs and SAg Staphylococcus enterotoxin A (SEA) for 7 days primed human T-cells to proliferate in a secondary culture in response to autologous APCs. This autologous secondary response was human MHC class II-dependent and was inhibited by anti-human LFA-1, anti-human CD2, and anti-human CD98. Surprisingly, both of these responses were also blocked by anti-SEA, suggesting that despite vigorous washing, a small amount of functionally important SAg was carried over from primary to secondary culture, probably bound to the surface of T-cells. Xenogeneic APCs, even those that fail to stimulate human T-cells directly, can serve as APCs for primary human T-cell responses. After such interactions T-cells can develop secondary responses in autologous interactions based on retention of minute amounts of SAg. Such interactions may have important implications for xenotransplantation.

Animals↗
PubMed2002

Macrophages, but not T and B lymphocytes, are critical for subepidermal blister formation in experimental bullous pemphigoid: macrophage-mediated neutrophil infiltration depends on mast cell activation.

Bullous pemphigoid (BP) is a subepidermal blistering disease associated with autoantibodies against two hemidesmosomal proteins, BP180 and BP230. Numerous inflammatory cells infiltrate the upper dermis in BP. We have previously shown by passive transfer studies that Abs to the ectodomain of murine BP180 are capable of triggering blisters in mice that closely mimic human BP. Experimental BP depends on complement activation and neutrophil infiltration. In the present study, we investigated the relative contribution of neutrophils, mast cells (MCs), macrophages (Mphi), and lymphocytes and their functional relationship in the immunopathogenesis of this disease model by using mice deficient in these cells. Wild-type, T cell-deficient, and T and B cell-deficient mice injected intradermally with pathogenic anti-murine BP180 IgG exhibited extensive subepidermal blisters. In contrast, mice deficient in neutrophils, MCs, and Mphi were resistant to experimental BP. MCs play a major role in neutrophil recruitment into the dermis. Furthermore, Mphi-mediated neutrophil infiltration depends on MC activation/degranulation.

Animals↗
PubMed2002

A subset of pemphigus foliaceus patients exhibits pathogenic autoantibodies against both desmoglein-1 and desmoglein-3.

In pemphigus vulgaris the major pathogenic antibody binds desmoglein-3, and mediates mucosal disease. Development of cutaneous disease is associated with acquisition of antibodies to desmoglein-1. In pemphigus foliaceus, and its endemic form, fogo selvagem by contrast, the major pathogenic antibody recognizes desmoglein-1 and mediates cutaneous disease only. In this study, we sought to determine the prevalence of antibodies to desmoglein-3 in patients with pemphigus foliaceus and fogo selvagem. We produced recombinant desmoglein-1 and desmoglein-3, and used them in highly sensitive and specific enzyme-linked immunosorbent assays, as well as immunoprecipitation assays. We detected antibodies to desmoglein-3 in 19 of 276 patients with pemphigus foliaceus and fogo selvagem, who had cutaneous disease only. We showed that these antibodies to desmoglein-3 could be absorbed in a concentration-dependent manner by desmoglein-3 but not by desmoglein-1. Also antibodies to desmoglein-1 could be absorbed in a concentration-dependent manner by desmoglein-1 but not desmoglein-3. This suggests that two separate species of antibody are present rather than one antibody capable of cross-reacting with both desmoglein-1 and desmoglein-3. Finally, it was shown that affinity-purified antibodies to desmoglein-3 from patients with pemphigus foliaceus and fogo selvagem induced a pemphigus vulgaris-like skin disease in mice by passive transfer. These results suggest that a subset of patients with pemphigus foliaceus and fogo selvagem have antibodies to desmoglein-3 that may be involved in the pathogenesis of their cutaneous disease.

Animals↗
PubMed2002

T cell receptor Beta chain gene usage in endemic pemphigus foliaceus (fogo selvagem).

The trimolecular complex comprised of the major histocompatibility complex, peptide antigen, and the T cell receptor is a requisite for T cell activation in normal and autoimmune responses. T cell receptor analysis is critical to further our understanding regarding mechanisms of T cell epitope selection and autoimmune initiation and progression and may help to identify targets for immunotherapy. Pemphigus foliaceus is an autoimmune blistering skin disease characterized by intraepidermal blisters and circulating autoantibodies directed against desmoglein 1, a 160 kDa transmembrane desmosomal molecule expressed in keratinocytes. As tissue damage is mediated by anti-desmoglein 1 antibodies, an initial T cell response is a likely requirement for autoantibody generation in this disease. To elucidate the role of pathogenic T cells in autoimmunity further, we have directly characterized the T cell receptor of T cells derived from pemphigus foliaceus patients. Complementary DNA was isolated from 17 desmoglein 1 specific T cell clones generated from pemphigus foliaceus patients by clonal expansion in vitro. To analyze the T cell repertoire, a panel of primers, collectively specific for the known human T cell receptor beta variable region (TCRBV) families were paired with a constant region primer to polymerase chain reaction to amplify one distinct T cell receptor beta variable region allele for each T cell clone studied. Polymerase chain reaction products were sequenced to determine exact beta chain gene usage. In the 17 clones tested, 10 distinct T cell receptor beta variable region usages and nine T cell receptor beta joining gene segment usages were identified. Furthermore, T cell receptor beta variable region and beta joining usage did not appear to be random, but oligoclonal in nature, with some preference shown for T cell receptor beta variable region 5S1 and T cell receptor BJ2S5.

Amino Acid Sequence↗