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Biomedical subjects

F Samaniego

Publications and source records attributed to F Samaniego.

At least 19 recordsLinked to original sources
PubMed1997

Inflammatory cytokines induce endothelial cells to produce and release basic fibroblast growth factor and to promote Kaposi's sarcoma-like lesions in nude mice.

Inflammatory cytokines including TNF-alpha, IL-1beta, and IFN-gamma are increased in sera and lesions of Kaposi's sarcoma (KS) patients. Previous data have indicated that the combination of these cytokines as found in conditioned media from activated T cells induces normal endothelial cells to acquire the features of KS spindle cells (KS cells) including spindle morphology, marker expression, and the responsiveness to the effects of HIV-1 Tat protein. Conditioned media from activated T cells or the single cytokines also induce AIDS-KS cells to produce and release basic fibroblast growth factor (bFGF). bFGF is highly expressed also by in situ KS cells and mediates KS-like lesion formation after inoculation of the cells in nude mice. Here we show that both large and small vessel endothelial cells chronically exposed to inflammatory cytokines produce and release bioactive bFGF in the absence of cell death. In addition, after this treatment, endothelial cells acquire angiogenic capability and induce KS-like lesions after inoculation in nude mice. Production and release of bFGF is induced in a synergistic fashion by TNF-alpha, IL-1beta, and IFN-gamma, and its release is further promoted by low cell density and by the serine proteases plasmin and thrombin. These results indicate that inflammatory cytokines induce endothelial cells to export bFGF and to acquire angiogenic properties, a key feature of the KS cell phenotype, and suggest a mechanism by which these cytokines can cooperate in the induction of KS.

Animals↗
PubMed1997

HIV-1 Tat protein exits from cells via a leaderless secretory pathway and binds to extracellular matrix-associated heparan sulfate proteoglycans through its basic region.

OBJECTIVE: To analyze the mechanisms of release and the extracellular fate of the HIV-1 Tat protein and to determine the Tat domain binding to the extracellular matrix. DESIGN AND METHODS: Release of Tat was studied by pulse-chase experiments with Tat-transfected COS-1 cells in the presence or absence of different serum concentrations, temperatures and drugs inhibiting the classical secretion pathway or endo-exocytosis, such as brefeldin A and methylamine. The binding of extracellular Tat to heparan sulfate proteoglycans (HSPG) was determined by using trypsin, heparin or heparinase in pulse-chase experiments, by gel shift and competition assays with radiolabeled heparin, and by heparin-affinity chromatography. The mapping of the Tat binding site to heparin was defined by functional assays of rescue of Tat-defective HIV-1 proviruses. RESULTS: Tat is released in the absence of cell death or permeability changes. Tat release is dependent upon the temperature and serum concentration, and it is not blocked by brefeldin A or methylamine. After release, a portion of the protein remains in a soluble form whereas the other binds to extracellular matrix (ECM)-associated HSPG. The HSPG-bound Tat can be retrieved into a soluble form by heparin, heparinase or trypsin. Binding to heparin is competed out by heparin-binding factors such as basic fibroblast growth factor (bFGF), and it is mediated by the Tat basic region which forms a specific complex with heparin which blocks HIV-1 rescue by exogenous Tat and allows purification of a highly biologically active protein. CONCLUSIONS: These results demonstrate that Tat exits from intact cells through a leaderless secretion pathway which shares several features with that of acid FGF or bFGF. The released Tat binds to HSPG through its basic region and this determines its storage into the ECM, as occurs for bFGF.

Animals↗
PubMed1995

Tumorigenesis and metastasis of neoplastic Kaposi's sarcoma cell line in immunodeficient mice blocked by a human pregnancy hormone.

Kaposi's sarcoma (KS) occurs more often in men than in women and HIV-1-associated KS has a high occurrence in homosexual men (over 30%). Most cultures of KS tumours yield cells with properties of hyperplastic (not malignant) endothelial cells under the control of several cytokines. The role of HIV-1 may be in promoting high levels of some cytokines and providing stimulation to angiogenesis by the HIV-1 Tat protein, which synergizes with basic fibroblast growth factor in promoting these effects. Here we describe an immortalized AIDS-KS cell line (KS Y-1) and show that these cells produce malignant metastatic tumours in nude mice and are killed in vitro and in vivo (apparently by apoptosis) by a pregnancy hormone, the beta-chain of human chorionic gonadotropin. Similarly, chorionic gonadotropin kills KS SLK, cells from another neoplastic cell line (established from a non-HIV-associated KS), as well as the hyperplastic KS cells from clinical specimens grown in short-term culture, but does not kill normal endothelial cells. These results provide evidence that KS can evolve into a malignancy and have implications for the hormonal treatment of this tumour.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Inflammatory cytokines induce AIDS-Kaposi's sarcoma-derived spindle cells to produce and release basic fibroblast growth factor and enhance Kaposi's sarcoma-like lesion formation in nude mice.

Homosexual males often present signs of immune activation and are likely to have increased levels of inflammatory cytokines such as IL-1 beta, TNF-alpha, and IFN-gamma. These individuals develop Kaposi's sarcoma (AIDS-KS) more frequently than other HIV-1-infected groups. Our previous work demonstrated that inflammatory cytokines stimulate the growth of spindle cells derived from AIDS-KS lesions (AIDS-KS cells) and that these cells produce high levels of bFGF that mediate autocrine and paracrine (endothelial) cell growth and angiogenesis. Here we show that AIDS-KS cells constitutively produce and release bioactive bFGF in the absence of cell death, and that extracellular bFGF exist in both a soluble and a bound form; the latter can be released by treatment with trypsin, heparin, or heparinase I. Inflammatory cytokines stimulate both the synthesis and release of biologically active bFGF from KS cells and enhance their ability to induce angiogenic KS-like lesions in nude mice. Because bFGF is highly expressed in primary KS lesions, and is a mediator of KS-like lesion formation, these results suggest that the export of bFGF induced by inflammatory cytokines may play a critical role in the induction and progression of KS in HIV-1-infected homosexual men.

Acquired Immunodeficiency Syndrome↗
PubMed1995

CD4+ cells in human ejaculates.

Using flow cytometry, we studied the expression of the CD4 antigen within the different cells present in human ejaculate, both in spermatozoa and round cells. In all, 20 samples of semen were obtained from fertile males; in 11 of these, we detected the presence of leukocytes, using the peroxidase test. Swim-up was performed for the analysis of the spermatozoa. From our results it may be concluded that there is no expression of the CD4 antigen on the surface of human spermatozoa or on CD45- ejaculate cells (epithelial and germinal cells). However, we did detect the presence of the CD4 antigen on the surface of the leukocyte cells (CD45+). A better characterization of these CD45+ cells made it apparent that the CD4+ cells of ejaculate are composed of T lymphocytes (helper/inducer T lymphocytes) and monocytes. Thus we may conclude that human spermatozoa do not express the CD4 antigen, the cell surface receptor for human immunodeficiency virus. However, we did detect CD4+ T lymphocytes and CD4+ monocytes in semen.

CD4 Antigens↗
PubMed1995

Cytokines from activated T cells induce normal endothelial cells to acquire the phenotypic and functional features of AIDS-Kaposi's sarcoma spindle cells.

Kaposi's sarcoma (KS) is a proliferative disease of vascular origin particularly frequent in HIV-1-infected homosexual men (AIDS-KS) and characterized by proliferating spindle-shaped cells, angiogenesis, and inflammatory cell infiltration. Previous work has suggested that KS spindle cells are of endothelial cell origin and that chronic immune activation via the release of inflammatory cytokines may cooperate with basic fibroblast growth factor (bFGF) and the HIV-1 Tat protein in the induction and progression of AIDS-KS. Here we show that KS spindle cells have features of activated endothelial cells, and that conditioned media from activated T cells, rich in the same inflammatory cytokines increased in HIV-1-infected individuals, induce normal endothelial cells to acquire the phenotypic and functional features of KS cells. These include (a) acquisition of a similar pattern of cell surface antigen expression; (b) similar proliferative response to bFGF; (c) induction of the responsiveness to the mitogenic effect of extracellular HIV-1 Tat protein that is now able to promote the G1-S transition of endothelial cell cycle; and (d) induction in nude mice of vascular lesions closely resembling early KS as well as the lesions induced by inoculation of KS cells. These results suggest that chronic immune activation, via release of inflammatory cytokines, may play a role in the induction of KS.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Molecular characterization of a second iron-responsive element binding protein, iron regulatory protein 2. Structure, function, and post-translational regulation.

Several genes critical to the uptake, sequestration, and utilization of iron are regulated at the post-transcriptional level. The mRNAs encoded by these genes contain highly conserved stem-loop structures called iron-responsive elements (IREs). IREs function as the nucleic acid-binding sites for a cytosolic RNA-binding protein called the IRE-binding protein or IRE-BP. Binding of the IRE-BP to IREs is reversibly regulated by the iron status of the cell. The IRE-BP is highly conserved among human, rat, mouse, and rabbit, and it is identical to the cytosolic form of aconitase. In this study, we demonstrate that a distinct human gene encoding a protein which is 57% identical to the initially described IRE-BP, now referred to as iron regulatory protein 1 or IRP1, is also capable of binding to IREs with the same in vitro affinity and specificity the originally identified protein. This second gene product, which we call IRP2, is expressed in many tissues, but its mRNA abundance and tissue distribution are different from IRP1. In most cell lines tested, levels of IRP2 are inversely regulated by iron levels due to iron-dependent regulation of the half-life of the protein. In addition to changes in total amounts of IRP2, we demonstrate that the IRE binding activity of IRP2 can also vary up to 4-fold in the absence of any change in IRP2 protein levels. The possible reasons for the existence of a second IRP are discussed.

Amino Acid Sequence↗
PubMed1993

CD5+ B lymphocytes in HIV infection: relationship to immunological progression of disease.

We analyzed CD5+ B cells in HIV-seropositive individuals because there is accumulating evidence of the involvement of this subset in natural immunity against virus and bacteria. There are also arguments maintaining that CD5+ B cells play a role in autoimmunity and lymphoid malignancies, both phenomena which are strongly associated with HIV infection. Seventy-two HIV-positive subjects (58 drug abusers, 7 homosexual men, 4 heterosexuals, and 3 hemophiliacs) were included in a phenotypic study of mononuclear cells. A direct immunofluorescence with doubly conjugated monoclonal antibodies was performed, and analysis was carried out in a FACScan cytometer. HIV-infected patients showed a striking increase in the percentage of CD5+ B lymphocytes (54.7 +/- 19% of circulating B cells) compared with HIV-negative drug users (35.5 + 14%) and with healthy controls (17 +/- 5%), P < 0.01 and P < 0.0001, respectively. In addition, levels of CD5+ B cells were correlated with CD4+ cell counts (r = -0.50373), WR staging (r = 0.5295), lymphocytopenia (r = 0.57356), and T4/T8 ratio (r = -0.3151) and showed a close association with the progression of immune system damage by HIV. Patients who developed hypergammaglobulinemia, thrombocytopenia, or other autoimmune manifestations associated with HIV infection showed levels of CD5+ B cells increased over those of the remaining HIV-seropositive individuals (P < 0.001, P < 0.001, and P < 0.05).

Adult↗
PubMed1993

Lack of expression of HLA antigens on immature germ cells from ejaculates with antisperm antibodies.

PROBLEM: The lack of expression of HLA antigen on immature germ cells from ejaculates with antisperm antibodies has been reported. METHOD: The expression of human leukocyte antigens on immature germ cells from ejaculates with antisperm antibodies (ASA) was investigated by indirect immunofluorescence using a panel of monoclonal antibodies (MAb) and automated flow cytometry. Patients were divided into two groups: fertile (prevasectomic; N = 10), and ejaculates with ASA (10 samples with IgG and IgA ASA, and five semen samples with only IgG ASA). ASA were detected on sperm using the direct immunobead test. After centrifuging semen samples on a Ficoll-Hypaque gradient, round cells obtained at the gradient interface were gated by a flow cytometer. The "immature germ cell window" was defined in terms of cellular volume and granularity. RESULTS: The percentage of gated round cells from semen samples that reacted with anti-CD45 was always less than 5%, and with anti-CD44 less than 3%. This lack of reactivity of gated round cells with MAb specific for leukocytes and epithelial cells suggests that they were immature germ cells. Immature germ cells were unreactive with W6/32 and anti-beta-2-microglobulin MAb, which suggests that these cells do not express HLA class I molecules. Similarly, no reactivity of the immature germ cells with the MAb that recognize HLA class II molecules was found. No significant differences were observed in the expression of HLA molecules on immature germ cells between the different semen samples studied: fertile, and ejaculates with ASA. CONCLUSION: The presence of ASA in ejaculate is not associated with abnormal HLA antigen expression on immature germ cells.

Animals↗
PubMed1992

An iron-sulfur cluster plays a novel regulatory role in the iron-responsive element binding protein.

Post-transcriptional regulation of genes important in iron metabolism, ferritin and the transferrin receptor (TfR), is achieved through regulated binding of a cytosolic protein, the iron-responsive element binding protein (IRE-BP), to RNA stem-loop motifs known as iron-responsive elements (IREs). Binding of the IRE-BP represses ferritin translation and represses degradation of the TfR mRNA. The IRE-BP senses iron levels and accordingly modifies binding to IREs through a novel sensing mechanism. An iron-sulfur cluster of the IRE-BP reversibly binds iron; when cytosolic iron levels are depleted, the cluster becomes depleted of iron and the IRE-BP acquires the capacity to bind IREs. When cytosolic iron levels are replete, the IRE-BP loses RNA binding capacity, but acquires enzymatic activity as a functional aconitase. RNA binding and aconitase activity are mutually exclusive activities of the IRE-BP, and the state of the iron-sulfur cluster determines how the IRE-BP will function.

Aconitate Hydratase↗
PubMed1992

[Diurnal variations in circulating leukocytes and subsets: relation to plasma cortisol and ACTH].

Surface cellular antigens of leukocytes, lymphocytes and corresponding subpopulations have been analysed by using monoclonal antibodies marked with fluorescein (PITC), parallel to those marked with phycoerythrin (PE). Cortisol and ACTH plasmatics have also been determined through RIA, on two samples at 8am. and 8pm. During this twelve hour evolution, a highly significant dependence of the leukocytes, T, T4 and T8 lymphocytes on the circulating ACTH has also been found. In general during the experiment time leukocytes, lymphocytes and subpopulations, have experimented an increase which is significantly related to the pituitary hormone secretion. The existence of this significant correlation establishes the presence of a possible mechanism that connects the cellular immunity to determined hypothalamus hormones.

Adrenocorticotropic Hormone↗
PubMed1991

Genetic analysis as an aid in diagnosis for patients with midline carcinomas of uncertain histologies.

The tumors of nine patients with carcinomas of uncertain histogenesis (eight with poorly differentiated carcinomas involving primarily midline structures and one with a diagnosis of seminoma and atypical clinical features) were studied by cytogenetic and Southern blot analyses. Four of the eight patients with poorly differentiated carcinomas had abnormalities of chromosome 12 consistent with a diagnosis of germ cell tumor. These abnormalities comprised an i(12p) in two patients and a del(12q) in a third patient detected by cytogenetic analysis and multiple copies of 12p detected by Southern blot analysis in a fourth patient. Three of these four patients with a diagnosis of germ cell tumor established by genetic analysis achieved a complete response to cisplatin-based chemotherapy. The tumor biopsy of one patient showed a t(11;22) (q24;q12), and this patient had chemotherapy directed to neuroepithelioma. Cytogenetic analysis was unsuccessful for the tumors of three patients; these tumors did not have multiple copies of 12p detected by Southern blot analysis. These patients did not respond to cisplatin-based chemotherapy. One patient with a diagnosis of extragonadal seminoma failed to respond to cisplatin-based chemotherapy and had a second tumor biopsy performed that demonstrated a t(8;14) (q24;q32). This patient's diagnosis was changed to a non-Hodgkin's lymphoma. Thus, genetic analysis provided a diagnosis in six of nine patients. Cytogenetic and molecular analyses are useful clinical tools for the determination of histogenesis in some patients with poorly differentiated carcinomas of uncertain histology.

Adult↗
PubMed1990

Cytogenetic and immunohistochemical evidence for the germ cell origin of a subset of acute leukemias associated with mediastinal germ cell tumors.

Most acute leukemias occurring in patients with mediastinal germ cell tumors (MGCTs) appear to be primary rather than therapy-related; however, no data have been obtained to date to confirm the hypothesized germ cell origin of the leukemias in this syndrome. We identified six male patients with this syndrome treated at Memorial Sloan-Kettering Cancer Center: in all six, the leukemia was studied immunohistochemically for various hematologic and germ cell antigens; in four, the karyotype of the leukemia was available; in one, the MGCT had also been karyotyped. In three patients, we found evidence of a germ cell origin of the acute leukemias. A 19-year-old male developed an acute myeloblastic leukemia 11 months after presenting with an MGCT; karyotypes of the two tumors showed them to be clonally related, both showing an i(12p), a cytogenetic marker of germ cell tumors. A 16-year-old male with probable Klinefelter's syndrome presented simultaneously with acute monocytic leukemia and an MGCT; although the MGCT was not karyotyped, the leukemia showed an i(12p). A 23-year-old male developed concurrently an MGCT and acute myelomonocytic leukemia; the leukemia cells coexpressed myelomonocytic antigens (HAM56, My4, My9) and cytokeratin, suggesting dual differentiation, myeloid and germ cell. Evidence for a germ cell origin of the acute leukemias in the three other patients was not obtained, although in all three the MGCT and the leukemia occurred simultaneously, supporting an etiologic relationship. Hence, these leukemias may represent another form of non-germ cell malignancy developing in germ cell tumors. All patients died of the leukemia, with a median survival of less than 2 months. This syndrome may be a useful pathologic model for the study of germ cell differentiation and hematopoietic ontogeny.

Adolescent↗
PubMed1990

Detection of preferential NRAS mutations in human male germ cell tumors by the polymerase chain reaction.

We have studied 31 male germ cell tumors (GCTs) for probable mutations in codons 12, 13, and 61 of HRAS, KRAS, and NRAS oncogenes using the polymerase chain reaction. Twenty of the thirty-one tumors exhibited NRAS gene mutations, 14 in codon 61, and six in codon 12, whereas no mutations were detected in HRAS and KRAS genes. The NRAS mutations were equally prevalent in seminomatous and nonseminomatous GCTs. Thus 13 of 22 seminomas, six of seven embryonal carcinomas, and one of two mixed tumors exhibited mutations. Two non-seminomatous tumors (an embryonal carcinoma and a yolk sac/teratoma) had mutations in both codons 12 and 61. The high frequency of NRAS mutations observed in the present study suggests that NRAS gene products may play an important role in growth regulatory functions of premalignant and malignant germ cells.

DNA Mutational Analysis↗
PubMed1990

Cytogenetic and molecular analysis of human male germ cell tumors: chromosome 12 abnormalities and gene amplification.

We report karyotypic analysis of 24 male germ cell tumors (GCTs) with clonally abnormal karyotypes biopsied from testicular and extragonadal lesions from 20 patients belonging to the histologic categories seminoma, teratoma, embryonal carcinoma, choriocarcinoma, and endodermal sinus tumor. Chromosomes 1, 7, 9, 12, 17, 21, 22, and the X chromosome were nonrandomly gained in these tumors. Nonrandom structural changes affected most frequently chromosomes 1 and 12, the latter as i(12p) and/or del(12)(q13----q22). The i(12p) was seen in 90% of tumors which included all histologic subtypes and gonadal as well as extragonadal presentation. Our present results, along with those from published data on fresh GCT biopsies, establish that i(12p) is a highly nonrandom chromosome marker of all histologic as well as anatomic presentations of GCTs. in contrast, we found del(12)(q13----q22) exclusively in nonseminomatous GCTs (NSGCTs) and mixed GCTs (MGCTs) occurring in 44% of such lesions. Because successful cytogenetic analysis of fresh tumor specimens is not always possible, we developed a method based on DNA analysis to detect i(12p) as increased copy number of 12p. In addition to the changes affecting chromosome 12 identified above, we have detected, for the first time, cytological evidence of gene amplification in the form of homogeneously staining regions (HSRs) and double minute chromosomes (dmins) in treated as well as untreated primary extragonadal and metastatic GCTs and confirmed the presence of amplified DNA in one of these tumors at the molecular level by the in-gel renaturation method. Hybridization of DNA from cultured cells from an HSR-bearing tumor with a panel of probes for genes known to be amplified or otherwise perturbed in diverse tumor systems did not identify the amplified gene, suggesting amplification of a novel gene or genes. This study comprises the largest series of GCT cytogenetics attempted so far. Notably, it includes data on a series of primary mediastinal tumors, a group which previously has not been studied in any detail.

Blotting, Southern↗
PubMed1990

Cloning of the cDNA encoding an RNA regulatory protein--the human iron-responsive element-binding protein.

Iron-responsive elements (IREs) are stemloop structures found in the mRNAs encoding ferritin and the transferrin receptor. These elements participate in the iron-induced regulation of the translation of ferritin and the stability of the transferrin receptor mRNA. Regulation in both instances is mediated by binding of a cytosolic protein to the IREs. High-affinity binding is seen when cells are starved of iron and results in repression of ferritin translation and inhibition of transferrin receptor mRNA degradation. The IRE-binding protein (IRE-BP) has been identified as an approximately 90-kDa protein that has been purified by both affinity and conventional chromatography. In this report we use RNA affinity chromatography and two-dimensional gel electrophoresis to isolate the IRE-BP for protein sequencing. A degenerate oligonucleotide probe derived from a single peptide sequence was used to isolate a cDNA clone that encodes a protein containing 13 other sequenced peptides obtained from the IRE-BP. Consistent with previous characterization of the IRE-BP, the cDNA encodes a protein of 87 kDa with a slightly acidic pI, and the corresponding mRNA of approximately 3.6 kilobases is found in a variety of cell types. The encoded protein contains a nucleotide-binding consensus sequence and regions of cysteine and histidine clusters. This mRNA is encoded by a single gene on human chromosome 9, a finding consistent with previous localization by functional mapping. The protein contains no previously defined consensus motifs for either RNA or DNA binding. The simultaneous cloning of a different, but highly homologous, cDNA suggests that the IRE-BP is a member of a distinct gene family.

Amino Acid Sequence↗
PubMed1990

Isochromosome 12p in non-seminoma cell lines: karyologic amplification of c-ki-ras2 without point-mutational activation.

We examined eight human germ cell cancer lines (GCCLs) for cytogenetic abnormalities and found an isochromosome 12p, i(12p), marker in all seven male nonseminoma GCCLs, but not in the single female teratocarcinoma cell line. Southern blot analysis of these cell lines showed increased copy number for c-ki-ras2, a gene located on 12p, in all the male GCCLs. The comparison of Southern blot analysis for a restriction fragment length polymorphism (RFLP) probe localized to 12p to a probe for int-1, which maps to 12q, indicates that the increased copy number for c-ki-ras2 is primarily from the greater numbers of 12p relative to 12q. Although Northern analysis revealed enhanced mRNA expression for c-ki-ras2 in the GCCLs with an i(12p), hybridization of specific end-labelled oligonucleotides to the polymerase chain reaction products of c-ki-ras2 codons 12, 13, or 61 did not identify c-ki-ras2 mutations of these codons in these cells. Thus, c-ki-ras2 activation through point mutation is an infrequent event in GCCLs. These data further suggest that increased 12p copy number is a common event in the transformation process leading to male germ cell cancer. We conclude that determination of 12p copy number by cytogenetic analysis or Southern blotting is useful in the diagnostic evaluation of human germ cell cancer.

Blotting, Southern↗