Growth factors in melanoma

Human melanoma cells in culture are the source of a wide variety of polypeptide growth factors. Melanoma-derived basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF)-A and PDGF-B chains, transforming growth factor (TGF)-alpha and TGF-beta, interleukin (IL)-1 alpha and IL-1 beta, and melanoma growth stimulatory activity (MGSA) have similar biochemical and functional properties when compared to their counterparts produced by untransformed cells. In contrast to melanoma cells, normal melanocytes, even under optimal growth conditions, express only TGF-beta 1 and MGSA at detectable levels suggesting that production of the other growth factors is a tumor-associated phenomenon. Recent evidence suggests that at least two of the growth factors, bFGF and MGSA, contribute to autocrine growth stimulation of melanoma cells. Whether PDGF, TGF-alpha, IL-1, and TGF-beta act in an autocrine mode is unclear at present. However, these four growth factors are among those secreted by melanoma cells and, therefore, can be expected to interact with normal cells of the tumor stroma in vivo. Such paracrine effects include not only growth modulation in the context of angiogenesis and stroma formation, but also tissue degradation by proteolytic enzymes, the modification of extracellular matrix composition, and expression of adhesion receptors.

Development of invasive and growth factor-independent cell variants from primary human melanomas

Growth autonomy and high levels of invasiveness are characteristics of human melanoma cells that are metastatic in vivo. By consecutive passage through a reconstructed basement membrane, we have selected from 5 of 6 primary melanoma cell lines variants which show an up to 10-fold increase in invasiveness. The invasive variants grew more rapidly than the parental, noninvasive cells in serum- and growth factor-free medium and one of the 3 variant cell lines with the highest invasive capacity in vitro metastasized to the lungs when injected s.c. into nude mice. In a second approach, variants of 6 primary melanoma cell lines were clonally selected in medium without exogenous growth factors (protein-free medium). These selected cells showed higher invasive properties in vitro and in vivo than the parental cells. Clones of invasive and growth factor-independent cell variants were heterogenous and changed over time in the absence of selected pressure to a phenotype similar to that of parental nonselected cells. These results indicate that primary melanoma cells contain subpopulations of cells that have the phenotype of an advanced (metastatic) stage of tumor progression, but this phenotype is not stable without selective pressure.

Transforming growth factor-alpha secretion by epidermal growth factor-dependent human tumor cell lines

Pairs of cell lines from spontaneous human tumors (cervical adenocarcinoma, melanoma, and synovial sarcoma) were established using serum-free culture conditions with and without exogenous epidermal growth factor (EGF). EGF-adapted cultures of melanoma and cervical adenocarcinoma origin secreted higher levels of bioactive transforming growth factor alpha (TGF-alpha) when compared to cultures maintained in the absence of EGF. Depletion of EGF for these EGF-adapted cultures resulted in growth arrest. In contrast, the sarcoma cell lines did not secrete TGF-alpha regardless of the culture conditions but EGF significantly stimulated proliferation of these cells in short-term assays. We show that exogenous EGF induces TGF-alpha production and supports proliferation of tumor cells of various tissue origin but is not essential for in vitro growth factor-deprived conditions.

Inhibition of TGF alpha-induced second messengers by anti-EGF receptor antibody-425

Monoclonal antibody 425 binds to a protein epitope of the human EGF receptor and blocks EGF dependent functions such as EGF receptor phosphorylation and mitogenesis (1). We now show that MAb 425 blocks TGF alpha-induced second messenger signals, namely inositol 1,4,5 triphosphate and Ca2+ in two carcinoma cell lines, A 431 and SW-948. In this study we have further characterized the specificity of this antibody for inhibiting TGF alpha induced mitogenesis in MRC-5, a EGF-receptor expressing fibroblast cell line.

Monoclonal antibody 425 inhibits growth stimulation of carcinoma cells by exogenous EGF and tumor-derived EGF/TGF-alpha

Carcinoma cells frequently coexpress transforming growth factor (TGF)-alpha and its receptor, the epidermal growth factor (EGF) receptor, implicating an autocrine function of carcinoma-derived TGF-alpha. Using a monoclonal antibody (425) to the EGF-receptor, we investigated the role of exogenous and tumor cell-derived EGF/TGF-alpha mitogenic activities in proliferation of cell lines derived from solid tumors. Monoclonal antibody 425 was chosen for these studies because it inhibits binding of EGF/TGF-alpha to the EGF-receptor and effectively blocks activation of the EGF-receptor by EGF/TGF-alpha. Seven malignant cell lines originating from carcinomas of colon, pancreas, breast, squamous epithelia, and bladder expressed surface EGF-receptor and secreted EGF/TGF-alpha-like mitogenic activities into their tissue culture media. All cell lines were maintained in a defined medium free of exogenous EGF/TGF-alpha. EGF and TGF-alpha added to the culture medium stimulated proliferation of five cell lines to comparable levels. EGF/TGF-alpha-dependent proliferation was significantly reduced by addition of MAb 425 to culture media. In addition, monoclonal antibody 425 reduced proliferation of the five EGF/TGF-alpha responsive cell lines in the absence of exogenous EGF/TGF-alpha. Antiproliferative effects induced by monoclonal antibody 425 were reversible and could be overcome by addition of EGF to culture media. Our results indicate that tumor-derived EGF-receptor-reactive mitogens can promote proliferation of carcinoma cells in an autocrine fashion.

Antigenic profile of tumor progression stages in human melanocytic nevi and melanomas

Sixteen monoclonal antibodies that were obtained after immunization of BALB/c mice with intact melanoma cells or extracts of melanoma cells were tested for reactivity with normal and malignant melanocytic cells in situ, using an immunoperoxidase technique on frozen tissue sections. Sections representing six histopathologically defined stages of tumor progression, ranging from normal melanocytes to highly malignant metastatic lesions, were used. Thirteen monoclonal antibodies (MAbs) did not stain normal melanocytes in situ, whereas three MAbs weakly stained between 1 and 12.5% of melanocytes in 6-22% of the skin sections examined. MAb B 73.1, which was produced by immunization of mice with human natural killer cells and which binds to the Fc receptor of natural killer cells and granulocytes, reacted exclusively with malignant cells that represent the last two stages of tumor progression, vertical growth phase (VGP) primary melanoma and metastatic melanoma. All other antibodies showed variable reactivity with benign proliferative lesions or radial growth phase (RGP), an early stage of primary melanoma. Staining by MAbs that were reactive with gangliosides, unknown antigens, receptors, and two proteins (120/94 kDa protein and 250 kDa glycoprotein) showed a gradual increase in subsequent stages of tumor progression. Two steps in tumor progression were characterized by significant quantitative changes in the expression of antigens detected by the MAbs used in this study. First, mature nevus cells showed significantly higher reactivity with a panel of six MAbs, when compared to normal melanocytes. Second, a separate panel of six MAbs discriminated between RGP and VGP primary melanoma cells. No significant differences in antigen expression were found between dysplastic nevus cells and RGP melanoma, except that some antigens (nerve growth factor receptor and GD2/GD3 gangliosides) appear to be expressed at lower levels in RGP lesions, nor did VGP primary and metastatic melanomas show significant differences in antigen expression. These results suggest that (a) tumor progression of melanocytic cells in vivo is accompanied by significant quantitative differences in the expression of antigens, (b) some of the antigens examined here are associated with biologically aggressive malignant lesions but not normal or premalignant melanocytic cells, and (c) RGP primary melanoma cells are antigenically more similar to nevus cells than to VGP primary melanoma cells.

Tumor progression in the human melanocytic system

The isolation and routine tissue culture of melanocytic cells from normal skin, precursor nevi, primary and metastatic melanomas has allowed the experimental study of different stages of tumor progression. Characteristic differences between cultured normal melanocytes and highly malignant metastatic melanoma cells were: 1) limited life span for normal melanocytes and non-malignant nevus cells versus infinite growth for malignant melanoma cells; 2) inability to grow anchorage-independently versus high colony forming-efficiency in soft agar; 3) non-tumorigenicity versus tumorigenicity in athymic nude mice; 4) dependence on exogenous growth factors and other mitogens versus autonomous growth in protein-free medium; 5) expression of melanocyte-associated antigens versus expression of melanoma-associated antigens; and 6) diploid karyotype versus non-random chromosomal abnormalities. The only major distinction found between advanced primary and metastatic melanomas was that only metastatic melanoma cells proliferated continuously in the absence of growth factors or other proteins. However, advanced primary melanoma cells could be clearly distinguished from dysplastic nevus cells by their growth behavior and growth factor requirements. Only limited information is available on the biologic, genetic, immunologic and molecular properties of dysplastic nevus cells and early (radial growth phase) primary melanoma cells but these cells appear to differ markedly from advanced primary and metastatic cells. The availability of cells from sequential steps of tumor progression in the human melanocytic system offers a unique experimental model for the study of malignant transformation.

Inhibition of metastases of a human melanoma xenograft by monoclonal antibody to the GD2/GD3 gangliosides

A human melanoma variant cell line was obtained from a lung metastasis that arose spontaneously after we inoculated melanoma cells sc into a nude mouse. In this model, IgG2a monoclonal antibody (MAb) ME 36.1 defining the GD2/GD3 gangliosides inhibited melanoma growth at the primary site and metastatic spread of the cells, whereas an IgG1 variant of MAb ME 36.1 inhibited lung metastasis formation only. Possible mechanisms of antitumor effects of MAb ME 36.1 are discussed.

Epidermal growth factor (EGF) and monoclonal antibody to cell surface EGF receptor bind to the same chromatin receptor

Cellular uptake, nuclear translocation, and chromatin binding of epidermal growth factor (EGF) and monoclonal antibodies (MAbs) against the protein domain of the EGF surface receptor (MAb 425) and against the carbohydrate Y determinant on the EGF receptor (MAb Br 15-6A) were analyzed in cell lines that express surface EGF receptor. Both EGF and MAb 425 were translocated to the nucleus and bound in nondegraded form to the chromatin of all cells tested. MAb Br 15-6A was taken up only by SW 948 colorectal carcinoma cells which express EGF receptor whereas neither EGF nor MAb 425 was taken up by SW 707 colorectal carcinoma cells which do not express EGF receptor. MAb 425 immunoprecipitated a 230- to 250-kDa chromatin protein, which appears to be the EGF chromatin receptor. EGF was localized in a single EcoRI DNA fragment suggesting that the chromatin binding was highly specific. Binding of EGF to primarily DNase II-sensitive chromatin regions protected these regions from nuclease action. The role of growth factor binding to chromatin in neoplastic transformation is discussed.

Growth and phenotypic characteristics of human nevus cells in culture

Nevus cells were isolated from the three cutaneous components, epidermis, basal layer, and dermis, of nonmalignant pigmented lesions and were cultured separately in the presence or absence of the phorbol ester 12-0-tetradecanoyl phorbol-13-acetate in medium that supports the rapid proliferation of melanocytic cells. The separation procedure used provided cultures that were essentially free from normal melanocytes (dermis) or fibroblasts (epidermis). In short term culture, nevus cells of all skin compartments expressed markers associated with differentiated melanocytes, such as presence of premelanosomes and melanosomes and elevated tyrosinase levels. Nevus cells also expressed melanoma-associated antigens, such as NGF-receptor, transferrin-related p97, proteoglycan, and HLA-DR as detected with monoclonal antibodies. After several subpassages, cells showed a decreased expression of melanoma-associated antigens, decreased tyrrosinase levels, and melanosomes could no longer be detected. Morphologically, these cells were similar to fibroblasts. The disappearance of melanoma-associated cell surface antigens was concomitant with the appearance of a melanocyte-associated 145 kd protein that might serve as a marker of fibroblast-like differentiation in nevus cells and normal melanocytes. Nevus cell cultures grown in the presence of 12-0-tetradecanoyl phorbol-13-acetate maintained a stable differentiated phenotype throughout their lifespan. As reported earlier, nevus cells in culture, irrespective of the presence or absence of 12-0-tetradecanoyl phorbol-13-acetate, have a finite lifespan in vitro, grow anchorage-independent in soft agar, but do not form tumors when xenografted to nude mice. These studies demonstrate that nevus cells isolated from the epidermal, basal layer, and dermal components of lesional skin can serve as models to characterize the initial steps of tumor progression in a human cell system.

Characteristics of cultured human melanocytes from different stages of tumor progression

Based on the clinicopathological delineation of distinct steps of tumor progression in the melanocytic system, the in vitro behavior of melanocytes with increasing malignant potential has been investigated. Tumor progression in melanocytes is characterized by an increasing growth autonomy and decreased requirement but enhanced utilization of exogenously provided polypetide growth factors (EGF, IGF-I). The endogenous production of growth factors such as alpha-TGF, PDGF, and bFGF by metastatic melanoma cells might contribute to their independence from exogenously provided factors. Although expression of some melanoma-associated antigens in vivo is detectable only on malignant cells, propagation of normal melanocytes in tissue culture leads to expression of the majority of these antigens. Many of these antigens can be grouped into functionally defined categories, including growth factor receptors, extracellular matrix proteins, and cell-substrate interacting antigens. One cell-substrate interacting antigen, the GD2/GD3 ganglioside, appears to play a critical role in the metastatic process of melanoma cells. The successful propagation and characterization of melanocytic cells of all stages of tumor progression in tissue culture provide a unique human experimental model for the study of mechanisms of malignant transformation.

Interactions between growth factor receptors and corresponding monoclonal antibodies in human tumors

Monoclonal antibodies (MAbs) to the human epidermal growth factor (EGF) receptor, the type I insulin-like growth factor (IGF) receptor, and the nerve growth factor (NGF) receptor were used to study the growth regulation of malignant cells. Anti-EGF receptor MAb 425 inhibited the growth of A 431 squamous carcinoma cells which express high numbers of EGF receptors on their surfaces. Growth inhibition induced by MAb 425 was accompanied by alterations of the cell-cycle distribution of these cells, indicating the ability of a monoclonal antibody to act as a biologically active ligand. Growth stimulation of melanoma cells by EGF was unrelated to EGF receptor expression on the cell surface. Insulin- and IGF-I-induced growth stimulation of melanoma cells was inhibited by MAb alpha IR-3 which reacts with the type I IGF receptor. This result indicates that the type I IGF receptor mediated growth stimulation not only by IGF-I but also by insulin. Normal melanocytes and cells of all stages of tumor progression expressed in tissue culture the receptor for NGF, but no effect on the growth of these cells has been observed.

Rapid dissociation of adherent human tumor cells by ultrasound

Cultured human melanoma and gastrointestinal carcinoma cells were detached from substrate and further dissociated by placing the culture vessel into a water-filled ultrasonic cleaner (43 kHz) and sonicating it for 10-50 s. Plating efficiency and long-term growth of three melanoma cell lines were similar after ultrasound or trypsin detachment. Binding of monoclonal antibodies that define normal and tumor-associated antigens on melanoma and colorectal carcinoma cells was not affected by ultrasound in 21 out of 23 cases. The 40 kDa colorectal carcinoma-associated antigen defined by monoclonal antibody CO 17-1A was more highly expressed after ultrasonication than trypsinization. The antigen defined by antibody CO 44.1 on these cells was more sensitive to sonication. This method represents a rapid, effective and gentle alternative to trypsin detachment of cultured cells, especially when repeated cell washing or centrifugation steps are required.

Metastatic but not primary melanoma cell lines grow in vitro independently of exogenous growth factors

Five out of 6 cell lines derived from metastatic melanoma lesions grew in a chemically defined base medium consisting of a mixture of calcium-supplemented MCDB 153 and L 15 media in the absence of any polypeptide growth factors. In contrast, under these conditions no growth was seen in any of 5 primary melanoma cell lines tested, including 2 cell lines from patients whose metastatic cells proliferated well in base medium. Growth stimulation of all 11 melanoma cell lines by epidermal growth factor (EGF), transferrin, insulin, and insulin-like growth factor (IGF)-1 alone and in various combinations was studied. Insulin represented the strongest single growth factor for primary and metastatic melanoma cell lines. The metastatic cell lines remained growth-responsive to EGF, insulin and transferrin and responded more vigorously to these exogenously provided mitogens than the primary cell lines. No synergistic or additive growth effects of insulin, transferrin, or EGF for primary and metastatic cell lines were observed. Cross-linking studies with 125I-IGF-1 demonstrate surface expression of the type-I IGF receptor on melanoma cells. Growth stimulation by insulin and IGF-1 was inhibited by adding to the culture medium a monoclonal antibody to the type-I IGF receptor. Our studies indicate that IGF-1 and insulin are major growth factors for melanoma cells and act via the type-I IGF receptor.

A mucin containing the X, Y, and H type 2 carbohydrate determinants is shed by carcinoma cells

Monoclonal antibody BR 15-6A directed to the Y carbohydrate determinant (Fuc alpha 1----2Gal beta 1----4GlcNAc(3----1Fuc) beta 1----3Gal beta 1----4Glc beta 1----1Cer) reacted with the cell surface and conditioned media of colorectal and breast carcinoma cell lines. Double determinant immunoassays using BR 15-6A as detector antibody showed that the Y determinant is part of a high molecular weight mucin that coexpressed other carbohydrate antigens based on a type 2 chain (X, H type 2). Type 1 chain carbohydrates such as sialylated Lewisa, Lewisa and Lewisb blood group antigens were predominantly expressed on a separate mucin molecule as determined by double-determinant immunoassays with other anticarbohydrate monoclonal antibodies. The X, Y, and H type 2-bearing mucin was present in conditioned media of the majority of colorectal carcinoma cell lines and in all three breast cancer cell lines tested. Thus, monoclonal antibodies against X, Y, and H type 2 determinants are potentially useful in the serodiagnosis of gastrointestinal and breast cancer.

Tumor growth modulation by a monoclonal antibody to the epidermal growth factor receptor: immunologically mediated and effector cell-independent effects

A monoclonal antibody of IgG2a isotype (425) is described that reacts with the epidermal growth factor receptor on human cells of different tissue origins. Monoclonal antibody 425 mediates tumor cytotoxicity in vitro using mouse and human effector cells and suppresses in vivo tumor cell growth of epidermoid (A 431) and colorectal (SW 948) carcinoma-derived cell lines. The tumoricidal effects in vitro are proportional to the antigen density on target cells. At concentrations higher than 1 nM, monoclonal antibody 425 inhibits growth of epidermal growth factor receptor-bearing A 431 cells, showing an epidermal growth factor-like agonist activity on the growth properties of these cells. A 431 cultures grown in the presence of growth-inhibiting doses of antibody or epidermal growth factor reveal a clear decrease of the relative number of cells in S phase. Additionally, cells treated with the antibody show a decrease of G2-M-phase cells in some, but not all, cultures tested.

Radioimmunodetection of human glioma xenografts by monoclonal antibody to epidermal growth factor receptor

Murine IgG2a monoclonal antibody (MAb) 425 specifically detects epidermal growth factor receptor, which is expressed on human gliomas and tumors of other tissue origin but rarely on normal brain tissues, and not at all on bone marrow and peripheral blood cells. 131I-labeled F(ab')2 fragments of this MAb injected into nude mice grafted with U-87 MG glioma cells preferentially localized in tumor tissue compared to normal mouse tissues, as determined by differential tissue counting of radioactivity. The mean tumor-to-tissue ratios of radioactivity ranged between 8.2 (blood) and 55.8 (muscle) at 2 days after the injection of 15 muCi of 131I-425 F(ab')2/mouse. Radiolabeled fragments of an anti-hepatitis virus IgG2a MAb did not localize in tumors. The localization index derived from the ratios of specific antibody to indifferent antibody in tumor tissue relative to blood was 9.94 at 2 days following the MAb injection. The labeled MAb did not localize in a xenograft of colorectal cancer tumor, which does not express the epidermal growth factor receptor. Tumors could be located by whole-body gamma-scintigraphy without background subtraction following the injection of 100 muCi of radiolabeled MAb 425 F(ab')2 fragments. The data suggest that MAb 425 is a likely candidate for clinical diagnostic and radioimmunotherapy trials.

Expression of melanoma-associated antigens in rapidly dividing human melanocytes in culture

Conditions were established to induce rapid clonal growth of melanocytes from newborn foreskin. Surface antigen expression was analyzed using monoclonal antibodies derived by immunization of mice with melanoma cell, melanocyte, and placental membrane preparations. Unlike resting melanocytes in normal skin, cultured melanocytes expressed most major melanoma-associated antigens tested, e.g., nerve growth factor receptor, proteoglycan, transferrin-related Mr 97,000 protein antigen, Mr 120,000 protein, and gangliosides 9-O-acetyl GD3 and GD3. HLA-DR antigen and ganglioside GD2 were expressed at very low levels or not expressed. After several subpassages, most melanocyte cultures, including clones and melanocytes, initially sorted by rosetting with monoclonal antibody to nerve growth factor receptor, lost their characteristic bipolar morphology and expression of nerve growth factor receptor and Mr 97,000 antigen but continued to express high molecular weight proteins such as proteoglycan, Mr 130,000/105,000 and 120,000 antigen. The few melanocyte cultures that did maintain their characteristic bipolar to spindle morphology continued to express all melanoma-associated antigens and even began to express HLA-DR antigens. Melanocytes cultured in the presence of the phorbol ester 12-O-tetradecanoylphorbol-13-acetate also maintained their bipolar morphology, were often pigmented, and continued to express melanoma-associated antigens for several passages; they did not express HLA-DR antigen. Our studies indicate that rapidly proliferating melanocytes in culture undergo antigenic changes associated with malignancy.

Presence of tumor-associated antigens in epidermal growth factor receptors from different human carcinomas

The epidermal growth factor (EGF) receptor in two colon carcinoma lines and in one vulval carcinoma line tested contains carbohydrate determinants that are recognized by monoclonal antibodies to tumor-associated antigens. These antibodies are directed to sialylated Lea and to difucosylated structures of the Y type. Cell lines which react with these antibodies express these antigens on their surface glycolipids and glycoproteins, including the EGF receptor. These unusual carbohydrates are absent in EGF receptors from normal untransformed cells, and from tumor cells which do not express these specific antigens. Although EGF receptor represents only 0.1-2% of total plasma membrane proteins of antigen-positive carcinomas, it accounts for 20-80% of total protein-associated sialylated Lea/Y type of nonsecreted carbohydrates present in these cells. The results of cell-binding, immunoprecipitation, and Western blot analyses of the antigen-positive carcinomas indicate that sialylated Lea/Y type of antigenicity is intrinsic to the EGF receptors of these cells, and that the antigen is present in receptors from both over-expressing and normal-expressing carcinomas.

Biology of tumor progression in human melanocytes

Tumor progression in the human melanocyte system can be delineated into 6 sequential stages. The first three steps represent nonmalignant melanocyte lesions from focal proliferations of structurally normal melanocytes to lesions with architectural and cytologic atypia. Primary melanoma may be divided into radial growth phase without competence for metastasis and vertical growth phase with metastatic competence. Melanocytes isolated from normal skin, nonmalignant pigmented lesions, and melanomas and maintained in culture have properties that are characteristic for each stage of tumor progression. Cytogenetic studies revealed nonrandom chromosomal abnormalities of advanced melanomas involving chromosomes 1, 6, and 7. Recent progress in tissue culture techniques has allowed studies of growth regulation of normal and malignant cells. Six growth factor receptor-growth factor systems seem to be of biologic significance in the melanocyte system: EGF, NGF, FGF, PDGF, insulin, and beta-TGF. Monoclonal antibodies have characterized a large number of antigens on melanocytes of the various stages of tumor progression, making melanoma one of the most widely studied human tumor systems.

Relative and absolute numbers of human lymphocyte subpopulations. A comparison of immunofluorescence microscopy and flow cytometric methodologies with special reference to precision and reference values

Lymphocyte subpopulations were determined in blood samples from blood donors (40 women and 45 men) using immunofluorescence microscopy and flow cytometric methodologies. The study demonstrates the value of both methods for the enumeration of lymphocyte subpopulations. The advantages of employing an automated flow cytometer system are better precision and speed. The automated systems require a large initial technical and financial burden and are therefore probably destined to be reserved for the larger laboratory. There is a need for an adequate lymphocyte standard which shows little variation between aliquots and can be used for interlaboratory comparisons.

Binding of an antagonistic monoclonal antibody to an intact and fragmented EGF-receptor polypeptide

A murine monoclonal antibody (No. 425) raised against human A431 carcinoma cells specifically immunoprecipitates the 170,000 molecular weight epidermal growth factor (EGF)-receptor from extracts of A431 cells as well as from extracts of human placenta and cultured fibroblasts, but does not recognize the murine receptor. Binding to the external domain of the human EGF-receptor was indicated by indirect immunofluorescent staining of fixed nonpermeable cells. The antibody binds to both glyco- and aglycoreceptor forms, indicating that the epitope is a part of the polypeptide chain. Binding of the antibody to the receptor is conformation dependent; i.e., denatured receptors lacking EGF-binding activity are not recognized by the antibody. The results of antibody binding studies indicate that the epitope is closely linked to the EGF binding active site, and is common to both high- and low-affinity EGF-receptors. Interaction of this epitope with the antibody inhibits EGF binding and bioactivity, and triggers receptor down-regulation, but does not generate EGFlike kinase-stimulatory or mitogenic responses either in vitro or in vivo. The antibody was tested for its ability to bind to domain-sized fragments of the 170-kDa EGF-receptor. It can recognize both the proteolytically generated 110-kDa EGF binding peptide, and a soluble 100-kDa EGF-receptor secreted by A431 cells. This indicates that the epitope recognized this antibody retains its conformation after proteolytic separation of the EGF binding domain from the rest of the receptor molecule.

Human melanoma cell lines of primary and metastatic origin express the genes encoding the chains of platelet-derived growth factor (PDGF) and produce a PDGF-like growth factor

Normal human melanocytes and five human melanoma cell lines were analyzed for production of platelet-derived growth factor (PDGF)-like activity. Three of the melanoma cell lines released an activity that inhibited binding of 125I-labeled PDGF to human foreskin fibroblasts and stimulated [3H]thymidine incorporation in such cells. These activities were inhibited by the addition of anti-PDGF antibodies. All three factor-producing cell lines were derived from the same patient--one originated from the primary tumor (WM 115), and two were from individual lymph-node metastases (WM 239A and WM 266-4). The factor produced by WM 266-4 cells was characterized biochemically in detail. Immunoprecipitated, the metabolically labeled factor migrated in NaDod-SO4/gel electrophoresis as a homogeneous Mr 31,000 species, which under reducing conditions was resolved into two species of Mr 16,500 and Mr 17,000, implying a dimeric structure of the molecule. The factor was purified to homogeneity. Analysis by reverse-phase high-pressure liquid chromatography of reduced and alkylated factor revealed an elution pattern identical to that of PDGF A chains. Thus, the native molecule appears to be a homodimer of PDGF A chains. Blot-hybridization analysis of poly(A)+ RNA from the cell lines with 32P-labeled PDGF A chain and B chain (SIS product) cDNA probes revealed a relative abundance of B chain transcripts in the cell line originating from the primary tumor tissue only but expression of A chain in all three cell lines. We conclude that the two structural genes encoding each of the subunit chains of PDGF can be expressed in human melanoma cells and that the two genes can be independently expressed in such cells.

Chromatin binding of epidermal growth factor, nerve growth factor, and platelet-derived growth factor in cells bearing the appropriate surface receptors

We analyzed the uptake and intracellular distribution of 125I-labeled epidermal growth factor, nerve growth factor, and platelet-derived growth factor in different cell lines that express or do not express the respective surface receptors for these factors. After 1 hr of incubation, all three growth factors were detected in the cytoplasmic fraction and in the nucleus, tightly bound to chromatin. The amount of chromatin-bound growth factors continued to increase during the incubation, and analysis at 48 hr revealed each chromatin-bound labeled growth factor in a nondegraded form. After limited digestion of chromatin with DNase II (10-20% digested sequences), specific release of all three growth factors was detected only after 1 hr of incubation but not after 24 and 48 hr, suggesting that the DNA regions involved in growth factor binding became nuclease-resistant. Binding of labeled epidermal growth factor and nerve growth factor to isolated chromatin was inhibited by monoclonal antibodies specific for the respective growth factor receptor. The data suggest that chromatin binding may represent an important step in the pathway of growth factor action.

[Follow-up of immunological parameters and therapy of systemic lupus erythematosus]

In a longitudinal study of a female patient with systemic lupus erythematosus, we determined numbers of T-lymphocytes and subpopulations (OKT4+- and OKT8+-lymphocytes), B-lymphocytes, production of anti-double-stranded DNA antibody (anti-ds-DNA-Ab), and we investigated the effects of corticosteroids and cyclophosphamide on these parameters and clinical disease activity. The results demonstrate that an increase of OKT4+-T-lymphocytes/OKT8+-T-lymphocytes ratio apparently augments B-lymphocyte numbers resulting in anti-ds-DNA-Ab production. Whereas steroids exerted limited, possibly dose-dependent effects on this sequence, cyclophosphamide seemed to cause normalization of OKT4+/OKT8+ ratio, precipitous drop of anti-ds-DNA-Ab titers, and dramatic clinical improvement.

T lymphocyte populations in multiple sclerosis

In 36 patients representing different clinical stages of multiple sclerosis (MS) (9 patients with acute exacerbations; 21 patients in remission; 5 patients with chronic progressive MS) determinations of T lymphocyte populations using monoclonal antibodies against surface antigens (OKT3 (pan T cells), OKT4 (helper T cells), OKT8 (cytotoxic/suppressor T cells] were performed. Compared to the control group (40 healthy individuals) a clear elevation of the T4/T8 ratio was found in acute exacerbations and to a lesser degree in patients with inactive phases of MS. Patients with chronic progressive disease did not show increased T4/T8 ratios. Serial determination of lymphocyte populations after corticosteroid therapy in 10 selected patients revealed no significant changes which could be attributed to this therapeutic modality. Pathogenetic and clinical implications of the shifts in surface antigen expression of T lymphocyte populations mirroring the clinical course of MS are discussed.

[Regulatory T-lymphocytes in the immune deficiency syndrome]

A 25-year-old patient presented with hypogammaglobulinemia diagnosed at the age of 7, causing recurrent infections of the gastrointestinal and bronchial tracts. He was treated with gammaglobulins and infusions of fresh human plasma. At admission he had an exacerbation of his chronic enteric symptoms. X-ray investigation and coloscopy showed mucosal changes as in enteritis regionalis . A biopsy of rectal mucosa showed accumulations of amyloid. Routine examination of humoral and cellular immune parameters revealed a pattern characteristic for common variable immunodeficiencies. Analysis of T-cell subsets with monoclonal antibodies of the OKT series showed unusually high relative numbers of OKT8+ cells (suppressor-T-lymphocytes) and a comparatively low number of OKT4+ cells (helper-T-lymphocytes). Suppressor-T-cells exert inhibitory effects on B-lymphocyte function (i.e. antibody production). The numerical excess of T-lymphocytes with suppressive properties could be a pathogenetically important factor with immunotherapeutic implications in a number of non-classifiable immunodeficiency syndromes.

[Age- and sex-dependent changes in human T-lymphocyte subpopulations]

Changes in the expression of T-lymphocyte membrane antigens are seen in many diseases, particularly in autoimmune diseases. The reliability of these parameters, as well as their changes associated with age and sex, were examined in 232 healthy subjects using monoclonal antibodies of the OKT series. The precision of the indirect immunofluorescence method for determining the T3, T4 and T8 antigens (corresponding antibodies OKT 3, OKT 4, OKT 8) is within a range expected for biological testing methods (median variation coefficients 7-20%). In both sexes a statistically significant reduction of the T3+ cells (P = 0.0001; T-lymphocytes) and of the T8+ cells (P = 0.0004; T-suppressor lymphocytes) was seen with increasing age. In women (n = 115) the rate of T3+ and T4+ cells was 2-5% higher on the average (the T4+ cell population contains T-helper lymphocytes). According to these findings there is a statistically significant increase of the T4+ to T8+ cell ratio (P = 0.0001); due to the greater number of helper cells, the average T4/T8 quotients are greater in women than in men (P = 0.0076). The changes in the ratio of T-helper to T-suppressor cells are discussed as predisposing factors in the genesis of autoimmune diseases.

[Trehalose-load test in gastroenterology]

In 35 infants trehalose-load-tests were carried out, biopsies of the intestinal mucosa of each patient were taken, and examined histologically. Furthermore, the enzyme activities of trehalase and lactase in each biopsy were determined. It was possible to demonstrate that morphology and function of the intestinal mucosa correlate differently depending on the severity of the mucosal damage. If there is only moderate mucosal damage, a rather weak correlation is seen either for the trehalose-load-test or for the disaccharidase activities with morphological changes. If damage was absent or severe, correlation improved. Both methods in comparison show a better correlation between trehalase activity and morphology than between trehalose-load-test and morphology. Furthermore, trehalase activity corroborated the histological findings better than lactase activity.