Purification by reverse-phase high-performance liquid chromatography of an epidermal growth factor-dependent transforming growth factor

A primer on cytokines

Cytokines are pleiotropic polypeptides that control the development of and responses mediated by immune cells. Cytokine classification predominantly relies on [1] the target receptor(s), [2] the primary structural features of the extracellular domains of their receptors, and [3] their receptor composition. Functionally, cytokines are either pro-inflammatory or anti-inflammatory, hematopoietic colony-stimulating factors, developmental and would healing maintaining immune homeostasis. When the balance in C can form complex networks amongst themselves that may affect the homeostasis and diseases. Cytokines can affect resistance and susceptibility for many diseases and their availability in the host cytokine production and interaction is disturbed, immunopathogenesis sets in. Therefore, cytokine-targeting bispecific, and chimeric antibodies form a significant mode of immnuo-therapeutics Although the field has grown deep and wide, many areas of cytokine biology remain unknown. Here, we have reviewed these cytokines along with the organization, signaling, and functions through respective cytokine-receptor-families. Being part of the special issue on the Role of Cytokines in Leishmaniasis, this review is intended to be used as an organized primer on cytokines and not a resource for detailed discussion- for which a two-volume Handbook of cytokines is available- on each of the cytokines. Priming the readers on cytokines, we next brief the role of cytokines in Leishmaniasis. In the brief, we do not provide an account of each of the involved cytokines known to date, instead, we offer a temporal relationship between the cytokines and the progress of the infection towards the alternate outcomes- healing or non-healing- of the infection.

On-Target Anti-TGF-β Therapies Are Not Succeeding in Clinical Cancer Treatments: What Are Remaining Challenges?

Metastasis is the leading cause of death for cancer patients. During cancer progression, the initial detachment of cells from the primary tumor and the later colonization of a secondary organ are characterized as limiting steps for metastasis. Epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET) are opposite dynamic multistep processes that enable these critical events in metastasis by altering the phenotype of cancer cells and improving their ability to migrate, invade and seed at distant organs. Among the molecular pathways that promote tumorigenesis in late-stage cancers, transforming growth factor-β (TGF-β) is described as an EMT master inducer by controlling different genes and proteins related to cytoskeleton assembly, cell-cell attachment and extracellular matrix remodeling. Still, despite the successful outcomes of different TGF-β pharmacological inhibitors in cell culture (in vitro) and animal models (in vivo), results in cancer clinical trials are poor or inconsistent at least, highlighting the existence of crucial components in human cancers that have not been properly explored. Here we review most recent findings to provide perspectives bridging the gap between on-target anti-TGF-β therapies in vitro and in pre-clinical models and the poor clinical outcomes in treating cancer patients. Specifically, we focus on (i) the dual roles of TGF-β signaling in cancer metastasis; (ii) dynamic signaling; (iii) functional differences of TGF-β free in solution vs. in exosomes; (iv) the regulatory effects of tumor microenvironment (TME) – particularly by cancer-associated fibroblasts – on TGF-β signaling pathway. Clearly identifying and establishing those missing links may provide strategies to revitalize and clinically improve the efficacy of TGF-β targeted therapies.

On-Target Anti-TGF-β Therapies Are Not Succeeding in Clinical Cancer Treatments: What Are Remaining Challenges?

Metastasis is the leading cause of death for cancer patients. During cancer progression, the initial detachment of cells from the primary tumor and the later colonization of a secondary organ are characterized as limiting steps for metastasis. Epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET) are opposite dynamic multistep processes that enable these critical events in metastasis by altering the phenotype of cancer cells and improving their ability to migrate, invade and seed at distant organs. Among the molecular pathways that promote tumorigenesis in late-stage cancers, transforming growth factor-β (TGF-β) is described as an EMT master inducer by controlling different genes and proteins related to cytoskeleton assembly, cell-cell attachment and extracellular matrix remodeling. Still, despite the successful outcomes of different TGF-β pharmacological inhibitors in cell culture (in vitro) and animal models (in vivo), results in cancer clinical trials are poor or inconsistent at least, highlighting the existence of crucial components in human cancers that have not been properly explored. Here we review most recent findings to provide perspectives bridging the gap between on-target anti-TGF-β therapies in vitro and in pre-clinical models and the poor clinical outcomes in treating cancer patients. Specifically, we focus on (i) the dual roles of TGF-β signaling in cancer metastasis; (ii) dynamic signaling; (iii) functional differences of TGF-β free in solution vs. in exosomes; (iv) the regulatory effects of tumor microenvironment (TME) - particularly by cancer-associated fibroblasts - on TGF-β signaling pathway. Clearly identifying and establishing those missing links may provide strategies to revitalize and clinically improve the efficacy of TGF-β targeted therapies.

The Discovery and Early Days of TGF-β: A Historical Perspective

Transforming growth factors (TGFs) were discovered as activities that were secreted by cancer cells, and later by normal cells, and had the ability to phenotypically and reversibly transform immortalized fibroblasts. TGF-β distinguished itself from TGF-α because it did not bind to the same epidermal growth factor (EGF) receptor as TGF-α and, therefore, acted through different cell-surface receptors and signaling mediators. This review summarizes the discovery of TGF-β, the early developments in its molecular and biological characterization with its many biological activities in different cell and tissue contexts and its roles in disease, the realization that there is a family of secreted TGF-β-related proteins with many differentiation functions in development and activities in normal cell and tissue physiology, and the subsequent identification and characterization of the receptors and effectors that mediate TGF-β family signaling responses.

Comparison of silica-based cyanopropyl and octyl reversed-phase packings for the separation of peptides and proteins

The performance of a silica-based C8 packing was compared with that of a less hydrophobic, silica-based cyanopropyl (CN) packing during their application to reversed-phase high-performance liquid chromatography (linear trifluoroacetic acid-water to trifluoroacetic acid-acetonitrile gradients) of peptides and proteins. It was found that: (1) the CN column showed excellent selectivity for peptides which varied widely in hydrophobicity and peptide chain length; (2) peptides which could not be resolved easily on the C8 column were widely separated on the CN column; (3) certain mixtures of peptides and small organic molecules which could not be resolved on the C8 column were completely separated on the CN column; (4) impurities arising from solid-phase peptide synthesis were resolved by a wide margin on the CN column, unlike on the C8 column, where these compounds were eluted very close to the peptide product of interest: and (5) specific protein mixtures exhibited superior resolution and peak shape on the CN column compared with the C8 column. The results clearly demonstrate the effectiveness of employing stationary phases of different selectivities (as opposed to the more common optimization protocol of manipulating the mobile phase) for specific peptide and protein applications, an approach underestimated in the past.

Cellular mechanisms of TGF-beta action

Transforming growth factor beta (TGF-beta), initially identified in platelet extracts by virtue of its ability to confer anchorage-independent growth and a neoplastic phenotype on mesenchymal cells, has subsequently been identified as a potent inhibitor of proliferation in most cells of epithelial origin. Our laboratory has investigated the role of specific second messengers in mediating the transcriptional responses of fibroblasts following addition of TGF-beta 1. Our studies indicate that TGF-beta 1, alone and in conjunction with epidermal growth factor (EGF), is capable of stimulating increases in both phosphoinositide metabolism and calcium influx, leading to significant increases in intracellular levels of Ca++ and inositol trisphosphate (IP3). Our data indicated that Ca++ influx and inositol phosphate release are coupled in Rat-1 cells, and suggested that influx of Ca++ from the extracellular medium is required for the change in IP3 accumulation observed in response to both EGF and TGF-beta 1. Using nuclear run-on analysis of the transcription of rat transin, a secreted metalloproteinase homologous to human stromelysin, we have also demonstrated a significant inhibition of transin transcription within 10 min of TGF-beta 1 treatment. The ability of TGF-beta 1 to inhibit transin gene transcription was not related to the TGF-beta 1-induced influx of Ca++ or to an increase in intracellular inositol phosphates, since inhibiting production of these second messengers failed to inhibit repression of the transin gene.

Transforming growth factor-ßs as modulators of pericellular proteolytic events

Since the discovery of transforming growth factor-ß:s an increasing number of different biological effects have been attributed to this group of proteins. Analysis of the cellular responses to TGFß stimulation at the molecular level has indicated that TGFß acts as an activator of transcription of several genes. This may in part explain the plethora of various functions that have been ascribed to TGFß. In addition to the TGFß family of polypeptides there is an increasing number of related factors, whose major roles appear to be involved in developmental processes. A distinct feature of TGFß is its ability to regulate pericellular proteolysis of cultured cells. As yet this property has not been associated with other members of this group of polypeptides. Depending on the target cell type TGFß may either increase or decrease pericellular proteolytic activity. Proteolytic activation of latent TGFß and its possible inhibition by TGFß-induced protease inhibitors could be a physiological feed-back mechanism in the control of proteolytic activity in the vicinity of cells.

Mesoderm induction and blood island formation by angiogenic growth factors and embryonic inducing factors

Factors which induce mesoderm, including endothelium lined cavities and primitive blood cells in omnipotent amphibian ectoderm, have been isolated from different sources. Recently it was shown that angiogenic factors, which belong to the protein families of the heparin binding growth factors (acidic and basic fibroblast growth factor) and the transforming growth factors (TGF-beta 1 and -beta 2), also induce mesodermal tissues in amphibian ectoderm. In triturus ectoderm, capillary like endothelial networks are induced preferentially by the transforming growth factors. The relationship between growth factors and inducing factors is discussed.

Sequence-specific 1H-NMR assignments and identification of two small antiparallel beta-sheets in the solution structure of recombinant human transforming growth factor alpha

Transforming growth factor alpha (TGF alpha) is a small mitogenic protein with about 35% sequence identity with epidermal growth factor (EGF). TGF alpha-like proteins have been proposed to play a role in oncogenesis and wound healing. This report describes sequence-specific 1H-NMR resonance assignments for recombinant human TGF alpha (hTGF alpha). These assignments provide the basis for interpreting NMR data which demonstrate that the solution structure of hTGF alpha includes an antiparallel beta-sheet involving residues Gly-19 to Leu-24 and Lys-29 to Cys-34 and a second, smaller, antiparallel beta-sheet involving residues Tyr-38 and Val-39 and His-45 and Ala-46. These data, together with constraints imposed by the disulfide bonds, are combined to construct a molecular model of the polypeptide chain fold for residues Cys-8 to Ala-46. The resulting structure is similar to that of mouse and human EGF. Human TGF alpha and mouse EGF, however, differ with respect to their structural dynamics, since amide proton/deuteron exchange is much faster for hTGF alpha than for mouse EGF at pH 3.5.

Regulation of growth inhibitory activity in transformed mouse embryo fibroblasts

Treatment of the transformed mouse embryo fibroblast cell line AKR-MCA with 1% N,N-dimethylformamide (DMF) resulted in the restoration of a nontransformed phenotype in these cells. In order to determine if an increase in growth inhibitory peptides might be responsible for these changes in growth properties of the DMF-treated AKR-MCA cells we examined the serum-free conditioned medium for its ability to inhibit the anchorage-independent growth of a human colon carcinoma cell line. The extracellular levels of inhibitory activity were two-fold higher in conditioned medium derived from AKR-MCA cells than in AKR-MCA cells grown in 1% DMF (AKR-MCA/DMF). Fractionation of the crude conditioned medium indicated the presence of an Mr 20,000 inhibitory fraction in AKR-MCA/DMF conditioned medium which was reduced in AKR-MCA cells. This Mr 20,000 inhibitory activity was acid and heat stable and sensitive to dithiothreitol and trypsin. In addition to inhibiting the growth of a human colon carcinoma cell line this protein induced colony formation in AKR-2B cells and competed for binding to the transforming growth factor beta (TGF-beta) receptor. Therefore, this Mr 20,000 inhibitory polypeptide induced by DMF is probably TGF-beta. TGF-beta was also shown to inhibit the growth of AKR-MCA cells in monolayer culture.

Method for complete separation of the high mobility group (HMG) proteins HMG I and HMG Y from HMG 14 and HMG 17 and a procedure for purification of HMG I and HMG Y

A purification procedure which separates the four low-molecular-weight high mobility group (HMG) proteins, HMG 14, 17, I and Y, is described. The procedure includes chromatography on phosphocellulose and Blue Sepharose combined with reversed-phase high-performance liquid chromatography. The blue Sepharose column separates HMG I and Y completely from HMG 14 and 17, and should therefore be an useful tool for the identification of these proteins which in several reports have been confused with HMG 14 and 17. HMG I and Y on the one hand and HMG 14 and 17 on the other exhibited considerable differences in their affinities for Blue Sepharose, probably reflecting fundamental differences in biological function.

Neuroblastoma cells express c-sis and produce a transforming growth factor antigenically related to the platelet-derived growth factor

Mouse neuroblastoma Neuro-2A cells produce transforming growth factors during exponential growth in a defined hormone-free medium, which, on Bio-Gel columns in 1 M HAc, elute at a molecular size of 15 to 20 kilodaltons (kDa). These neuroblastoma-derived transforming growth factors have strong mitogenic activity, but they do not compete with epidermal growth factor for receptor binding (E. J. J. van Zoelen, D. R. Twardzik, T. M. J. van Oostwaard, P. T. van der Saag, S. W. de Laat, and G. J. Todaro, Proc. Natl. Acad. Sci. U.S.A. 81:4085-4089, 1984). In this study approximately 80% of the mitogenic activity was immunoprecipitated by antibodies raised against platelet-derived growth factor (PDGF). Immunoblotting indicated a true molecular size of 32 kDa for this PDGF-like growth factor. Analysis of poly(A)+ RNA from Neuro-2A cells demonstrated the expression of the c-sis oncogene in this cell line, whereas in vitro translation of the RNA yielded a 20-kDa protein recognized by anti-PDGF antibodies. Separation by reverse-phase high-pressure liquid chromatography demonstrated the presence of two distinct mitogenic activities in neuroblastoma-derived transforming growth factor preparations, one of which is antigenically related to PDGF. Both activities had the ability to induce anchorage-independent growth in normal rat kidney cells, both in the presence and in the absence of epidermal growth factor. It is concluded that Neuro-2A cells express c-sis with concomitant production and secretion of a PDGF-like growth factor, which plays a role in the induction of phenotypic transformation on normal rat kidney cells.

Shaping future strategies for the pharmacological control of tumor cell metastases

The eradication of established metastases in patients with malignant tumors is the single most important objective in clinical oncology. The current panel of antineoplastic agents discovered through random and semiempirical screening procedures has proven largely ineffective in treating disseminated disease and there is a clear and urgent need for more efficient antimetastatic drugs. Unfortunately, although progress has been made in examining the biology of metastatic spread, our understanding of the pharmacology, biochemistry and molecular genetics of this process is meager and insufficient to provide a rational foundation for the design of mechanism-based antineoplastic agents. Faced on the one hand with the failure of existing drugs to control metastatic spread and on the other with a dearth of alternative pharmacological approaches, the prospect of offering significantly improved therapy to the cancer patient of the 1990's is poor. The challenge of the coming decade lies in obtaining better insights into the molecular mechanisms of metastasis and using this information to identify pharmacological opportunities to curtail the proliferation of secondary tumor growths. As a first step toward this goal we need to define more rigorously what constitutes a therapeutic target in malignant disease and what steps in the pathogenesis of cancer metastasis represent the gravest risk to the patient and thus are most eligible for direct pharmacological intervention. In addressing these issues and developing future strategies for antimetastatic drugs, Paget's 100 year-old 'seed and soil' hypothesis continues to offer a useful conceptual framework for analysis of metastatic behavior. Although Paget's proposal has been validated by a century of clinical observation, efforts to define the 'seed and soil' theory in molecular terms have not been attempted. With the advent of more efficient methodologies for culturing human normal and neoplastic cells coupled with the availability of microanalytical technologies it now becomes possible to investigate and identify the complementary biochemical components of the tumor cell 'seed' and organ 'soil' that combine to encourage the proliferation of metastases. With this information the design of specific pharmacological strategies to uncouple the 'seed and soil' relationship may emerge as a potential therapeutic approach for antagonizing the growth of disseminated malignant tumors.

Pathogenesis of hypercalcaemia of malignancy

The hypercalcaemia of malignancy is multi-factorial, even within individual tumours. In most cases, hypercalcaemia is due to a combination of increased bone resorption associated with decreased renal capacity to excrete the increased extracellular fluid calcium. In solid tumours such as carcinoma of the lung, tumour-derived growth factors are probably primarily responsible for the increased bone resorption, and a separate family of factors which interact with some parathyroid hormone (PTH) receptors cause increased renal tubular calcium reabsorption. PTH production by non-parathyroid tumours rarely if ever occurs. In contrast, haematological malignancies such as myeloma and T-cell lymphomas produce locally acting bone resorbing lymphokines in excessive amounts. Some T-cell lymphomas in addition have the capacity to metabolize 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D. In myeloma, impaired glomerular filtration frequently contributes to the pathogenesis of hypercalcaemia by impairing renal compensatory mechanisms for maintaining normal serum calcium concentrations in the presence of increased bone resorption.

Neuroblastoma cells express c-sis and produce a transforming growth factor antigenically related to the platelet-derived growth factor

Mouse neuroblastoma Neuro-2A cells produce transforming growth factors during exponential growth in a defined hormone-free medium, which, on Bio-Gel columns in 1 M HAc, elute at a molecular size of 15 to 20 kilodaltons (kDa). These neuroblastoma-derived transforming growth factors have strong mitogenic activity, but they do not compete with epidermal growth factor for receptor binding (E. J. J. van Zoelen, D. R. Twardzik, T. M. J. van Oostwaard, P. T. van der Saag, S. W. de Laat, and G. J. Todaro, Proc. Natl. Acad. Sci. U.S.A. 81:4085-4089, 1984). In this study approximately 80% of the mitogenic activity was immunoprecipitated by antibodies raised against platelet-derived growth factor (PDGF). Immunoblotting indicated a true molecular size of 32 kDa for this PDGF-like growth factor. Analysis of poly(A)+ RNA from Neuro-2A cells demonstrated the expression of the c-sis oncogene in this cell line, whereas in vitro translation of the RNA yielded a 20-kDa protein recognized by anti-PDGF antibodies. Separation by reverse-phase high-pressure liquid chromatography demonstrated the presence of two distinct mitogenic activities in neuroblastoma-derived transforming growth factor preparations, one of which is antigenically related to PDGF. Both activities had the ability to induce anchorage-independent growth in normal rat kidney cells, both in the presence and in the absence of epidermal growth factor. It is concluded that Neuro-2A cells express c-sis with concomitant production and secretion of a PDGF-like growth factor, which plays a role in the induction of phenotypic transformation on normal rat kidney cells.

Loss of epidermal growth factor receptors and release of transforming growth factors do not correlate with sarcoma virus-transformation in clonally-related NIH/3T3-derived cell lines

Transformation of NIH/3T3 cells by Kirsten murine sarcoma virus (MSV) caused a dramatic reduction in the number of cell-surface receptors for epidermal growth factor (EGF). However, the number of EGF receptors remained at a very low level in a non-tumourigenic revertant cell line isolated from the virus-transformed cells, indicating that an increase in EGF receptors is not a requirement for the phenotypic reversion of Kirsten MSV-transformed 3T3 cells. Serum-free conditioned medium from normal and virus-transformed cell lines contained similar amounts of cell growth-promoting activity as assayed by the ability to stimulate DNA synthesis in quiescent Swiss 3T3 cell cultures. However, the concentrated conditioned medium from these cell lines showed no evidence of beta-transforming growth factor (TGF) activity as assayed by promotion of anchorage-independent growth of untransformed normal rat kidney (NRK) fibroblasts in agarose. The cellular release of alpha-TGF activity was assayed by measuring the ability of concentrated conditioned medium to inhibit the binding of 125I-EGF to Swiss 3T3 cells. Conditioned medium protein from the virus-transformed cell line inhibited 125I-EGF binding but only to the same extent as conditioned medium protein prepared from the untransformed cell line. The alpha-TGF secretion by these cell lines was estimated to be 30-45-fold lower than the level of alpha-TGF released by a well-characterized alpha-TGF-producing cell line (3B11). These results suggest that the induction of TGF release is not a necessary event in the transformation of NIH/3T3 cells by Kirsten MSV.

Isolation of pituitary fibroblast growth factor by fast protein liquid chromatography (FPLC): partial chemical and biological characterization

Bovine pituitary fibroblast growth factor has been purified 222,000-fold to homogeneity by a combination of differential salt extraction, gel filtration, and ion exchange chromatography on Mono S column. Pituitary FGF is a single-chain polypeptide with an apparent molecular mass of 15,800 and an isoelectric point of 9.6. It is highly active in triggering the proliferation of bovine and human vascular endothelial cell [half-maximal stimulation at 23-40 pg/ml (1.5-2.6 pM) and saturation between 140 and 280 pg/ml (9.3-18.6 pM)]. It displays a similar activity on bovine vascular smooth muscle cells, corneal endothelial cells, granulosa and adrenal cortex cells, and rabbit costal chondrocytes.

Purification and partial biochemical characterization of normal human interleukin 1

A protocol for the rapid, efficient purification of the major charged species of human interleukin 1 (IL-1) has been developed using high performance anion exchange and size exclusion chromatography. The isolated material is pure as determined by sodium dodecyl sulfate (SDS) gradient polyacrylamide gel electrophoresis (PAGE) and analytical isoelectric focusing (IEF). The molecular weight of the purified material is 15,000 and the isoelectric point (pI) is 6.8, values that are in good agreement with those previously reported for human IL-1. 10(-10) M concentrations of the purified material give half-maximal stimulation in the thymocyte proliferation assay. Amounts of IL-1 sufficient for receptor studies and detailed biochemical analysis can now be produced on a regular basis.

Identification of a tumor inhibitory factor in rat ascites fluid

A polypeptide which inhibits the growth of human carcinoma cells has been characterized from Novikoff rat ascites fluid. This tumor inhibitory factor co-purified with transforming growth factor activity through acid/ethanol extraction and Bio-Gel chromatography. The two activities were completely separated by reverse phase HPLC. The tumor inhibitory factor is heat stable and requires disulfide bonds for bioactivity. This factor inhibited the anchorage independent growth of the more differentiated human colon carcinoma cell lines but did not affect the less differentiated carcinoma cells. The presence of stimulatory and inhibitory activities in the same extracts suggests that the relative concentrations of these factors may be important in the control of cell growth.

Separation of peptides by reverse-phase high-performance liquid chromatography using propyl- and cyanopropylsilyl supports

The separation of peptides and proteins by reverse-phase high-performance liquid chromatography with cyanopropylsilyl and large-pore propylsilyl supports, together with aqueous trifluoroacetic acid/acetonitrile gradients, was studied. Operating parameters (trifluoroacetic acid concentration, flow rate, and gradient slope) were evaluated using different enzymatic digests of horse cytochrome c and bovine serum albumin. Peptides ranging in size from five amino acids to 68 kDa could be separated on the propylsilyl column in a single chromatographic run. The cyanopropylsilyl column is suitable as a supplement to the use of the large-pore column for medium size (5-20 amino acids) peptides. The chromatographic supports and conditions presented here offer a simple, sensitive, and rapid separation system for a wide size range of peptides and proteins. They extend the versatility of separation methodology for these molecules.

Purification and characterization of acidic fibroblast growth factor from bovine brain

Acidic brain fibroblast growth factor has been purified a minimum of 35,000-fold to apparent homogeneity by a combination of differential salt precipitation, ion exchange chromatography, gel filtration, isoelectric focusing, and hydrophobic chromatography on a C4 reversed-phase HPLC column. Two microheterogeneous forms of the molecule are obtained with apparent molecular masses of 16,600 and 16,800 daltons. The mitogen is highly active with half-maximal stimulation of BALB/c 3T3 fibroblasts at about 40 pg/ml in an assay using incorporation of [methyl-3H]thymidine into DNA.

Morphologic and mitogenic responses of rabbit synovial fibroblasts to transforming growth factor beta require transforming growth factor alpha or epidermal growth factor

We tested the hypothesis that normal synovial fibroblasts might proliferate in response to transforming growth factors (TGFs), peptides that are extracted with acid-ethanol from bovine kidney or salivary gland and that cause anchorage-independent growth of normal cells. A 72-hour exposure of confluent monolayers of rabbit synovial fibroblasts in 10% fetal calf serum to partially purified TGF-beta in the presence of TGF-alpha gave a 2- to 5-fold increase in incorporation of 3H-thymidine, protein content, and cell number. Similar results were obtained with high pressure liquid chromatography-purified TGF-beta in the presence of epidermal growth factor (EGF) (a type of TGF-alpha). By itself, purified TGF-beta was not mitogenic; it depended absolutely on EGF. However, only TGF-beta along with EGF, and not EGF alone, induced a marked morphologic change: a piling up of cells into foci resembling those commonly seen in primary cultures of rheumatoid synovial cells. Mitogenic responses induced by the TGF-beta-EGF combination were prevented by all-trans-retinoic acid but not by indomethacin or dexamethasone. The data indicate that TGF-beta, a peptide extracted from normal cells, can act in concert with EGF to cause proliferation and piling up of synovial cells and raise the possibility that these factors may play a role in rheumatoid arthritis and other proliferative but nonmalignant diseases as well.

High pressure liquid chromatographic detection of intracellular retinoid binding proteins from cultured cell and tumor cytosols

We report the first application of high pressure liquid chromatography (HPLC) in the rapid detection of cellular retinoic acid binding protein (CRABP) and cellular retinol binding protein (CRBP). Cytosols from cultured cells (3T6 and MCF-7) or from tumors (melanoma and ovarian) were labeled with [3H]retinoic acid (30 Ci/mmol) and [3H]retinol (43 Ci/mmol) and analyzed via HPLC employing a 60 cm TSK 3000 sw column. In each case CRABP and CRBP were readily detectable at an elution volume of 22.5 ml, consistent with their molecular weights of 14,600. Identity of the binding protein peaks was established by saturability, specificity, and selective inhibition of binding by an organomercurial. Thus, this method, which resolves CRABP and CRBP in crude mixtures from the majority of cytosolic proteins, should be a valuable tool in the evaluation of vitamin A-binding protein interactions and their biological significance.

Sarcoma growth factor from conditioned medium of virally transformed cells is composed of both type alpha and type beta transforming growth factors

Sarcoma growth factor (SGF) derived from conditioned medium of Moloney sarcoma virus-transformed cells and partially purified by gel filtration (crude SGF) has been characterized by its ability both to compete with epidermal growth factor (EGF) for binding to membrane receptors and to induce anchorage-independent growth of untransformed cells. We now show that further purification of crude SGF by reverse-phase HPLC on muBondapak C18 and CN columns at pH 2 resolves it into two distinctly different polypeptides, which we call types alpha and beta transforming growth factors (TGFs). Type alpha TGF (TGF-alpha), but not type beta TGF (TGF-beta), competes for binding to the EGF receptor and induces the formation of small colonies (1,000-2,000 micron2) of normal rat kidney cells in soft agar. Both TGF-beta and EGF or TGF-alpha must be present in order to induce the formation of large colonies (7,000-15,000 micron2). Based on EGF competing equivalents as determined from a radioreceptor assay with 125I-labeled EGF in normal rat kidney cells, the relative ability of EGF and TGF-alpha to potentiate TGF-beta-dependent colony formation is in the order conditioned-medium TGF-alpha greater than EGF greater than intracellular TGF-alpha. Suboptimal concentrations of the same polypeptides give additive potentiation of the TGF-beta-dependent colony-forming response; saturating levels potentiate a similar maximum response whether used alone or in various combinations. The data indicate that the EGF-competing activity of crude SGF is due to its TGF-alpha component alone, whereas the soft-agar colony-forming activity is due to the combined action of two distinct polypeptides, TGF-alpha and TGF-beta.

Antibodies to the epidermal growth factor receptor block the biological activities of sarcoma growth factor

The role of the epidermal growth factor (EGF) receptor system in mediating the biological activities of sarcoma growth factor (SGF) has been assessed by using specific anti-EGF receptor antibodies. There are two classes of anti-EGF receptor antibodies, those that block binding of 125I-labeled EGF (125I-EGF) and those that do not block binding but do interact with a portion of the EGF receptor on the surface of intact cells. Antisera of both types have been assayed for their capacity to affect the biological activities of SGF. The antisera that block 125I-EGF binding to its receptor block the induction of DNA synthesis in human fibroblasts by either EGF or SGF but not by other polypeptide mitogens. Titration of the anti-EGF receptor antiserum indicates the presence of one population of antibody that blocks the site of both EGF and SGF action. Antisera to the EGF receptor that block 125I-EGF binding also inhibited the SGF-dependent anchorage-independent growth of normal cells in soft agar. The antisera to the EGF receptor that does not block 125I-EGF binding or EGF activity did not inhibit any of the biological activities of SGF. The results suggest that occupation of the EGF receptor is required for both the mitogenic and colony-forming activity of SGF.

Use of size-exclusion and ion-exchange high-performance liquid chromatography for the isolation of biologically active growth factors

Size-exclusion and ion-exchange high-performance liquid chromatography were used to purify biologically active growth factors as measured by the ability of the factors to stimulate DNA synthesis in 3T3 cells. Chromatography was performed in aqueous buffer and at neutral pH to avoid possible inactivation of biological activity. The growth factors analyzed were chondrosarcoma growth factor (CHSA-GF), human milk growth factor (HMGF), retinal-derived growth factor (RDGF) and mouse epidermal growth factor (EGF). CHSA-GF, HMGF, and RDGF were eluted from TSK 2000 columns as well-defined peaks of activity with molecular weights of 12,000-15,000, 5000-6000, and 16,000-18,000, respectively. EGF was found to have an abnormally low molecular weight after chromatography on TSK 2000. However, incorporation of guanidine . HCl into the TSK column resulted in the elution of EGF at its known molecular weight of ca. 6000. Anion-exchange high-performance liquid chromatography on AX 300 was used for the purification of HMGF and RDGF, and cation-exchange high-performance liquid chromatography on CM 300 was used for the purification of CHSA-GF. The results show that size-exclusion and ion-exchange chromatography can be used without organic solvents or extremes in pH to purify a number of different growth factors successfully with retention of biological activity.

Polypeptide transforming growth factors isolated from bovine sources and used for wound healing in vivo

Transforming growth factors, which are polypeptides that induce the transformed phenotype in nonneoplastic cells, have been isolated in bulk amounts from bovine salivary gland and kidney. In experiments in which wound healing chambers were implanted subcutaneously in the backs of rats, these bovine transforming growth factors accelerated the accumulation of total protein, collagen, and DNA in treated chambers. These studies thus show an effect of an isolated transforming growth factor in vivo.

Normal mouse serum contains peptides which induce fibroblasts to grow in soft agar

The untransformed mouse fibroblast cells NIH/3T3, C3H/10T1/2, and rat NRK cells do not grow in soft agar in medium supplemented with 10% fetal calf serum. When fetal calf serum in the growth medium was supplemented with less than 1% of sera from mice or other vertebrates, however, these cells responded, forming large colonies. The morphology of soft agar colonies was a function of the treated cell type. In the presence of 10% serum from C57BL/6 mice, NRK cells grew to smooth-surfaced spherical colonies, while NIH/3T3 colonies showed individual round cells on their surface and C3H/10T1/2 cells grew as extended cells forming columns of end to end connected fibroblasts. Mus Musculus Castaneus-Epithelial (MMC- E) cells were not stimulated to grow in soft agar under these conditions. The major fibroblast colony-inducing factor (F-CIF) was partially purified from mouse serum by acid/ethanol-extraction, gel permeation chromatography, and reverse-phase high-pressure liquid chromatography. F-CIF is a polypeptide, which does not compete for binding to epidermal growth factor (EGF) receptors, but stimulates normal fibroblasts to form small colonies in semisolid medium and very large colonies in the presence of added EGF (2 ng/ml). In contrast to unfractionated mouse serum, purified F-CIF did not induce C3H/10T1/2 cells to grow in soft agar, suggesting that serum contains additional cell type-specific agar growth-stimulating activities.