Purification and characterization of a low and a high molecular weight form of epidermal growth factor from rat urine

Two forms of epidermal growth factor (EGF) have been purified to homogeneity from rat urine by immunoaffinity chromatography and gel filtration. For one of the purified peptides the molecular mass has been determined to be 5891 by mass spectrometry. This peptide consists of 51 amino acid residues. The sequence of the first 48 amino acid residues is identical to the previously published sequence for submandibular rat EGF. The C-terminal three residues (49-51) are Trp-Trp-Lys. The other purified peptide has a molecular mass of 45 kDa as determined by SDS-polyacrylamide gel electrophoresis. The N-terminal sequence is Asn-Tyr-Lys-Asp-(Cys)-Gly-Pro-Gly-Gly-(Cys)-Gly-Ser-His-Ala. Both the high and the low molecular mass form of urinary rat EGF are able to bind to the human placenta receptor for EGF.     

Heparin-binding (fibroblast) growth factors are potential autocrine regulators of esophageal epithelial cell proliferation

Summary A serum-free culture system supplemented with neural tissue extract for normal and tumor human esophagi was applied to the culture of mouse esophageal epithelium. Similar to mouse mesenchyme and skin epithelium, esophageal epithelial lines (MEE) emerged after serial culture. The cells had an apparent unlimited life span but retained morphology and other characteristics of normal epithelial cells. The cells formed a small cyst consisting of keratined squamous epithelium in syngenic hosts. A screen for growth factors that stimulated growth of the nonmalignant MEE cells in the absence of neural extract revealed that epidermal growth factor (EGF) and heparin-binding (fibroblast) growth factors (HBGF) were most effective. An HBGF-like activity was apparent in extracts of rapidly proliferating but not quiescent MEE cells at low or confluent densities. A cloned cell line (MEE/C8) was selected from MEE cell cultures in the absence of neural extract. MEE/C8 cells proliferated independent of either EGF or HBGF at rates equal to MEE cells, cell extracts exhibited HBGF-like activity at all stages of proliferation, and the cells formed large invasive tumors in syngenic hosts. The HBGF-like activity present in extracts of tumorigenic MEE/C8 and proliferating nonmalignant MEE cells had properties similar to HBGF-1 (acidic fibroblast growth factor). These results constitute a cultured mouse esophageal epithelial cell model for study of conversion of immortalized premalignant cells to malignant cells, and suggest that conversion from a state of cell cycle-dependent autocrine expression of one or more members of the HBGF family to a state of constitutive expression correlates with and may contribute to malignancy. The work was supported in part by grants CA37589 and DK35310 to Dr. McKeehan, from the National Cancer Institute, Bethesda, MD.     

Epidermal growth factor-like transforming growth factor. I. Isolation, chemical characterization, and potentiation by other transforming factors from feline sarcoma virus-transformed rat cells

An acid-stable transforming growth factor (TGF) that interacts with epidermal growth factor (EGF) receptors and is structurally related to EGF was isolated from serum-free culture fluids of Snyder-Theilen feline sarcoma virus-transformed rat embryo (FeSV-Fre) cells. Purification of this EGF-like TGF (eTGF) was achieved by molecular filtration chromatography and successive reverse-phase high pressure liquid chromatography steps on octadecyl support eluted with acetonitrile and 1-propanol gradients, respectively. Rat eTGF consists of a 7.4-kD single polypeptide chain that co-migrates with biological activity in dodecyl sulfate-polyacrylamide electrophoresis gels. Like preparations of a related TGF from human melanoma cells (Marquardt, H., and Todaro, G.J. (1982) J. Biol. Chem. 257, 5220-5225), but unlike EGF from rat, human, or mouse, rat eTGF has phenylalanine and lacks methionine. However, the sequence of the first 30 amino acid residues in rat eTGF is H2N-Val-Val-Ser-His-Phe-Asn-Lys-Cys-Pro-Asp-Ser-His-Thr-Gln-Tyr-Cys-Phe-His-Gly - Thr-(x)-Arg-Phe-Leu-Val-Gln-Glu-Glu-(Lys)-(Lys)-, which is significantly (20% and 28%) homologous to the NH2-terminal region of mouse EGF and human EGF, respectively. In addition to eTGF, molecular filtration chromatography of acid-soluble extracts from medium conditioned by FeSV-Fre cells resolved a 14-kD transforming factor(s) apparently devoid of intrinsic mitogenic activity but able to elicit a strong anchorage-independent growth response in the presence of eTGF or EGF. These results show that: 1) a 7.4-kDa TGF structurally and functionally related to EGF has been isolated from FeSV-Fre cells and 2) the full anchorage-independent growth-promoting activity of medium conditioned by FeSV-Fre cells is due to the coordinate action of at least two types of factors, the 7.4-kDa eTGF and a second 14-kDa transforming factor(s).     

Effects of aging on growth factors gene and protein expression in the dorsal and ventral lobes of rat prostate

We hypothesize that various growth factors and their receptors gene and protein are modulated in dorsal and ventral lobes of aging prostate. To test this hypothesis, TGFbeta1, TGFbeta2 TGFbeta3, TGFbetaR-I, TGFbetaR-II, TGFalpha, EGF, EGFR, KGF and KGFR gene and protein expression were analyzed in dorsal and ventral lobes of aging rat prostates (1, 3, 6, 9, 12, 18, 24, and 28/30 months). KGF gene expression was very weak or absent in 1, 3, and 6 month old rat dorsal and ventral lobes of prostate whereas it re-expressed in 9, 12, 18, 24 and 30 month old rat prostate. All growth factors and their receptors expect KGF and EGFR were mainly localized in epithelium of ventral and dorsal lobes of aging rat prostates. EGF, TGFalpha, TGFbeta1, and TGFbetaR-I protein expression was lacking in stroma of dorsal and ventral lobes of 1, 3, 6, 9, 12/18 months old rat prostates. However, EGF, TGFbeta1 and TGFbetaR-I proteins re-expressed in stroma of 24 and 28 months old rat prostates. KGF protein expression was lacking in epithelium of dorsal and ventral lobes of all aging rat prostates. This is the first report to demonstrate differential gene and protein expression of growth factors in dorsal and ventral lobes is associated with aging rat prostate, suggesting their role in pathogenesis of prostatic diseases with aging.     

Different hormonal requirements for androgen-independent growth of normal and tumor epithelial cells from rat prostate

Summary The proliferation of isolated normal prostate epithelial cells from rat and man is androgen-independent and requires cholera toxin, insulin, dexamethasone, epidermal growth factor (EGF) and one or more polypeptide factors that are concentrated in bovine neural tissue. The active agents in the neural tissue extract are heparin-binding polypeptides (prostatropins), the predominant form of which has a molecular weight of 17400 and an acetylalanine at the aminoterminus. Prostatropins supported a half-maximal increase in normal prostate epithelial cell number at 50 picomolar. The proliferation of primary and serially-cultured epithelial cells from androgen-responsive Dunning R3327 rat prostate tumors was also androgen-independent, but exhibited dramatic alterations in response to hormones that stimulated normal cell proliferation. At low cell density, androgen-independent growth of isolated tumor-derived epithelial cells was independent on cholera toxin, was stimulated by dexamethasone, required insulin andeither EGFor prostatropin. The presence of either EGF or prostatropin masked the response to the other factor. In the absence of EGF, purified prostatropins supported a half-maximal increase in tumor cell number at 7 picomolar. Endogenous production of EGF-like and prostatropin-like factors or both was suggested by the reduced requirement for EGF and prostatropin at high prostate tumor cell density. These results suggest that anti-hormonal therapies against prostate tumor growth should be based on intervention with the activity of insulin (or insulin-like factors) or simultaneous intervention with both EGF and prostatropin (or their homologues). This work was supported by NIH grants CA 37589 and HL 33847, and grant 1718 from the Council for Tobacco Research. Editor’s Statement This paper is the first report of the comparison of the hormone requirements of primary cultures of normal and tumor prostate epithelial cells from the same system.     

Synthesis and secretion of an epidermal growth factor (EGF) by human fibroblast cells in culture

Human fibroblast (WS-1) cells in culture synthesized and secreted an epidermal growth factor which cross-reacted with human epidermal growth factor (hEGF) purified from human urine. hEGF secreted by the cells (designated as WS-1 EGF or fibroblast EGF) and hEGF isolated from urine (designated as urine EGF) were immunologically indistinguishable. The molecular weight of fibroblast EGF estimated by gel filtration was identical with that of hEGF from urine. On chromatofocusing chromatography, fibroblast EGF was eluted mainly at pH 4.26 as a sharp symmetric peak with a minor peak at pH 4.62, like urine EGF. These results suggested that EGF synthesized and secreted by human fibroblast cells is an identical molecule to that of hEGF in human urine.     

Insulin-like growth factor I-mediated degradation of insulin receptor substrate-1 is inhibited by epidermal growth factor in prostate epithelial cells

We have sought to determine whether insulin-like growth factor I (IGF-I) regulates the levels of insulin receptor substrate-1 (IRS-1) in prostate epithelial cells. Exposure of prostate epithelial cells to IGF-I in the absence of other growth factors leads to a reduction in IRS-1 levels. Ubiquitin content of IRS-1 is increased in the presence of IGF-I, and inhibitors of the proteasome prevented the reduction of IRS-1 levels seen following IGF-I exposure. These results imply that IRS-1 is targeted to the proteasome upon exposure to IGF-I. The addition of epidermal growth factor (EGF) maintained IRS-1 levels even in the presence of IGF-I and inhibits IGF-I-dependent ubiquitination of IRS-1. Thus, these two growth factors, IGF-I and EGF, had antagonistic effects on IRS-1 protein levels in prostate epithelial cells. This regulation of IRS-1 reveals a novel level of cross-talk between the IGF-I and EGF signal pathways, which may have implications in tumors that harbor activating mutations in the EGF receptor.     

Regulation of rat proximal tubule epithelial cell growth by fibroblast growth factors, insulin-like growth factor-1 and transforming growth factor-beta, and analysis of fibroblast growth factors in rat kidney.

Growth factors may play an important role in regulating the growth of the proximal tubule epithelium. To determine which growth factors could be involved, we have investigated the mitogenicity of various purified factors in rat kidney proximal tubule epithelial (RPTE) cells cultured in defined medium. Fibroblast growth factors, aFGF (acidic FGF) and bFGF (basic FGF), stimulate DNA synthesis in a dose-dependent manner, with ED50 values of 4.5 and 3.2 ng/ml, respectively; their effects are not additive. With cholera toxin in the medium, both aFGF and bFGF can replace insulin or epidermal growth factor (EGF) to attain the maximum level of cell growth, but they cannot replace cholera toxin. Cholera toxin specifically potentiates the effects of FGFs on DNA synthesis. At high cell density, both insulin and insulin-like growth factor 1 (IGF-1) induce DNA synthesis more effectively than EGF, FGFs and cholera toxin. The high concentration (0.2-1.0 microgram/ml) of insulin required for cell growth can be replaced by a low concentration of IGF-1 (10-20 ng/ml), indicating that insulin probably acts through a low affinity interaction with the IGF-1 receptor. Transforming growth factor-beta 1 (TGF-beta 1) inhibits DNA synthesis induced by individual factors and combinations of factors in a concentration-dependent manner. Northern blot analysis shows that mRNA for TGF-beta 1, IGF-1, and aFGF, but not bFGF are present in rat kidney. Western blot analysis and bioassay data confirmed that the majority of FGF-like protein in rat kidney is aFGF. The data suggest that in addition to EGF, IGFs, and TGF-beta, FGFs may also be important kidney-derived regulators of proximal tubule epithelial cell growth in vivo and in vitro.     

Proliferation of epithelial cells derived from rat dorsolateral prostate in serum-free primary cell culture and their response to androgen

Summary Primary cultured epithelial cells derived from the rat dorsolateral prostate proliferated in serum-free nutrient medium WAJC 404 supplemented with mitogens: insulin (650 nM), cholera toxin (120 pM), epidermal growth factor (EGF) (2.5 nM), dexamethasone (300 nM), and bovine pituitary extract (25 μg/ml). The culture consisted of two types of epithelial cell colonies: one originated from single cells or small cell aggregates and the other was epithelial cell outgrowth from small tissue fragments attached to a substratum. There were differences in requirements for the mitogens between the two types of colonies. Requirements for cholera toxin, bovine pituitary extract, and dexamethasone were higher in the former type of colonies, and those for EGF were higher in the latter type of colonies. Proliferation of the epithelial cells in either type, of colony was suppressed more than 50% by 1 nM dihydrotestosterone. This suppressive effect was not mediated by stromal component in the tissue fragments, and was counteracted by cyproterone acetate, indicating specific and direct action of the androgen on prostate epithelial cells. The results suggest that there is discrete participation of polypeptide growth factors and androgen in proliferation and differentiation, respectively, of prostate epithelial cells in vivo.     

Comparison of the effects of class 1 and class 2 heparin-binding growth factors on protein synthesis and actin mRNA expression in BALB/c-3T3 cells

Biological effects of class 1 or class 2 heparin-binding growth factors (HBGFs) were compared in BALB/c-3T3 cells. Changes in protein synthesis, as monitored by two-dimensional gel electrophoresis, reveal that while both HBGFs induce the same changes in the synthesis of intracellular proteins, class 2 HBGF selectively increases the synthesis of a 43-kD extracellular protein. Heparin, which potentiates the mitogenic activity of class 1 but not class 2 HBGF, does not potentiate the changes in protein synthesis elicited by HBGF-1. Since each HBGF increases actin synthesis, regulation of actin mRNA expression was examined. Actin mRNA levels increase rapidly and transiently in response to either HBGF, and similar superinduction responses are observed in the presence of HBGF and cycloheximide. Although the maximum increase in actin mRNA stimulated by either HBGF is similar, the levels of mRNA induced by class 2 HBGF remain elevated up to 48 hours compared to the level induced by class 1 HBGF. These results imply that in the same cell type class 1 and class 2 HBGFs may modulate some biological effects differently.     

Androgenic regulation of epidermal growth factor in the mouse ventral prostate

Castration of adult male mice caused a marked reduction in the amount of immunoreactive epidermal growth factor (EGF) in the ventral prostate, and the treatment of such castrated mice with testosterone increased the EGF level significantly. Gel filtration of prostate extract showed that the immunoreactive EGF in the prostate had the same molecular weight (6,045) as the submandibular gland EGF. Moreover, its isoelectric point (pH 4.5) was almost similar to that (pH 4.55) of the submandibular gland peptide. These results suggest that under the control of androgens, mouse ventral prostate synthesizes EGF structurally and functionally identical to the submandibular gland EGF.     

Effects of growth factors on an intestinal epithelial cell line: transforming growth factor beta inhibits proliferation and stimulates differentiation

The effects of epidermal growth factor transforming growth factor beta (TGF beta) and other growth factors on the proliferation and differentiation of a cell line derived from rat intestinal crypt epithelium (IEC-6) were defined. Incorporation of [3H]-thymidine was stimulated 1.4-2.4 fold by insulin, insulin like growth factor (IGF), platelet derived growth factor (PDGF), epidermal growth factor (EGF) and 2% fetal calf serum (FCS) respectively. Additive stimulation was observed when FCS was supplemented by insulin,IGF-I or PDGF but not EGF. Incorporation of [3H]-thymidine by IEC-6 was strongly inhibited by TGF beta with greater than 80% inhibition of incorporation at concentration approximately equal to 2.0 pM. IEC-6 cells bound 4.1 +/- 0.15 X 10(4) molecules TGF beta/cell and appeared to have only a single class of high affinity receptors (Kd approximately equal to 0.5 pM). TGF beta inhibition was unaffected by the presence of insulin or IGF-I suggesting it inhibits proliferation at a step subsequent to that at which these growth factors stimulate [3H]-thymidine incorporation. TGF beta also reduced the stimulation induced by FCS by 65%. In contrast EGF reduced TGF beta inhibition by 60%. IEC-6 cells demonstrated the appearance of sucrase activity after greater than 18 hours treatment with TGF beta. These findings suggest that TGF beta may inhibit proliferative activity and promote the development of differentiated function in intestinal epithelial cells.     

Heparin-binding growth factor/prostatropin attenuates inhibition of rat prostate tumor epithelial cell growth by transforming growth factor type beta

Summary Normal rat prostate epithelial cell growth requires both epidermal growth factor and heparin-binding growth factor/prostatropin. In contrast, epithelial cells derived from the transplantable Dunning R3327H rat tumor require either epidermal growth factor or heparin-binding growth factor/prostatropin. Transforming growth factor type beta inhibited normal epithelial cell growth. Transforming growth factor beta inhibited epidermal growth factor-dependent growth of tumor epithelial cells, independent of epidermal growth factor concentrations. Transforming growth factor beta increased the effective dose of heparin-binding growth factor type 1 required to support tumor epithelial cell growth by 10-fold but saturating levels of heparin-binding growth factor type 1 (290 pM) completely attenuated the inhibitory effect of transforming growth factor beta. These results suggest that prostate tumor epithelial cells may escape the inhibitory effect of transforming growth factor beta as a consequence of alteration of the concurrent requirement for both epidermal growth factor (or homologues) and heparin-binding growth factors. This work was supported by NCI Grant CA37589. Editor’s Statement The observation that heparin-binding growth factor/prostatropin can counteract the inhibitory effect of transforming growth factor beta in prostate epithelial cells may help explain how some cancers avoid the action of growth inhibitors and provides a model for studying how inhibitory peptides overcome the stimulatory signals generated by growth factors.     

Immunohistochemical localization of nerve growth factor and epidermal growth factor in guinea pig prostate gland

Summary Prostate glands of adult guinea pigs were stained for nerve growth factor (NGF) and epidermal growth factor (EGF) by immunohistochemical methods. Both NGF and EGF were localized diffusely in the cytoplasm of the glandular epithelial cells, and also in their secretory products. These findings suggest that NGF and EGF are synthesized, stored, and secreted by the glandular epithelial cells of the prostate.     

Isolation and characterization of epidermal growth factor from human milk

Epidermal growth factor (EGF) has been purified from human milk. The purification was monitored with a human placental membrane radioreceptor assay using murine salivary epidermal growth factor I (mEGF I) as a competitive ligand and was achieved exclusively by the use of reverse-phase liquid chromatography (RPLC). The sequential use of preparative, semipreparative and analytical RPLC on an octylsilica support with solvent systems of different solute selectivity such as pyridine formate, triethylammonnium phosphate or perfluorocarbonic acids in the presence of n-propanol or acetonitrile allowed purification to homogeneity with 5 consecutive runs. The molecular mass, amino acid composition and NH2-terminal sequence of human EGF were determined. Gas-phase microsequencing of residues 1-17 revealed the following sequence: Asn-Ser-Asp-Ser-Glu-X-Pro-Leu-Ser-His-Asp-Gly-Tyr-X-Leu-X-Asp which is identical with the NH2-terminof urogastrone from human urine. The purified polypeptide competes with mEGF for the placental membrane receptor with a ki of 1 ng. Furthermore, it stimulates the anchorage-dependent as well as -independent proliferation of human and rat indicator cells with half-maximal stimulation at 1 and 2.5 ng/ml, respectively. Although human epidermal growth factor has been unequivocally identified in human milk and -for the first time-shown to be identical with urogastrone from human urine, the high-resolution techniques employed have also revealed the presence of EGF-related molecules which await further characterization. It is possible that EGF and the EGF-related growth factors possess important regulatory functions in normal growth of the human breast during pregnancy and lactation as well as in abnormal growth during mammary tumor formation and progression.     

Production of growth factors by type 5 adenovirus transformed rat embryo cells

Transformation of Sprague-Dawley rat embryo (RE) cells and a cloned Fischer rat embryo cell line (CREF) with wild-type (Ad5) or a temperature-sensitive DNA-minus mutant (H5ts125) of type 5 adenovirus results in a reduction in binding of epidermal growth factor (EGF) to cell surface receptors. A reduction in EGF binding is also seen in a Syrian hamster embryo cell line transformed by a hexon mutant of Ad5. In contrast, a human embryonic kidney cell line (293) transformed by sheared Ad5 DNA or transfected clones of KB cells expressing the E1 transforming region of Ad5 do not show a decrease in receptor binding. When cocultivated, the adenovirus transformed rat cells were able to induce the growth in agar of normal CREF cells. Medium from Ad5 transformed RE cells stimulated the growth in agar of CREF cells and also inhibited [125I]-EGF binding in CREF cells. When fractionated by gel filtration, two peaks of [125I]-EGF inhibiting activities were obtained with apparent molecular weights of 35,000 and 16,000. These results provide the first evidence that cells transformed by an adenovirus can produce a growth factor(s) that inhibits EGF-receptor binding and induces anchorage-independent growth of normal cells.     

Purification and characterization of heparin-binding endothelial cell growth factors

Thirteen endothelial cell growth factors have been purified to homogeneity by heparin affinity and reversed-phase high performance liquid chromatography, and their chromatographic and electrophoretic properties were compared. The amino acid compositions of 10 of these mitogens have also been determined. The results indicate that these heparin-binding growth factors (HBGFs) can be subdivided into two classes. Class 1 HBGFs are anionic mitogens of molecular weight 15,000-17,000 found in high levels in neural tissue and include acidic brain fibroblast growth factor and retina-derived growth factor. Class 2 HBGFs are cationic mitogens of molecular weight 18,000-20,000 found in a variety of normal tissues and are typified by pituitary fibroblast growth factor and cartilage-derived growth factor. Typical class 2 HBGFs have also been isolated from a rat chondrosarcoma, a human melanoma, and a human hepatoma, suggesting that tumors do not make a structurally distinct HBGF class. These results provide a sound basis for the evaluation of the HBGFs purified from a variety of tissues and species and for the delineation of their normal and pathological functions in vivo.     

Type beta transforming growth factor from feline sarcoma virus-transformed rat cells. Isolation and biological properties

We have isolated a strongly mitogenic, type beta transforming growth factor (beta TGF) released by Snyder-Theilen feline sarcoma virus-transformed rat embryo (FeSV-Fre) cells that induces phenotypic transformation of normal NRK cells when they are concomitantly stimulated by analogues of epidermal growth factor (EGF). Molecule filtration chromatography separates beta TGF from an EGF-like TGF (eTGF) which is also present in acid extracts from medium conditioned by FeSV-Fre cells (J. Massagué, (1983) J. Biol. Chem. 258, 13606-13613). Final purification of beta TGF is achieved by reverse phase high pressure liquid chromatography (HPLC) on octadecyl support, molecular filtration HPLC, and nonreducing dodecyl sulfate-polyacrylamide gel electrophoresis steps, yielding a 300,000-fold purified polypeptide with a final recovery of 21%. The purified rat beta TGF consists of two Mr = 11,000-12,000 polypeptide chains disulfide-linked as a Mr = 23,000 dimer. Induction of anchorage-independent proliferation of NRK cells by rat beta TGF depends on the simultaneous presence of eTGF or EGF. In the presence of a saturating (300 pM) concentration of either rat eTGF or mouse EGF, half-maximal anchorage-independent proliferation of NRK cells is obtained with 4-6 pM rat beta TGF. In the presence of a saturating (20 pM) concentration of rat beta TGF, half-maximal anchorage-independent proliferation of NRK cells is obtained with either rat eTGF or mouse EGF at a 50-70 pM concentration. Rat beta TGF is also able to induce DNA synthesis and cell proliferation on growth-arrested NRK, human lung, and Swiss mouse 3T3 fibroblast monolayers, this effect being half-maximal at 2-3 pM beta TGF for NRK cells. These results identify eTGF and beta TGF as the two synergistically acting factors responsible for the transforming action of culture fluids from FeSV-Fre cells.     

Prediction of the three-dimensional structures of the nerve growth factor and epidermal growth factor binding proteins (kallikreins) and an hypothetical structure of the high molecular weight complex of epidermal growth factor with its binding protein.

We have predicted the three-dimensional structures of the serine protease subunits (gamma-NGF, alpha-NGF, and EGF-BP) of the high molecular weight complexes of nerve growth factor (7S NGF) and epidermal growth factor (HMW-EGF) from the mouse submandibular gland (from the X-ray crystal structures of two related glandular kallikreins). The conformations of three of the six loops surrounding the active site are relatively well defined in the models of gamma-NGF and EGF-BP, but three other loops are likely to have flexible conformations. Although the amino acid sequence of alpha-NGF is closely related to those of gamma-NGF and EGF-BP, it is catalytically inactive. Model-building studies on alpha-NGF suggested that mutations (in alpha-NGF) just prior to the active site serine (195) and an unusual N-terminal sequence are consistent with alpha-NGF having a zymogen-like conformation (similar to that in chymotrypsinogen). An hypothetical model of the quaternary structure of HMW-EGF has been constructed using this model of EGF-BP and the NMR structure of murine EGF. The C-terminal arm of EGF was modeled into the active site of EGF-BP based on data indicating that the C-terminal arginine of EGF occupies the S1 subsite of EGF-BP. Data suggesting one of the surface loops of EGF-BP is buried in the HMW-EGF complex and symmetry constraints were important in deriving a schematic model. A molecular docking program was used to fit EGF to EGF-BP.     

Immunohistochemical localization of nerve growth factor and epidermal growth factor in guinea pig prostate gland

Prostate glands of adult guinea pigs were stained for nerve growth factor (NGF) and epidermal growth factor (EGF) by immunohistochemical methods. Both NGF and EGF were localized diffusely in the cytoplasm of the glandular epithelial cells, and also in their secretory products. These findings suggest that NGF and EGF are synthesized, stored, and secreted by the glandular epithelial cells of the prostate.