The source of urinary epidermal growth factor in humans

Growth signaling autonomy in circulating tumor cells aids metastatic seeding

Self-sufficiency (autonomy) in growth signaling, the earliest recognized hallmark of cancer, is fueled by the tumor cell's ability to "secrete-and-sense" growth factors (GFs); this translates into cell survival and proliferation that is self-sustained by autocrine/paracrine secretion. A Golgi-localized circuitry comprised of two GTPase switches has recently been implicated in the orchestration of growth signaling autonomy. Using breast cancer cells that are either endowed or impaired (by gene editing) in their ability to assemble the circuitry for growth signaling autonomy, here we define the transcriptome, proteome, and phenome of such an autonomous state, and unravel its role during cancer progression. We show that autonomy is associated with enhanced molecular programs for stemness, proliferation, and epithelial-mesenchymal plasticity. Autonomy is both necessary and sufficient for anchorage-independent GF-restricted proliferation and resistance to anticancer drugs and is required for metastatic progression. Transcriptomic and proteomic studies show that autonomy is associated, with a surprising degree of specificity, with self-sustained epidermal growth factor receptor (EGFR)/ErbB signaling. Derivation of a gene expression signature for autonomy revealed that growth signaling autonomy is uniquely induced in circulating tumor cells (CTCs), the harshest phase in the life of tumor cells when it is deprived of biologically available epidermal growth factor (EGF). We also show that autonomy in CTCs tracks therapeutic response and prognosticates outcome. These data support a role for growth signaling autonomy in multiple processes essential for the blood-borne dissemination of human breast cancer.

Epidermal growth factor deficiency predisposes to progressive renal disease

Epidermal growth factor (EGF) is produced in the kidney by thick ascending limbs of the loop of Henle and by distal convoluted tubules (DCTs). Reduced urinary EGF levels have been associated with chronic kidney disease but it is not known whether physiological levels of EGF protect the kidney from progressive renal disease. Here, we show that EGF-deficient mice on a mixed genetic background had increased urinary microalbumin, and a subset of these mice developed severe progressive renal disease with azotemia that was not seen in WT or TGFα-deficient littermates with this mixed genetic background. These azotemic EGF-deficient mice developed crescentic glomerulonephritis linked to HB-EGF/EGFR hyperactivation in glomeruli, as well as attenuation of the proximal tubule brush border, distal convoluted tubule (DCT) dilatation, and kidney fibrosis associated with renal β-catenin/mTOR hyperactivation. The observation of these severe renal pathologies only in a subset of EGF-deficient mice suggests that independent segregation of strain-specific modifier alleles contributes to the severity of the renal abnormalities that only manifest when EGF is lacking. These findings link the lack of EGF to renal pathologies in the adult mammalian kidney, in support of a role of physiological levels of EGF for maintaining the function of glomeruli, proximal tubules, and DCTs. These observations suggest that diminished EGF levels predispose kidneys to progressive renal disease.

Urinary epidermal growth factor is a novel biomarker for early diagnosis of antibody mediated kidney allograft rejection: A urinary proteomics analysis

Although antibody mediated rejection (AMR) accounts for 20-30% of all acute renal allograft rejections, introducing biomarkers for a timely detection of allograft rejection has been remained challenging. This study investigated novel diagnostic biomarkers of AMR by examining of urine proteome in renal transplant patients. Thirty-six patients with kidney transplantation including 22 AMR patients and 14 patients with stable renal function (control group) were enrolled in this study. Urinary samples were collected and Label free quantification (LFQ) proteomics technique was applied on urine samples and data was subjected to Random Forest (RF) algorithm to predict main candidate proteins contributing in AMR. Finally, applicability of candidate diagnostic biomarkers was evaluated in new sets of AMR subjects, stable patients and healthy volunteers. A total of 1020 proteins were detected in urine proteome. RF algorithm predicted 20 differentially expressed proteins with the highest sensitivity and specificity and combination of EGF, COL6A, and NID-1 was identified as possible panel for early diagnosis of AMR. Applicability of EGF as diagnostic biomarker was validated in urine samples of independent set of AMR subjects. This is the first urinary proteomics study in AMR patients demonstrating that urinary EGF might be used as early diagnostic biomarker for AMR. SIGNIFICANCE: Renal antibody mediated rejection (AMR) accounts for 20-30% of all acute rejections of allografted kidneys. Although several possible biomarkers have been proposed to predict AMR, ineffectiveness of current urinary biomarkers in early diagnosing of AMR patients and in distinguishing AMR subjects from patients with stable kidney function casts doubts on their applicability in clinic. Here for the first time and based on the analysis of urinary proteome we showed that uEGF and uEGF/Cr might be candidate biomarkers to predict AMR with high diagnostic power.

Association Between Urinary Epidermal Growth Factor and Renal Prognosis in Lupus Nephritis

OBJECTIVE

To evaluate the role of urinary epidermal growth factor (EGF) as a biomarker of chronic kidney damage in lupus nephritis (LN).

METHODS

A proteomics approach was used to identify urinary EGF as a biomarker of interest in a discovery cohort of patients with LN. The expression of urinary EGF was characterized in 2 large multiethnic LN cohorts, and the association between urinary EGF levels at the time of flare and kidney outcomes was evaluated in a subset of 120 patients with long-term follow-up data. For longitudinal studies, the expression of urinary EGF over time was determined in 2 longitudinal cohorts of patients with LN from whom serial urine samples were collected.

RESULTS

Discovery analysis showed the urinary EGF levels as being low in patients with active LN (median peptide count 8.4, interquartile range [IQR] 2.8-12.3 in patients with active LN versus median 48.0, IQR 45.3-64.6 in healthy controls). The peptide sequence was consistent with that of proEGF, and this was confirmed by immunoblotting. The discovery findings were verified by enzyme-linked immunosorbent assay. Patients with active LN had a significantly lower level of urinary EGF compared to that in patients with active nonrenal systemic lupus erythematosus (SLE), patients with inactive SLE, and healthy kidney donors (each P < 0.05). The urinary EGF level was inversely correlated with the chronicity index of histologic features assessed in kidney biopsy tissue (Spearman's r = -0.67, P < 0.001). Multivariate survival analysis showed that the urinary EGF level was associated with time to doubling of the serum creatinine level (DSCr), a marker of future end-stage kidney disease (ESKD) (hazard ratio 0.88, 95% confidence interval 0.77-0.99, P = 0.045). Patients whose LN symptoms progressed to DSCr and those who experienced progression to ESKD had a lower urinary EGF level at the time of flare, and urinary EGF levels decreased over the 12 months following flare. All patients who experienced progression to ESKD were identified based on a urinary EGF cutoff level of <5.3 ng/mg.

CONCLUSION

Urinary EGF levels are correlated with histologic kidney damage in patients with LN. Low urinary EGF levels at the time of flare and decreasing urinary EGF levels over time are associated with adverse long-term kidney outcomes.

Urinary Epidermal Growth Factor/Creatinine Ratio and Graft Failure in Renal Transplant Recipients: A Prospective Cohort Study

Graft failure (GF) remains a significant limitation to improve long-term outcomes in renal transplant recipients (RTR). Urinary epidermal growth factor (uEGF) is involved in kidney tissue integrity, with a reduction of its urinary excretion being associated with fibrotic processes and a wide range of renal pathologies. We aimed to investigate whether, in RTR, uEGF is prospectively associated with GF. In this prospective cohort study, RTR with a functioning allograft ≥1-year were recruited and followed-up for three years. uEGF was measured in 24-hours urine samples and normalized by urinary creatinine (Cr). Its association with risk of GF was assessed by Cox-regression analyses and its predictive ability by C-statistic. In 706 patients, uEGF/Cr at enrollment was 6.43 [IQR 4.07–10.77] ng/mg. During follow-up, 41(6%) RTR developed GF. uEGF/Cr was inversely associated with the risk of GF (HR 0.68 [95% CI 0.59–0.78]; P < 0.001), which remained significant after adjustment for immunosuppressive therapy, estimated Glomerular Filtration Rate, and proteinuria. C-statistic of uEGF/Cr for GF was 0.81 (P < 0.001). We concluded that uEGF/Cr is independently and inversely associated with the risk of GF and depicts strong prediction ability for this outcome. Further studies seem warranted to elucidate whether uEGF might be a promising marker for use in clinical practice.

Urinary epidermal growth factor in different renal conditions in children

Several studies have demonstrated the important role of growth factors, particularly epidermal growth factor (EGF) and transforming growth factor alpha (TGFalpha), in cellular growth after renal damage. EGF is mainly synthesized by the kidney. Many studies indicate that urinary EGF concentration significantly decreases in patients with acute and chronic renal failure. In this study we determined urinary EGF concentrations in children with renal and/or urological pathologies. We investigated 38 patients, 17 males and 21 females, of 3.34+/-2.96 years (mean +/- standard deviation), who were followed in the Nephrologic Unit of the Pediatric Department of the University of Verona for recurrent urinary tract infections: seven of these had vesicoureteric reflux and 4 had hypodysplasia. The results were compared with those from a healthy age-matched group of 44 children. In all patients, we assessed renal function including an examination of the urine with a microbiological evaluation. Moreover, a renal ultrasound and a voiding cystourethrogram were performed.

Immunohistochemical localization of epidermal growth factor in cat paradental tissues during tooth movement

Epidermal growth factor enhances proliferation and differentiation of cells during growth, maturation, and tissue healing. The objectives were to localize the epidermal growth factor in paradental cells and to determine the effect of orthodontic treatment on its concentrations in periodontal ligament fibroblasts, alveolar bone surface lining cells, and epithelial rests of Malassez. Sixty male cats, 1 year old, were divided into 2 groups: active and sham, and further divided into 10 time groups. In the active group, 1 maxillary canine was retracted by 80 g force; in the sham group, the animals received an inactive appliance. Sagittal sections of each half maxilla were stained for epidermal growth factor; staining intensity was measured microphotometrically in 10 periodontal ligament fibroblasts, alveolar bone surface lining cells, and epithelial rests of Malassez cells in sites of periodontal ligament tension and compression, and in corresponding sites near control and sham canines. The overall mean staining intensity of the cells of the active group animals was 30.47%, whereas that of the sham group was 21.78% (P <.0001). In all 3 types, cells near the actively treated canines stained significantly darker (P <.0001) than cells near the sham or control canines, particularly between 12 hours and 7 days. These results demonstrate that orthodontic forces increase epidermal growth factor concentrations in paradental cells, suggesting that epidermal growth factor participates in the tissue remodeling that facilitates tooth movement.

Internalization of extraintestinal Escherichia coli O18 strains by epithelial cells is modulated by EGF, insulin, and effectors of transmembrane signal transduction

Adhesion to and internalization into host cells is an essential step in the pathogenesis of various bacterial infections. Here we investigated the effects of growth factors on the internalization of Escherichia coli O18 strains isolated from patients with urinary tract infection (UTI) by human epithelial cells. A dramatic increase in the uptake of Escherichia coli was observed after treatment of epithelial cells with epidermal growth factor (EGF) and to a lower extent with insulin. EGF-dependent internalization can be suppressed by tyrosine kinase inhibitors suggesting an involvement of the receptor tyrosine kinases in the regulation of the endocytotic process. Inhibitors of phospholipase A2, lipoxygenase, and cyclooxygenase significantly decreased internalization of bacteria induced by EGF. Finally, the specific inhibitor of PI 3-kinases Wortmannin was shown to suppress completely the EGF-independent internalization. The data of this analysis indicate the involvement of several signaling paths in bacterial internalization of uropathogenic Escherichia coli O18 strains and contribute to the comprehension of the pathogenesis of recurrent UTI.

Decreased urinary epidermal growth factor in children with acute renal failure: epidermal growth factor/creatinine ratio not a reliable parameter for urinary epidermal growth factor excretion

To verify some animal experimental results in humans, we have studied urinary epidermal growth factor (EGF) excretion in normal children as well as children with acute renal failure (ARF). Urinary EGF excretion was expressed as a ratio of urinary EGF to urinary creatinine concentration (EGF/Cr) for random and 24-h urine, and a daily total urinary EGF for 24-h urine. The highest urinary EGF/Cr in children was found at 1 mo to 3 y of age. There was a highly significant correlation between random urine EGF/Cr and 24-h urine EGF/Cr (r = 0.92, p < 0.001), whereas no correlation of urinary EGF/Cr with daily total urine EGF was found. During the course of ARF, a decline in urinary EGF/Cr from the period before peak serum creatinine to the period after the declination of serum creatinine was noted (p = 0.013, n = 13, by repeated measure analysis), with a constant low daily total urine EGF (p value not significant). However, a rise in both urinary EGF/Cr and daily total urine EGF was found between the period of serum creatinine decline and the period of completely normal serum creatinine (p < 0.001). Serum EGF remained unchanged throughout the course of ARF. These results suggest 1) the possible role of EGF in renal growth or maturation during the first 2 or 3 y of life, 2) the possible renal origin of human urinary EGF, and 3) decreased urinary EGF excretion in children with ARF. In particular, EGF/Cr is not a reliable indicator for the expression of actual urinary EGF excretion in ARF. Instead of urinary EGF/Cr, urinary EGF concentration may be used to predict the daily total urinary EGF excretion during ARF. These results provide the pattern of urinary EGF excretion during ARF in children and may be of help for further clinical studies.

Urinary excretion of epidermal growth factor in living human kidney donors and their recipients

Epidermal growth factor (EGF) is a growth-promoting peptide that is synthesized in the distal tubules of the kidney and excreted in urine. EGF has been suggested to play a role in the repair after renal tissue damage, as well as in compensatory growth of the remaining kidney after uninephrectomy. The present study examined the urinary EGF excretion after uninephrectomy and transplantation among relatives. The urinary EGF excretion rate and the glomerular filtration rate (GFR) were followed for 26-54 days in 16 healthy kidney donors and nine recipients. After uninephrectomy the median urinary EGF excretion rate in the donors was not 50% of the pre-operative value, but around 65% (95% confidence limits of the median on the fifth post-operative day: 59-72%). This suggests that there is a compensatory increase in the EGF excretion rate from the remaining kidney of around 30% after uninephrectomy. A similar compensatory increase was demonstrated for GFR, indicating that the compensatory changes in EGF excretion rate and GFR might be correlated. In the transplanted kidneys, GFR was consistently around 15% lower and EGF excretion rate around 40% lower than in the corresponding kidneys remaining in the donors. This might reflect ischaemic and drug-induced damage of the transplanted kidneys. The present study demonstrated a compensatory increase of around 30% in urinary EGF excretion from the remaining kidney after uninephrectomy in healthy humans. Whether EGF plays a role in the adaptive processes in the remaining kidney or whether changes in EGF excretion are merely of a secondary nature is still uncertain.

Human cytotrophoblast invasion is up-regulated by epidermal growth factor: evidence that paracrine factors modify this process

Formation of the human placenta requires a subset of cytotrophoblast stem cells to acquire an invasive phenotype. We examined the effect on cytotrophoblast invasiveness of growth factors that control the differentiation of other cells. Exogenous TGF-beta 1, PDGF-AA, PDGF-BB, and TNF-alpha affected neither cell morphology nor the rate of cytotrophoblast invasion in vitro. In contrast, addition of EGF to first trimester cytotrophoblast cultures produced dramatic changes in morphology and a severalfold increase in invasive capacity. The effects of EGF on later gestation cytotrophoblasts, whose invasive capacity is diminished, were much less pronounced. Next we investigated whether cytotrophoblasts themselves produce ligands that interact with the EGF receptor. A radioimmunoassay and a radioreceptor assay failed to detect EGF receptor ligands in cytotrophoblast-conditioned medium. Likewise, by RT-PCR cytotrophoblasts expressed neither EGF nor TGF-alpha mRNA. In contrast, EGF receptor mRNA was expressed and its protein levels remained constant during the experiment. Immunolocalization using F(ab') fragments of an anti-human EGF antibody failed to detect this growth factor in the chorionic villus. We conclude that maternal ligands that interact with the EGF receptor could play an important role by up-regulating trophoblast invasion, particularly during the early stages of pregnancy.

Epidermal growth factor secretion by submandibular glands is not perturbed in the early phase of streptozotocin-induced diabetes in mice

In rodents, diabetes mellitus is accompanied by a decreased concentration of epidermal growth factor (EGF) in plasma and urine and by a reduced number of EGF receptors on the surface of target cells. A combination of these two abnormalities may reduce the effects of EGF and could be implicated in some complications of diabetes. The aim of the present work was to investigate the possible implication of the major source of EGF in the organism, the submandibular glands, upon the reduced EGF concentration in blood and urine. Firstly, we measured the content of mice submandibular gland EGF by radioimmunoassay and by morphometric determinations of the relative volume occupied by granular convoluted tubules in the gland and by the EGF-containing granules in the cells at the light and electron microscopical levels respectively. We found no differences in the EGF content of submandibular glands of streptozotocin-treated diabetic animals compared to control ones. Secondly, we estimated stimulus-secretion coupling by EGF-secreting cells, present in an enriched preparation of granular convoluted tubules (GCT) perifused in thermoregulated chambers. Phenylephrine was the only agent tested that was capable of stimulating EGF secretion. The stimulation was dose-dependent and similar in streptozotocin-diabetic and control mice. Thus, the EGF deficiency observed in diabetic mice is related neither to a defect of EGF content in the submandibular glands nor to an abnormal EGF secretion by the glands.

Influence of kidney or heart transplantation on the urinary excretion of epidermal growth factor

We studied urinary epidermal growth factor (uEGF) in kidney transplant patients with normal and elevated serum creatinine, in cardiac transplant patients with normal serum creatinine, and in patients with chronic renal failure. Patients with chronic renal failure had the lowest uEGF levels. uEGF was reduced in normally functioning kidney transplant patients. If the kidney graft was failing, this reduction was more marked. Cardiac transplant patients had normal uEGF. The type of immunosuppressive therapy did not influence the uEGF excretion. Kidney function and kidney tissue mass appeared to be the most important factors in uEGF excretion.

Urinary excretion of epidermal growth factor and transforming growth factor-alpha in breast-fed and formula-fed infants

Urinary epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha) concentrations were determined by radioimmunoassay in a longitudinal study analyzing 348 24-h urine specimens of 32 infants (16 breast-fed, 16 formula-fed) during the first 16 weeks of life. EGF excretion showed a statistically significant increase from 6.0 +/- 2.5 to 14.1 +/- 4.9 micrograms/g creatinine (mean +/- 1 SD) during the investigation period. TGF-alpha levels were fairly constant throughout this period. Comparing breast-fed infants, with more than 100-fold higher ingestion of EGF and TGF-alpha, with formula-fed infants, no significant differences in urinary EGF and TGF-alpha excretion were observed. These results do not rule out a systemic effect of EGF and TGF-alpha after intestinal absorption in breast-fed infants. The results suggest, however, that urinary EGF and TGF-alpha originate mainly from sources other than intestinal absorption.

Exogenous epidermal growth factor fails to accelerate functional recovery in the autotransplanted ischemic pig kidney

The reversibility of ischemic renal injury is dependent on epithelial cell regeneration and repopulation of the nephron. Renal cells produce and respond to many growth factors. In the rat, epidermal growth factor (EGF) is mitogenic for tubular cells and accelerates renal recovery after ischemia. We used a pig renal autotransplant model to evaluate the effect of exogenous EGF on renal recovery in a large animal more analogous to man. Group 1 animals underwent left autotransplant after 120 minutes of warm ischemia and received either a single intra-arterial dose of recombinant human EGF (EGF, 10(-7) M.) (N = 11) or vehicle alone (N = 6). Group 2 animals underwent left autotransplant after 72 hours of cold preservation with Collins' solution and received a similar intra-arterial dose plus a subcutaneous dose of EGF (0.5 ml. of 10(-3) M.) (N = 8) or vehicle alone (N = 6). Contralateral nephrectomy was performed in all animals. Daily creatinine measurements revealed no beneficial effect from EGF on recovery of renal function in Group 1 or 2 animals. Studies of EGF on pig proximal tubular cells demonstrated in vitro mitogenesis; autoradiography with 125I-EGF revealed binding of EGF throughout the kidney. Immunohistochemistry showed significant tubular cell proliferation in response to ischemic injury, without further enhancement from EGF. Thus, although exogenous EGF bound to pig kidney cells and stimulated cell proliferation, we were unable to demonstrate a clinically significant acceleration of recovery from ischemic injury.

Effect of water deprivation, desmopressin (DDAVP) infusion, and oral loads of water, Na+ and NH4+ on urinary excretion of epidermal growth factor in the rat

Epidermal growth factor (EGF) is synthesized in the kidneys and excreted in urine. Administration of exogenous EGF modulates the reabsorption of Na+ and the vasopressin stimulated reabsorption of water in the collecting tubules. In order to clarify whether this reflects a physiological role for urinary EGF we examined the effects of changes in the oral loads of water, Na+ and NH4+ as well as the effect of infusion of the vasopressin analogue, desmopressin (DDAVP) on the endogenous urinary EGF excretion in the rat. Water deprivation for 48 h reduced the urinary excretion of EGF by 25% and the urinary EGF/creatinine ratio by 8%. Also, urinary volume, Na+ excretion, and urinary pH were reduced by water deprivation. Infusion of DDAVP, low plasma vasopressin induced by polydipsia, and changes in the renal excretion of Na+ and H+ did not affect the urinary excretion of EGF.

IN CONCLUSION

it seems unlikely that nephrogenous EGF excreted in the urine plays a physiological role in the regulation of the renal excretion of Na+ and H+ and in the vasopressin stimulated reabsorption of water in the rat. However, since water deprivation reduced the urinary excretion of EGF it remains possible that urinary EGF plays a role in the complex physiological response to dehydration.

Excretion of urinary epidermal growth factor in non-insulin dependent diabetes mellitus

Morning urine samples were assayed for human EGF (hEGF) in 137 non-insulin dependent diabetic patients with normal serum creatinine and beta 2-microglobulin levels. Serving as controls, 80 age- and sex-matched healthy subjects were also examined. A significant positive correlation between hEGF excretion and the level of hemoglobin A1C (HbA1c) was present in those patients with a HbA1c value exceeding 8% (r = 0.37; p = 0.003) but not in the overall patients. The urinary hEGF level did not correlate with the concentration of glucose in urine or plasma. The mean urinary hEGF level of diabetic patients was significantly lower than that of healthy subjects. The mean urinary hEGF level was significantly lower in the patients with a diabetic history that exceeded five years as compared with those with a history below five years. The mean urinary hEGF level was significantly lower in the patients with retinopathy vs. those without retinopathy. In the patients with HbA1c value below 8%, the mean urinary hEGF level was lower in the patients whose urinary albumin level exceeded 1.7 mg/mmol.creatinine as compared with those whose urinary albumin excretion was below 1.7 mg/mmol.creatinine. These findings suggest that urinary hEGF excretion may decrease with the progression of diabetic complications in the patients with well-controlled glycemia, and that inadequate glycemic control may lead to an increased excretion of urinary hEGF in the early disease stage.

Urinary and amniotic epidermal growth factor during normal and abnormal pregnancies. A comparison based upon umbilical Doppler velocimetry

Fetal growth retardation is associated with abnormal umbilical flow velocity. We have begun a systematic study of growth factors and their relationship to this specific pattern of growth retardation. Using a specific double-antibody epidermal growth factor (EGF) 125I-radioimmunoassay, we studied urinary EGF in normal pregnancy from 5 to 42 weeks of gestation, and amniotic fluid EGF from 18 to 24 weeks. EGF levels increased from early pregnancy until 21-28 weeks, when they declined to a level at term similar to non-pregnant controls and first-trimester pregnancy levels. There was no significant difference in urinary EGF levels between women delivering appropriate-for-gestational-age (AGA) infants, and those delivering small-for-gestational-age infants (SGA). We conclude that the urinary EGF is not different in the SGA pregnancy from normal pregnancy.

Origin of urinary epidermal growth factor in humans: excretion of endogenous EGF and infused [131I]-human EGF and kidney histochemistry

1. This study examined (i) whether blood-infused epidermal growth factor (EGF) can pass into urine; (ii) whether infused labelled EGF behaves like endogenous plasma immunoreactive EGF; and (iii) which parts of the human nephron show morphological evidence of EGF synthesis? 2. We infused human [131I]-EGF into a volunteer. After 6 min, only 66% of the plasma counts represented intact EGF. At the end of infusion, the T1/2 of EGF was calculated to be 1.6 min. The tail of the curve lasted for at least another 2 h. The total excretion of the labelled EGF was 2.45% of the infused dose and was proportional to the urine volume. 3. After a water load, the excretion of endogenous EGF was, on the contrary, inversely related to urine volume. 4. Immunohistochemically, human kidneys were not stained by monoclonal anti-EGF antibodies but showed positive in situ hybridization for EGF mRNA in the nuclei of glomerular mesangial cells, distal convoluted tubules and collecting tubules. 5. We conclude that human kidneys synthesize EGF and release it into urine. Plasma-derived EGF constitutes under normal conditions only a small part of the urinary EGF. Contrasting volume-dependency of the excretion of endogenous and [131I]-EGF requires further study and cautions against extrapolating results obtained with labelled EGF to physiological conditions.

Immunoreactive low-molecular-weight epidermal growth factor in urine of patients with renal cell carcinoma

A specific heterogeneous enzyme-linked immunosorbent assay (ELISA) has been established in order to determine levels of low-molecular-weight epidermal growth factor (EGF) in the urine of patients with renal cell carcinoma who had undergone unilateral radical nephrectomy. Urine specimens, i.e., 20 pre- and postsurgical specimens from a group of patients and 22 from a control group, were assayed after the urine had been freed from high-molecular-weight proteins (greater than 30 kDa) and salts. EGF levels were expressed as urinary EGF/creatinine ratios, and a highly significant decrease (alpha = 0.0005 by Student's t-test) of urinary EGF was found in the patient group prior to surgery. The cancer patients also showed an additional loss of urinary EGF after unilateral nephrectomy (alpha = 0.0005 by Student's t-test). These data correlate with our previous findings that pro-EGF gene expression is decreased in human renal carcinoma and support the concept that low-molecular-weight urinary EGF is derived from high-molecular-weight kidney pro-EGF.

The membrane fraction of homogenized rat kidney contains an enzyme that releases epidermal growth factor from the kidney membranes

High levels of epidermal growth factor (EGF) are excreted in the urine and high levels of mRNA for the EGF-precursor have been demonstrated in the kidney. The EGF-precursor is a membrane bound peptide in the kidney, but little is known about the renal processing of the precursor. The present study shows that the membrane fraction of homogenized rat kidney contains an enzyme that releases immuno and receptor reactive EGF from the kidney membranes when incubated at 37 degrees C. Gel filtration shows that the EGF reactivity released from the membranes is similar to the EGF reactivity in rat urine. The EGF releasing enzyme is inhibited by the serine proteinase inhibitor aprotinin and by low temperatures (4 degrees C). The pH optimum of the reaction is pH 7.5-8.0.

EGF receptor-binding activity in the urine of normal horses and horses affected by chronic laminitis

A heterologous radioreceptor binding assay (RRA) has been developed capable of detecting nanogram amounts of epidermal growth factor (EGF) receptor-binding activity in equine urine. The binding parameters of [125I]mEGF (murine EGF) to EGF receptors on equine plasma membranes are in good agreement with values from other EGF-RRA systems. The dissociation constant estimated from equilibrium methods (KD = 4 X 10(-10) M) is in reasonable agreement with that determined from the rate constants (KD = 6 X 10(-10) M) and is in good agreement with values determined in other species. The assay is specific for equine EGF (eEGF) receptor-binding activity and capable of detecting less than 0.34 nM eEGF receptor-binding activity in urine. Equine EGF receptor-binding activity in equine urine form adult horses varied widely between samples (8.5 +/- 6.5 nM). This variability was somewhat reduced when values were adjusted for dilutional effects using urine creatinine as an indicator (3.6 +/- 2.0 nanomoles/g creatinine). No significant differences were demonstrated between the means of EGF binding activity concentrations in clinically normal horses and horses affected by chronic laminitis.

Polypeptide growth factors and the kidney: a developmental perspective

A variety of polypeptides with stimulatory or inhibitory effects on cell proliferation have been identified. In addition to stimulating or inhibiting the proliferation of cells and maintaining their viability, polypeptide growth factors play significant roles in embryogenesis and differentiation. The current review focuses on five specific polypeptide growth factor families (epidermal growth factor, insulin-like growth factors, transforming growth factors, platelet-derived growth factor, and fibroblast growth factors) and discusses their possible relationship to normal renal physiology, abnormal renal pathophysiology, and renal organogenesis. On the basis of current data, it is clear that polypeptide growth factors are multifunctional agents with important effects on renal function and renal organogenesis.