The effects of chronic administration of epidermal growth factor (EGF) to rats on the levels of endogenous EGF in the submandibular glands and kidneys

Epidermal growth factor in clinical practice - a review of its biological actions, clinical indications and safety implications

Chemotaxis, mitogenesis, motogenesis and cytoprotection are common cellular events involved in both tumourigenesis and tissue repair, which appear amplified upon growth factors exposure. Epidermal growth factor (EGF) promotes these events in epithelial and mesenchymal cells through the binding to a specific tyrosine kinase receptor. In experimental oncology settings, EGF does not initiate malignant transformation but exhibits 'tumour promotion'. These observations have raised doubts on the clinical use of EGF despite solid demonstrations of efficacy in experimental conditions and clinical trials. The results of a Pubmed and Bioline investigation on EGF clinical uses and preclinical safety data are presented here. EGF topical administration has been used since 1989 to enhance the healing process of a variety of peripheral tissues wounds (16 clinical reports), as well as its intravenous, oral and rectal administration for gastrointestinal damages (11 clinical reports). EGF therapeutic efficacy and excellent tolerability seem demonstrated. Lack of long-term adverse effects is highlighted in those studies with 6, 12 and 24 months of patients follow-up. Although post-treatment follow-up may fall short for malignant growth, there are no reports on evidences linking EGF clinical use with cancer. A multicentre, nationwide survey in Cuba, 15 years after randomly using silver sulphadiazine with EGF or not in burn victims yielded that cancer incidence was comparable between EGF-treated and control subjects and that such incidence rate does not differ from the age-matched national incidence for those 15-year period. All the animal species subjected to long-term EGF systemic administration exhibit dose-dependent and reversible epithelial organs hyperplasia with no changes in cells phenotypic differentiation. Histotypic pre-malignant markers were not identified. The results emerged from co-carcinogenesis studies and from transgenic mice over-expressing EGF are conflicting and indicate that EGF overexposure, either innate or postnatal, may not be sufficient to transform cells. The ability of EGF to heal injured tissues in life-threatening scenarios or to assist in preventing physical and social disability advocates for its clinical use under a rational medical risk/benefit balance.

Epidermal growth factor potentiates renal cell death in hydronephrotic neonatal mice, but cell survival in rats

BACKGROUND

Epidermal growth factor (EGF) markedly attenuates tubular apoptosis induced by unilateral ureteral obstruction (UUO) in the neonatal rat, and reduces apoptosis induced by mechanical stretch of cultured rat tubular cells.

METHODS

To investigate the role of EGF in modulating apoptosis resulting from UUO, neonatal wild type and mutant mice lacking EGF (knockout), or with diminished EGF receptor activity (waved-2 mutant) were compared to control mice for tubular apoptosis and atrophy. Rat and mouse kidneys were compared for localization of the EGF receptor. Apoptosis was also measured in cultured mouse tubular cells subjected to stretch and exposed to EGF.

RESULTS

UUO reduced endogenous renal EGF expression in wild-type mice. Unlike the rat, exogenous EGF did not decrease tubular apoptosis or atrophy in the obstructed kidney, and significantly increased stretch-induced apoptosis of cultured mouse tubular cells. Tubular apoptosis was 50% lower in the obstructed kidney of EGF knockout and waved-2 mice relative to wild type and heterozygous animals. Exogenous EGF increased tubular apoptosis and doubled atrophy in the obstructed kidney of waved-2 mice. Species differences in EGF receptor localization were detected in 3-day-old kidneys.

CONCLUSION

EGF acts as a survival factor in the neonatal rat, but potentiates tubular cell death in the neonatal mouse. Species differences are maintained in cultured cells, suggesting that differences in EGF receptor signaling underlie these opposing effects.

Progesterone Induces the Proliferation of Urothelial Cells in an Epidermal Growth Factor Dependent Manner

PURPOSE

We have previously reported that estrogen induced proliferation of urothelial cells is modulated by nerve growth factor (NGF). In this study we investigated whether progesterone induces urothelial cell proliferation and whether this effect is modulated by NGF or by epidermal growth factor (EGF).

MATERIALS AND METHODS

Experiments were performed using human urothelial cells immortalized by human papillomavirus E6. Cell proliferation was determined using the alamarBlue (Trek Diagnostic, Westlake, New York) assay. Human papillomavirus were seeded in 48-well plates. They were incubated with 5% alamarBlue and different concentrations of progesterone, EGF or NGF in the presence or absence of neutralizing EGF or NGF antibody, K252a (an inhibitor of trkA, the high affinity receptor for NGF), Ru-486 (an antagonist of progesterone and glucocorticoid receptor) or ZK 137 316 (a specific antagonist of progesterone receptor). Immunoblotting was performed using specific antibodies for progesterone receptor, glucocorticoid receptor or EGF receptor. EGF content in conditioned medium was determined by enzyme-linked immunosorbent assay.

RESULTS

In the presence of 10 nM to 1 microM progesterone urothelial cell proliferation was significantly increased 8.6% to 51.1%. This effect was abolished by ZK137 316 or by Ru-486. Hydrocortisone also induced urothelial cell proliferation. This effect was blocked by Ru-486 but not by ZK137 316. In addition, progesterone stimulated urothelial cell proliferation was inhibited by neutralizing EGF antibody but not by NGF antiserum or K252a. We also found that EGF synthesis and release by urothelial cells was increased by exogenous progesterone. This effect of progesterone was inhibited by ZK 137 316.

CONCLUSIONS

These findings indicate that progesterone has the capacity to induce urothelial cell proliferation through its cognate receptor and this effect is mediated by EGF but not by NGF.

Time-dependent changes of levels of endogenous epidermal growth factor in submandibular glands, in kidneys, and in urine in rats during systemic treatment with EGF

BACKGROUND

Exogenous EGF influences the levels of endogenous EGF differently in the submandibular glands (SMG) and the kidneys. The aim of the present study was to examine the time-dependent changes in levels of endogenous EGF during 1-4 weeks of EGF treatment.

METHODS

Female rats were allocated into five groups receiving EGF subcutaneously (150 microg/kg/day) for 0 (controls), 1, 2, 3 and 4 weeks prior to sacrifice at an age of 12 weeks. At the end of the study period, 24-h urine samples were collected.

RESULTS

The weight of the SMG increased during EGF treatment (303+/-33 (controls), 359+/-37 (1 week EGF, P < 0.01), 390+/-30 (4 weeks EGF, P < 0.001) (mg mean+/-S.D.)). The EGF content of the SMG was unchanged after 1 week but threefold decreased after 4 weeks of treatment, respectively. The expression of EGF mRNA was decreased after 1 and 4 weeks as assessed with in situ hybridization. The weight of the kidneys was unchanged after 1 week and increased after 4 weeks of treatment (828+/-105 mg (controls) vs. 935+/-44 mg (4 weeks EGF, P < 0.005)). The renal content and the urinary excretion of EGF were significantly increased by 20-30% only in the group treated for 4 weeks.

CONCLUSION

EGF treatment induces a time-dependent decrease in the EGF content in the SMG most likely by reducing the biosynthesis of endogenous EGF. In contrast, the EGF content in kidneys and in urine was unchanged after 1 week and increased after prolonged treatment.