Specific binding sites for insulin and insulin-like growth factor I in human endometrial cancer

Association of IGF-1 CA(n) and IGFBP3 rs2854746 Polymorphisms with Endometrial Polyp Risk

INTRODUCTION

Insulin-like growth factor 1 (IGF-1) is a peptide growth factor that promotes cell proliferation and inhibits apoptosis. The bioavailability of IGF-1 is regulated by the insulin-like growth factor binding protein 3 (IGFBP3). Genetic variations influence the levels of IGF-1 and IGFBP3. The purpose of this study was to examine the association of polymorphisms IGF-1 CA(n) and IGFBP3 rs2854746 with risk of endometrial polyps.

MATERIALS AND METHODS

Case control observational study, composed of 104 women with antecedent of endometrial polyp (case group) and 81 postmenopausal women without antecedent of endometrial diseases (control group). Genotyping of IGF-1 CA(n) was performed by PCR and fragment analysis by capillary electrophoresis, and genotyping of IGFBP3 rs2854746 was performed by PCR-HRM. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by logistic regression.

RESULTS

The genotype IGF-1 CA(19)/CA(19) was associated with an increased endometrial polyp risk (OR=2,57; IC 95%= 1,09 - 6,01); this was also found when combining it with CA(>19)/CA(n) genotypes (OR=2,18; IC 95%= 1,06-4,47). The IGFBP3 rs2854746 analyses showed the CG genotype having a protective effect for endometrial polyp (OR=0,37; IC 95%= 0,19-0,73), fact also observed when grouping CG and GG carriers (OR=0,51; IC 95%= 0,28-0,93).

CONCLUSION

The genotypes CA(19)/CA(19) and CA(19)/CA(19) + CA(>19)/CA(n) of the IGF-1 CA(n) may be considered a risk for endometrial polyp, whereas the genotypes CG and CG + GG of IGFBP3 rs2854746 polymorphism have an inverse effect of endometrial polyp risk.

PCOS and cancer risk

Polycystic ovary syndrome (PCOS) affects approximately 5 to 10% of women of reproductive age. It is the most common reason of anovulation in infertile women. PCOS is accompanied by such conditions as oligo- or anovulation, hipertestosteronism, lower cell sensitivity to insulin, type II diabetes, hyperlipidemia and obesity. Each of the above-mentioned conditions is an approved risk factor proved to predispose towards cancer. However, PCOS is also a disease entity which differs in its clinical manifestation. For example not all patients suffer from obesity or hipertestosteronism related symptoms. From the analysis of literature it is possible to draw conclusions, that there is a possible correlation between PCOS and endometrial cancer, which emerges from clinical trials or research focused on molecular changes in endometrium patients with PCOS. On the other hand, correlation between PCOS and breast or ovary cancer is not so strong, in spite of single papers which are showing the link. The main problem in researching the correlation between PCOS and any cancer risk, is there is a very small group of women or the trial is imperfect (e.g. no control group). There is no meta-analysis focused on this correlation in literature. The change of criteria of PCOS in the past is also a big problem, because there was a number of definitions of PCOS, which results in inconsistent PCOS diagnoses over time. In this paper we would like to provide a description of studies that aimed at showing correlation between PCOS and cancer risk and underlying theoretical assumptions.

Up-regulation of genes involved in the insulin signalling pathway (IGF1, PTEN and IGFBP1) in the endometrium may link polycystic ovarian syndrome and endometrial cancer

BACKGROUND

Endometrial cancer (EC) is the most common gynaecological cancer amongst women in the UK. Although previous studies have found that women with polycystic ovary syndrome (PCOS) have at least a three-fold increase in endometrial cancer (EC) risk compared to women without PCOS, the precise molecular mechanisms which link between PCOS and EC remain unclear. It has been suggested that insulin resistance may contribute to the increased risk of EC in PCOS. The specific expression of genes related to the insulin-signalling pathway including the IGF system in the endometrium of women with PCOS has however never been measured and compared to that in women with EC without PCOS and control women without EC or PCOS. .

OBJECTIVES

To test the hypothesis that insulin signalling plays a key role in the development of EC in women with PCOS by measuring and comparing the expression of three key genes involved in the insulin signalling pathway (IGF1, PTEN and IGFBP1) in endometrial tissue obtained from three groups of women; PCOS without EC, women with EC without PCOS and non-PCOS women without EC (controls). We also aimed to determine the correlation between the gene expressions to various clinical variables among participants.

METHODS

This was a cross-sectional study of 102 women in 3 groups (PCOS, EC and controls) at a University teaching hospital in the United Kingdom. Clinical assessment (blood pressure, body mass index (BMI) and waist-hip-circumference ratio), venepuntures (fasting blood sugar, insulin, lipid profile, hormones) and endometrial tissue biopsies were taken in all participants. Endometrial tissue RNA extraction was performed before real time polymerase-chain-reaction for the genes of interest (IGF1, IGFBP1 and PTEN) was carried out. To compare the baseline characteristics of the study population, One-Way-ANOVA test or the Independent t-test was used. For variables that were not normally distributed, the Spearman correlation test was used to calculate the r value. A "p" value of <0.05 was considered statistically significant.

RESULTS

IGF1, IGFBP1 and PTEN gene expression were significantly up-regulated in the endometrium of PCOS and EC women compared to controls. However there was no significant difference in the expression of these genes in PCOS compared to EC endometrium. The BMI of women with PCOS and controls, were not significantly different (29.28 (± 2.91) vs 28.58 (± 2.62) kg/m(2)) respectively, women with EC however had a higher mean BMI (32.22 (± 5.70) kg/m(2)). PCOS women were younger (31.8 (± 5.97) years) than women with EC (63.44 (± 10.07) years) and controls (43.68 (± 13.12) years). The changes in gene expression were independent of BMI, waist hip ratio, estradiol and androgen levels. Protein validation test in the serum samples in the three groups were consistent with the gene findings.

CONCLUSION

Women with PCOS and EC have an increased endometrial expression of genes (IGF1, IGFBP1 and PTEN) involved in the insulin signalling pathway compared with control women. This may explain the increased risk of EC in PCOS women. This study provides a strong basis for clinical trials aiming to prevent EC in women with PCOS by investigating drugs targeting the insulin signalling pathway. This panel of genes may also serve as clinically useful early biomarkers which predict which women with PCOS will go on to develop EC.

Insulin resistance and endometrial cancer risk: A systematic review and meta-analysis

AIM

It has been suggested that chronic hyperinsulinemia from insulin resistance is involved in the etiology of endometrial cancer (EC). We performed a systematic review and meta-analysis to assess whether insulin resistance is associated with the risk of EC.

METHODS

We searched PubMed-Medline, Embase, Scopus, and Web of Science for articles published from database inception through 30th September 2014. We included all observational studies evaluating components defining insulin resistance in women with and without EC. Quality of the included studies was assessed by Newcastle-Ottawa scale. Random-effects models and inverse variance method were used to meta-analyze the association between insulin resistance components and EC.

RESULTS

Twenty-five studies satisfied our inclusion criteria. Fasting insulin levels (13 studies, n = 4088) were higher in women with EC (mean difference [MD] 33.94 pmol/L, 95% confidence interval [CI] 15.04-52.85, p = 0.0004). No differences were seen in postmenopausal versus pre- and postmenopausal subgroup analysis. Similarly, non-fasting/fasting C-peptide levels (five studies, n = 1938) were also higher in women with EC (MD 0.14 nmol/L, 95% CI 0.08-0.21, p < 0.00001). Homeostatic model assessment - insulin resistance (HOMA-IR) values (six studies, n = 1859) in EC patients were significantly higher than in women without EC (MD 1.13, 95% CI 0.20-2.06, p = 0.02). There was moderate-to-high heterogeneity among the included studies.

CONCLUSION

Currently available epidemiologic evidence is suggestive of significantly higher risk of EC in women with high fasting insulin, non-fasting/fasting C-peptide and HOMA-IR values.

Global gene expression profiling of porcine endometria on Days 12 and 16 of the estrous cycle and pregnancy

The objective of the study was to investigate transcriptomic profile of pig endometrium on Days 12 and 16 of pregnancy in comparison with the respective days of the estrous cycle. Labeled complementary DNA was hybridized to Porcine Long Oligo microarray containing 13,297 oligonucleotide probes, which represented complementary DNA and expressed sequence tags. Statistical analysis revealed 110 differentially expressed genes (DEGs) on Day 12 of pregnancy and 179 DEGs on Day 16 of pregnancy. In silico analysis of gene function and functionality networks revealed links between genes implicated in cell death and survival, protein synthesis, lipid metabolism, cellular movement, tissue development, and cell-to-cell signaling. On Day 12 of pregnancy, estrogen, transforming growth factor (TGF) β1, and fibroblast growth factor (FGF) 2, and on Day 16 of pregnancy, epidermal growth factor (EGF), insulin, interleukin 11 (IL-11), and FGF family members were indicated as possible upstream regulators of several DEGs. Obtained results showed changes in global endometrial gene expression at the time of maternal recognition of pregnancy and embryo implantation. Additionally, these data revealed signaling molecules, which together with E2, may evoke molecular changes in the uterus, leading to successful pregnancy establishment.

Prospective evaluation of insulin resistance among endometrial cancer patients

OBJECTIVE

Obesity and estrogen are strong risk factors for endometrial cancer (EC). Whereas diabetes also increases the risk, little is known about related insulin resistance (IR). The purpose of this study was to determine the prevalence of IR in newly diagnosed EC patients.

STUDY DESIGN

EC patients from a large, metropolitan county were prospectively enrolled from 2005 to 2008. Fasting serum was analyzed for glucose and insulin. IR was defined as a history of diabetes or a quantitative insulin sensitivity check index (QUICKI) (1/[log fasting insulin + log fasting glucose]) value of less than 0.357.

RESULTS

Among 99 patients, diabetes was present in 30, and an abnormal QUICKI was found in 36 additional patients. Increased risk of IR was significantly associated with higher body mass index (P < .001), lower socioeconomic status (P = .007), and nulliparity (P = .029).

CONCLUSION

IR was highly prevalent in endometrial cancer patients, including nonobese women. Better characterization of metabolic risks in addition to obesity may provide avenues for targeted cancer prevention in the future.

Role of metformin in the management of polycystic ovary syndrome

Polycystic ovary syndrome is the most common endocrinological disorder affecting 4-12% of women and also the most controversial. Metformin was logically introduced to establish the extent to which hyperinsulinaemia influences the pathogenesis of the condition. Early studies were very encouraging. Randomized controlled studies and several metaanalyses have changed the picture and put the drug that was once heralded as magic in a much contracted place. More work is needed to establish its right place in particular with regards to the prevention of many gestational and long-term complications.

Evidence-based and potential benefits of metformin in the polycystic ovary syndrome: a comprehensive review

Metformin is an insulin sensitizer widely used for the treatment of patients affected by type 2 diabetes mellitus. Because many women with polycystic ovary syndrome (PCOS) are insulin resistant, metformin was introduced in clinical practice to treat these patients also. Moreover, metformin's effect has other targets beside its insulin-sensitizing action. The present review was aimed at describing all evidence-based and potential uses of metformin in PCOS patients. In particular, we will analyze the uses of metformin not only for the treatment of all PCOS-related disturbances such as menstrual disorders, anovulatory infertility, increased abortion, or complicated pregnancy risk, hyperandrogenism, endometrial, metabolic and cardiovascular abnormalities, but also for the prevention of the syndrome.

Hormonal heterogeneity of endometrial cancer

Endometrial cancer is the most common malignant tumor of the female genital tract in the developed world. Increasing evidence suggests that the majority of cases can be divided into two different types ofendometrial cancer based on clinico-pathological and molecular characteristics. Type I is associated with an endocrine milieu of estrogen predominance. These tumors are ofendometroid histology and develop from endometrial hyperplasia. They have good prognosis and are sensitive to endocrine treatment. Type II endometrial cancers are not associated with a history of unopposed estrogens and develop from the atrophic endometrium of elderly women. Mainly, they are of serous papillary or clear cell morphology, have a poor prognosis and do not react to endocrine treatment. Both types of endometrial cancer probably differ markedly with regard to the molecular mechanisms of transformation. The transition from normal endometrium to a malignant tumor is thought to involve a stepwise accumulation of alterations in cellular mechanisms leading to dysfunctional cell growth. This chapter reviews the current knowledge of the molecular mechanisms commonly associated with development of type I and type II endometrial cancer.

Endometrium in PCOS: Implantation and predisposition to endocrine CA

Polycystic ovarian syndrome (PCOS) is a common endocrinopathy characterized by oligo/anovulatiaon and elevated circulating androgens or evidence of hyperandrogenism after all known potential causes have been excluded. In addition, insulin resistance and accompanying hyperinsulinemia commonly occur in women with PCOS. There is increasing evidence that the endocrinologic and metabolic abnormalities in PCOS may have complex effects on the endometrium, contributing to the infertility and endometrial disorders observed in women with this syndrome. Androgen receptors and steroid receptor co-activators are over-expressed in the endometrium of women with PCOS. Also, biomarkers of endometrial receptivity to embryonic implantation-such as alpha(v)beta3-integrin and glycodelin-are decreased, and epithelial expression of estrogen receptor alpha (ERalpha) abnormally persists in the window of implantation in endometrium in women with PCOS. In addition to being responsive to the steroid hormones estradiol, progesterone, and androgens, the endometrium is also a target for insulin, the receptor for which is cyclically regulated in normo-ovulatory women. In vitro, insulin inhibits the normal process of endometrial stromal differentiation (decidualization). In addition, insulin-like growth factors (IGFs) and their binding proteins are regulated in and act on endometrial cellular constituents, and hyperinsulinemia down-regulates hepatic IGFBP-1, resulting in elevated free IGF-I in the circulation. Thus, elevated estrogen (without the opposing effects of progesterone in the absence of ovulation), hyperinsulinemia, elevated free IGF-I and androgens, and obesity all likely contribute to endometrial dysfunction, infertility, increased miscarriage rate, endometrial hyperplasia, and endometrial cancer common in women with PCOS. The potential mechanisms underlying these disorders, specifically in women with PCOS, are complex and await additional transdisciplinary research for their complete elucidation.

[Polycystic ovary syndrome associated neoplasms]

Polycystic ovary syndrome (PCOS) is the most common endocrine disease in women on reproductive age. PCOS is characterized by the presence of anovulation, infertility and hyperandrogenism and is associated with obesity and insulin resistance. A major risk for neoplasms of the reproductive tract, like endometrial, breast and ovary cancer seems to be related to PCOS. While several studies have shown an increased risk for endometrial hyperplasia and cancer in PCOS patients, the variability of the selection criteria for PCOS has been recognized as a potential bias for these data. PCOS women also present clinical characteristics that are related to risk factors for breast cancer and some epidemiological evidences have been described on this issue. However, until now, a clear association between the presence of PCOS and breast carcinoma has yet not been found. Finally, high local steroid and growth factor concentrations are considered risk factors for ovary carcinoma, and are frequently observed in PCOS women. In turn, few studies have addressed the possibility of a link between PCOS and ovarian cancer and the results are conflicting but suggest that this association is unlikely.

Polycystic ovary syndrome and gynecological cancers: is there a link?

Polycystic ovary syndrome [PCOS] is the most common endocrinopathy of women in reproductive age. An association between PCOS and type-1 endometrial cancer has often been reported in the literature. The prolonged anovulation with consequent continued secretion of estrogen unopposed by progesterone may enhance the development and growth of this malignancy, particularly in young women. Hypersecretion of luteinizing hormone [LH], chronic hyperinsulinemia and increased serum insulin-like growth factor [IGF]-I levels may represent risk factors for endometrial cancer. However, data available in the literature do not allow a meta-analysis to be carried out to calculate an estimate of the relative risk of endometrial cancer in women with PCOS. Anecdotal cases of low-grade endometrial stromal sarcoma and carcinosarcoma have been reported in association with prolonged unopposed estrogen stimulation, and in particular with PCOS. A few studies have addressed the possibility of an association between PCOS and epithelial ovarian cancer risk, and the results are conflicting but generally reassuring, and similarly the few available data appear to exclude a strong association between PCOS and breast cancer.

Polycystic ovary syndrome and endometrial carcinoma

CONTEXT

An association between polycystic ovary syndrome (PCOS)and endometrial carcinoma was first suggested in 1949, 14 years after the original description of the syndrome. Since then several studies have been published that seem to support this association. The prescription of hormonal treatment to reduce the risk of this complication is supported by the Guidelines for Good Clinical Practice of the Royal College of Obstetricians and Gynaecologists, UK, the Health Information website of the National Library of Medicine, USA, and in textbooks of gynaecological oncology.

STARTING POINT

A recent practice bulletin from the American College of Obstetricians and Gynecologists on the clinical management of PCOS (Obstet Gynecol 2002; 100: 1389-402) says that there is still no consensus on the "optimal progestin, duration and frequency of treatment to prevent endometrial cancer in women with PCOS". Chronic anovulation, obesity, and hyperinsulinaemia are all associated with PCOS as well as with endometrial carcinoma. It has been assumed that PCOS predisposes to endometrial cancer. However, the evidence for such an association is inconclusive. Although PCOS is associated with risk factors for endometrial cancer, it does not necessarily follow that the incidence or mortality from endometrial cancer is increased.

WHERE NEXT

Large-scale studies of morbidity and mortality in unselected populations of women with PCOS are needed. Women with PCOS are increasingly aware of the possible risks, and it will be necessary to identify which of them, if any, are at increased risk and how this risk can be effectively reduced.

Plasma adiponectin concentrations in relation to endometrial cancer: a case-control study in Greece

Adiponectin is a hormone secreted exclusively by adipocytes, and obesity is an established risk factor for endometrial cancer. We have, thus, evaluated the association of adiponectin with the occurrence of endometrial cancer. Questionnaire information and blood samples were taken before treatment from 84 women with newly diagnosed, histologically confirmed endometrial cancer and 84 control women who were admitted for minor gynecologic problems, mainly pelvic prolapse. Adiponectin levels were measured by immunoassay. The results were analyzed through multiple logistic regression and controlled for known risk factors for endometrial cancer, leptin, as well as major components of the IGF system (IGF-I, IGF-II, and IGF-binding protein 3). Among control women, there was no significant association of adiponectin with age or parity. Although there was no association of adiponectin with endometrial cancer among women 65 yr or older, there was an inverse, fairly strong, and statistically significant inverse association among younger women. Among women younger than 65 yr, an increase of adiponectin by 1 SD was associated with a more than 50% reduction of the risk for endometrial cancer [odds ratio (OR) 0.44; 95% confidence interval (CI) 0.24-0.81], even after controlling for body mass index and other potential confounders. Among all women, the adjusted OR for a 1 SD increase in adiponectin was not significant (OR, 0.78; 95% CI, 0.56-1.10) but was significant for a one quintile increase in adiponectin (OR, 0.74; 95% CI, 0.56-0.97). In women younger than 65 yr, among whom obesity represents a powerful risk factor for endometrial cancer, adiponectin is inversely and significantly related to the risk of this disease. This association is independent of possible effects of major components of the IGF system, leptin, body mass index, sociodemographic variables, and known endometrial cancer risk factors. Future studies are needed to prove causality and provide insight on both the mechanism of action of this hormone and its potential role in endometrial cancer.

Insulin stimulates transepithelial sodium transport by activation of a protein phosphatase that increases Na-K ATPase activity in endometrial epithelial cells

The objective of this study was to investigate the effects of insulin and insulin-like growth factor I on transepithelial Na(+) transport across porcine glandular endometrial epithelial cells grown in primary culture. Insulin and insulin-like growth factor I acutely stimulated Na(+) transport two- to threefold by increasing Na(+)-K(+) ATPase transport activity and basolateral membrane K(+) conductance without increasing the apical membrane amiloride-sensitive Na(+) conductance. Long-term exposure to insulin for 4 d resulted in enhanced Na(+) absorption with a further increase in Na(+)-K(+) ATPase transport activity and an increase in apical membrane amiloride-sensitive Na(+) conductance. The effect of insulin on the Na(+)-K(+) ATPase was the result of an increase in V(max) for extracellular K(+) and intracellular Na(+), and an increase in affinity of the pump for Na(+). Immunohistochemical localization along with Western blot analysis of cultured porcine endometrial epithelial cells revealed the presence of alpha-1 and alpha-2 isoforms, but not the alpha-3 isoform of Na(+)-K(+) ATPase, which did not change in the presence of insulin. Insulin-stimulated Na(+) transport was inhibited by hydroxy-2-naphthalenylmethylphosphonic acid tris-acetoxymethyl ester [HNMPA-(AM)(3)], a specific inhibitor of insulin receptor tyrosine kinase activity, suggesting that the regulation of Na(+) transport by insulin involves receptor autophosphorylation. Pretreatment with wortmannin, a specific inhibitor of phosphatidylinositol 3-kinase as well as okadaic acid and calyculin A, inhibitors of protein phosphatase activity, also blocked the insulin-stimulated increase in short circuit and pump currents, suggesting that activation of phosphatidylinositol 3-kinase and subsequent stimulation of a protein phosphatase mediates the action of insulin on Na(+)-K(+) ATPase activation.

Specific binding and growth-promoting activity of insulin in endometrial cancer cells in culture

OBJECTIVE

Insulin is known to be mitogenic to a variety of cells in culture. The purpose of this study was to investigate the possible role of insulin in the growth and development of endometrial cancers.

STUDY DESIGN

Specific binding and growth effects of insulin were studied in 5 different human endometrial cancer cell lines derived from cancers with different degrees of differentiation: HEC-1-A and HEC-1-B (from a moderately well-differentiated adenocarcinoma), RL95-2 (from a moderately well-differentiated adenosquamous carcinoma), KLE (from poorly differentiated carcinoma), and AN3 CA (from a metastatic undifferentiated endometrial carcinoma). The receptors were further characterized by competitive binding and chemical cross-linking studies.

RESULTS

Binding studies with 125I-insulin revealed the presence of high-affinity binding sites for insulin on all the 5 cell lines. Binding of insulin was found to be highly specific. Competitive binding studies with 125I-insulin revealed that insulin was most effective in displacing the labeled hormone, whereas insulin-like growth factor-I and insulin-like growth factor-II competed for binding only at very high concentrations. Scatchard analysis of the binding data revealed that the association constant for the high-affinity binding sites ranged from 0.72 to 1.91 x 10(9) L/mol. Estrogen-receptor-negative cell lines HEC-1-A and HEC-1-B had the highest number of insulin receptors, whereas the estrogen-receptor-positive cell line RL95-2 had the least number of receptors. The effect of insulin on cell proliferation was studied by monitoring cell number and incorporating [3H]thymidine into deoxyribonucleic acid of the cells. Insulin stimulated cell growth of all the cell lines.

CONCLUSIONS

The results of this study indicate the potential role of hyperinsulinemia in the growth and development of endometrial cancer.

Expression of IGFs and their receptors is a potential marker for embryo quality

PROBLEM

Insulin-like growth factors (IGFs) and insulin have been demonstrated to stimulate oocyte maturation and embryo development. Therefore, the expression of IGFs and their receptors may be an important intrinsic factor for embryo growth and may be a potential marker for embryo quality.

METHOD OF STUDY

Thirty donated day 3 embryos were cultured in vitro for an additional 3 days to observe their developmental potential and were semiquantitatively analyzed for the expression of IGF-I, IGF-II, IGF-IR, IGF-IIR, and insulin-R.

RESULTS

Our results show that the activity of these gene expressions correlates well with the morphological assessment and that high and more gene expressions were often associated with embryos of high growth potential.

CONCLUSION

The IGF system may indeed play an important role in human embryogenesis; IGF gene expressions can be a good indicator of embryonic developmental stage and/or growth potential; finally, the IGF system can serve as a marker for embryo quality.

Insulin-like growth factor II mediates epidermal growth factor-induced mitogenesis in cervical cancer cells

There is increasing evidence that activation of the insulin-like growth factor I (IGF-I) receptor plays a major role in the control of cellular proliferation of many cell types. We studied the mitogenic effects of IGF-I, IGF-II, and epidermal growth factor (EGF) on growth-arrested HT-3 cells, a human cervical cancer cell line. All three growth factors promoted dose-dependent increases in cell proliferation. In untransformed cells, EGF usually requires stimulation by a "progression" factor such as IGF-I, IGF-II, or insulin (in supraphysiologic concentrations) in order to exert a mitogenic effect. Accordingly, we investigated whether an autocrine pathway involving IGF-I or IGF-II participated in the EGF-induced mitogenesis of HT-3 cells. With the RNase protection assay, IGF-I mRNA was not detected. However, IGF-II mRNA increased in a time-dependent manner following EGF stimulation. The EGF-induced mitogenesis was abrogated in a dose-dependent manner by IGF-binding protein 5 (IGFBP-5), which binds to IGF-II and neutralizes it. An antisense oligonucleotide to IGF-II also inhibited the proliferative response to EGF. In addition, prolonged, but not short-term, stimulation with EGF resulted in autophosphorylation of the IGF-I receptor, and coincubations with both EGF and IGFBP-5 attenuated this effect. These data demonstrate that autocrine secretion of IGF-II in HT-3 cervical cancer cells can participate in EGF-induced mitogenesis and suggest that autocrine signals involving the IGF-I receptor occur "downstream" of competence growth factor receptors such as the EGF receptor.

Localization and timing of appearance of insulin, insulin-like growth factor-I, and their receptors in the human fetal müllerian tract

OBJECTIVE

The factors that regulate fetal müllerian tract development are still unknown. Insulin and insulin-like growth factor-I are peptides postulated to serve as autocrine or paracrine regulators of cell activity. We have previously demonstrated that messenger ribonucleic acid for insulin and insulin-like growth factor-I receptors are expressed in fetal uterine tissues. We undertook this study to determine by immunohistochemical techniques the exact location of these two growth factors and their receptors in the human fetal uterus.

STUDY DESIGN

We obtained freshly discarded human fetal uteri (n = 12) between 15 and 22 weeks of gestation from elective pregnancy terminations. Frozen-section specimens were incubated with antibodies against insulin, insulin-like growth factor-I, insulin receptor, and insulin-like growth factor-I receptor. These sections were then incubated with a second antibody conjugated to fluorescein isothiocyanate and examined under phase and fluorescent microscopy.

RESULTS

The fetal endometrium at 19 and 22 weeks of gestation contained insulin, insulin-like growth factor-I, insulin receptor, and insulin-like growth factor-I receptor. The distribution of immunofluorescence in the endometrium is similar for both insulin and its receptor. The same pattern of immunostaining was likewise demonstrated for insulin-like growth factor-I and its receptor.

CONCLUSION

The localization of these growth factors and their receptors, combined with our previous messenger ribonucleic acid data, suggest an autocrine or paracrine role for insulin and insulin-like growth factor-I in the developing human fetal müllerian tract.

Growth factors and growth modulators in human uterine endometrium: their potential relevance to reproductive medicine

OBJECTIVE

To provide an up-to-date, comprehensive review on the presence and regulation of growth factors (GFs), GF receptors, and GF regulatory proteins in human endometrium in an effort to understand the potential roles of these proteins in endometrial cell mitosis and differentiation and in endometrial-trophoblast interactions.

DESIGN

Relevant studies were identified through a computerized bibliographic search (MEDLINE; BRS Information Technologies, a division of Maxwell Online, Inc., McLean, VA) and through manual scanning of recent relevant journals.

RESULTS

Several GFs, their receptors, and regulatory proteins have been identified in endometrium, and cellular localization and steroid-dependence of these proteins as well as action of several growth modulators on endometrial cell function have been studied. Epidermal growth factor, transforming growth factor (TGF)-alpha, platelet-derived growth factor, insulin-like growth factors (IGFs) and their binding proteins, fibroblast growth factor (FGF), TGF-beta, colony-stimulating factor (CSF)-1, and interferon-gamma regulate mitosis of endometrial cellular components in vitro. Endothelin-1 may participate in vasoconstriction and FGF may participate in angiogenesis in this tissue in vivo. Interleukins-1 and -6 are believed to be involved in endometrial T-cell activation, and TGF-beta, CSF-1, the interleukins, and the IGFs likely mediate endometrial-trophoblast interactions. The role of tumor necrosis factor in endometrium remains uncertain.

CONCLUSIONS

Current evidence supports the thesis that GFs play a central role in cyclic mitosis and differentiation of endometrial cellular components, recruitment of macrophages in decidualizing endometrium, endometrial-trophoblast interactions, early pregnancy maintenance, tissue shedding in the absence of implantation, and endometrial functionalis regeneration.

Insulin-like growth factor regulation of human endometrial stromal cell function: coordinate effects on insulin-like growth factor binding protein-1, cell proliferation and prolactin secretion

The insulin-like growth factor (IGF) autocrine/paracrine system is believed to be involved in endometrial differentiation, but there is limited information on the specific cellular functions regulated by IGFs in uterine tissues and their regulation of IGF-binding proteins (IGFBPs). We have investigated the regulation by insulin, IGF-I, and IGF-II, of IGFBP secretion in human endometrial stromal cells decidualized in vitro, and examined the interrelationship between the induced changes in IGFBP levels and the biological responses of stromal cells to IGFs. IGFBPs in conditioned media were analyzed by Western ligand blotting, and IGFBP-1 was quantified by an immunoenzymometric assay (IEMA). In the absence of peptides, decidualized stromal cells secreted 25.5 +/- 3.2 micrograms/day per 10(6) cells of IGFBP-1. Insulin caused a dose-dependent reduction of IGFBP-1 secretion (half-maximal inhibition at < 1 ng/ml) to a maximum of 1% of control values. Northern analysis using a specific cDNA probe showed the expression in decidualized stromal cells of a single 1.5 kb transcript for IGFBP-1, which was absent in insulin-treated cells. The effects of IGF-I and IGF-II on IGFBP-1 secretion were biphasic, with initial stimulation (200-250%) that peaked at 1 and 10 ng/ml, respectively, followed by inhibition at higher concentrations (half maximal inhibition at 3 ng/ml and 30 ng/ml, respectively). The decrease in IGFBP-1 levels in decidualized stromal cultures was associated with the induction of mitogenesis by IGF-I and IGF-II, while IGF effects on prolactin secretion paralleled those of IGFBP-1 secretion, with stimulation (243-324%) in the low concentration range followed by inhibition at higher concentrations. These data indicate that endometrial stromal cell IGFBP-1 is regulated by insulin, at concentrations that are compatible with insulin acting via its own receptor, while the effects of IGF-I and IGF-II on IGFBP-1 secretion, are suggestive of their acting probably through the type I IGF receptor. The present study describes distinct effects of the IGFs on stromal cell IGFBPs, that correlate with changes in the proliferative and secretory responses of decidualized stromal cells to the IGFs. Our findings suggest that complex IGF-IGFBP interactions may participate in the regulation of endometrial cell function, and support a role for IGF-II in stromal cell mitogenesis during decidualization, and as a local regulator of decidual cell function during the late secretory phase and early pregnancy.

Regulation of endometrial cancer cell growth by insulin-like growth factors and the luteinizing hormone-releasing hormone antagonist SB-75

The involvement of IGFs in growth regulation of the Ishikawa endometrial tumor cell line and the possible interference of LH-RH analogues with a potential autocrine or paracrine loop involving IGFs was evaluated. The mitogenic effects of IGF-I, IGF-II, and insulin were compared. IGF-I was found to be 3-fold more potent than IGF-II and 30-fold more potent than insulin, suggesting that the effects of these growth factors are mediated by the IGF-I receptor. Ishikawa endometrial cancer cells secrete IGF-II, but not IGF-I, and insulin (1 microM) stimulates IGF-II release. The LH-RH antagonist [Ac-D-Nal(2)1, D-Phe(4Cl)2, D-Pal(3)3, D-Cit6, D-Ala10]-GnRH (SB-75, CETRORELIX) inhibited basal and IGF-induced growth. Moreover, this antagonist almost completely inhibited IGF-II release from Ishikawa cells, while having no significant effect on the number or affinity of IGF-I binding sites. Inhibition of IGF-II release occurred at a lower SB-75 concentration than that needed for a reduction in cell number. The ED50 of SB-75 for IGF-II release was 0.3 microM as compared to 1.5 microns concentration which is required for reduction in cell number, suggesting that inhibition of growth factor release precedes cell growth inhibition. We conclude that the LH-RH antagonist SB-75 can inhibit the growth of endometrial cancer cells by interfering with the autocrine action of IGF-II and also by directly inhibiting the growth-stimulatory effects of IGFs, probably through effects on a post-receptor mechanism.