Objective: To study the isoforms of insulin-like growth factor binding protein-1 (IGFBP-1) in cervical secretion and to evaluate whether their assessment could serve in prediction of cervical ripeness at term. Methods: We measured the concentrations of IGFBP-1 in cervical swab samples of 64 women scheduled for labor induction by amniotomy or cervical ripening with prostaglandin E2 gel. Two immunoenzymometric assays were used: a previously described assay 1, which detects the nonphosphorylated and lesser phosphorylated isoforms, and a novel assay 2, which detects the lesser and highly phosphorylated isoforms of IGFBP-1. A set of 39 amniotic fluid (AF) samples also was analyzed to compare the phosphorylation status of IGFBP-1 in cervical secretion with that in AF. Results: In all cervical samples, IGFBP-1 concentration was higher by assay 2 than by assay 1, whereas in all AF samples, the results were the opposite. Initially, the median IGFBP-1 concentration in the ripe cervices (Bishop scores 6 or greater; n = 29) was approximately four times as high as that in the unripe cervices (Bishop scores 5 or less; n = 35). The cervical IGFBP-1 concentrations increased eight-fold in 6 hours after the first application of PGE2. Conclusion: Phosphorylated isoforms of IGFBP-1, different from those in AF, are present in the cervical secretion of women with intact fetal membranes and reflect cervical ripeness. A bedside test for those IGFBP-1 isoforms might help in predicting amenability for labor induction.
The insulin-like growth factor (IGF) system is thought to function as a mediator of steroid hormone actions in the endometrium. IGFs (IGF-I and IGF-II) are also potent mitogens in endometrial cancer. The biological actions of IGFs are modulated by specific binding proteins (IGFBP)--6 cloned and sequenced so far--which may either inhibit or enhance the effects of IGF at the cellular level. In the endometrium, IGFBP-1 gene expression is stimulated by progesterone and inhibited by insulin, while IGFBP-1 inhibits the mitogenic action of IGF-I. In this study, we used a quantitative reverse transcriptase polymerase chain reaction (RT-PCR) to investigate IGFBP-1, IGFBP-2, IGFBP-4, IGFBP-5 and IGFBP-6 gene expression in endometrial cancer tissues. Endometrial cancer tissue samples were collected from 20 women (aged 54-79 yrs) with stage I to II well-differentiated endometrial adenocarcinoma. Samples of normal endometrium (n = 14) obtained from women undergoing tubal ligation in various phases of the menstrual cycle, and normal early-pregnancy endometrium (decidua) were studied for comparison. In endometrial cancer tissues, the IGFBP-1 mRNA was undetectable or minimally expressed when studied by RT-PCR. The mean (+ SD) levels of IGFBP-2 and IGFBP-4 and IGFBP-5 mRNAs in endometrial cancer tissues did not differ from those in normal endometrium, in which no cyclic variation was observed, suggesting that the genes encoding IGFBP-2, IGFBP-4 and IGFBP-5 are not hormonally regulated in the endometrium. The IGFBP-6 mRNA expression showed a significant cyclic variation in normal endometrium, with low levels in late-proliferative and early- to mid-secretory phases and high expression in late-secretory and early-proliferative phases. In endometrial cancer tissues, the mean IGFBP-6 mRNA level was similar to that in cycling endometrium during the peri-ovulatory period. In summary, a continuous stimulation of the endometrial epithelial cells by IGFs with suppressed IGFBP-1 expression may lead to an imbalance in the IGF system of the endometrium and trigger an uncontrolled cell proliferation, ultimately resulting in malignant transformation.
Abstract The circulating levels of the immunoreactive alpha subunit of glycoprotein hormones were measured by the hCG alpha subunit radioimmunoassay in 101 patients with non‐trophoblastic gynaecological cancer and in 164 serum samples obtained from 10 patients with choriocarcinoma and five patients with hydatidiform mole. Serum samples from six patients with choriocarcinoma and four with hydatidiform mole were further examined for the existence of free alpha by chromatography on a calibrated Sephadex G‐100 column. In patients with non‐trophoblastic cancer the immunoreactive alpha subunit levels were not different from those of controls in the corresponding age groups. In trophoblastic disease all hCG‐positive samples showed also alpha subunit immunoreactivity when tested by radioimmunoassay, but no isolated alpha elevation was found. Chromatographic analyses revealed free alpha subunits in three out of six patients with choriocarcinoma and two out of four patients with hydatidiform mole. A patient who eventually died of choriocarcinoma was carefully followed for the free alpha secretion, and no alpha elevation was found in any of the 16 serum samples taken at various phases of disease. The present study shows that, unlike pancreatic islet cell tumours in vivo and HeLa cells in vitro , non‐trophoblastic gynaecologic cancer in vivo does not appear to have any significant alpha secretion. In trophoblastic disease free alpha subunits may coexist with native hCG more frequently than it was originally assumed, but no isolated alpha secretion could be demonstrated. The intriguing disparity between the alpha secretion by normal and abnormal trophoblasts was confirmed in this study, but the biological basis and significance of this phenomenon remain obscure.
Data from a number of studies reported during the past two decades indicate that the insulin-like growth factor (IGF) system, including IGF-I and IGF-II, their receptors and six high-affinity binding proteins, is involved in the control of foetal and placental growth and development. Recent studies that addressed the role of the IGF system in pregnancy and the clinical usefulness of IGF and IGF-binding protein measurements in obstetrics are reviewed and discussed.
Dear Editor,
With great interest I read the recently published guidelines for the management of spontaneous preterm labor [1]. I was delighted to see that unlike the previous guidelines published in 2006 [2], these new ones also take into consideration the diagnostic marker insulin-like growth factor binding protein-1 (IGFBP-1) that I have worked with since the early 80s. However, I would like to bring the readers’ attention to some errors and points that may be misleading regarding evaluation of IGFBP-1 as a marker of ruptured fetal membranes (ROM) and in comparing it with placental α microglobulin-1 (PAMG-1).
Firstly, human IGFBP-1 is a well characterized protein since more than 20 years [3,4]. Its synthesis by the liver and decidua, and levels in amniotic fluid and other body fluids have been thoroughly examined in all stages of pregnancy [5,6] and the data have been published in peer-reviewed journals. Meanwhile, the data available on PAMG-1 is more limited and partly confusing. In the most often cited papers regarding the PAMG-1 levels in amniotic fluid, blood and other body fluids [7–9], the values are quite different from those reported in the guidelines. This makes comparison between IGFBP-1 and PAMG-1 difficult.
IGFBP-1 has been used as a marker of ROM since the mid 90s (Actim PROM test). Since then, several studies have consistently shown that this test identifies membrane rupture with high accuracy. Unfortunately, many of these studies were omitted in the analysis presented in Table I of the guidelines comparing the performance of the different tests [10–12]. As a consequence, the sensitivity and specificity of the IGFBP-1 test remain underestimated. For example, the lowest sensitivity (74%) is from a study by Lockwood 1994 using a quantitative radioimmunoassay with frozen samples in the laboratory with a different detection limit and assay conditions from the current IGFBP-1 based bed-side PROM test [13].
Secondly, the guidelines state that the detection limit of PAMG-1 with Amnisure ROM test (5 ng/ml) is lower than the detection limit of IGFBP-1 with Actim PROM test (25 ng/ml). This comparison is irrelevant, since the quoted levels of PAMG-1 protein in amniotic fluid (2000−25,000 ng/ml) are clearly lower than the known levels of IGFBP-1 (10,500−350,000 ng/ml [14]), which naturally calls for a need of a lower detection limit. In the guidelines the lowest level of IGFBP-1 is quoted to be 27 ng/ml in early pregnancy. Such low levels have not been reported at pregnancy weeks clinically relevant for diagnosis of ROM [15].
Thirdly, the sensitivity and specificity of any test has to be interpreted in the clinical context. The methods used for estimation of the accuracy and reliability of the PAMG-1 test compared to the IGFBP-1 test are questionable for several reasons. For example, samples of pure blood-free amniotic fluid obtained during intra-operative amniocentesis at cesarean section were diluted with 0.9% saline and serial dilutions were tested using both tests [16,17]. The study design does not correspond to the bed-side situation where amniotic fluid is contaminated by vaginal discharge or other possible fluids like urine, semen or blood that may affect the test result causing false positives, if the test is too sensitive. A high rate of positive PAMG-1 test results has been found among patients with intact membranes and labor at term [18] and in patients with a short cervix [19]. This data has not been considered when analyzing the specificity of PAMG-1 test. Also, the publication on the intra-amniotic dye test and its comparison with the PAMG-1 test is a congress abstract only, with no information on the numbers of patients or the study design [20].
Finally, IGFBP-1 test results have repeatedly been shown to be unaffected by the presence of blood [10,21,22]. Indeed, the monoclonal antibody used in the Actim PROM test does not recognize the highly phosphorylated IGFBP-1 which is the predominant isoform in maternal and fetal blood and decidua [4]. Since blood may be present in approximately 25% of cases with suspected PROM, this information is critical in order to estimate the accuracy and clinical usefulness of the marker. Suspected rupture of membranes in the presence of bleeding is the most challenging situation in the clinic, since the therapeutic measures differ depending on whether the membranes in such a case are intact or not. Yet, no information is available on the accuracy of the PAMG-1 test in patients with suspected membrane rupture and bleeding since patients with bleeding have systematically been excluded in PAMG-1 clinical studies, suggesting that PAMG-1 test cannot be used in such challenging cases.
The statement that presence of blood up to 50% does not interfere with the PAMG-1 test result is only based on a conference poster, reporting serial dilutions of peripheral blood in 0.9% saline in vitro [23]. Again, the study design is not equivalent to the clinical situation where amniotic fluid in cervicovaginal swab sample is mixed with vaginal secretion and other possible contaminants. Also, this high rate of positive Amnisure results in the presence of blood raises a question on the validity of the reported range in the maternal blood (0.5–2 ng/ml) that should not react in a test with a detection limit of 5 ng/ml.
Considering all the points above, the currently available data does not unequivocally support the superiority of the PAMG-1 test as compared with the IGFBP-1 test.
We have previously shown that placental protein 12 (PP12) is synthesized and secreted by human term pregnancy decidua in vitro. In the present study, fragments of proliferative and secretory phase endometrium were cultured in media in the presence and absence of progesterone (P) and 17β-estradiol (E2) for 96 h. The PP12 concentrations in the media and tissues were measured by RIA, and de novo synthesis was investigated by measuring the incorporation of [35S]methionine into PP12. Before culture, PP12 could not be detected in any proliferative endometria, whereas all secretory endometria contained PP12. All secretory endometria released PP12 into the medium in the presence and absence of added P and E2. Secretory endometria released significantly more PP12 than proliferative endometria. Three of seven proliferative endometria did not release PP12 in the absence of P, but all did so after P had been added. The addition of P to culture medium caused a 2.4- to over 71-fold increase in PP12 secretion over control values in proliferative endometria and up to a 3.5-fold increase in secretory endometrium. E2 had no significant effect. Cycloheximide totally inhibited the PP12 release induced by P from proliferative endometrium, and in secretory endometrium, it either totally blocked PP12 release or inhibited the stimulation due to P. [35S]Methionine was incorporated into immunoprecipitable PP12 in cultures of secretory and P-treated proliferative phase endometria. These results demonstrate de novo synthesis of PP12 by nonpregnant endometrium in tissue culture and suggest that the biosynthesis and secretion of PP12 by nonpregnant endometrium are regulated by P. (Endocrinology118: 1067–1071, 1986)
Women with prior preeclampsia are characterized by hyperinsulinemia and a 2- to 3-fold excess risk of hypertension and ischemic heart disease in later life. We therefore studied whether these women present changes in pituitary, ovarian, and endothelial factors that could also affect the risk of vascular disorders. Twenty-two women with prior preeclampsia and 22 control women matched by age and body mass index were studied an average of 17 yr after delivery. Women with prior preeclampsia had elevated serum free testosterone levels (20.6 +/- 2.2 vs. 15.0 +/- 1.3 pmol/L, mean +/- SE, P = 0.03), an elevated free androgen index (3.2 +/- 0.5 vs. 1.9 +/- 0.2, P = 0.04), and an elevated free testosterone estradiol ratio (0.089 +/- 0.017 vs. 0.046 +/- 0.006, P = 0.02). The levels of insulin-like growth factor binding protein-1 decreased as expected during a 3-h oral glucose tolerance test without differences between the groups. Levels of FSH, LH, androstenedione, dehydroepiandrosterone sulfate, and endothelin-1, as well as urinary output of prostacyclin and thromboxane A2 metabolites, showed no difference between study groups. A history of preeclampsia an average of 17 yr earlier thus appears to be associated with elevated levels of testosterone, which may contribute to the increased risk of vascular morbidity in such women.
