Plasma luteinizing hormone-releasing hormone levels in normal women and patients with amenorrhea

P-cadherin cooperates with insulin-like growth factor-1 receptor to promote metastatic signaling of gonadotropin-releasing hormone in ovarian cancer via p120 catenin

Gonadotropin-releasing hormone (GnRH) is a potent prometastatic factor in ovarian cancer, but the intracellular signaling events are not well understood. The classical Gα(q)-phospholipase C signal transduction pathway known to operate in the pituitary is not involved in GnRH actions at non-pituitary targets. Here we showed that GnRH treatment of ovarian cancer cells led to a rapid and remarkable tyrosine phosphorylation of p120 catenin (p120(ctn)), which was mediated by P-cadherin. The use of P-cadherin small interfering RNA or neutralizing antibodies to inhibit P-cadherin expression and function resulted in diminished p120(ctn) activation, confirming that the effect was P-cadherin specific. On exploring how P-cadherin, which lacks intrinsic kinase activity, might regulate the activation of p120(ctn), we found that P-cadherin could induce the ligand-independent activation of insulin-like growth factor-1 receptor (IGF-1R). Inhibition of IGF-1R expression or its activity significantly inhibited GnRH-induced p120(ctn) activation, and the subsequent cell migration and invasion. In addition, we showed that IGF-1R regulation by P-cadherin was associated with complex formation between IGF-1R and P-cadherin, and this regulation was also observed to be in vivo correlated with metastasis. Furthermore, using a mouse model of ovarian cancer metastasis, GnRH receptor knockdown was shown to diminish peritoneal dissemination of tumors and ascites formation. These findings suggest for the first time that GnRH can initiate an outside-in p120(ctn) signal transduction through the cross-talk between P-cadherin and IGF-1R, thus providing a novel molecular mechanism by which GnRH may control the high level of aggressiveness and invasion and metastasis potential that are characteristic of ovarian cancer.

Development of a radioimmunoassay for measuring gonadotrophin releasing hormone in patients receiving treatment

A radioimmunoassay for the measurement of gonadotrophin releasing hormone (GnRH) in plasma and urine using readily available reagents was developed. The GnRH assay showed good precision, recovery, and parallelism over a wide range of GnRH concentrations with a sensitivity of 15 pg/ml. The assay was compared with a commercially available kit (Buhlmann Laboratories). Although the Buhlmann kit showed acceptable precision, recovery, sensitivity, and correlation with the developed GnRH assay for plasma samples, lack of parallelism of serially diluted plasma and urine samples was consistently observed, together with a poor correlation with the developed GnRH assay for urine, suggesting a matrix effect with the Buhlmann kit. The developed assay is suitable for measuring GnRH in samples obtained from patients receiving pulsatile infusions of GnRH. In contrast, the commercially available Buhlmann kit was unsuitable for measuring plasma GnRH as the kit had a top standard of only 160 pg/ml, well below the peak plasma concentration. It would not be possible to dilute samples for analysis because of the lack of parallelism of diluted samples compared with standards obtained with the Buhlmann assay.

Pituitary and ovarian responses to LHRH stimulation in women with clinical features of the polycystic ovary syndrome

The gonadotrophin release and the changes in ovarian and adrenal steroid levels following the administration of a low dose of LHRH were assessed in a group of women with clinical features of the polycystic ovary syndrome (PCO syndrome). The results were compared with those obtained in a group of normal ovulatory women. A significant increase in LH and FSH levels and a decrease in cortisol concentrations were demonstrated in both study groups following the administration of LHRH. The LH response was significantly exaggerated in the PCO group when compared with the control women. The estrone and estradiol levels did not change in either group. The androstenedione and testosterone concentrations did not change or decreased in the control group, whereas an increase of these hormones was seen in the PCO group. In the PCO group a positive correlation between the LH response and the androstenedione response was noticed. These findings indicate that the hyperandrogenic state encountered in PCO patients is at least in part of ovarian origin.