Prolactin, prolactin disorders, and dopamine agonists during pregnancy

Letrozole Decreased Testosterone-Induced Cell Proliferation and Prolactin Secretion also Increased Apoptosis in MMQ and GH3 Rat Prolactinoma Cell Lines

Aromatase enzyme plays an essential role in estrogen-induced tumorigenesis. It is expressed in the normal pituitary and more significantly in prolactinoma tissues. The aim of this study was to investigate the effects of an aromatase inhibitor, letrozole, on MMQ and GH3 rat prolactinoma cell lines and evaluate the possible mechanism of action. MMQ and GH3 cells were characterized with demonstrating aromatase enzyme and estrogen receptor alpha expression by PCR and immunofluorescence staining. After dose optimization for testosterone (T) and letrozole (L), four groups were established: only the testosteron-treated group (T) to detect cell proliferation; only letrozole-treated group (L) to investigate apoptotic effects; testosterone and letrozole concomitant-treated group to demonstrate inhibition of testosterone induced cell proliferation with letrozole treatment s(T + L) and control group (C) with no treatment. The proliferation rate of cells was determined by WST-1. For the detection of apoptotic and necrotic cells, Annexin V and caspase-3 labeling was used. Prolactin and estrogen levels were measured with ELISA, and the mRNA expression of aromatase and Esr1 was also determined. Testosterone induced the proliferation of MMQ and GH3 cells and further increased prolactin and estradiol levels. Adding letrozole to testosterone resulted in decreased cellular proliferation and even induced apoptosis. Also, letrozole administration significantly decreased prolactin and estradiol levels. However, letrozole alone had no effects on proliferation and apoptosis. Gene expression of aromatase and Esr1 was also significantly decreased by letrozole treatment. This in vitro study demonstrated that treatment of testosterone proliferating cells with letrozole resulted in decreased prolactin levels and cell proliferation and induced apoptosis, and further loss of aromatase and Esr1 mRNA expression were observed. Although this is an in vivo study, the results showed unique and novel findings which may easily be adapted to clinical use for further verification.

Cabergoline Failure and a Spontaneous Pregnancy in a Microprolactinoma with High Prolactin Levels

We report a particular case of a spontaneously occurring pregnancy in a long-term amenorrheic patient due to a prolactinoma with high serum prolactin (PRL) following the failure of dopamine agonist therapy (DA) for infertility. Initially, clinical, laboratory, and genital ultrasounds were normal, but the serum PRL was 10,074 μIU/mL (n.v.: 127−637 μIU/mL), the PEG fraction was 71% (laboratory cut-off > 60%), and luteinizing hormone (LH) was significantly lower. An MRI revealed a pituitary tumor of 12.8/10 mm with a subacute intratumoral hemorrhage. DA was initiated, and menstrual bleeding reappeared with a reduction in the tumor’s volume to 1.9/2.2 mm at 12 months. Two years later, the patient renounced DA and follow-ups. After another 2 years, she became spontaneously pregnant. Serum PRL was 18,325 μIU/mL, and an MRI revealed a microprolactinoma of 2.1/2 mm. The patient gave birth to a normal baby at term, and she breastfed for six months, after which she asked for ablactation, and DA was administered. This case highlights the possibility of the occurrence of a normal pregnancy during a long period of amenorrhea induced by a microprolactinoma with a high level of serum PRL, even if DA fails to correct infertility. There was no compulsory relationship between the tumoral volume’s evolution and the evolution of its lactophore activity. The hypogonadotrophic hypogonadism induced by high PRL was mainly manifested by low LH, and in this situation, normal levels of FSH and estradiol do not always induce follicle recruitment and development without abnormalities in the ovary ultrasound.

Anti-c-myc efficacy block EGFL7 induced prolactinoma tumorigenesis

Resistance to Dopamine agonists therapy is still a key factor that hinders the clinical treatment of prolactinoma. Consequently, a large number of investigations have been carried out to identify novel therapeutic targets. Our previous studies have suggested that the epidermal growth factor-like domain 7 (EGFL7) plays a crucial role in tumorigenesis of pituitary adenomas via EGFR/AKT/MAPK signaling pathway. In the present research, we found a positive staining of c-myc intimately associated with high-level EGFL7 in invasive prolactinoma compared to non-invasive prolactinoma and the normal pituitary gland. Meanwhile, PI3K/Akt and MAPK signaling cascades closely related to the activation of c-myc. Therefore, this research was conducted to explore the cooperation effect of c-myc and EGFL7 in prolactinoma. The inhibition of c-myc with anti-c-myc antibodies significantly reduced the proliferation, PRL secretion and invasion of rat prolactinoma MMQ cells. Notably, down regulation c-Myc by in vitro administration of anti-c-Myc antibodies could significantly depress EGFL7 induced MMQ cell proliferation, PRL secretion and invasion. An anti-c-Myc antibody could block EGFL7 induced Akt activation, but the expression of p-ERK was not altered by an anti-c-Myc antibody. Thus, our results suggest that anti-c-myc efficacy could block EGFL7 induced prolactinoma tumorigenesis via inhibited Akt activation in MMQ cells.