17β-estradiol binding to ERα promotes the progression of prolactinoma through estrogen-response element-induced CaBP-9k up-regulation

Treatment Strategies for Dopamine Agonist-Resistant and Aggressive Prolactinomas: A Comprehensive Analysis of the Literature

Despite most of the prolactinomas can be treated with endocrine therapy and/or surgery, a significant percentage of these tumors can be resistant to endocrine treatments and/or recur with prominent invasion into the surrounding anatomical structures. Hence, clinical, pathological, and molecular definitions of aggressive prolactinomas are important to guide for classical and novel treatment modalities. In this review, we aimed to define molecular endocrinological features of dopamine agonist-resistant and aggressive prolactinomas for designing future multimodality treatments. Besides surgery, temozolomide chemotherapy and radiotherapy, peptide receptor radionuclide therapy, estrogen pathway modulators, progesterone antagonists or agonists, mTOR/akt inhibitors, pasireotide, gefitinib/lapatinib, everolimus, and metformin are tested in preclinical models, anecdotal cases, and in small case series. Moreover, chorionic gonadotropin, gonadotropin releasing hormone, TGFβ and PRDM2 may seem like possible future targets for managing aggressive prolactinomas. Lastly, we discussed our management of a unique prolactinoma case by asking which tumors' proliferative index (Ki67) increased from 5-6% to 26% in two subsequent surgeries performed in a 2-year period, exerted massive invasive growth, and secreted huge levels of prolactin leading up to levels of 1 605 671 ng/dl in blood.

Galectin-3 and Estrogen Receptor Alpha as Prognostic Markers in Prolactinoma: Preliminary Results From a Pilot Study

INTRODUCTION

Prolactin-secreting pituitary tumors (PRL-omas) are generally benign neoplasia. However, a percentage of cases show aggressive behavior. Prognostic markers may allow for the identification of aggressive cases. In this study, we investigated the prognostic role of galectin-3 and the estrogen receptor alpha (ERα), as predictive biomarkers of aggressiveness and poor prognosis.

PATIENTS AND METHODS

A mono-centric and retrospective study was conducted on consecutive cases of PRL-omas that underwent first line treatment with surgery and were followed-up for at least five years. The immunohistochemical expression of ERα and galectin-3 was investigated in each case.

RESULTS

36 patients were enrolled. Galectin-3 resulted positive in 11 patients (30.6%). The median expression of ERα was 85% (IQR: 37). Among the group of 21 patients who underwent radical surgery (58.3%), recurrence occurred in 12 cases (33.3%). 27 patients were treated post-surgery with a dopamine agonist (DA) (12 for recurrence and 22 for a history of partial surgery). 13 patients (48.1%) were responsive to DA. Six of 11 cases positive for galactin-3 underwent partial surgery (54.5%, p<0.001). Recurrence occurred in all five cases that underwent radical surgery, which were also positive for galectin-3 (p=0.03). Galectin-3 resulted positive in 9 patients resistant to DA treatment (81.1%, p=0.01). ERα expression was lower in tumors positive for galectin-3 (p<0.001), with mitotic activity (p=0.012), with higher Ki67 Li (p<0.001), and in males with post-surgical recurrence (p<0.001).

CONCLUSION

Galectin-3 and ERα play as markers of aggressiveness and prognosis in PRL-omas and may be tested to identify the aggressive forms of the disease.

Estrogen receptor α/prolactin receptor bilateral crosstalk promotes bromocriptine resistance in prolactinomas

Prolactinomas are the most common type of functional pituitary adenoma. Although bromocriptine is the preferred first line treatment for prolactinoma, resistance frequently occurs, posing a prominent clinical challenge. Both the prolactin receptor (PRLR) and estrogen receptor α (ERα) serve critical roles in the development and progression of prolactinomas, and whether this interaction between PRLR and ERα contributes to bromocriptine resistance remains to be clarified. In the present study, increased levels of ERα and PRLR protein expression were detected in bromocriptine-resistant prolactinomas and MMQ cells. Prolactin (PRL) and estradiol (E2) were found to exert synergistic effects on prolactinoma cell proliferation. Furthermore, PRL induced the phosphorylation of ERα via the JAK2-PI3K/Akt-MEK/ERK pathway, while estrogen promoted PRLR upregulation via pERα. ERα inhibition abolished E2-induced PRLR upregulation and PRL-induced ERα phosphorylation, and fulvestrant, an ERα inhibitor, restored pituitary adenoma cell sensitivity to bromocriptine by activating JNK-MEK/ERK-p38 MAPK signaling and cyclin D1 downregulation. Collectively, these data suggest that the interaction between the estrogen/ERα and PRL/PRLR pathways may contribute to bromocriptine resistance, and therefore, that combination treatment with fulvestrant and bromocriptine (as opposed to either drug alone) may exert potent antitumor effects on bromocriptine-resistant prolactinomas.