Exosome-Transmitted lncRNA H19 Inhibits the Growth of Pituitary Adenoma.

CONTEXT: Our previous study demonstrated that the expression of long noncoding RNA (lncRNA) H19 was frequently downregulated in human primary pituitary adenomas and negatively correlated with tumor progression. However, the role of exosomal lncRNA H19 in the inhibition of pituitary tumor growth remains unclear. OBJECTIVE: To investigate whether exosomal H19 could be transported across the cell membrane to exert its inhibitory effect on pituitary tumor growth. DESIGN: Empty lentivirus GH3 cells with or without H19 overexpression were used to establish a xenograft model. Isolated exosomes were identified by transmission electron microscopy, nanoparticle tracking, and Western blotting. The expression levels of serum exosomal H19 from 200 healthy subjects and 206 patients with various subtypes of pituitary tumors were detected by ultracentrifugation and quantitative real-time PCR. RESULTS: The growth of distal tumor cells was inhibited by transferring exosomal H19, which could be transported through cell membrane and exert its inhibitory effect. Cabergoline increased H19 expression and played a synergic therapeutic effect with exosomal H19. Exosomal H19 inhibited phosphorylation of the mTORC1 substrate 4E-BP1. Of note, the expression level of exosomal H19 in the patients with all subtypes of pituitary tumors was significantly lower than that in the healthy subjects. The change of plasma exosomal H19 level may be correlated with the prognosis or drug response of the patients. CONCLUSION: Exosomal H19 inhibits the growth of distal pituitary tumors through inhibiting 4E-BP1 phosphorylation. Plasma exosomal H19 may serve as an important biomarker for predicting medical responses of patients with prolactinomas.

DEPTOR inhibits cell proliferation and confers sensitivity to dopamine agonist in pituitary adenoma.

DEP domain-containing mechanistic target of rapamycin (mTOR)-interacting protein (DEPTOR) is an important modulator of mTOR, a highly conserved kinase whose hyperactivation is critically involved in a variety of human tumors. The role of DEPTOR playing in pituitary adenoma (PA) is largely unknown. Here, we reported that DEPTOR was downregulated in PA tissues, especially dopamine-resistant prolactinomas. Consistently, overexpression of DEPTOR inhibited pituitary tumor GH3 and MMQ cells proliferation in vitro and in vivo, and sensitized GH3 and MMQ cells to cabergoline (CAB), a dopamine agonist (DA). Conversely, knockdown of DEPTOR promoted GH3 and MMQ cells proliferation, and conferred cells resistance to CAB. Mechanistically, DEPTOR inhibited both mTOR Complex 1 (mTORC1) and 2 (mTORC2) activities in PA cells. In addition, DEPTOR expression level was increased to suppress mTOR kinase activity via decreasing E3 ubiquitin ligase, ßTrCP1, in response to CAB. Furthermore, DEPTOR enhanced autophagy-dependent cell death to confer cells sensitivity to CAB. Taken together, our results suggest that DEPTOR may be a potential target for the treatment of PAs.

Inhibition of mTORC1 by lncRNA H19 via disrupting 4E-BP1/Raptor interaction in pituitary tumours.

Aberrant expression of long noncoding RNA H19 has been associated with tumour progression, but the underlying molecular tumourigenesis mechanisms remain largely unknown. Here, we report that H19 expression is frequently downregulated in human primary pituitary adenomas and is negatively correlated with tumour progression. Consistently, upregulation of H19 expression inhibits pituitary tumour cell proliferation in vitro and tumour growth in vivo. Importantly, we uncover a function of H19, which controls cell/tumour growth through inhibiting function of mTORC1 but not mTORC2. Mechanistically, we show that H19 could block mTORC1-mediated 4E-BP1 phosphorylation without affecting S6K1 activation. At the molecular level, H19 interacted with 4E-BP1 at the TOS motif and competitively inhibited 4E-BP1 binding to Raptor. Finally, we demonstrate that H19 is more effective than cabergoline treatment in the suppression of pituitary tumours. Together, our study uncovered the role of H19-mTOR-4E-BP1 axis in pituitary tumour growth regulation that may be a potential therapeutic target for human pituitary tumours.

Pituitary Tumor Suppression by Combination of Cabergoline and Chloroquine.

Context: The dopamine agonist cabergoline (CAB) has been used widely in the treatment of prolactinomas and other types of pituitary adenomas, but its clinical use is hampered by intolerance in some patients with prolactinoma and lack of effectiveness in other pituitary tumor types. Chloroquine (CQ) is an old drug widely used to treat malaria. Recent studies, including our own, have revealed that CAB and CQ are involved in induction of autophagy and activation of autophagic cell death. Objective: To test whether CAB and CQ can function cooperatively to suppress growth of pituitary adenomas as well as other cancers. Results: In vitro studies using the rat pituitary tumor cell lines MMQ and GH3, human pituitary tumor cell primary cultures, and several human cancer cell lines showed that CQ enhanced suppression of cell proliferation by CAB. These results were confirmed in in vivo xenograft models in nude mice and estrogen-induced rat prolactinomas. To understand the mechanism of combined CAB and CQ action, we established a low-CAB-dose condition in which CAB was able to induce autophagy but failed to suppress cell growth. Addition of CQ to low-dose CAB blocked normal autophagic cycles and induced apoptosis, evidenced by the further accumulation of p62/caspase-8/LC3-II. Conclusion: The data suggest that combined use of CAB and CQ may increase clinical effectiveness in treatment of human pituitary adenomas, as well as other cancers, making it an attractive option in tumor and cancer therapies.

Activation of DRD5 (dopamine receptor D5) inhibits tumor growth by autophagic cell death.

Dopamine agonists such as bromocriptine and cabergoline have been successfully used in the treatment of pituitary prolactinomas and other neuroendocrine tumors. However, their therapeutic mechanisms are not fully understood. In this study we demonstrated that DRD5 (dopamine receptor D5) agonists were potent inhibitors of pituitary tumor growth. We further found that DRD5 activation increased production of reactive oxygen species (ROS), inhibited the MTOR pathway, induced macroautophagy/autophagy, and led to autophagic cell death (ACD) in vitro and in vivo. In addition, DRD5 protein was highly expressed in the majority of human pituitary adenomas, and treatment of different human pituitary tumor cell cultures with the DRD5 agonist SKF83959 resulted in growth suppression, and the efficacy was correlated with the expression levels of DRD5 in the tumors. Furthermore, we found that DRD5 was expressed in other human cancer cells such as glioblastomas, colon cancer, and gastric cancer. DRD5 activation in these cell lines suppressed their growth, inhibited MTOR activity, and induced autophagy. Finally, in vivo SKF83959 also inhibited human gastric cancer cell growth in nude mice. Our studies revealed novel mechanisms for the tumor suppressive effects of DRD5 agonists, and suggested a potential use of DRD5 agonists as a novel therapeutic approach in the treatment of different human tumors and cancers.

Long-Term Clinical Outcomes of Invasive Giant Prolactinomas after a Mean Ten-Year Followup.

Objective. The aim of this study is to observe clinical outcomes after more than ten years of followup in a group of patients with invasive giant prolactinomas (IGPs) treated with dopamine agonists (DAs). Methods. Twenty-five patients met the criteria of IGPs, among which 16 patients primarily received bromocriptine (BRC) and the other nine had undergone unsuccessful microsurgery prior to BRC treatment. Results. After a mean follow-up period of 135.5 ± 4.7 months, the clinical symptoms in all patients improved by different degrees. Tumor volume was decreased by a mean of 98.6%, and the tumors of 19 patients had almost completely disappeared. The mean duration of treatment at maximal doses of BRC was 48.5 months. At the last follow-up visit, nineteen patients had normal PRL levels, and 14 of these patients had received the low-dose BRC treatment (at an average of 2.9 ± 0.3 mg/d). Younger patients < 25 years had a significantly higher rate of persistent hyperprolactinemia after long-term BRC treatment (p = 0.043). Conclusion. DAs are a first-line therapy for IGPs because they can effectively achieve long-term control in both shrinking tumor volume and normalizing the PRL level, and majority of patients need low-dose DA maintenance. Younger patients are prone to persistent hyperprolactinemia despite long-term DA treatment.

Suppression of mTOR pathway and induction of autophagy-dependent cell death by cabergoline.

Cabergoline (CAB), the first-line drug for treatment of prolactinomas, is effective in suppressing prolactin hypersecretion, reducing tumor size, and restoring gonadal function. However, mechanisms for CAB-mediated tumor shrinkage are largely unknown. Here we report a novel cytotoxic mechanism for CAB. CAB induced formation of autophagosome in rat pituitary tumor MMQ and GH3 cells at the early stage through inhibiting mTOR pathway, resulting in higher conversion rates of LC3-I to LC3-II, GFP-LC3 aggregation, and increased autophagosome formation. Interestingly, CAB treatment augmented lysosome acidification and resulted in impaired proteolytic degradation within autolysosomes. This blocked the autophagic flux, leading to the accumulation of p62 aggregation and undigested autolysosomes. Knockdown of ATG7, ATG5, or Becn1, could significantly rescue the CAB-mediated cell death of MMQ cells (p < 0.05). CAB-induced autophagy and blockade of autophagy flux participated in antitumoral action in vivo. In conclusion, our study provides evidence that CAB concomitantly induces autophagy and inhibits the autophagic flux, leading to autophagy-dependent cell death. These findings elucidate novel mechanisms for CAB action.

MicroRNA expression profile of bromocriptine-resistant prolactinomas.

MicroRNAs (miRNA) have been implicated in the resistance of tumors to chemotherapy. However, little is known about miRNA expression in bromocriptine-resistant prolactinomas. In this study, 23 prolactinoma samples were classified as bromocriptine-sensitive or -resistant according to the clinical definition of bromocriptine resistance, and their miRNA expression profiles were determined using Solexa sequencing. We found 41 miRNAs that were differentially expressed between the two groups, and 12 of these were validated by stem-loop qRT-PCR. Hsa-mir-93, hsa-mir-17, hsa-mir-22*, hsa-mir-126*, hsa-mir-142-3p, hsa-mir-144*, hsa-mir-486-5p, hsa-mir-451, and hsa-mir-92a were up-regulated and hsa-mir-30a, hsa-mir-382, and hsa-mir-136 were down-regulated in bromocriptine-resistant prolactinomas in comparison with bromocriptine-sensitive prolactinomas. Furthermore, silencing of mir-93 significantly increased the sensitivity of MMQ cells to dopamine agonist treatment. Mir-93 directly affected p21 expression in MMQ cells by targeting the 3'-UTR. Our study is the first to identify a miRNA expression profile associated with bromocriptine-resistant prolactinoma.

Preoperative assessment using multimodal functional magnetic resonance imaging techniques in patients with brain gliomas.

AIM: To evaluate the value of magnetic resonance spectroscopy (MRS), blood oxygen level-dependent imaging (BOLD) and diffusion tensor imaging (DTI) for preoperative assessment in patients with brain gliomas. MATERIAL AND METHODS: Twenty-three consecutive glioma patients underwent MRS, BOLD and DTI before operation. The characteristics of images were analysed according to histopathological results. RESULTS: There is significant elevation of the choline (Cho) /creatine (Cr) ratio, Cho peak and depression of the N-acetylaspartate (NAA) peak in gliomas. Elevation of the Cho/Cr, Cho/NAA ratio and the presence of a lipids peak, were consistent with high-grade malignancy. A motor activation scan was achieved by using a motor task paradigm in 20 patients. Deformation and displacement of the motor activations was found in 5 cases. The margin of tumor and peritumoural white matter tracts were identified using apparent diffusion coefficient (ADC) and fractional anisotropy (FA) maps. Three patterns of white matter tracts alteration were identified: displacement, infiltration, and disruption. In all 23 patients, the tumors were completely resected in 6 patients, subtotal resected in 8 patients, partial resected in 9 patients. No secondary neurological deficit was occurred in all patients after operation. CONCLUSION: The combination of MRS, BOLD, and DTI techniques allows appropriate presurgical planning of brain gliomas.