PIT1 upregulation by HMGA proteins has a role in pituitary tumorigenesis

SLC20A1 is a prospective prognostic and therapy response predictive biomarker in head and neck squamous cell carcinoma

BACKGROUND

SLC20A1, a prominent biomarker in several cancers, has been understudied in its predictive role in head and neck squamous cell carcinoma (HNSCC).

METHODS

The Cancer Genome Atlas (TCGA) database was used to analyze HNSCC prognosis, SLC20A1 overexpression, and clinical characteristics. Quantitative real-time PCR and Western blot analysis confirmed SLC20A1 expression in HNSCC tissues. Cellular behaviors such as invasion, migration and proliferation were assessed using Transwell, wound healing and colony formation assays. Immune system data were obtained from the Tumor Immune Estimation Resource (TIMER) and CIBERSORT databases. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Gene Set Enrichment Analysis (GSEA) were used to explore biological parameters and pathways associated with SLC20A1 overexpression in HNSCC.

RESULTS

In 499 HNSCC samples, SLC20A1 mRNA and protein expression were significantly higher than in 44 normal counterparts, confirmed by 24 paired samples. Patients were categorized based on SLC20A1 levels, survival status and overall survival. High SLC20A1 expression correlated with advanced T stage, increased risk scores and decreased survival. Stage, age and SLC20A1 expression emerged as independent predictive factors for HNSCC in univariate and multivariate analyses. SLC20A1 overexpression, which is associated with poor prognosis, may influence cell proliferation, migration, invasion, chemotherapy response, and the immune milieu.

CONCLUSIONS

SLC20A1 overexpression in HNSCC, characterized by increased cellular invasion, migration and proliferation, is a potential prognostic biomarker and therapeutic response indicator.

An Overview of Pituitary Neuroendocrine Tumors (PitNET) and Algorithmic Approach to Diagnosis

The diagnostic algorithm and nomenclature of pituitary neuroendocrine tumors have evolved over the past decade, beginning with simpler categorical schemes focused on histomorphologic features and moving to a more sophisticated lineage-specific categorization. This contemporary overview highlights a multimodal approach to pituitary neuroendocrine tumors with a focus on changes in nomenclature, classification, and subclassification; including, brief comments on treatment, and new guidelines for genetic screening, particularly for young patients with such neoplasms.

HMGA1 promotes gastric cancer growth and metastasis by transactivating SUZ12 and CCDC43 expression

HMGA1 protein is an architectural transcription factor that has been implicated in the progression of multiple malignant tumors. However, the role of HMGA1 in the growth and metastasis of gastric cancer (GC) has not yet been elucidated. Here, we show that HMGA1 is overexpressed in GC cells and the high expression of HMGA1 was correlated with worse survival in GC patients using a bioinformatics assay. Functionally, HMGA1 affected the EdU incorporation, colony formation, migration and invasion of GC cells by exogenously increasing or decreasing the expression of HMGA1. Mechanistically, HMGA1 directly bound to the SUZ12 and CCDC43 promoter and transactivated its expression in GC cells. Inhibition of SUZ12 and CCDC43 attenuated the proliferation, migration and invasiveness of HMGA1-overexpressing GC cells in vitro. Moreover, both HMGA1 and SUZ12/CCDC43 were highly expressed in cancer cells but not in normal gastric tissues, and their expressions were positively correlated. Finally, a tail vein metastatic assay showed that HMGA1 promoted SUZ12/CCDC43-mediated GC cell metastasis in vivo. Our findings suggest that HMGA1 promotes GC growth and metastasis by transactivating SUZ12 and CCDC43 expression, highlighting HMGA1 as a potential prognostic biomarker in the treatment of GC.

HMGA1B/2 transcriptionally activated-POU1F1 facilitates gastric carcinoma metastasis via CXCL12/CXCR4 axis-mediated macrophage polarization

Tumor-associated macrophages (TAMs) in the tumor microenvironment contribute to poor prognosis in gastric cancer (GC). However, the underlying mechanism by which TAMs promote GC progression and metastasis remains elusive. Expression of POU1F1 was detected in 60 matched GC-normal tissue pairs using qRT-PCR and immunohistochemistry (IHC) analysis. The correlation between POU1F1 and the clinical-pathological factors of GC patients were further assessed. Cell proliferation was monitored by CCK-8, colony formation, and 5-Ethynyl-2'-deoxyuridine (EdU) incorporation assays. Cell migration and invasion were assessed by transwell assays. The impact on angiogenesis was evaluated by tube formation assay. Xenograft model was generated to investigate the role of POU1F1 on tumor growth and lung metastasis in vivo. GST pull-down and Co-immunoprecipitation (Co-IP) were used to study the interaction between HMGA1B/2 and POU1F1. Chromatin immunoprecipitation (ChIP) and dual luciferase reporter assays were performed to investigate the transcriptional regulation of POU1F1. Flow cytometry was performed to detect the surface expression of macrophage markers. Upregulated POU1F1 observed both in GC tissues and cell lines was positively correlated with poor prognosis. Knockdown of POU1F1 inhibited cell proliferation, migration, invasion, and angiogenesis in vitro, and suppressed tumor growth in vivo. HMGA1B/2 transcriptionally activated-POU1F1. POU1F1 promoted GC progression via regulating macrophage proliferation, migration, polarization, and angiogenesis in a CXCL12/CXCR4-dependent manner. POU1F1 also promoted GC metastasis in lung by modulating macrophage polarization through CXCL12/CXCR4 axis in vivo. HMGA1B/2-upregulated POU1F1 promoted GC metastasis via regulating macrophage polarization in a CXCL12/CXCR4-dependent manner.

Loss of CBX2 induces genome instability and senescence-associated chromosomal rearrangements

The polycomb group protein CBX2 is an important epigenetic reader involved in cell proliferation and differentiation. While CBX2 overexpression occurs in a wide range of human tumors, targeted deletion results in homeotic transformation, proliferative defects, and premature senescence. However, its cellular function(s) and whether it plays a role in maintenance of genome stability remain to be determined. Here, we demonstrate that loss of CBX2 in mouse fibroblasts induces abnormal large-scale chromatin structure and chromosome instability. Integrative transcriptome analysis and ATAC-seq revealed a significant dysregulation of transcripts involved in DNA repair, chromocenter formation, and tumorigenesis in addition to changes in chromatin accessibility of genes involved in lateral sclerosis, basal transcription factors, and folate metabolism. Notably, Cbx2^−/− cells exhibit prominent decondensation of satellite DNA sequences at metaphase and increased sister chromatid recombination events leading to rampant chromosome instability. The presence of extensive centromere and telomere defects suggests a prominent role for CBX2 in heterochromatin homeostasis and the regulation of nuclear architecture.

MEG3/MIR-376B-3P/HMGA2 axis is involved in pituitary tumor invasiveness

OBJECTIVE

To date, long noncoding RNAs (lncRNAs) have proven to function as key regulators in tumorigenesis. Among these lncRNAs, MEG3 displays low levels in various neoplasms and tumor cell lines. However, the regulatory mechanism of MEG3 and MIR-376B-3P, one of the microRNAs from downstream gene clusters of the DLK1-MEG3 locus, remains insufficiently defined.

METHODS

The authors used quantitative real-time polymerase chain reaction analysis to analyze whether decreased MEG3 and MIR-376B-3P expression levels were associated with the invasiveness of clinical nonfunctioning pituitary adenomas (CNFPAs) in 30 patients. Furthermore, functional experiments unveiled the pathophysiological role of MEG3, MIR-376B-3P, and HMGA2 in pituitary-derived folliculostellate (PDFS) cell lines. Moreover, dual-luciferase reporter assay, Western blot analysis, and immunofluorescence were applied to reveal the correlations among MEG3, MIR-376B-3P, and HMGA2.

RESULTS

MEG3 and MIR-376B-3P were decreased in patients with CNFPA, and their transcriptional levels were highly associated with invasive CNFPAs. Moreover, excessive expression of MEG3 and MIR-376B-3P inhibited tumorigenesis and promoted apoptosis in PDFS cells. Importantly, the authors found that MEG3 acted as an enhancer of MIR-376B-3P expression. Furthermore, as a target gene of MIR-376B-3P, HMGA2 served as an oncogene in pituitary adenoma and could be negatively regulated by MEG3 via enriching MIR-376B-3P.

CONCLUSIONS

This study offers a novel mechanism of an MEG3/MIR-376B-3P/HMGA2 regulatory network in CNFPAs, which may become a breakthrough for anticancer treatments.

Targeting the intrinsically disordered architectural High Mobility Group A (HMGA) oncoproteins in breast cancer: learning from the past to design future strategies

INTRODUCTION

Triple-negative breast cancer (TNBC) is the most difficult breast cancer subtype to treat because of its heterogeneity and lack of specific therapeutic targets. High Mobility Group A (HMGA) proteins are chromatin architectural factors that have multiple oncogenic functions in breast cancer, and they represent promising molecular therapeutic targets for this disease.

AREAS COVERED

We offer an overview of the strategies that have been exploited to counteract HMGA oncoprotein activities at the transcriptional and post-transcriptional levels. We also present the possibility of targeting cancer-associated factors that lie downstream of HMGA proteins and discuss the contribution of HMGA proteins to chemoresistance.

EXPERT OPINION

Different strategies have been exploited to counteract HMGA protein activities; these involve interfering with their nucleic acid binding properties and the blocking of HMGA expression. Some approaches have provided promising results. However, some unique characteristics of the HMGA proteins have not been exploited; these include their extensive protein-protein interaction network and their intrinsically disordered status that present the possibility that HMGA proteins could be involved in the formation of proteinaceous membrane-less organelles (PMLO) by liquid-liquid phase separation. These unexplored characteristics could open new pharmacological avenues to counteract the oncogenic contributions of HMGA proteins.

HMGA and Cancer: A Review on Patent Literatures

BACKGROUND

The high mobility group A proteins modulate the transcription of numerous genes by interacting with transcription factors and/or altering the structure of chromatin. These proteins are involved in both benign and malignant neoplasias as a result of several pathways. A large amount of benign human mesenchymal tumors has rearrangements of HMGA genes. On the contrary, malignant tumors show unarranged HMGA overexpression that is frequently and causally related to neoplastic cell transformation. Here, we review the function of the HMGA proteins in human neoplastic disorders, the pathways by which they contribute to carcinogenesis and the new patents focused on targeting HMGA proteins.

OBJECTIVE

Current review was conducted to check the involvement of HMGA as a druggable target in cancer treatment.

METHODS

We reviewed the most recent patents focused on targeting HMGA in cancer treatment analyzing patent literature published during the last years, including the World Intellectual Property Organization (WIPO®), United States Patent Trademark Office (USPTO®), Espacenet®, and Google Patents.

RESULTS

HMGA proteins are intriguing targets for cancer therapy and are objects of different patents based on the use of DNA aptamers, inhibitors, oncolytic viruses, antisense molecules able to block their oncogenic functions.

CONCLUSION

Powerful strategies able to selectively interfere with HMGA expression and function could represent a helpful approach in the development of new anti-cancer therapies.

HMGA1-Regulating microRNAs Let-7a and miR-26a are Downregulated in Human Seminomas

Background: Recent studies have underlined HMGA protein’s key role in the onset of testicular germ cell tumors, where HMGA1 is differently expressed with respect to the state of differentiation, suggesting its fine regulation as master regulator in testicular tumorigenesis. Several studies have highlighted that the HMGA1 transcript is strictly regulated by a set of inhibitory microRNAs. Thus, the aim of this study is to test whether HMGA1 overexpression in human seminomas may be induced by the deregulation of miR-26a and Let-7a—two HMGA1-targeting microRNAs. Methods: HMGA1 mRNA and Let-7a and miR-26a levels were measured in a seminoma dataset available in the Cancer Genome Atlas database and confirmed in a subset of seminomas by qRT-PCR and western blot. A TCam-2 seminoma cell line was then transfected with Let-7a and miR-26a and tested for proliferation and motility abilities. Results: an inverse correlation was found between the expression of miR-26a and Let-7a and HMGA1 expression levels in seminomas samples, suggesting a critical role of these microRNAs in HMGA1 levels regulation. Accordingly, functional studies showed that miR-26a and Let-7a inhibited the proliferation, migration and invasion capabilities of the human seminoma derived cell line TCam-2. Conclusions: these data strongly support that the upregulation of HMGA1 levels occurring in seminoma is—at least in part—due to the downregulation of HMGA1-targeting microRNAs.

Genetic and Epigenetic Causes of Pituitary Adenomas

Pituitary adenomas (PAs) can be classified as non-secreting adenomas, somatotroph adenomas, corticotroph adenomas, lactotroph adenomas, and thyrotroph adenomas. Substantial advances have been made in our knowledge of the pathobiology of PAs. To obtain a comprehensive understanding of the molecular biological characteristics of different types of PAs, we reviewed the important advances that have been made involving genetic and epigenetic variation, comprising genetic mutations, chromosome number variations, DNA methylation, microRNA regulation, and transcription factor regulation. Classical tumor predisposition syndromes include multiple endocrine neoplasia type 1 (MEN1) and type 4 (MEN4) syndromes, Carney complex, and X-LAG syndromes. PAs have also been described in association with succinate dehydrogenase-related familial PA, neurofibromatosis type 1, and von Hippel-Lindau, DICER1, and Lynch syndromes. Patients with aryl hydrocarbon receptor-interacting protein (AIP) mutations often present with pituitary gigantism, either in familial or sporadic adenomas. In contrast, guanine nucleotide-binding protein G(s) subunit alpha (GNAS) and G protein-coupled receptor 101 (GPR101) mutations can lead to excess growth hormone. Moreover, the deubiquitinase gene USP8, USP48, and BRAF mutations are associated with adrenocorticotropic hormone production. In this review, we describe the genetic and epigenetic landscape of PAs and summarize novel insights into the regulation of pituitary tumorigenesis.

Emerging Role of USP8, HMGA, and Non-Coding RNAs in Pituitary Tumorigenesis

Two novel molecular mechanisms with a driver role in pituitary tumorigenesis have been recently identified. They are (a) mutations in the Ubiquitin-Specific Protease 8 (USP8) gene in corticotroph tumors and (b) overexpression of the HMGA1 and HMGA2 genes in most of the pituitary tumors. Moreover, deregulated expression of the non-coding RNAs has been very frequently observed in this neoplasia. The aim of this review is to better elucidate the role, the mechanisms, and the possible clinical impact of these novel alterations in the development of pituitary neoplasia.

The HMGA1 Pseudogene 7 Induces miR-483 and miR-675 Upregulation by Activating Egr1 through a ceRNA Mechanism

Several studies have established that pseudogene mRNAs can work as competing endogenous RNAs and, when deregulated, play a key role in the onset of human neoplasias. Recently, we have isolated two HMGA1 pseudogenes, HMGA1P6 and HMGA1P7. These pseudogenes have a critical role in cancer progression, acting as micro RNA (miRNA) sponges for HMGA1 and other cancer-related genes. HMGA1 pseudogenes were found overexpressed in several human carcinomas, and their expression levels positively correlate with an advanced cancer stage and a poor prognosis. In order to investigate the molecular alterations following HMGA1 pseudogene 7 overexpression, we carried out miRNA sequencing analysis on HMGA1P7 overexpressing mouse embryonic fibroblasts. Intriguingly, the most upregulated miRNAs were miR-483 and miR-675 that have been described as key regulators in cancer progression. Here, we report that HMGA1P7 upregulates miR-483 and miR-675 through a competing endogenous RNA mechanism with Egr1, a transcriptional factor that positively regulates miR-483 and miR-675 expression.

Genetic Aspects of Pituitary Adenomas

Although most of pituitary adenomas are benign, they may cause significant burden to patients. Sporadic adenomas represent the vast majority of the cases, where recognized somatic mutations (eg, GNAS or USP8), as well as altered gene-expression profile often affecting cell cycle proteins have been identified. More rarely, germline mutations predisposing to pituitary adenomas -as part of a syndrome (eg, MEN1 or Carney complex), or isolated to the pituitary (AIP or GPR101) can be identified. These alterations influence the biological behavior, clinical presentations and therapeutic responses, and their full understanding helps to provide appropriate care for these patients.

Over-Expression of POU Class 1 Homeobox 1 Transcription Factor (Pit-1) Predicts Poor Prognosis for Breast Cancer Patients

Background

The POU class 1 homeobox 1 transcription factor (POU1F1, also known as Pit-1) was reported to be associated with tumor progression and metastasis. The purpose of this study was to evaluate the prognostic value of Pit-1 in breast cancer patients.

Material/Methods

The relative expression levels of Pit-1 in breast cancer patients were detected by quantitative real-time PCR (qRT-PCR). Chi-square analysis was used to analyze the association between Pit-1 expression and clinical features. The Kaplan-Meier method was used to estimate the overall survival of the patients and Cox regression analysis was used to analyze the prognostic value of Pit-1.

Results

Increased expression of Pit-1 was detected in the tumor tissues compared with the normal tissues (1.086 vs. 0.541) and the abnormal expression was associated with tumor size, clinical stage, tumor grade, and lymph node metastasis (P<0.05). High expression level of Pit-1 was significantly associated with poor overall survival of the patients (P=0.001) and Cox regression analysis indicated that Pit-1 might be a prognostic factor for breast cancer prognosis (HR=1.955, 95% CI=1.295–3.035, P=0.003).

Conclusions

Pit-1 may be a potential prognostic biomarker for breast cancer patients and it is associated with tumor progression.

HMGA1-pseudogene expression is induced in human pituitary tumors

Numerous studies have established that High Mobility Group A (HMGA) proteins play a pivotal role on the onset of human pituitary tumors. They are overexpressed in pituitary tumors, and, consistently, transgenic mice overexpressing either the Hmga1 or the Hmga2 gene develop pituitary tumors. In contrast with HMGA2, HMGA1 overexpression is not related to any rearrangement or amplification of the HMGA1 locus in these tumors. We have recently identified 2 HMGA1 pseudogenes, HMGA1P6 and HMGA1P7, acting as competitive endogenous RNA decoys for HMGA1 and other cancer related genes. Here, we show that HMGA1 pseudogene expression significantly correlates with HMGA1 mRNA levels in growth hormone and nonfunctioning pituitary adenomas likely inhibiting the repression of HMGA1 through microRNAs action. According to our functional studies, these HMGA1 pseudogenes enhance the proliferation and migration of the mouse pituitary tumor cell line, at least in part, through their upregulation. Our results point out that the overexpression of HMGA1P6 and HMGA1P7 could contribute to increase HMGA1 levels in human pituitary tumors, and then to pituitary tumorigenesis.

Pituitary adenomas: historical perspective, surgical management and future directions

Pituitary adenomas are among the most common central nervous system tumors. They represent a diverse group of neoplasms that may or may not secrete hormones based on their cell of origin. Epidemiologic studies have documented the incidence of pituitary adenomas within the general population to be as high as 16.7%. A growing body of work has helped to elucidate the pathogenesis of these tumors. Each subtype has been shown to demonstrate unique cellular changes potentially leading to tumorigenesis. Surgical advancements over several decades have included microsurgery and the employment of the endoscope for surgical resection. These advancements increase the likelihood of gross-total resection and have resulted in decreased patient morbidity.

HMGA1-pseudogene overexpression contributes to cancer progression

Two pseudogenes for HMGA1, whose overexpression has a critical role in cancer progression, have been identified. They act as decoy for miRNAs that are able to target the HMGA1 gene then enhancing cell proliferation and migration. Moreover, these pseudogenes contain sequences that are potential target sites for cancer-related miRNAs. Interestingly, HMGA1 pseudogenes are highly expressed in human anaplastic thyroid carcinomas, that is one of the most aggressive tumor in mankind, but almost undetectable in well differentiated thyroid carcinomas.

HMGA1 pseudogenes as candidate proto-oncogenic competitive endogenous RNAs

The High Mobility Group A (HMGA) are nuclear proteins that participate in the organization of nucleoprotein complexes involved in chromatin structure, replication and gene transcription. HMGA overexpression is a feature of human cancer and plays a causal role in cell transformation. Since non-coding RNAs and pseudogenes are now recognized to be important in physiology and disease, we investigated HMGA1 pseudogenes in cancer settings using bioinformatics analysis. Here we report the identification and characterization of two HMGA1 non-coding pseudogenes, HMGA1P6 and HMGA1P7. We show that their overexpression increases the levels of HMGA1 and other cancer-related proteins by inhibiting the suppression of their synthesis mediated by microRNAs. Consistently, embryonic fibroblasts from HMGA1P7-overexpressing transgenic mice displayed a higher growth rate and reduced susceptibility to senescence. Moreover, HMGA1P6 and HMGA1P7 were overexpressed in human anaplastic thyroid carcinomas, which are highly aggressive, but not in differentiated papillary carcinomas, which are less aggressive. Lastly, the expression of the HMGA1 pseudogenes was significantly correlated with HMGA1 protein levels thereby implicating HMGA1P overexpression in cancer progression. In conclusion, HMGA1P6 and HMGA1P7 are potential proto-oncogenic competitive endogenous RNAs.

Epigenetic Mechanisms Leading to Overexpression of HMGA Proteins in Human Pituitary Adenomas

Overexpression of the high-mobility group A (HMGA)1 and HMGA2 proteins is a feature of all human pituitary adenoma (PAs) subtypes. However, amplification and/or rearrangement of the HMGA2 have been described in human prolactinomas, but rarely in other pituitary subtypes, and no genomic amplification of HMGA1 was detected in PAs. Here, we summarize the functional role of HMGA proteins in pituitary tumorigenesis and the epigenetic mechanisms contributing to HMGA overexpression in these tumors focusing on recent studies indicating a critical role of non-coding RNAs in modulating HMGA protein levels.

Somatotropinomas, but not nonfunctioning pituitary adenomas, maintain a functional apoptotic RET/Pit1/ARF/p53 pathway that is blocked by excess GDNF

Acromegaly is caused by somatotroph cell adenomas (somatotropinomas [ACROs]), which secrete GH. Human and rodent somatotroph cells express the RET receptor. In rodents, when normal somatotrophs are deprived of the RET ligand, GDNF (Glial Cell Derived Neurotrophic Factor), RET is processed intracellularly to induce overexpression of Pit1 [Transcription factor (gene : POUF1) essential for transcription of Pituitary hormones GH, PRL and TSHb], which in turn leads to p19Arf/p53-dependent apoptosis. Our purpose was to ascertain whether human ACROs maintain the RET/Pit1/p14ARF/p53/apoptosis pathway, relative to nonfunctioning pituitary adenomas (NFPAs). Apoptosis in the absence and presence of GDNF was studied in primary cultures of 8 ACROs and 3 NFPAs. Parallel protein extracts were analyzed for expression of RET, Pit1, p19Arf, p53, and phospho-Akt. When GDNF deprived, ACRO cells, but not NFPAs, presented marked level of apoptosis that was prevented in the presence of GDNF. Apoptosis was accompanied by RET processing, Pit1 accumulation, and p14ARF and p53 induction. GDNF prevented all these effects via activation of phospho-AKT. Overexpression of human Pit1 (hPit1) directly induced p19Arf/p53 and apoptosis in a pituitary cell line. Using in silico studies, 2 CCAAT/enhancer binding protein alpha (cEBPα) consensus-binding sites were found to be 100% conserved in mouse, rat, and hPit1 promoters. Deletion of 1 cEBPα site prevented the RET-induced increase in hPit1 promoter expression. TaqMan qRT-PCR (real time RT-PCR) for RET, Pit1, Arf, TP53, GDNF, steroidogenic factor 1, and GH was performed in RNA from whole ACRO and NFPA tumors. ACRO but not NFPA adenomas express RET and Pit1. GDNF expression in the tumors was positively correlated with RET and negatively correlated with p53. In conclusion, ACROs maintain an active RET/Pit1/p14Arf/p53/apoptosis pathway that is inhibited by GDNF. Disruption of GDNF's survival function might constitute a new therapeutic route in acromegaly.

Epidemiology and etiopathogenesis of pituitary adenomas

Pituitary adenomas are usually benign monoclonal tumours presenting either due to hypersecretion of pituitary hormones, and/or due to local space occupying effects and hyposecretion of some or all of the pituitary hormones. Some pituitary adenomas cause prominent symptoms, while others may result in slowly developing, insidious, non-specific complains delaying accurate diagnosis, with a third group remaining symptomless and recognised only incidentally. Therefore, it is a challenge to accurately determine the prevalence and incidence of pituitary adenomas in the general population. The vast majority of pituitary adenomas occur sporadically, but familial cases are now increasingly recognised. Hereditary predisposition, somatic mutations and endocrine factors were shown to have a pathophysiologic role in the initiation and progression of pituitary adenomas, which interestingly almost always remain benign. Here, we summarize the available epidemiological data and the known pathogenesis of the pituitary adenomas.

The molecular pathogenesis of pituitary adenomas: an update

Pituitary tumors represent the most common intracranial neoplasms accompanying serious morbidity through mass effects and inappropriate secretion of pituitary hormones. Understanding the etiology of pituitary tumorigenesis will facilitate the development of satisfactory treatment for pituitary adenomas. Although the pathogenesis of pituitary adenomas is largely unknown, considerable evidence indicates that the pituitary tumorigenesis is a complex process involving multiple factors, including genetic and epigenetic changes. This review summarized the recent progress in the study of pituitary tumorigenesis, focusing on the role of tumor suppressor genes, oncogenes and microRNAs.

Transgenesis-mediated reproductive dysfunction and tumorigenesis: effects of immunological neutralization

Human chorionic gonadotropin (hCG) was initially thought to be made only during pregnancy, but is now known to also be synthesized by a variety of cancers and is associated with poor patient prognosis. Transgenic expression of βhCG in mice causes hyper-luteinized ovaries, a loss in estrous cyclicity and infertility, increased body weight, prolactinomas and mammary gland tumors. Strategies were devised to generate antibody responses against hCG to investigate whether reversal of the molecular processes driving tumorigenesis would follow. hCG-immunized transgenic mice did not exhibit increases in body weight or serum prolactin levels, and gross ovarian and pituitary morphology remained normal. While non-immunized transgenic animals demonstrated heightened levels of transcripts associated with pituitary tumorigenesis (HMG2A, E2F1, CCND1, PRL, GH, GAL, PTTG1, BMP4) and decreased levels of CDK inhibitors CDKN1B (p27), CDKN2A (p16) and CDKN2c (p18), immunization led to a reversal to levels found in non-transgenic animals. Serum derived from transgenic (but not non-transgenic) mice led to enhanced transcription as well as expression of VEGF, IL-8, KC (murine IL-8) and MMP-9 in tumor cells, effects not seen when sera derived from hCG-immunized transgenic mice was employed. As the definitive indication of the restoration of the reproductive axis, immunization led to the resumption of estrous cyclicity as well as fertility in transgenic mice. These results indicate that hCG may influence cancer pathogenesis and progression via several distinct mechanisms. Using a stringent in vivo system in which βhCG acts both a “self” antigen and a tumor-promoting moiety (putatively akin to the situation in humans), the data builds a case for anti-gonadotropin vaccination strategies in the treatment of gonadotropin-dependent or secreting malignancies that frequently acquire resistance to conventional therapy.