GSPalpha mutations in Mexican patients with acromegaly: potential impact on long term prognosis

The molecular biology of sporadic acromegaly

GH-secreting tumors represent 15 % to 20 % of all pituitary neuroendocrine tumors (pitNETs), of which 95 % occur in a sporadic context, without an identifiable inherited cause. Recent multi-omic approaches have characterized the epigenomic, genomic, transcriptomic, proteomic and kynomic landscape of pituitary tumors. Transcriptomic analysis has allowed us to discover specific transcription factors driving the differentiation of pituitary tumors and gene expression patterns. GH-secreting, along with PRL- and TSH-secreting pitNETs are driven by POU1F1; ACTH-secreting tumors are determined by TBX19; and non-functioning tumors, which are predominantly of gonadotrope differentiation are conditioned by NR5A1. Upregulation of certain miRNAs, such as miR-107, is associated with tumor progression, while downregulation of others, like miR-15a and miR-16-1, correlates with tumor size reduction. Additionally, miRNA expression profiles are linked to treatment resistance and clinical outcomes, providing insights into potential therapeutic targets. Specific somatic mutations in GNAS, PTTG1, GIPR, HGMA2, MAST and somatic variants associated with cAMP, calcium signaling, and ATP pathways have also been associated with the development of acromegaly. This review focuses on the oncogenic mechanisms by which sporadic acromegaly can develop, covering a complex series of molecular alterations that ultimately alter the balance between proliferation and apoptosis, and dysregulated hormonal secretion.

Genetic diagnosis in acromegaly and gigantism: From research to clinical practice

It is usually considered that only 5% of all pituitary neuroendocrine tumours are due to inheritable causes. Since this estimate was reported, however, multiple genetic defects driving syndromic and nonsyndromic somatotrophinomas have been unveiled. This heterogeneous genetic background results in overlapping phenotypes of GH excess. Genetic tests should be part of the approach to patients with acromegaly and gigantism because they can refine the clinical diagnoses, opening the possibility to tailor the clinical conduct to each patient. Even more, genetic testing and clinical screening of at-risk individuals have a positive impact on disease outcomes, by allowing for the timely detection and treatment of somatotrophinomas at early stages. Future research should focus on determining the actual frequency of novel genetic drivers of somatotrophinomas in the general population, developing up-to-date disease-specific multi-gene panels for clinical use, and finding strategies to improve access to modern genetic testing worldwide.

The hallmarks of cancer… in pituitary tumors?

Over 20 years ago, Hanahan and Weinberg published a seminal review that addressed the biological processes that underly malignant transformation. This classical review, along with two revisions published in 2011 and 2022, has remain a classic of the oncology literature. Since many of the addressed biological processes may apply to non-malignant tumorigenesis, we evaluated to what extent these hallmarks pertain to the development of pituitary adenomas.Some of the biological processes analyzed in this review include genome instability generated by somatic USP8 and GNAS mutations in Cushing's diseases and acromegaly respectively; non-mutational epigenetic reprograming through changes in methylation; induction of angiogenesis through alterations of VEGF gene expression; promotion of proliferative signals mediated by EGFR; evasion of growth suppression by disrupting cyclin dependent kinase inhibitors; avoidance of immune destruction; and the promotion of inflammation mediated by alteration of gene expression of immune check points. We also elaborate further on the existence of oncogene induced senescence in pituitary tumors. We conclude that a better understanding of these processes can help us dilucidated why pituitary tumors are so resistant to malignant transformation and can potentially contribute to the development of novel anticancer treatments.

Disease Modeling of Pituitary Adenoma Using Human Pluripotent Stem Cells

Simple Summary

Pituitary adenoma pathophysiology has been studied mainly using murine cell lines, animal models, and pituitary tumor samples. However, the lack of human pituitary cell line is a significant limiting factor in studying the molecular mechanisms of human pituitary tumors. Recently, pituitary induction methods from human-induced pluripotent stem cells (hiPSCs) have been established. These methods can induce human pituitary hormone-producing cells that retain physiological properties. hiPSCs in which tumor-causing gene mutations are introduced using genome-editing techniques, such as CRISPR/Cas9 systems, provide great opportunities to establish in vitro human pituitary adenoma disease models. The models will be a novel platform to discover novel drugs and investigate tumorigenesis and pathophysiology. The purpose of this review is to provide an overview of the applications of iPSCs for pituitary and neoplastic disorder research and genome-editing technologies to create strategies for developing pituitary adenoma models using iPSCs.

Abstract

Pituitary adenomas are characterized by abnormal growth in the pituitary gland. Surgical excision is the first-line treatment for functional (hormone-producing) pituitary adenomas, except for prolactin-producing adenomas; however, complete excision is technically challenging, and many patients require long-term medication after the treatment. In addition, the pathophysiology of pituitary adenomas, such as tumorigenesis, has not been fully understood. Pituitary adenoma pathophysiology has mainly been studied using animal models and animal tumor-derived cell lines. Nevertheless, experimental studies on human pituitary adenomas are difficult because of the significant differences among species and the lack of reliable cell lines. Recently, several methods have been established to differentiate pituitary cells from human pluripotent stem cells (hPSCs). The induced pituitary hormone-producing cells retain the physiological properties already lost in tumor-derived cell lines. Moreover, CRISPR/Cas9 systems have expedited the introduction of causative gene mutations in various malignant tumors into hPSCs. Therefore, hPSC-derived pituitary cells have great potential as a novel platform for studying the pathophysiology of human-specific pituitary adenomas and developing novel drugs. This review presents an overview of the recent progresses in hPSC applications for pituitary research, functional pituitary adenoma pathogenesis, and genome-editing techniques for introducing causative mutations. We also discuss future applications of hPSCs for studying pituitary adenomas.

GH/PRL-secreting pituitary macroadenoma associated with GNAS p.Gln227Leu mutation: pediatric case report and review

GH-secreting pituitary adenomas (GHomas) are rare in the pediatric population. Guanine nucleotide-binding protein, alpha stimulating (GNAS) somatic mutations are often found in patients with GHoma. Here, we report an 8-year-old girl with GH-secreting pituitary adenoma successfully treated by operative tumor resection and postoperative treatment with octreotide long-acting release (LAR). Tumor DNA sequence analysis revealed a somatic heterozygous c.680A>T (p.Gln227Leu) mutation in GNAS. We reviewed 1,084 cases of GHomas, 409 (37.7%) of which harbored GNAS mutations. In pediatrics cases, aged 15 years or younger, 11 harbored a GNAS mutation, and GNAS p.Arg201Cys was identified in five cases. No other cases of codon 227 mutation were detected. These cases suggest that, in pediatric patients, the clinical features of GHoma may differ from those observed in adults. This is possibly related to octreotide or dopamine agonist resistance. Of six patients with surgical resistance, only one was reactive when treated with octreotide. Our case shows that octreotide LAR is an effective choice for treating GNAS-induced GHoma. This is the first report detailing the effectiveness of octreotide LAR in a GNAS codon 227 mutation-induced GHoma in a pediatric case. Examination of the relationship between genetic variation and clinical features in pediatric patients will enable us to assess the long-term effects of surgical and medical treatment of GHomas.

Study of major genetic factors involved in pituitary tumorigenesis and their impact on clinical and biological characteristics of sporadic somatotropinomas and non-functioning pituitary adenomas

Genetic and functional aberrations of guanine nucleotide-binding protein, alpha stimulating (GNAS), aryl hydrocarbon receptor interacting protein (AIP), and pituitary tumor transforming gene (PTTG) are among the most prominent events in pituitary tumorigenesis. A cohort of Brazilian patients with somatotropinomas (n=41) and non-functioning pituitary adenomas (NFPA, n=21) from a single tertiary-referral center were evaluated for GNAS and AIP mutations and gene expression of AIP and PTTG. Results were compared to the clinical and biological (Ki67 and p53 expression) characteristics of tumors and their response to therapy, if applicable. Genetic analysis revealed that 27% of somatotropinomas and 4.8% of NFPA harbored GNAS mutations (P=0.05). However, no differences were observed in clinical characteristics, tumor extension, response to somatostatin analog therapy, hormonal/surgical remission rates, Ki67 index, and p53 expression between mutated and non-mutated somatotropinomas patients. PTTG overexpression (RQ mean=10.6, min=4.39, max=11.9) and AIP underexpression (RQ mean=0.56, min=0.46-max=0.92) were found in virtually all cases without a statistically significant relationship with clinical and biological tumor features. No patients exhibited somatic or germline pathogenic AIP mutations. In conclusion, mutations in GNAS and abnormal PTTG and AIP expression had no impact on tumor features and treatment outcomes in this cohort. Our data support some previous studies and point to the need for further investigations, probably involving epigenetic and transcriptome analysis, to improve our understanding of pituitary tumor behavior.

The curious case of Gαs gain-of-function in neoplasia

BACKGROUND

Mutations activating the α subunit of heterotrimeric Gs protein are associated with a number of highly specific pathological molecular phenotypes. One of the best characterized is the McCune Albright syndrome. The disease presents with an increased incidence of neoplasias in specific tissues.

MAIN BODY

A similar repertoire of neoplasms can develop whether mutations occur spontaneously in somatic tissues during fetal development or after birth. Glands are the most "permissive" tissues, recently found to include the entire gastrointestinal tract. High frequency of activating Gαs mutations is associated with precise diagnoses (e.g., IPMN, Pyloric gland adenoma, pituitary toxic adenoma). Typically, most neoplastic lesions, from thyroid to pancreas, remain well differentiated but may be a precursor to aggressive cancer.

CONCLUSIONS

Here we propose the possibility that gain-of-function mutations of Gαs interfere with signals in the microenvironment of permissive tissues and lead to a transversal neoplastic phenotype.

Impact of gsp mutations in somatotroph pituitary adenomas on growth hormone response to somatostatin analogs: a meta-analysis

OBJECTIVE

Somatic mutations in the GNAS1 gene, which encodes the alpha-subunit of G stimulatory proteins (gsp), are frequently detected in somatotroph pituitary tumors and have been associated to specific clinical and histopathological characteristics. However, the question whether the presence of a somatic gsp mutation affects the response to somatostatin analog treatment remains unresolved.

DESIGN

Following a literature search, we performed a meta-analysis, including 8 eligible studies, in order to estimate the effect of gsp mutation on the percent reduction of growth hormone (GH) levels during an acute octreotide suppression test (OST). A total of 310 patients with acromegaly [126 gsp (+) and 184 gsp (-)] were included in the analysis.

RESULTS

The presence of the gsp mutation was related with a greater reduction in GH levels on OST [Weighted Mean Difference (WMD): 9.08 % (95 % CI, 2.73, 15.42); p = 0.005; random effects model]. There was significant heterogeneity for this effect estimate (I(2) = 58 %, p value for heterogeneity = 0.02). A sensitivity analysis after exclusion of a study with different methodology of OST provided similar estimates [WMD: 6.93 % (95 % CI, 1.40, 12.46); p = 0.01], albeit with no significant heterogeneity (I(2) = 35 %, p value for heterogeneity = 0.16).

CONCLUSIONS

The present meta-analysis suggests a role for gsp mutation as a prognostic factor of treatment response to somatostatin analogs.

Landscape of Familial Isolated and Young-Onset Pituitary Adenomas: Prospective Diagnosis in AIP Mutation Carriers

CONTEXT

Familial isolated pituitary adenoma (FIPA) due to aryl hydrocarbon receptor interacting protein (AIP) gene mutations is an autosomal dominant disease with incomplete penetrance. Clinical screening of apparently unaffected AIP mutation (AIPmut) carriers could identify previously unrecognized disease.

OBJECTIVE

To determine the AIP mutational status of FIPA and young pituitary adenoma patients, analyzing their clinical characteristics, and to perform clinical screening of apparently unaffected AIPmut carrier family members.

DESIGN

This was an observational, longitudinal study conducted over 7 years.

SETTING

International collaborative study conducted at referral centers for pituitary diseases.

PARTICIPANTS

FIPA families (n 216) and sporadic young-onset (30 y) pituitary adenoma patients (n 404) participated in the study.

INTERVENTIONS

We performed genetic screening of patients for AIPmuts, clinical assessment of their family members, and genetic screening for somatic GNAS1 mutations and the germline FGFR4 p.G388R variant.

MAIN OUTCOME MEASURE(S)

We assessed clinical disease in mutation carriers, comparison of characteristics of AIPmut positive and negative patients, results of GNAS1, and FGFR4 analysis.

RESULTS

Thirty-seven FIPA families and 34 sporadic patients had AIPmuts. Patients with truncating AIPmuts had a younger age at disease onset and diagnosis, compared with patients with nontruncating AIPmuts. Somatic GNAS1 mutations were absent in tumors from AIPmut-positive patients, and the studied FGFR4 variant did not modify the disease behavior or penetrance in AIPmut-positive individuals. A total of 164 AIPmut-positive unaffected family members were identified; pituitary disease was detected in 18 of those who underwent clinical screening.

CONCLUSIONS

A quarter of the AIPmut carriers screened were diagnosed with pituitary disease, justifying this screening and suggesting a variable clinical course for AIPmut-positive pituitary adenomas.

Granulation pattern, but not GSP or GHR mutation, is associated with clinical characteristics in somatostatin-naive patients with somatotroph adenomas

OBJECTIVE

Somatotroph adenomas causing acromegaly are histologically classified into densely granulated (DG) and sparsely granulated (SG) subtypes with different morphology, clinical characteristics and treatment outcomes. Granulation pattern has been reported to co-segregate with a recurrent mutation at codon 49 in growth hormone receptor (GHR) and GSP oncogene. This study examines response to the octreotide suppression test (OST) in relation to granulation pattern and mutation in GHR and GSP.

DESIGN

This is a retrospective, single-centre study of 52 patients with pathologically confirmed somatotroph adenoma who were naïve to medical therapy presenting between January 2001 and October 2010.

METHODS

Clinical, radiological and hormonal data at diagnosis were recorded. GHR and GSP were genotyped, granulation pattern determined and response to the OST measured.

RESULTS

SG adenomas were larger (P=0.038), occurred in younger patients (P=0.029), were more common in females (P=0.026) and were more invasive (P<0.0001 and P=0.001), with diminished responses to the OST (P=0.007) compared with DG adenomas. GSP mutation was unrelated to granulation pattern but associated with smaller tumours (P=0.027), producing more GH (P=0.048) that responded better to the OST (P=0.022). Codon 49 of GHR was not mutated.

CONCLUSIONS

Adenoma histological phenotype, not genotype, corresponds to clinical and biochemical characteristics and response to the OST. SG adenomas constitute a clinically more unfavourable subtype but are not associated with GHR mutations in our series. Ascertainment of the adenoma subtype may become an important consideration in the management of acromegaly.

Adenoma granulation pattern correlates with clinical variables and effect of somatostatin analogue treatment in a large series of patients with acromegaly

CONTEXT

Somatotroph adenomas have been classified into densely granulated (DG) and sparsely granulated (SG) tumours with a transitional, intermediate group. Gsp oncogenes are activating mutations in the Gsα subunit gene, found in approximately 40% of somatotroph adenomas.

OBJECTIVES

To explore granulation pattern and presence of gsp oncogene in acromegaly with correlations to clinical and biochemical variables and to the effect of treatment with somatostatin analogues (SA), as well as to describe granulation pattern in adenomas with and without SA pretreatment.

DESIGN/SETTINGS/PATIENTS

Seventy-eight patients with active acromegaly were included. Long-term SA efficacy was evaluated in 29 patients treated preoperatively and in ten treated postoperatively. Granulation pattern was examined, as were immunohistochemical analyses for E-cadherin and SSTR2a. Protein levels of E-cadherin and SSTR2a were measured (Western blot). Gsp mutation analysis was available for 74 adenomas.

RESULTS

DG adenomas and the transitional group had higher serum levels of IGF-1 per tumour volume than SG (P = 0·009; P = 0·005). Acute and long-term SA responses were lower in SG (P = 0·001; P = 0·043). No correlation between gsp mutation and granulation was found, and no difference in granulation pattern according to preoperative SA treatment was demonstrated. A significant correlation between granulation and E-cadherin was found, where SG had lowest immunohistochemical expression, substantiated by protein levels, and a highly significant gradient was observed from DG, through the transitional group, to SG.

CONCLUSIONS

Densely granulated adenomas were highly responsive to somatostatin analogues in contrast to SG adenomas. The transitional group behaved clinically more like DG adenomas. However, based on E-cadherin, a marker of dedifferentiation, the transitional group seemed to be a true intermediate.

Impact of gsp oncogene on the mRNA content for somatostatin and dopamine receptors in human somatotropinomas

INTRODUCTION

It has been reported in some series that gsp+ somatotropinomas are more sensitive to somatostatin analogues (SA) and dopamine's actions which may be related to their somatostatin receptor (SSTR) and dopamine receptor (DR) profile. No previous studies have been undertaken to evaluate the SSTR and DR profile related with the gsp status in somatotropinomas.

OBJECTIVES

To determine if (1) gsp status is correlated with response to octreotide LAR (LAR) and tumor expression patterns of SSTR1-5 and DR1-5 and (2) cAMP level can directly modulate SSTR and DR mRNA levels.

METHODS

Response to SA was evaluated by GH and IGF-I percent reduction after 3 and 6 months of treatment with LAR. Conventional PCR and sequencing were used to identify gsp+ tumors. Quantitative real-time PCR was used to determine SSTR and DR tumor expression. Primary pituitary cell cultures of primates were used to study whether SSTR and DR expression is regulated by forskolin.

RESULTS

The response to LAR did not significantly differ between patients with gsp+ and gsp- tumors; however, gsp+ tumors expressed higher levels of SSTR1, SSTR2, DR2 and a lower level of SSTR3. Forskolin increased SSTR1, SSTR2, DR1 and DR2 expression in cell cultures.

CONCLUSION

Elevated SSTR1, SSTR2, and DR2 tumor expression may help improve responsiveness to SA and DA therapy; however, this study may not have been appropriately powered to observe significant effects in the clinical response. Elevated cAMP levels could be directly responsible for the upregulation in SSTR1, SSTR2 and DR2 mRNA levels observed in gsp+ patients.

Prevalence of gsp oncogene in somatotropinomas and clinically non-functioning pituitary adenomas: our experience

The purpose of the present study is to evaluate the prevalence of the gsp oncogene in Brazilian patients harboring somatotropinomas and non-functioning pituitary adenomas (NFPA). Patients and methods Deoxyribonucleic acid was extracted from 54 somatotropinomas and 14 NFPA. Exons 8 and 9 (including codons 201 and 227, respectively) of the GNAS gene were amplified by polymerase chain reaction (PCR). The PCR products were then purified and sequenced using the same primers. Results The gsp oncogene was found in nine tumors (eight somatotropinomas). The prevalence among somatotropinomas was 15% and among NFPA was 7%. The mutation was found in codon 201 in eight tumors and in codon 227 in one tumor (a somatotropinoma). No differences were found in age, sex, GH, and IGF-I levels or tumor volume at diagnosis between gsp+ and gsp- patients. Conclusion We found a lower than expected prevalence of gsp mutations in somatotropinomas and a similar prevalence in NFPA compared to previous studies from other countries.

A prospective, multicentre study to investigate the efficacy, safety and tolerability of octreotide LAR (long-acting repeatable octreotide) in the primary therapy of patients with acromegaly

OBJECTIVE

To evaluate the efficacy, safety and tolerability of octreotide LAR (long-acting repeatable octreotide) in the primary therapy of acromegaly.

DESIGN AND PATIENTS

Ninety-eight previously untreated acromegalics were recruited into this prospective multicentre study. A total of 68 patients successfully completed 48 weeks of the study period, received 12 doses of octreotide LAR 10-30 mg every 4 weeks, and constituted the population used for this analysis.

MEASUREMENTS AND RESULTS

A clinically relevant reduction (i.e. to < or = 5 microg/l) in mean GH (mGH) was recorded in 72% of patients after 24 weeks of treatment, and 42% reached a 'safe' GH value (< or = 2.5 microg/l). At week 48, 16 more patients were considered partial GH responders (GH > 2.5 microg/l and < or = 5 microg/l) and 44% had reached a GH level < or = 2.5 microg/l. IGF-1 levels normalized in 38% and 34% of patients after 24 and 48 weeks of treatment, respectively. At study completion, 10 patients (14.7%) who had not normalized their IGF-1 levels had achieved at least a 50% decrement in this marker. In eight microadenoma patients, tumour volume decreased from a mean baseline level of 298 +/- 145 mm3 to 139 +/- 94 mm3 after 24 weeks and to 99 +/- 70 mm3 after 48 weeks of therapy. In 60 patients with macroadenoma, the corresponding values were 3885 +/- 5077 mm3 at baseline and 2723 +/- 3435 and 2406 +/- 3207 mm3 after 24 and 48 weeks, respectively. At weeks 24 and 48, a significant (> 20%) tumour volume reduction was reported in 63% and 75% of patients, respectively. A reduction in the severity of symptoms of acromegaly was observed early in treatment and was maintained throughout the study period.

CONCLUSION

Octreotide LAR represents a viable alternative to surgery for primary treatment of acromegaly leading to a progressive regression of tumour volume, a sustained control of biochemical abnormalities and an adequate relief of symptoms of the disease.

Analysis of GNAS mutations in 60 growth hormone secreting pituitary tumors: correlation with clinical and pathological characteristics and surgical outcome based on highly sensitive GH and IGF-I criteria for remission

Although the molecular mechanisms underlying GH secreting pituitary tumor formation are not well understood, mutations in the alpha-subunit of the stimulatory G gene, GNAS, have been identified in up to 40%. As these mutations could play a role in tumor growth, we screened 60 GH secreting tumors for GNAS mutations and assessed whether mutation status correlated with their clinical and pathological characteristics. Tumor specimens obtained at surgery were snap frozen. Tumor DNA was extracted, and PCR was used to amplify regions containing 2 sites of recurrent activating somatic mutations in codons 201 and 227 in GNAS. Amplicons were bi-directionally sequenced and analyzed. GNAS mutations were present in 24/60 (40%) of tumors; these were arg201cys(n = 15), arg201ser(n = 2), arg201his(n = 2), gln227leu(n = 4), gln227arg(n = 1). Preoperative IGF-I levels (age-adjusted) were higher (p = 0.01), but GH levels were slightly higher (p = 0.18) in mutation positive vs. negative groups. Mutation positive tumors were somewhat smaller than negative tumors (p = 0.07). The proportion of tumors >2 cm was somewhat less among positive (8.3%) vs. negative tumors (25%) (p = 0.10). Neither mib proliferation index, the proportion of invasive tumors nor surgical remission rates differed in the groups. IGF-I normalization rate with somatostatin analog therapy was similar in positive (3 of 6) vs. negative (3 of 7) patients. GH secreting tumors harboring GNAS mutations had higher preoperative IGF-I levels, somewhat higher preoperative GH levels and tended to be smaller than tumors without mutations. Presence of a GNAS mutation did not predict a difference in a proliferation marker, surgical remission or response to somatostatin analog therapy.

McCune-Albright syndrome with acromegaly and fibrous dysplasia associated with the GNAS gene mutation identified by sensitive PNA-clamping method

A 16-year-old girl presented with McCune-Albright syndrome associated with acromegaly and fibrous dysplasia. Brain MRI demonstrated a pituitary tumor. X-ray films showed bone deformities, and 99TmO4 bone scintigraphy revealed increased uptake of radioactivity in the affected bones. Although the serum FGF23 level was increased, the serum calcium, phosphate, and active vitamin D levels were all within normal limits. GNAS gene mutation was detected at neither codon 201 nor 227 by conventional PCR-based direct sequencing analysis. We performed a selective PCR with peptide nucleic acid (PNA) clamping to increase the sensitivity for gene mutation detection and identified the R201C GNAS mutation.