USP8 and TP53 Drivers are Associated with CNV in a Corticotroph Adenoma Cohort Enriched for Aggressive Tumors

A long-term prognosis study of human USP8-mutated ACTH-secreting pituitary neuroendocrine tumours

OBJECTIVE

Somatic variants in the ubiquitin-specific protease 8 (USP8) gene are the most common genetic cause of Cushing disease. We aimed to explore the relationship between clinical outcomes and USP8 status in a single centre.

DESIGN, PATIENTS AND MEASUREMENTS

We investigated the USP8 status in 48 patients with pituitary corticotroph tumours. A median of 62 months of follow-up was conducted after surgery from November 2013 to January 2015. The clinical, biochemical and imaging features were collected and analysed.

RESULTS

Seven USP8 variants (p.Ser718Pro, p.Ser719del, p.Pro720Arg, p.Pro720Gln, p.Ser718del, p.Ser718Phe, p.Lys713Arg) were identified in 24 patients (50%). USP8 variants showed a female predominance (100% vs. 75% in wild type [WT], p = .022). Patients with p.Ser719del showed an older age at surgery compared to patients with the p.Pro720Arg variant (47- vs. 24-year-olds, p = .033). Patients with p.Pro720Arg showed a higher rate of macroadenoma compared to patients harbouring the p.Ser718Pro variant (60% vs. 0%, p = .037). No significant differences were observed in serum and urinary cortisol and adrenocorticotropin hormone (ACTH) levels. Immediate surgical remission (79% vs. 75%) and long-term hormone remission (79% vs. 67%) were not significantly different between the two groups. The recurrence rate was 21% (4/19) in patients harbouring USP8 variants and 13% (2/16) in WT patients. Recurrence-free survival presented a tendency to be shorter in USP8-mutated individuals (76.7 vs. 109.2 months, p = .068).

CONCLUSIONS

Somatic USP8 variants accounted for 50% of the genetic causes in this cohort with a significant female frequency. A long-term follow-up revealed a tendency toward shorter recurrence-free survival in USP8-mutant patients.

Genome-wide loss of heterozygosity predicts aggressive, treatment-refractory behavior in pituitary neuroendocrine tumors

Pituitary neuroendocrine tumors (PitNETs) exhibiting aggressive, treatment-refractory behavior are the rare subset that progress after surgery, conventional medical therapies, and an initial course of radiation and are characterized by unrelenting growth and/or metastatic dissemination. Two groups of patients with PitNETs were sequenced: a prospective group of patients (n = 66) who consented to sequencing prior to surgery and a retrospective group (n = 26) comprised of aggressive/higher risk PitNETs. A higher mutational burden and fraction of loss of heterozygosity (LOH) was found in the aggressive, treatment-refractory PitNETs compared to the benign tumors (p = 1.3 × 10-10 and p = 8.5 × 10-9, respectively). Within the corticotroph lineage, a characteristic pattern of recurrent chromosomal LOH in 12 specific chromosomes was associated with treatment-refractoriness (occurring in 11 of 14 treatment-refractory versus 1 of 14 benign corticotroph PitNETs, p = 1.7 × 10-4). Across the cohort, a higher fraction of LOH was identified in tumors with TP53 mutations (p = 3.3 × 10-8). A machine learning approach identified loss of heterozygosity as the most predictive variable for aggressive, treatment-refractory behavior, outperforming the most common gene-level alteration, TP53, with an accuracy of 0.88 (95% CI: 0.70-0.96). Aggressive, treatment-refractory PitNETs are characterized by significant aneuploidy due to widespread chromosomal LOH, most prominently in the corticotroph tumors. This LOH predicts treatment-refractoriness with high accuracy and represents a novel biomarker for this poorly defined PitNET category.

Relevance of mutations in protein deubiquitinases genes and TP53 in corticotroph pituitary tumors

Introduction

Corticotroph pituitary neuroendocrine tumors (PitNETs) develop from ACTH-producing cells. They commonly cause Cushing's disease (CD), however, some remain clinically silent. Recurrent USP8, USP48, BRAF and TP53 mutations occur in corticotroph PitNETs. The aim of our study was to determine frequency and relevance of these mutations in a possibly large series of corticotroph PitNETs.

Methods

Study included 147 patients (100 CD and 47 silent tumors) that were screened for hot-spot mutations in USP8, USP48 and BRAF with Sanger sequencing, while 128 of these patients were screened for TP53 mutations with next generation sequencing and immunohistochemistry.

Results

USP8 mutations were found in 41% CD and 8,5% silent tumors, while USP48 mutations were found in 6% CD patients only. Both were more prevalent in women. They were related to higher rate of biochemical remission, non-invasive tumor growth, its smaller size and densely granulated histology, suggesting that these mutation may be favorable clinical features. Multivariate survival analyses did not confirm possible prognostic value of mutation in protein deubiquitinases. No BRAF mutations were found. Four TP53 mutations were identified (2 in CD, 2 in silent tumors) in tumors with size >10mm including 3 invasive ones. They were found in Crooke's cell and sparsely granulated tumors. Tumors with missense TP53 mutations had higher TP53 immunoreactivity score than wild-type tumors. Tumor with frameshift TP53 variant had low protein expression. TP53 mutation was a poor prognostic factor in CD according to uni- and multivariate survival analyses in spite of low mutations frequency.

Conclusions

We confirmed high prevalence of USP8 mutations and low incidence of USP48 and TP53 mutations. Changes in protein deubiquitinases genes appear to be favorable prognostic factors in CD. TP53 mutations are rare, occur in both functioning and silent tumors and are related to poor clinical outcome in CD.

Cushing's syndrome

Endogenous Cushing's syndrome results from excess glucocorticoid secretion, which leads to a myriad of clinical manifestations, comorbidities, and increased mortality despite treatment. Molecular mechanisms and genetic alterations associated with different causes of Cushing's syndrome have been described in the last decade. Imaging modalities and biochemical testing have evolved; however, both the diagnosis and management of Cushing's syndrome remain challenging. Surgery is the preferred treatment for all causes, but medical therapy has markedly advanced, with new drug options becoming available. Nevertheless, several comorbidities remain even after patient remission, which can affect quality of life. Accurate and timely diagnosis and treatment are essential for mitigating chronic complications of excess glucocorticoids and improving patient quality of life. In this Seminar, we aim to update several important aspects of diagnosis, complications, and treatment of endogenous Cushing's syndrome of all causes.

Clinical Spectrum of USP8 Pathogenic Variants in Cushing's Disease

Cushing's disease (CD) is a life-threatening condition with a challenging diagnostic process and scarce treatment options. CD is caused by usually benign adrenocorticotrophic hormone (ACTH)-secreting pituitary neuroendocrine tumors (PitNETs), known as corticotropinomas. These tumors are predominantly of sporadic origin, and usually derive from the monoclonal expansion of a mutated cell. Somatic activating variants located within a hotspot of the USP8 gene are present in 11-62% of corticotropinomas, making USP8 the most frequent genetic driver of corticotroph neoplasia. In contrast, other somatic defects such as those affecting the glucocorticoid receptor gene (NR3C1), the BRAF oncogene, the deubiquitinase-encoding gene USP48, and TP53 are infrequent. Moreover, patients with familial tumor syndromes, such as multiple endocrine neoplasia, familial isolated pituitary adenoma, and DICER1 rarely develop corticotropinomas. One of the main molecular alterations in USP8-driven tumors is an overactivation of the epidermal growth factor receptor (EGFR) signaling pathway, which induces ACTH production. Hotspot USP8 variants lead to persistent EGFR overexpression, thereby perpetuating the hyper-synthesis of ACTH. More importantly, they condition a characteristic transcriptomic signature that might be useful for the clinical prognosis of patients with CD. Nevertheless, the clinical phenotype associated with USP8 variants is less well defined. Hereby we discuss the current knowledge on the molecular pathogenesis and clinical picture associated with USP8 hotspot variants. We focus on the potential significance of the USP8 mutational status for the design of tailored clinical strategies in CD.

Metastatic pituitary tumors: an institutional case series

PURPOSE

Pituitary carcinomas are a rare entity that respond poorly to multimodal therapy. Patients follow a variable disease course that remains ill-defined.

METHODS

We present an institutional case series of patients treated for pituitary carcinomas over a 30-year period from 1992 to 2022. A systematic review was conducted to identify prior case series of patients with pituitary carcinomas.

RESULTS

Fourteen patients with a mean age at pituitary carcinoma diagnosis of 52.5 years (standard deviation [SD] 19.4) met inclusion criteria. All 14 patients had tumor subtypes confirmed by immunohistochemistry and hormone testing, with the most common being ACTH-producing pituitary adenomas (n = 12). Patients had a median progression-free survival (PFS) of 1.4 years (range 0.7-10.0) and a median overall survival (OS) of 8.4 years (range 2.3-24.0) from pituitary adenoma diagnosis. Median PFS and OS were 0.6 years (range 0.0-2.2) and 1.5 years (range 0.1-9.6) respectively upon development of metastases. Most patients (n = 12) had locally invasive disease to the cavernous sinus, dorsum sellae dura, or sphenoid sinus prior to metastasis. Common sites of metastasis included the central nervous system, liver, lung, and bone. In a pooled analysis including additional cases from the literature, treatment of metastases with chemotherapy or a combination of radiation therapy and chemotherapy significantly prolonged PFS (p = 0.02), while failing to significantly improve OS (p = 0.14).

CONCLUSION

Pituitary carcinomas are highly recurrent, heterogenous tumors with variable responses to treatment. Multidisciplinary management with an experienced neuro-endocrine and neuro-oncology team is needed given the unrelenting nature of this disease.

Prevalence and clinical correlations of SF3B1 variants in lactotroph tumours

OBJECTIVE

A somatic mutational hotspot in the SF3B1 gene was reported in lactotroph tumours. The aim of our study was to examine the prevalence of driver SF3B1 variants in a multicentre independent cohort of patients with lactotroph tumours and correlate with clinical data.

DESIGN AND METHODS

This was a retrospective, multicentre study involving 282 patients with lactotroph tumours (including 6 metastatic lactotroph tumours) from 8 European centres. We screened SF3B1 exon 14 hotspot for somatic variants using Sanger sequencing and correlated with clinicopathological data.

RESULTS

We detected SF3B1 variants in seven patients with lactotroph tumours: c.1874G > A (p.Arg625His) (n = 4, 3 of which metastatic) and a previously undescribed in pituitary tumours variant c.1873C > T (p.Arg625Cys) (n = 3 aggressive pituitary tumours). In two metastatic lactotroph tumours with tissue available, the variant was detected in both primary tumour and metastasis. The overall prevalence of likely pathogenic SF3B1 variants in lactotroph tumours was 2.5%, but when we considered only metastatic cases, it reached the 50%. SF3B1 variants correlated with significantly larger tumour size; higher Ki67 proliferation index; multiple treatments, including radiotherapy and chemotherapy; increased disease-specific death; and shorter postoperative survival.

CONCLUSIONS

SF3B1 variants are uncommon in lactotroph tumours but may be frequent in metastatic lactotroph tumours. When present, they associate with aggressive tumour behaviour and worse clinical outcome.

Pathology of Crooke Cells in the Human Pituitaries: A Timely Review

Crooke cell change was first found in the regressed and suppressed corticotroph (adrenocorticotropic hormone-producing) cells, and now is known to occur in pituitary tumors. The tumor cells of this type can be recognized by morphology with immunohistochemistry, and are well known to predict aggressive behavior such as invasion and rare metastases. This is one of the representative neuroendocrine tumors in the pituitary which is now considered to have malignant potential as proposed in the pancreas and gastrointestinal tracts. It is important to emphasize the pituitary tumor pathology such as Crooke cell change for prognostication and appropriate therapies. This review article describes the evolution from the Crooke cells to Crooke cell tumors which is timely along with the Fifth WHO classification 2022 published online.

The hidden hedgehog of the pituitary: hedgehog signaling in development, adulthood and disease of the hypothalamic-pituitary axis

Hedgehog signaling plays pivotal roles in embryonic development, adult homeostasis and tumorigenesis. However, its engagement in the pituitary gland has been long underestimated although Hedgehog signaling and pituitary embryogenic development are closely linked. Thus, deregulation of this signaling pathway during pituitary development results in malformation of the gland. Research of the last years further implicates a regulatory role of Hedgehog signaling in the function of the adult pituitary, because its activity is also interlinked with homeostasis, hormone production, and most likely also formation of neoplasms of the gland. The fact that this pathway can be efficiently targeted by validated therapeutic strategies makes it a promising candidate for treating pituitary diseases. We here summarize the current knowledge about the importance of Hedgehog signaling during pituitary development and review recent data that highlight the impact of Hedgehog signaling in the healthy and the diseased adult pituitary gland.

Aggressive Pituitary Tumors and Pituitary Carcinomas: From Pathology to Treatment

Aggressive pituitary tumors (APTs) and pituitary carcinomas (PCs) are heterogeneous with regard to clinical presentation, proliferative markers, clinical course, and response to therapy. Half of them show an aggressive course only many years after the first apparently benign presentation. APTs and PCs share several properties, but a Ki67 index greater than or equal to 10% and extensive p53 expression are more prevalent in PCs. Mutations in TP53 and ATRX are the most common genetic alterations; their detection might be of value for early identification of aggressiveness. Treatment requires a multimodal approach including surgery, radiotherapy, and drugs. Temozolomide is the recommended first-line chemotherapy, with response rates of about 40%. Immune checkpoint inhibitors have emerged as second-line treatment in PCs, with currently no evidence for a superior effect of dual therapy compared to monotherapy with PD-1 blockers. Bevacizumab has resulted in partial response (PR) in few patients; tyrosine kinase inhibitors and everolimus have generally not been useful. The effect of peptide receptor radionuclide therapy is limited as well. Management of APT/PC is challenging and should be discussed within an expert team with consideration of clinical and pathological findings, age, and general condition of the patient. Considering that APT/PCs are rare, new therapies should preferably be evaluated in shared standardized protocols. Prognostic and predictive markers to guide treatment decisions are needed and are the scope of ongoing research.

Refractory corticotroph adenomas

The majority of corticotroph adenomas are benign but some are locally invasive, demonstrate high rates of recurrence, and exhibit a relatively poor response to often repeated surgical, medical, and radiation treatment. Herein, we summarize the currently known somatic and genetic mutations and other molecular factors that influence the pathogenesis of these tumors and discuss currently available therapies. Although recent molecular studies have advanced our understanding of the pathogenesis and behavior of these refractory corticotroph adenomas, these insights do not reliably guide treatment choices at present. Development of additional diagnostic tools and novel tumor-directed therapies that offer efficacious treatment choices for patients with refractory corticotroph adenomas are needed.

Initial pathology in aggressive pituitary tumours and carcinomas: 2b or not 2b?-that is the question

From a cohort of 171 patients comprising 121 aggressive pituitary tumours (APT) and 50 pituitary carcinomas (PC), the clinicopathological or five-tiered classification based on tumour invasion and proliferation evaluated by at least 2 proliferative markers over the cut-offs (Ki-67 ≥3% or ≥10%, p53 positive or expressed in %, mitotic count >2%), could be applied on 43 tumours: 20 PC and 23 APT. At the initial surgery, 29/43 tumours (67.4%) were grade 2b (invasive and proliferative) of which 44.8% developed metastases during follow-up (PC, grade 3). Out of these 29 tumours, 55.1% had a Ki-67 ≥10%, and were classified grade 2b* (invasive and highly proliferative). There was one tumour grade 1b* (non-invasive and highly proliferative) which metastazed. Out of the 43 tumours, 30.2 % were grade 2a (invasive and non-proliferative). The sensitivity and the specificity of grade 2b for the diagnosis of APT at the initial surgery, were 68% and 90% respectively. The comparison of the high percentage (67.4%) of grade 2b tumours in this selected cohort of APT/PC with the low percentage (8.8%) in a surgical cohort of unselected tumours shows that the initial pathological diagnosis of grade 2b tumour may be considered, in the clinic, as representing a diagnosis of APT. In addition, a significant subgroup of tumours, which will develop metastases supports the proposal that an aggressive grade 2b tumour is “a tumour with malignant potential” or “a malignant tumour without metastases”. So, the clinician may take into account the pathological diagnosis, at the initial surgery, to propose a strict follow-up and to consider earlier use of radiotherapy and/or of temozolomide in the presence of tumours with aggressive behaviour.

Genetic drivers of Cushing's disease: Frequency and associated phenotypes

PURPOSE

Cushing's disease (CD) is often explained by a single somatic sequence change. Germline defects, however, often go unrecognized. We aimed to determine the frequency and associated phenotypes of genetic drivers of CD in a large cohort.

METHODS

We studied 245 unrelated patients with CD (139 female, 56.7%), including 230 (93.9%) pediatric and 15 (6.1%) adult patients. Germline exome sequencing was performed in 184 patients; tumor exome sequencing was also done in 27 of them. A total of 43 germline samples and 92 tumor samples underwent Sanger sequencing of specific genes. Rare variants of uncertain significance, likely pathogenic (LP), or pathogenic variants in CD-associated genes, were identified.

RESULTS

Germline variants (13 variants of uncertain significance, 8 LP, and 11 pathogenic) were found in 8 of 19 patients (42.1%) with positive family history and in 23 of 226 sporadic patients (10.2%). Somatic variants (1 LP and 7 pathogenic) were found in 20 of 119 tested individuals (16.8%); one of them had a coexistent germline defect. Altogether, variants of interest were identified at the germline level in 12.2% of patients, at the somatic level in 7.8%, and coexisting germline and somatic variants in 0.4%, accounting for one-fifth of the cohort.

CONCLUSION

We report an estimate of the contribution of multiple germline and somatic genetic defects underlying CD in a single cohort.

Epigenomic and somatic mutations of pituitary tumors with clinical and pathological correlations in 111 patients

OBJECTIVE

To profile clinically non-aggressive and aggressive pituitary adenomas (PAs)/pituitary neuroendocrine tumours (PitNETs) and pituitary carcinomas for somatic mutations and epigenetic alterations of genes involved in cell proliferation/differentiation, microRNAs (miRNA)/long noncoding RNA (LncRNA)-post-transcriptional regulators and therapy targets.

DESIGN

Retrospective observational study.

PATIENTS AND MEASUREMENTS

A total of 64 non-aggressive and 41 aggressive PAs/PitNETs and 6 pituitary carcinomas treated by endoscopic surgery with ≥1-year follow-up were included. Somatic mutations of 17 genes and DNA methylation of 22 genes were assessed. Ten normal pituitaries were used as control.

RESULTS

We found at least one mutation in 17 tumours, including 6/64 non-aggressive, 10/41 aggressive PAs/PitNETs, and 1/6 pituitary carcinoma. AIP (N = 6) was the most frequently mutated gene, followed by NOTCH (4), and TP53 (3). Hypermethylation of PARP15, LINC00599, ZAP70 was more common in aggressive than non-aggressive PAs/PITNETs (p < .05). Lower levels of methylation of AIP, GNAS and PDCD1 were detected in aggressive PAs/PITNETs than non-aggressive ones (p < .05). For X-linked genes, males presented higher level of methylation of FLNA, UXT and MAGE family (MAGEA11, MAGEA1, MAGEC2) genes in aggressive vs. non-aggressive PAs/PITNETs (p < .05). In pituitary carcinomas, methylation of autosomal genes PARP15, LINC00599, MIR193 and ZAP70 was higher than in PAs/PITNETs, while X-linked genes methylation level was lower.

CONCLUSIONS

Somatic mutations and methylation levels of genes involved in cell proliferation/differentiation, miRNA/LncRNA-post-transcriptional regulators and targets of antineoplastic therapies are different in non-aggressive and in aggressive PAs/PitNETs. Methylation profile also varies according to gender. Combined genetic-epigenetic analysis, in association with clinico-radiological-pathological data, may be of help in predicting PA/PitNET behaviour.

Clinical Biology of the Pituitary Adenoma

All endocrine glands are susceptible to neoplastic growth, yet the health consequences of these neoplasms differ between endocrine tissues. Pituitary neoplasms are highly prevalent and overwhelmingly benign, exhibiting a spectrum of diverse behaviors and impact on health. To understand the clinical biology of these common yet often innocuous neoplasms, we review pituitary physiology and adenoma epidemiology, pathophysiology, behavior, and clinical consequences. The anterior pituitary develops in response to a range of complex brain signals integrating with intrinsic ectodermal cell transcriptional events that together determine gland growth, cell type differentiation, and hormonal production, in turn maintaining optimal endocrine health. Pituitary adenomas occur in 10% of the population; however, the overwhelming majority remain harmless during life. Triggered by somatic or germline mutations, disease-causing adenomas manifest pathogenic mechanisms that disrupt intrapituitary signaling to promote benign cell proliferation associated with chromosomal instability. Cellular senescence acts as a mechanistic buffer protecting against malignant transformation, an extremely rare event. It is estimated that fewer than one-thousandth of all pituitary adenomas cause clinically significant disease. Adenomas variably and adversely affect morbidity and mortality depending on cell type, hormone secretory activity, and growth behavior. For most clinically apparent adenomas, multimodal therapy controlling hormone secretion and adenoma growth lead to improved quality of life and normalized mortality. The clinical biology of pituitary adenomas, and particularly their benign nature, stands in marked contrast to other tumors of the endocrine system, such as thyroid and neuroendocrine tumors.

Diagnosis and management of hypertension in patients with Cushing's syndrome: a position statement and consensus of the Working Group on Endocrine Hypertension of the European Society of Hypertension

Endogenous/exogenous Cushing's syndrome is characterized by a cluster of systemic manifestations of hypercortisolism, which cause increased cardiovascular risk. Its biological basis is glucocorticoid excess, acting on various pathogenic processes inducing cardiovascular damage. Hypertension is a common feature in Cushing's syndrome and may persist after normalizing hormone excess and discontinuing steroid therapy. In endogenous Cushing's syndrome, the earlier the diagnosis the sooner management can be employed to offset the deleterious effects of excess cortisol. Such management includes combined treatments directed against the underlying cause and tailored antihypertensive drugs aimed at controlling the consequences of glucocorticoid excess. Experts on endocrine hypertension and members of the Working Group on Endocrine Hypertension of the European Society of Hypertension (ESH) prepared this Consensus document, which summarizes the current knowledge in epidemiology, genetics, diagnosis, and treatment of hypertension in Cushing's syndrome.

Genetics of Cushing's disease: from the lab to clinical practice

Cushing's disease is a rare, but devastating condition, caused by corticotroph tumors. It rarely manifests as syndrome and very few isolated cases present with germline mutations. Instead, the vast majority of corticotroph tumors are sporadic monoclonal neoplasms. At present, the major recurrent somatic driver mutations are found in the USP8 gene, which encodes for a deubiquitinase that rescues proteins regulating ACTH synthesis. Almost half of functional corticotroph tumors carry somatic USP8 mutations that associate with a distinct transcriptomic and clinical profile. Other genes mutated in a small fraction of corticotroph tumors include the deubiquitinase encoding gene USP48 and the glucocorticoid receptor expressing NR3C1. Recent reports on somatic TP53 and ATRX mutations in corticotroph macroadenomas and carcinomas indicate that within specific patient subpopulations they are not as rare as assumed.

Aggressive pituitary tumours and carcinomas, characteristics and management of 171 patients

OBJECTIVE

To describe clinical and pathological characteristics and treatment outcomes in a large cohort of aggressive pituitary tumours (APT)/pituitary carcinomas (PC).

DESIGN

Electronic survey August 2020-May 2021.

RESULTS

96% of 171 (121 APT, 50 PC), initially presented as macro/giant tumours, 6 were microadenomas (5 corticotroph). Ninety-seven tumours, initially considered clinically benign, demonstrated aggressive behaviour after 5.5 years (IQR: 2.8-12). Of the patients, 63% were men. Adrenocorticotrophic hormone (ACTH)-secreting tumours constituted 30% of the APT/PC, and the gonadotroph subtypes were under-represented. Five out of 13 silent corticotroph tumours and 2/6 silent somatotroph tumours became secreting. Metastases were observed after median 6.3 years (IQR 3.7-12.1) from diagnosis. At the first surgery, the Ki67 index was ≥3% in 74/93 (80%) and ≥10% in 38/93 (41%) tumours. An absolute increase of Ki67 ≥ 10% after median of 6 years from the first surgery occurred in 18/49 examined tumours. Tumours with an aggressive course from outset had higher Ki67, mitotic counts, and p53. Temozolomide treatment in 156/171 patients resulted in complete response in 9.6%, partial response in 30.1%, stable disease in 28.1%, and progressive disease in 32.2% of the patients. Treatment with bevacizumab, immune checkpoint inhibitors, and peptide receptor radionuclide therapy resulted in partial regression in 1/10, 1/6, and 3/11, respectively. Median survival in APT and PC was 17.2 and 11.3 years, respectively. Tumours with Ki67 ≥ 10% and ACTH-secretion were associated with worse prognosis.

CONCLUSION

APT/PCs exhibit a wide and challenging spectrum of behaviour. Temozolomide is the first-line chemotherapy, and other oncological therapies are emerging. Treatment response continues to be difficult to predict with currently studied biomarkers.

TP53 mutations in functional corticotroph tumors are linked to invasion and worse clinical outcome

Corticotroph macroadenomas are rare but difficult to manage intracranial neoplasms. Mutations in the two Cushing's disease mutational hotspots USP8 and USP48 are less frequent in corticotroph macroadenomas and invasive tumors. There is evidence that TP53 mutations are not as rare as previously thought in these tumors. The aim of this study was to determine the prevalence of TP53 mutations in corticotroph tumors, with emphasis on macroadenomas, and their possible association with clinical and tumor characteristics. To this end, the entire TP53 coding region was sequenced in 86 functional corticotroph tumors (61 USP8 wild type; 66 macroadenomas) and the clinical characteristics of patients with TP53 mutant tumors were compared with TP53/USP8 wild type and USP8 mutant tumors. We found pathogenic TP53 variants in 9 corticotroph tumors (all macroadenomas and USP8 wild type). TP53 mutant tumors represented 14% of all functional corticotroph macroadenomas and 24% of all invasive tumors, were significantly larger and invasive, and had higher Ki67 indices and Knosp grades compared to wild type tumors. Patients with TP53 mutant tumors had undergone more therapeutic interventions, including radiation and bilateral adrenalectomy. In conclusion, pathogenic TP53 variants are more frequent than expected, representing a relevant amount of functional corticotroph macroadenomas and invasive tumors. TP53 mutations associated with more aggressive tumor features and difficult to manage disease.

Aggressive corticotroph tumors and carcinomas

Pituitary tumors are generally benign, although in rare cases aggressive pituitary tumors (APTs) and carcinomas present important diagnostic and therapeutic challenges and are associated with a high mortality rate. Almost half of these APTs and carcinomas are corticotroph tumors, suggesting a specific prognosis. Clinical, pathological and molecular prognostic markers are limited and do not allow early management of these tumors. Temozolomide remains the first-line treatment once a diagnosis of aggressive pituitary tumor or carcinoma has been made. Novel alternative treatments exist, including immune checkpoint inhibitors, which can be used in the case of temozolomide treatment failure. The aim of this review is to present the clinical, pathological and molecular characteristics of aggressive corticotroph tumors and carcinomas, and to describe the results obtained with currently available treatments.

Genetics of Cushing's disease

Corticotroph tumours are primarily sporadic monoclonal neoplasms and only rarely found in genetic syndromes. Recurrent mutations in the ubiquitin specific protease 8 (USP8) gene are found in around half of cases. Mutations in other genes such as USP48 and NR3C1 are less frequent, found in less than ~20% of cases. TP53 and ATXR mutations are reported in up to one out of four cases, when focusing in USP8 wild type or aggressive corticotroph tumours and carcinomas. At present, USP8 mutations are the primary driver alterations in sporadic corticotroph tumours, TP53 and ATXR mutations may indicate transition to more aggressive tumour phenotype. Next generation sequencing efforts have identified additional genomic alterations, whose role and importance in corticotroph tumorigenesis remains to be elucidated.

Genetic Basis of ACTH-Secreting Adenomas

Cushing's disease represents 60-70% of all cases of Cushing's syndrome, presenting with a constellation of clinical features associated with sustained hypercortisolism. Molecular alterations in corticotrope cells lead to the formation of ACTH-secreting adenomas, with subsequent excessive production of endogenous glucocorticoids. In the last few years, many authors have contributed to analyzing the etiopathogenesis and pathophysiology of corticotrope adenomas, which still need to be fully clarified. New molecular modifications such as somatic mutations of USP8 and other genes have been identified, and several case series and case reports have been published, highlighting new molecular alterations that need to be explored. To investigate the current knowledge of the genetics of ACTH-secreting adenomas, we performed a bibliographic search of the recent scientific literature to identify all pertinent articles. This review presents the most recent updates on somatic and germline mutations underlying Cushing's disease. The prognostic implications of these mutations, in terms of clinical outcomes and therapeutic scenarios, are still debated. Further research is needed to define the clinical features associated with the different genotypes and potential pharmacological targets.

The Genomic Landscape of Corticotroph Tumors: From Silent Adenomas to ACTH-Secreting Carcinomas

Corticotroph cells give rise to aggressive and rare pituitary neoplasms comprising ACTH-producing adenomas resulting in Cushing disease (CD), clinically silent ACTH adenomas (SCA), Crooke cell adenomas (CCA) and ACTH-producing carcinomas (CA). The molecular pathogenesis of these tumors is still poorly understood. To better understand the genomic landscape of all the lesions of the corticotroph lineage, we sequenced the whole exome of three SCA, one CCA, four ACTH-secreting PA causing CD, one corticotrophinoma occurring in a CD patient who developed Nelson syndrome after adrenalectomy and one patient with an ACTH-producing CA. The ACTH-producing CA was the lesion with the highest number of single nucleotide variants (SNV) in genes such as USP8, TP53, AURKA, EGFR, HSD3B1 and CDKN1A. The USP8 variant was found only in the ACTH-CA and in the corticotrophinoma occurring in a patient with Nelson syndrome. In CCA, SNV in TP53, EGFR, HSD3B1 and CDKN1A SNV were present. HSD3B1 and CDKN1A SNVs were present in all three SCA, whereas in two of these tumors SNV in TP53, AURKA and EGFR were found. None of the analyzed tumors showed SNV in USP48, BRAF, BRG1 or CABLES1. The amplification of 17q12 was found in all tumors, except for the ACTH-producing carcinoma. The four clinically functioning ACTH adenomas and the ACTH-CA shared the amplification of 10q11.22 and showed more copy-number variation (CNV) gains and single-nucleotide variations than the nonfunctioning tumors.

Exosomal miRNA Profiling is a Potential Screening Route for Non-Functional Pituitary Adenoma

Non-functional pituitary adenomas (NFPAs) are one of the most prevalent pituitary adenoma subtypes. The lack of reliable screening approach for NFPAs for the insidious clinical course usually leads to delays in medical therapy and consequently worse prognosis. Hence, we employed a sequence cohort (patient: control, 6:2) and a validation cohort (patient: control, 22:8) to develop a serum exosomal miRNA profile-based method for NFPA screening and prognosis prediction. We found that a total of 1,395 kinds of human miRNA were detected. Compared with healthy donors, 18 up-regulated and 36 down-regulated miRNAs showed significant expression alterations in NFPA patients. Target genes of differentially expressed miRNAs are mainly enriched in axonogenesis and cancer-associated terms. After validation, hsa-miR-486-5p, hsa-miR-151a-5p, hsa-miR-652-3p_R+1, and hsa-miR-1180-3p were promising biomarkers for NFPA, in which miR-486-5p was the most competent one. After a median of 33 months of prospective follow-up, exosomal hsa-miR-486-5p also was an efficient predictive biomarker for progression or relapse of NFPAs. By protein-protein interaction network construction of hsa-miR-486-5p targeted genes, the core modules revealed a high possibility that exosomal hsa-miR-486-5p regulated tumor progression by epigenetic regulation of MAPK signaling pathways. In conclusion, exosomal hsa-miR-486-5p, hsa-miR-151a-5p, hsa-miR-652-3p_R+1, and hsa-miR-1180-3p are candidate biomarkers for diagnosis and screening of NFPAs. More importantly, prospective follow-up reveals that hsa-miR-486-5p can be regarded as a significant predictor for prognosis of NFPAs.

Pituitary carcinoma: reclassification and implications in the NET schema

The entity known as pituitary carcinoma has been traditionally defined as a tumor of adenohypophysial cells that metastasizes systemically or craniospinally independent of the histological appearance of the lesion. Reported cases of pituitary carcinoma have clinically and histologically resembled their non-metastatic counterparts that were classified as adenomas; the majority of cases were initially diagnosed as adenomas, and with tumor progression and spread, the diagnosis was changed to carcinoma. This classification has been challenged since the definition of malignancy in most organs is not based only on metastatic spread. The extent of local invasion resulting in an inability to completely resect an adenohypophysial tumor can have serious consequences that can cause harm and are therefore not benign. To address this dilemma, it was proposed that pituitary tumors be classified as neuroendocrine tumors. This change in nomenclature is totally appropriate since these tumors are composed of classical neuroendocrine cells; as with other neuroendocrine tumors, they have variable behavior that can be indolent but can involve metastasis. With the new nomenclature, there is no requirement for a distinction between adenomas and carcinomas. Moreover, the WHO/IARC has provided an overarching classification for neuroendocrine neoplasms at all body sites; in this new classification, the term 'neuroendocrine carcinoma' is reserved for poorly differentiated high-grade malignancies that are clinically, morphologically and genetically distinct from well-differentiated neuroendocrine tumors. It remains to be determined if there are true pituitary neuroendocrine carcinomas.

Molecular characterisation of hepatocellular carcinoma in patients with non-alcoholic steatohepatitis

BACKGROUND AND AIMS

Non-alcoholic steatohepatitis (NASH)-related hepatocellular carcinoma (HCC) is increasing globally, but its molecular features are not well defined. We aimed to identify unique molecular traits characterising NASH-HCC compared to other HCC aetiologies.

METHODS

We collected 80 NASH-HCC and 125 NASH samples from 5 institutions. Expression array (n = 53 NASH-HCC; n = 74 NASH) and whole exome sequencing (n = 52 NASH-HCC) data were compared to HCCs of other aetiologies (n = 184). Three NASH-HCC mouse models were analysed by RNA-seq/expression-array (n = 20). Activin A receptor type 2A (ACVR2A) was silenced in HCC cells and proliferation assessed by colorimetric and colony formation assays.

RESULTS

Mutational profiling of NASH-HCC tumours revealed TERT promoter (56%), CTNNB1 (28%), TP53 (18%) and ACVR2A (10%) as the most frequently mutated genes. ACVR2A mutation rates were higher in NASH-HCC than in other HCC aetiologies (10% vs. 3%, p <0.05). In vitro, ACVR2A silencing prompted a significant increase in cell proliferation in HCC cells. We identified a novel mutational signature (MutSig-NASH-HCC) significantly associated with NASH-HCC (16% vs. 2% in viral/alcohol-HCC, p = 0.03). Tumour mutational burden was higher in non-cirrhotic than in cirrhotic NASH-HCCs (1.45 vs. 0.94 mutations/megabase; p <0.0017). Compared to other aetiologies of HCC, NASH-HCCs were enriched in bile and fatty acid signalling, oxidative stress and inflammation, and presented a higher fraction of Wnt/TGF-β proliferation subclass tumours (42% vs. 26%, p = 0.01) and a lower prevalence of the CTNNB1 subclass. Compared to other aetiologies, NASH-HCC showed a significantly higher prevalence of an immunosuppressive cancer field. In 3 murine models of NASH-HCC, key features of human NASH-HCC were preserved.

CONCLUSIONS

NASH-HCCs display unique molecular features including higher rates of ACVR2A mutations and the presence of a newly identified mutational signature.

LAY SUMMARY

The prevalence of hepatocellular carcinoma (HCC) associated with non-alcoholic steatohepatitis (NASH) is increasing globally, but its molecular traits are not well characterised. In this study, we uncovered higher rates of ACVR2A mutations (10%) - a potential tumour suppressor - and the presence of a novel mutational signature that characterises NASH-related HCC.

Aggressive Cushing's Disease: Molecular Pathology and Its Therapeutic Approach

Cushing's disease is a syndromic pathological condition caused by adrenocorticotropic hormone (ACTH)-secreting pituitary adenomas (ACTHomas) mediated by hypercortisolemia. It may have a severe clinical course, including infection, psychiatric disorders, hypercoagulability, and metabolic abnormalities, despite the generally small, nonaggressive nature of the tumors. Up to 20% of ACTHomas show aggressive behavior, which is related to poor surgical outcomes, postsurgical recurrence, serious clinical course, and high mortality. Although several gene variants have been identified in both germline and somatic changes in Cushing's disease, the pathophysiology of aggressive ACTHomas is poorly understood. In this review, we focused on the aggressiveness of ACTHomas, its pathology, the current status of medical therapy, and future prospects. Crooke's cell adenoma (CCA), Nelson syndrome, and corticotroph pituitary carcinoma are representative refractory pituitary tumors that secrete superphysiological ACTH. Although clinically asymptomatic, silent corticotroph adenoma is an aggressive ACTH-producing pituitary adenoma. In this review, we summarize the current understanding of the pathophysiology of aggressive ACTHomas, including these tumors, from a molecular point of view based on genetic, pathological, and experimental evidence. The treatment of aggressive ACTHomas is clinically challenging and usually resistant to standard treatment, including surgery, radiotherapy, and established medical therapy (e.g., pasireotide and cabergoline). Temozolomide is the most prescribed pharmaceutical treatment for these tumors. Reports have shown that several treatments for patients with refractory ACTHomas include chemotherapy, such as cyclohexyl-chloroethyl-nitrosourea combined with 5-fluorouracil, or targeted therapies against several molecules including vascular endothelial growth factor receptor, cytotoxic T lymphocyte antigen 4, programmed cell death protein 1 (PD-1), and ligand for PD-1. Genetic and experimental evidence indicates that some possible therapeutic candidates are expected, such as epidermal growth factor receptor tyrosine kinase inhibitor, cyclin-dependent kinase inhibitor, and BRAF inhibitor. The development of novel treatment options for aggressive ACTHomas is an emerging task.

Treatment of Aggressive Pituitary Adenomas: A Case-Based Narrative Review

Management of aggressive pituitary adenomas is challenging due to a paucity of rigorous evidence supporting available treatment approaches. Recent guidelines emphasize the need to maximize standard therapies as well as the use of temozolomide and radiation therapy to treat disease recurrence. However, often these adenomas continue to progress over time, necessitating the use of additional targeted therapies which also impact quality of life and long-term outcomes. In this review, we present 9 cases of aggressive pituitary adenomas to illustrate the importance of a multidisciplinary, individualized approach. The timing and rationale for surgery, radiation therapy, temozolomide, somatostatin receptor ligands, and EGFR, VEGF, and mTOR inhibitors in each case are discussed within the context of evidence-based guidelines and clarify strategies for implementing an individualized approach in the management of these difficult-to-treat-adenomas.