Pituitary Neuroendocrine Tumors Research Articles

Single-cell transcriptomics link gene expression signatures to clinicopathological features of gonadotroph and lactotroph PitNET.

Pituitary neuroendocrine tumors (PitNET) are among the most common intracranial tumors. Despite a frequent benign course, aggressive behavior can occur. Tumor behavior is known to be under the influence of the tumor microenvironment (TME). However, the relationship between TME cells and aggressive tumor behavior has not been adequately explored in PitNET. We performed differential expression analysis as well as gene expression program identification based on single-cell RNA sequencing to comparatively characterize the transcriptome of seven gonadotroph and three lactotroph PitNET and correlate it with clinical features using bulk RNA-seq data from an independent cohort of 134 PitNET. Tumor immune infiltration was quantified via immunostaining on tissue sections of gonadotroph and lactotroph PitNET. In lactotroph PitNET, we detect a highly proliferative gene profile with significantly increased expression levels in aggressively growing tumors within bulk RNA-seq data of an independent cohort of 134 PitNET samples. We also report high intratumoral heterogeneity in gonadotroph PitNET (GoPN) and lactotroph PitNET (LaPN) and identify signatures of epithelial, endocrine, and immunological gene networks in both subtypes. A comparison of their TME composition shows enrichment of SPP1+ macrophages and CD4+ T cells in GoPN, as well as enrichment of CD4/CD8 double-negative T cells (DN) and natural killer cells (NK) in LaPN. Also notable is the presence of proliferative lymphocytes, the occurrence of which positively correlates with more aggressive tumor behavior in the bulk RNA-seq cohort. However, increased CD8+ T and NK cell abundances correlate significantly with reduced aggressiveness indicating potential anti-tumoral effects. Our study expands the knowledge of the differences in cellular composition of gonadotroph and lactotroph PitNET subtypes. It lays the foundation for further studies on the influence of lymphoid cells on the variable aggressive behavior of PitNET. Regarding the treatment of drug-resistant lactotroph PitNET, proliferative lymphocytes, CD8+ T, and NK cells could represent potentially valuable targets for developing new cancer immunotherapies.

Radiation therapy in functioning and no functioning pituitary neuroendocrine tumor: systematic review of the recent literature after 2011

SummaryNeuroendocrine pituitary tumor, a benign cells proliferation, can cause significant morbidity due to its local invasiveness and secretory properties. Historically, radiotherapy has been employed as a second or third-line treatment option, with studies dating back to the mid-20th century. However, advancements in radiotherapy techniques, such as intensity-modulated radiation therapy (IMRT), stereotactic radiosurgery, and proton therapy, have revolutionized treatment approaches. This review aims to critically evaluate the recent literature (2011–2022) on the use of radiotherapy in both functioning and nonfunctioning neuroendocrine pituitary tumor. We employed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) methodology to systematically analyze 52 articles, focusing on local and hormonal control, radiotherapy protocols, and treatment-related side effects.

TMIC-02. SINGLE-CELL HIGH-DIMENSIONAL MASS CYTOMETRY (CYTOF) REVEALS IMMUNE LANDSCAPE OF PITUITARY NEUROENDOCRINE TUMORS

Abstract Pituitary neuroendocrine tumors (pitNETs) are a group of neoplasms in the sellar region, ranking as the second most common primary brain tumors, with some exhibiting aggressive behaviors. While immunohistochemical staining has been utilized to characterize the tumor immune microenvironment (TIME) of pitNETs, single-cell analysis remains underexplored. High-dimensional mass cytometry (CyTOF) offers a valuable approach for precise quantification of intratumoral leukocytes and potential therapeutic insights. We prospectively enrolled 56 patients with pitNETs of varying endocrine function, histology, and lineage. CyTOF, employing heavy metal-tagged antibodies, was employed to simultaneously measure 37 cellular parameters at single-cell resolution. Analysis revealed a total of 71,049 CD45+ immune cells. Macrophages (mean, 50.7%) and T cells (mean, 28.7%) were the predominant leukocytes, followed by NK cells, dendritic cells, B cells, and neutrophils. The immune cell composition within the TIME exhibited heterogeneity, with distinct patterns observed between functioning and non-functioning pitNETs. Functioning pitNETs displayed fewer macrophages (28.9% vs. 62.9%) and more T cells (44.9% vs. 19.6%) compared to non-functioning pitNETs. Subgroups within functioning (somatotroph, mammosomatotroph, lactotroph) and those within non-functioning pitNETs (null-cell, gonadotroph, corticotroph) shared similar immune profiles, respectively. PIT-1 lineage pitNETs demonstrated a T cell-dominated pattern, while SF-1, T-PIT, and null-cell lineage pitNETs exhibited macrophage predominance. In functioning pitNETs, macrophage abundance negatively correlated with invasiveness, Ki-67 index, and recurrence, while CD4 T cells showed positive correlations. Further unsupervised clustering identified 27 subpopulations of intratumoral immune cells, with some serving as critical predictors of tumor behavior. Our study provides a comprehensive single-cell immune profile of pitNETs, revealing distinct features across subtypes and targeted therapeutic implications.

TMOD-06. ESTABLISHMENT OF PITUITARY NEUROENDOCRINE TUMOR (PITNET) ORGANOID MODELS

Abstract Pituitary neuroendocrine tumors (PitNETs) are tumors that originate from the anterior pituitary gland. While they are mostly benign, they can cause various clinical symptoms due to hormonal secretion abnormalities. PitNET can be broadly categorized into three lineages, each of which has its differentiation controlled by specific transcription factors. Treatment options for PitNET include surgical resection and pharmacotherapy, but available drugs are limited, and their efficacy markers remain unclear. To develop novel drugs for PitNET and identify their efficacy markers, it is necessary to develop new research models. In recent years, organoid models have garnered attention as novel research models for various cancer types. In this study, we established novel organoid models derived from PitNET patients and analyzed their histological and endocrinological characteristics. Surgical specimens from 4 cases of somatotroph adenoma, 1 case of double adenoma, 1 case of gonadotroph adenoma, and 1 case of corticotroph adenoma were minced in dissection medium and embedded in Matrigel basement membrane matrix respectively. The organoids were cultured under 5% CO2 at 37°C using media supplemented with various growth factors. After 28 days of culture, formalin-fixed paraffin-embedded sections were prepared to examine histological homology with patient tumors. Hematoxylin and eosin staining results showed that all organoids maintained cell morphology and tissue structure similar to the original tumors. Immunohistochemical staining for markers specific to each PitNET revealed similar staining patterns between the organoids and the original tumors. Furthermore, analysis of hormone levels in the culture medium showed that hormone production capabilities, such as growth hormone and follicle stimulating hormone, were maintained even after long-term culture. In this study, we successfully established PitNET organoid models that retain histological and endocrinological characteristics. These models are expected to serve as useful research tools for elucidating the molecular mechanisms of PitNET and developing novel therapies targeting critical molecular abnormalities.

EPID-35. COLLISION TUMORS AT THE SKULL BASE: UNVEILING A PETROCLIVAL MENINGIOMA COEXISTING WITH A GROWTH HORMONE-PRODUCING PITUITARY ADENOMA

Abstract Collision tumors are rare occurrences characterized by coexistence of two histologically different tumor types within the same anatomical location. While collision tumors involving skull base meningiomas and pituitary adenomas are uncommon, they pose distinct diagnostic challenges. We report the case of a 57-year-old female initially diagnosed with petroclival meningioma WHO 1, subsequently found to harbor a collision tumor with a growth hormone-producing pituitary adenoma. The patient initially presented with aphasia, right-sided weakness, and gait instability, prompting a diagnosed of left petroclival mass with left temporal horn entrapment. Patient underwent craniotomy and partial resection of the tumor in 2022 and was diagnosed with meningothelial meningioma, WHO1. The patient had history of uncontrolled diabetes and physical features of large hands with hypertrophied terminal phalangeal tufts but patient reported that she has had similar hands since childbirths for decades. Screening pituitary function tests were ordered due to the petroclival meningioma involving suprasellar region, revealing significantly elevated growth hormone, and insulin-like growth factor-1(IGF-1) levels, raising suspicion for pituitary adenoma. Subsequent endoscopic resection of the sellar mass via a transsphenoidal approach in 2024 confirmed the presence of somatotroph pituitary neuroendocrine tumor. Retrospectively growth hormone producing pituitary adenoma likely contributed to patient’s uncontrolled diabetes and coarse, large hands. This case highlights the importance of a high index of suspicion for collision tumors, particularly in patients with skull base tumors involving supra sellar region, especially when presenting with atypical clinical features.

SURG-56. TRANSCRIPTION FACTOR CELL LINEAGE DETERMINES AGGRESSIVE BEHAVIOR AMONG NONFUNCTIONAL PITUITARY ADENOMAS

Abstract INTRODUCTION Pituitary neuroendocrine tumors (PitNETs) are the second most common intracranial neoplasm. Silent or non-functional PitNETs represent a common neuro-oncological challenge due to their size and unpredictable invasion of parasellar structures. This makes their complete surgical resection difficult and puts patients at higher risk for recurrence. OBJECTIVE To characterize differences in tumor volume, cavernous sinus invasion, and recurrence in nonfunctional PitNETs. METHODS Out of 615 transsphenoidal surgeries from 2012 to 2024, there were 309 overall PitNETs and 181 nonfunctional PitNETs. Based on new WHO criteria for transcription factor profiling (PIT-1, TPIT, and SF-1), there were 98 silent gonadotroph adenomas (SGA), 31 silent corticotroph adenomas (SCA), 10 silent pleurihormonal tumors (PHT), and 2 null cell adenomas. Tumor volume was calculated using (AxBxC/2). Knosp grade was calculated. Cavernous sinus invasion was defined as Knosp ≥ 3. Residual disease at 3 months postoperative was recorded and surgical intervention for growing residual disease was captured. RESULTS Average tumor volume of PHT (18.08 cm3) was significantly higher than SGA (8.44 cm3, p=0.007) and similar to SCA (10.33 cm3, p=0.11). Percentage of cavernous sinus invasion was significantly different between SCA (31.82%) and SGA (10.20%, p=0.003), but not PHT (33.33%; p>0.05). There was a significantly higher residual rate in SCA compared to SGA (31.71% vs. 11.22%, p=0.006). There were significantly more reoperations in the SCA group compared to SGA and PHT. CONCLUSIONS Despite similar tumor volume between SCA and SGA, there was a significantly higher rate of cavernous sinus invasion and residual disease among SCA. This has important neuro-oncological implications regarding surgical technique, postoperative surveillance, and need for adjuvant therapy to mitigate aggressive recurrent disease.

PIT-1/SF-1 co-expression in pituitary neuroendocrine tumors (PitNETs) with comprehensive review of the literature: How should we best characterize these neoplasms?

The nomenclature and classification of neuroendocrine tumors of the anterior pituitary have undergone significant change over the last few years. Despite the updated classification system as devised by the World Health Organization, some tumors do not fit neatly into the currently defined categories. The most common tumor type not defined by the updated guidelines is a pituitary neuroendocrine tumor with co-expression of SF-1 and PIT-1. In this manuscript, we provide our institutional experience with such unusual cases and combine our findings with those in the available literature to provide the largest, most comprehensive dataset regarding clinical and pathologic information for these unique tumors. Based on our findings, we also propose a classification scheme for pituitary neuroendocrine tumors to integrate lineage, hormonal expression, and clinical function as we believe this constellation of information will best help the clinical teams treating these patients.

The gut microbiome in patients with Cushing’s disease affects depression- and anxiety-like behavior in mice

BackgroundDepression and anxiety significantly impact the quality of life in individuals with Cushing’s disease (CD), which originates from pituitary neuroendocrine tumors (PitNETs), yet our understanding of the underlying mechanisms is limited. There is substantial evidence linking gut microbes to depression, anxiety, and endocrinology.ResultsThe gut bacterial phenotype of patients with Cushing’s disease was significantly different from that of the control group, and when the mice were treated with fecal bacteria from these patients, both anxiety- and depression-like behavior were significantly increased. However, this effect can be alleviated by supplementing with 2-(14, 15-epoxyeicosatrienoyl) glycerol (2–14,15-EG) which was found at reduced levels in the peripheral blood of mice treated with coprofecal bacteria from Cushing’s disease. In this process, the effects of hormone levels and immune factors were not significant. In addition, in an animal model, corticosterone has been observed to affect behavioral changes in mice through gut microbiota composition, clarifying the cause-and-effect relationship between hormones, microbiota, and behavior. Finally, there was no significant difference in gut microbiome composition and its effects on mouse behavior in patients with Cushing’s disease with different levels of depression and anxiety.ConclusionsIn summary, this research enhances our current understanding of how gut microbes in patients with Cushing’s disease contribute to depression and anxiety, offering novel insights for clinical treatment approaches.5dhu2eBu8fQWFpV1_knqDYVideo

Comprehensive mapping of somatotroph pituitary neuroendocrine tumour heterogeneity using spatial and single-cell transcriptomics.

Pituitary neuroendocrine tumours (PitNETs) are common intracranial tumours that are highly heterogeneous with unpredictable growth patterns. The driver genes and mechanisms that are crucial for tumour progression in somatotroph PitNETs are poorly understood. In this study, we performed integrative spatial transcriptomics (ST) and single-cell RNA sequencing (scRNA-seq) analysis on somatotroph tumours and normal pituitary samples to comprehensively characterize the differences in cellular characteristics. By analyzing combined copy number variations (CNVs), tumour tissues were divided into two regions, which included the CNVhigh and CNVlow areas. The protumour genes DLK1 and RCN1 were highly expressed in the CNVhigh area, which might be related to tumour progression and could be targeted for precision therapy. We also found that the transforming growth factor beta signalling pathway participated in tumour progression and identified heterogeneity in the expression profiles of key genes. We assessed the intertumoral and intratumoral heterogeneity in somatotroph PitNETs and emphasized the importance of individualized treatment. In summary, we visualized the cellular distribution and transcriptional differences in normal pituitary and somatotroph PitNETs by ST and scRNA-seq for the first time. This study provides a strong theoretical foundation to comprehensively understand the crucial mechanisms involved in tumour progression and develop new strategies to treat somatotroph PitNETs. The first-ever visualization of cellular distributions in normal and tumor pituitary tissues. The inter- and intra-tumoral transcriptomic heterogeneity of somatotroph PitNETs was comprehensively revealed. Identification of potential protumor factors and critical signaling pathways, opening new avenues for therapeutic intervention.

Pituitary neuroendocrine tumors treated with stereotactic radiosurgery.

Pituitary neuroendocrine tumors (pitNETs) are benign tumors that may recur after surgical resection or persist following medical management. The objective of this study was to evaluate outcomes and toxicities of patients with pitNETs treated with stereotactic radiosurgery (SRS) at a single institution. We completed a retrospective, single-institution study of patients with pitNETs treated with frame-based, single-fraction, cobalt-60 SRS between September 2005 and June 2023. The primary endpoint was local tumor control. Secondary endpoints included endocrine control (for functional tumors), overall survival, and toxicities. A total of 88 lesions in 83 patients were treated with SRS. Most lesions (70%) were non-functional tumors. Of the 26 functioning tumors, 6 patients achieved endocrine remission with SRS alone (23%), and the remainder achieved remission with combined medical management. With a median patient follow-up of 4.7 years, no local tumor recurrences were observed with an estimated local control probability of 100%. Two- and five-year overall survival estimates were 97% (95% confidence interval [CI] 89-99) and 95% (95% CI 84-98), respectively. Causes of death were unrelated to PitNET or SRS. Twelve patients (14%) developed hypopituitarism after SRS. Despite the 34 lesions that were ≤ 3mm from optic structures, no patients developed any optic neuropathy or visual decline post SRS. SRS is a highly effective modality for recurrent or residual pitNETs. This study observed a local control of 100% with no cases of optic toxicities after a median follow-up of 4.7 years. These observed findings suggest that dose de-escalation may be possible for future treatment of pitNETs.

An Update on Advances in Hypopituitarism: Etiology, Diagnosis, and Current Management.

This article provides an updated review of hypopituitarism (HP), an endocrine disorder characterized by a deficiency of one or more pituitary hormones. The various etiologies are reviewed, including pituitary neuroendocrine tumors (PitNETs), hypothalamic lesions, genetic mutations, and acquired factors such as head trauma, medications, neoplasms, and infiltrative diseases. It is noted that PitNETs are responsible for approximately half of the cases in adults, whereas in children the causes are predominantly congenital. Diagnosis is based on clinical evaluation and hormonal testing, with identification of the specific hormonal deficiencies essential for effective treatment. Laboratory tests present challenges and limitations that must be understood and addressed. Hormone replacement therapy is the mainstay of treatment, significantly improving patients' quality of life. It is important to know the possible interactions between hormone replacement therapies in HP. Recent advances in understanding the pathophysiology of HP and the importance of a multidisciplinary approach to the management of associated complications are discussed. This article emphasizes the need for comprehensive evaluation and continuous follow-up to optimize outcomes in patients with HP and highlights the importance of ongoing research to improve diagnostic and treatment strategies.

Variable anatomical features of acromegaly in the nasal cavity and paranasal sinuses: implications for endoscopic endonasal transsphenoidal surgery.

Growth hormone (GH)-secreting pituitary neuroendocrine tumors (PitNETs) are the most common cause of acromegaly. The endoscopic endonasal transsphenoidal approach (EEA) is commonly employed to remove them. Although morphological differences in the nasal cavity exist between acromegaly patients and those with other types of PitNET, few quantitative studies have been performed. This study aimed to evaluate the anatomical features of the nasal cavity and paranasal sinuses in patients with acromegaly. Preoperative computed tomography images of the nasal cavity and paranasal sinuses were compared between 20 patients with a GH-secreting PitNET (acromegaly group) and 22 with a non-functioning PitNET (control group). In the acromegaly group, the relationships between preoperative GH and/or insulin-like growth factor 1 (IGF-1) levels and anatomical characteristics were assessed. In the acromegaly group, the distance between the nostril and dorsum sellae was significantly longer and the distance between the parasellar internal carotid arteries was significantly shorter (p = 0.0022 and 0.0092, respectively). Pneumatization volume in the nasal cavity did not differ between the groups. Nasal mucosa and bony hypertrophy were observed in the acromegaly group. Preoperative GH level was correlated with the width of the piriform aperture (p = 0.0171). The nasal and paranasal changes associated with acromegaly can make EEA challenging to perform. Widening the surgical corridor anterior to the sphenoid sinus is important in these patients.

Fluorescence detection of pituitary neuroendocrine tumour during endoscopic transsphenoidal surgery using bevacizumab-800CW: a non-randomised, non-blinded, single centre feasibility and dose finding trial [DEPARTURE trial

Achieving endocrine remission by gross total resection is challenging in pituitary neuroendocrine tumours (PitNETs) with cavernous sinus invasion. This study aims to assess the safety, feasibility, and optimal dose for intraoperative fluorescence imaging as an added instrument to discriminate PitNET from surrounding tissue using bevacizumab-800CW, targeting vascular endothelial growth factor A (VEGF-A). In part I, dose-escalation (0-4∙5-10-25mg) was performed in 4 groups of 3 patients with PitNETs Knosp grade 3-4. In part II, after interim analysis, the 10mg and 25mg groups were expanded to a total of 6 patients. Quantitative fluoroscence molecular endoscopy consisted of wide field fluorescence molecular endoscopy and multi-diameter single fiber reflectance / single fiber fluorescence spectroscopy. Mean fluorescence intensity (MFI) of the fresh surgical specimen was calculated and VEGF-staining was performed. Eighteen patients were included. All doses were well tolerated. Three serious adverse events were registered, but none were tracer-related. Part I showed an adequate in-vivo tumour-to-background ratio for both 10mg (TBR 2∙00 [1∙86, 2∙19]) and 25mg (TBR 2∙10, [1∙86, 2∙58]). Part II revealed a substantially higher MFI in the 25mg group. With both 10mg and 25mg a statistically significant difference between tumour and surrounding tissue was detected (p < 0∙0001). All surgical specimens had VEGF-A expression. This study demonstrates the safety and feasibility of quantitative fluorescence molecular endoscopy during PitNET surgery. Both 10mg and 25mg bevacizumab-800CW result in clear differentiation in-vivo, with improved contrast ex-vivo (MFI) in the 25mg group. NCT04212793 / Study Details| Detection of PitNET Tissue During TSS Using Bevacizumab800CW| ClinicalTrials.gov.

High-Grade Progression, Sarcomatous Transformation, and/or Metastasis of Pituitary Neuroendocrine Neoplasms (PitNENs): The UCSF Experience.

Pituitary neuroendocrine tumors (PitNET) that metastasize comprise ~ 0.2% of adenohypophyseal tumors are aggressive and are challenging to treat. However, many non-metastatic tumors are also aggressive. Herein, we review 21 specimens from 13 patients at UCSF with metastatic PitNETs (CSF or systemic, N = 7 patients), high-grade pituitary neuroendocrine neoplasms (HG-PitNEN, N = 4 patients), and/or PitNETs with sarcomatous transformation (PitNET-ST, N = 5 patients). We subtyped cases using the World Health Organization (WHO) and International Agency for Research on Cancer (IARC) criteria for neuroendocrine neoplasms (NENs). Lineage subtypes included acidophil stem cell, null cell, thyrotroph, corticotroph, lactotroph, and gonadotroph tumors. The median Ki-67 labeling index was 25% (range 5-70%). Lack of p16 was seen in 3 cases, with overexpression in 2. Strong diffuse p53 immunopositivity was present in 3 specimens from 2 patients. Loss of Rb expression was seen in 2 cases, with ATRX loss in one. Molecular analysis in 4 tumors variably revealed TERT alterations, homozygous CDKN2A deletion, aneuploidy, and mutations in PTEN, TP53, PDGFRB, and/or PIK3CA. Eight patients (62%) died of disease, 4 were alive at the last follow-up, and 1 was lost to the follow-up. All primary tumors had worrisome features, including aggressive lineage subtype, high mitotic count, and/or high Ki-67 indices. Additional evidence of high-grade progression included immunohistochemical loss of neuroendocrine, transcription factor, and/or hormone markers. We conclude that metastatic PitNET is not the only high-grade form of pituitary NEN. If further confirmed, these histopathologic and/or molecular features could provide advanced warning of biological aggressiveness and be applied towards a future grading scheme.

8773 CD44 Variant Isoforms Expressed Within PAX7/SOX2-Positive Pituitary Neuroendocrine Tumors Attribute To Therapy Resistance And Recurrence Of Cushing’s Disease

Abstract Disclosure: J. Chakrabarti: None. J. Eschbacher: None. S. Mallick: None. E. Ferris: None. B. Hermes: None. A. Little: None. Y. Zavros: None. Background: Cushing’s disease (CD) is a serious rare endocrine disease caused by an adrenocorticotropic hormone (ACTH)-secreting pituitary neuroendocrine tumor (PitNET) that subsequently stimulates the adrenal glands to overproduce cortisol. Approximately 56% of patients will experience disease recurrence during the 2 to 10-year follow-up period. Surgical failures and late recurrences of CD are common, and despite multiple treatments, biochemical control is achieved in only 50% of patients. Therefore, there is a need to advance targeted therapies that prevent recurrence and therapy resistance. The Cluster of Differentiation (CD) 44 transmembrane glycoprotein (CD44) is a prominent WNT signaling target, and deregulation of the Wnt pathway is associated with constitutively active βcatenin in SOX2-positive cells. Although a similar mechanism has been proposed in PitNETs, it has not been fully tested. The alternative mRNA splice variant, CD44v9 is expressed on cancer stem cells promotes resistance to ROS through the stabilization of the SLC7A11 (xCT) cystine glutamate transporter. Proteolytic cleavage of CD44 releases the CD44 intracellular domain which translocates to the nucleus activating cell stemness genes including SOX2. Although CD44 is a known cancer stem cell marker that plays multiple key roles including drug resistance and tumor cell invasiveness, the mechanisms underlying human PitNET tumorigenesis are unclear. Hypothesis: CD44 expressed on PAX7/SOX2-positive corticotroph PitNET cells define a cell population that attributes to therapy resistance and disease recurrence. Methods: CD patient PitNET tissues and matched PitNET-generated organoids (PitNETOs) were used for CosMx™ Spatial Molecular Imaging (SMI) and scRNAseq analyses respectively. Resistance to drug- and radiation-induced apoptosis was analyzed using PitNETOs generated. Results: SMI and scRNAseq data revealed a cell population co-expressing PAX7 and SOX2, CD44 and EpCAM that was abundant in invasive and silent corticotroph PitNET subtypes with Knosp grades 3-4. Invasive and silent corticotroph PitNETs also expressed an increased cell population of CD163+ macrophages, myofibroblast cancer associated fibroblasts (myCAFs), inflammatory CAFs. While cells isolated from the dura revealed growth of PitNETOs, adherent cells expressed increased proliferation (Ki67), and expression of somatostatin receptor subtype 2, cancer stem markers (CD44, SOX2, NESTIN, FUT4, PROM1), PAX7 progenitor cell population expressing stem cell markers NESTIN, SOX2, CD44 and EpCAM. Increased CD44/SLCA7A11 expression in CD44/PAX7/SOX2-positive PitNETOs rendered tumor cells resistant to radiation-induced apoptosis. Conclusions: Drugs targeting the CD44 variant isoforms may increase the efficacy of medical therapies and stereotactic radiosurgery to prevent residual and recurrent PitNETs in CD patients. Presentation: 6/3/2024

7559 TRIM21 Regulates Activation of ERK1/2 to Promote Growth and Drug Resistance in Pituitary Neuroendocrine Tumors

Abstract Disclosure: Y. Liu: None. F. Liu: None. C. Li: None. T. Zhang: None. L. Xue: None. Z. Wu: None. Objective: To investigate the role of the TRIM family genes in pituitary neuroendocrine tumors (PitNETs) and provide new targets and strategies for the clinical treatment of these tumors. Methods: A CRISPR screening system targeting the TRIM family was constructed and validated using next-generation sequencing. Stable cell lines overexpressing or knocking out TRIM21 were generated, and functional validation was performed using assays such as CCK-8, colony formation, and xenograft tumor growth in nude mice. RNA-seq, mass spectrometry, immunohistochemistry, and immunoblotting were employed to explore the signaling pathways and mechanisms underlying TRIM21's actions. Immunoprecipitation, immunofluorescence, GST-pulldown, NanoBiT assays, and ubiquitination experiments were conducted to investigate the effects of TRIM21 on ERK1/2. Immunohistochemistry and immunoblotting were used to explore the role of TRIM21 in drug- resistant prolactinomas and the correlation between TRIM21 and p-ERK. Results: Through screening the proliferative and drug-resistant effects of the TRIM family in MMQ and GH3 cells, we found that knocking out TRIM21 may inhibit cell growth and enhance drug sensitivity. Subsequently, stable cell lines overexpressing or knocking out TRIM21 were generated in MMQ and GH3 cells, revealing that TRIM21 overexpression promotes pituitary tumor cell growth and resistance to drug treatment, while TRIM21 knockout inhibits cell growth and enhances drug sensitivity. Cell-derived xenograft models showed that TRIM21 overexpression promoted growth of GH3 cells in vivo and resistance to cabergoline (CAB), while TRIM21 knockout suppressed growth of MMQ cells in vivo. Further exploration of the signaling pathways influenced by TRIM21 revealed that TRIM21 knockout downregulates the MAPK signaling pathway, while TRIM21 overexpression upregulates it. TRIM21 overexpression upregulates p-ERK1/2 in the MAPK pathway, while TRIM21 knockout decreases p-ERK. However, there is no significant influence on ERK1/2, JNK, p-JNK, p38, or p-p38. Mechanically, TRIM21 interacted with ERK1/2, enhancing the K27-linked ubiquitination of ERK1/2 and promoting their interaction with MEK1/2. In addition, the TRIM21 with D-docking mutant or ERK1/2 with CD-domain mutant resulted in the loss of their interaction. Furthermore, TRIM21 and p-ERK levels were significantly elevated in drug-resistant prolactinomas and immunohistochemical semi-quantitative analysis demonstrated a positive correlation between TRIM21 and p-ERK. Conclusion: The ubiquitin ligase TRIM21 catalyzes K27-linked ubiquitination of ERK1/2, enhancing its interaction with MEK1/2 and activation, thereby promoting growth and drug resistance in pituitary neuroendocrine tumors. TRIM21 may serve as a potential target for the treatment of pituitary neuroendocrine tumors. Presentation: 6/3/2024

6743 Decline in IGF-1 after surgery of the nonfunctioning pituitary neuroendocrine tumor

Abstract Disclosure: J. Sugata: None. S. Fujio: None. R. Makino: None. T. Hanada: None. R. Hanaya: None. Background: Patients undergoing surgical treatment for nonfunctioning pituitary neuroendocrine tumors (PitNET) may experience impaired secretion of growth hormone (GH). The optimal timing for assessing GH secretory function postoperatively remains unclear. In our department, we typically conduct hormone-loading tests three months after surgery. However, even in some cases without a diagnosis of growth hormone deficiency (GHD) at that point, there might be a gradual decline in Insulin-like growth factor-1 (IGF-1). Methods: We studied patients who exhibited peak GH levels &amp;gt; 1.8ng/ml in an insulin tolerance test (ITT) three months after undergoing surgery for nonfunctioning PitNET. We evaluated the levels of IGF-1 during the last observation, excluding cases where reoperation or radiosurgery was performed. Results: We identified 67 cases (29 males, 38 females) meeting the study criteria, with a median age of 54 years. The median follow-up time spanned 6 years (range 1-13 years). The median standard deviation (SD) scores of IGF-1 three months after surgery were -0.96, with 14 cases (21%) below -2.0 SD. At the end of the follow-up period, the median SD scores of IGF-1 were -1.31. This was significantly lower than the three-month time point (p&amp;lt;0.01), and 21 cases (31%) recorded were below -2.0 SD. In 6 cases suspected of severe GHD due to subjective symptoms or decreased IGF-1, ITT, or GH-releasing peptide-2 were retested. Among these, 2 cases were diagnosed with severe GHD, while the remaining demonstrated normal secretion of GH despite the low concentration of IGF-1. The IGF-1 SD scores at the end of follow-up and the three-month time-point exhibited a significant correlation (R2=0.74, p&amp;lt;0.01). However, no correlation was found between IGF-1 scores and peak GH concentration, age, tumor size, pituitary apoplexy, or preoperative IGF-1 SD scores. Conclusions: IGF-1 exhibited a progressive decrease in the majority of cases without severe GHD, with some cases showing reductions greater than -2.0 SD. Our findings emphasize the importance of cases with long-term clinical follow-up low IGF-1 after PitNET surgery, even when GH secretion appears normal. Presentation: 6/1/2024

8594 Pasireotide and Pasireotide Combined Treatment in Aggressive, Giant Pituitary Neuroendocrine Tumours

Abstract Disclosure: K. Ciszek: None. A. Bogusławska: None. M. Komisarz-Calik: None. J. Kunicki: None. A. Hubalewska-Dydejczyk: None. A. Gilis-Januszewska: None. Pasireotide is a second-generation somatostatin analogue that gained recognition as a treatment option for acromegaly and Cushing disease. Recently, there are single reports of pasireotide treatment in other subtype of pituitary neuroendocrine tumours (PitNETs).We present a case series of aggressive, giant PitNETs which were treated with pasireotide alone or as combined multimodal treatment. Case 1: A 59-year-old male presented in our Unit due to severe headaches and visual field deficits. The patient underwent transsphenoidal surgery (TSS) ten years ago. Histopathology results showed partially acidophilic adenoma (FSH- LH- GH- ACTH- PRL-). Control MRI showed tumour regrowth - 56x56x89mm and invasion of local structures. The patient was qualified for radiotherapy, to which he did not consent. Due to the progression of symptoms, temozolomide and pasireotide were introduced. After 5 months, significant improvement in headaches and vision was observed. In MRI stable pituitary mass was noted. Case 2: A 17-year-old male presented in our clinic due to daily severe headaches and peripheral vision loss who underwent two non-radical surgeries for dopamine-resistant giant prolactinoma. In control MRIs progressing mass 38x34x33mm invading local structures was observed. Due to resistance to dopamine agonists and worsening of the symptoms, pasireotide was introduced resulting in a decrease of headaches and improvement in vision. The tumour size remained stationary. Case 3: A 59-year-old male presented with severe headaches and life threatening tumour mass effect.In MRI a 48x48x33mm mass was observed. The patient underwent two non-radical TSS, 4 cycles of pasireotide, and cyberknife treatment. Histopathology showed gonadotroph PitNET. MRI showed tumour shrinkage to 45x46x29mm, with persistent severe headaches. The patient was re-qualified for pasireotide treatment. Case 4: A 33-year-old male reported to the Clinic due to severe headaches and vomiting. In MRI pituitary mass 33x39x55mm and a cerebral oedema were revealed. TSS with external ventricular drainage was performed -histopathology results showed densely granulated silent corticotroph adenoma subtype 1, Ki67&amp;lt;1%. After 3 months, MRI showed tumour progression to 39x40x30mm. Two emergency TSS followed by stereotactic radiotherapy were performed. Combined therapy with pasireotide, cabergoline and temozolomide was introduced. After 18 months, stabilization of the disease was observed with the complete disappearance of headaches. Conclusions: Our study demonstrates the clinical potential of pasireotide treatment in aggressive, giant PitNETs. The therapy alone, or in combination has a potential role in reducing the tumour size, and allows the stabilization of the disease. The analgesic and anti-inflammatory effect of pasireotide could potentially alleviate headaches in this subset of patients. Presentation: 6/2/2024

8738 Unveiling Potential Therapeutic Candidates for ACTH-Silent Pituitary Neuroendocrine Tumors Through High Throughput Drug Screening

Abstract Disclosure: J.M. Marques: None. N.D. D' Alessandre: None. G.D. Guardia: None. F.L. Craveiro: None. C. Grutzmacher: None. G.O. Silva: None. B.B. Mendonca: None. L.R. Carvalho: None. F. Fattahi: None. P.A. Galante: None. R.L. Batista: None. Introduction: ACTH-silent pituitary neuroendocrine tumours (PitNETs) are a subtype of PitNETs that arise from corticotroph cells of the anterior pituitary gland. They can show positive immunoreactivity for adrenocorticotropic hormone (ACTH) but with no clinical or laboratory evidence of hypercortisolism. ACTH-silent PitNETs display notably more aggressive behavior and treatment resistance. Currently, there is no established pharmacological therapy for this specific tumor subtype. Aim: To use high throughput drug screening to identify compounds that modulate ACTH secretion and tumor progression in ACTH-silent PitNETs. Methods: WTC11 cells (GM25256) were differentiated into pituitary using E6 with SB431542 10µM, SHH 200ng/mL, FGF8 100ng/mL and FGF10 50ng/mL until day 30. Pituitary cells were passaged in 384 well plates and treated with FDA-approved compound library with 3113 drugs at 1μM for 72h (#L1300, Selleckchem). Cells were stained with ACTH and imaged on ImageXpress® HCS. ACTH intensity was normalized to total cell number, measured by DAPI, using MetaXpress Software and compounds z-score was calculated, considering -2.5 for analysis. Gene and pathway enrichment analysis were performed and PitNET RNAseq data, publicly available (GSE207937), was used to determine target drugs based on similar target pathways and gene expression. To validate hits, we collected tumor samples from a patient with an aggressive silent ACTH PitNET. PitNET was histologically confirmed and hypercortisolism was excluded clinically and laboratory. Samples were cultured on DMEN/F12 with 10% FBS and 1% antibiotic and pituitary hormones were measured at days 3, 6 and 8. Cells were treated with 1uM of Letrozole, Linsitinib and Raloxifene for 48h and sample for RNA and hormone dosage were collected. Results: We identified 8 drugs that decreased ACTH in induced pituitary cells and selected 3 of them for validation. PitNET was successfully cultured and treated with selected drugs and ACTH secretion was detected at all periods (972.1 pg/mL to 10490 pg/mL), gonadotropins were below the detected level. Letrozole significantly reduced ACTH in the PitNET culture at day 8 (600.9 ± 25.8pg/mL, p&amp;lt;0,001). ACTH was also decreased in Linsitinib treated cells (932 ± 12.7pg/mL, p&amp;lt;0.05), while Raloxifene did not change ACTH secretion (980 ± 95.1pg/mL, p=0.061). Microscopically, PitNET cells aggregate in spheres and this seems to be affected by letrozole treatment, not influencing cell viability. Conclusion: We performed a high throughput drug screen using induced pituitary cells that led to the discovery of 3 compounds that might be used as an alternative for PitNET treatment. Pathway and gene expression analysis from target drugs and PitNET RNAseq may help in the understanding of drug effect in the PitNET context and improve the understanding of tumorigenesis and pharmacological treatment. Presentation: 6/1/2024

8785 Does Somatostatin Receptor Expression Intensity Impact Prognosis in Non Pituitary Neuroendocrine Tumors Treated with Somatostatin Analogues?

Abstract Disclosure: N. Saleh Jouneghani: None. S. Fazeli: None. S. Chang: None. A. Hosseini: None. R. Marandi: None. A. Siddiqui: None. M. Talley: None. B. Salehian: None. Does Somatostatin Receptor Expression Intensity Impact Prognosis in Non Pituitary Neuroendocrine Tumors Treated with Somatostatin Analogues? Introduction: Non-pituitary neuroendocrine tumors (NETs) show different somatostatin receptor subtype (SSTR) expression, but their role in tumor progression and prognosis is not well known. We hypothesized that NETs with higher expression of SSTR2, SSRT5, or co-expression of SSTR2 and SSTR5 will have better outcome when treated with Somatostatin Analogues (SSA). Method: Retrospectively, patients with non-pituitary neuroendocrine tumors, followed for more than one year between 1985 and 2022, and treated with SSA (Octreotide or Lanreotide) who had available tissue were selected. Tissue immunostaining performed for SSTR2 and SSTR5 with use of monoclonal antibodies. Expression analysis of the SSTR2 and SSTR5 were evaluated by the validated semi-quantitatively method, reported by an intensity score of 0 -3. The progression free survival and overall survival were calculated by Kaplan Meier and compared in different subgroups with SSTR expression intensity. Response evaluation was assessed using RECIST v1.1. Results: Of 279 non-pituitary neuroendocrine tumors, 51 meet the criteria and tissue sent for analysis. The median age at diagnosis was 62; male 49%, with median follow up 7 years, 85% stage IV at diagnosis, most common primary tumor was in gut 54% followed by pancreas 33%. Positive SSRT5 tumors had 93% SSRT2 co-expression. There were no significant differences in progression-free survival (PFS) observed between tumors with low or high SSTR2 intensity expression (P=0.62). The presence or absences of SSRT5 expression did not have any impact on PFS (p=0.57) or overall survival (p=0.3). Conclusion: in the patient with non-pituitary neuroendocrine tumors, higher SSTR2 expression intensity or having SSRT5 co-expression, did not correlate with a better PFS or overall survival in response to SSA, in our study. Further prospective studies are needed to clarify if higher expression intensity of SSRTs correlates with better response to SSAs in NETs. Presentation: 6/1/2024