INSM1 Expression Is Frequent in Primary Central Nervous System Neoplasms but Not in the Adult Brain Parenchyma

Ibrutinib disrupts blood-tumor barrier integrity and prolongs survival in rodent glioma model

In malignant glioma, cytotoxic drugs are often inhibited from accessing the tumor site due to the blood-tumor barrier (BTB). Ibrutinib, FDA-approved lymphoma agent, inhibits Bruton tyrosine kinase (BTK) and has previously been shown to independently impair aortic endothelial adhesion and increase rodent glioma model survival in combination with cytotoxic therapy. Yet additional research is required to understand ibrutinib's effect on BTB function. In this study, we detail baseline BTK expression in glioma cells and its surrounding vasculature, then measure endothelial junctional expression/function changes with varied ibrutinib doses in vitro. Rat glioma cells and rodent glioma models were treated with ibrutinib alone (1-10 µM and 25 mg/kg) and in combination with doxil (10-100 µM and 3 mg/kg) to assess additive effects on viability, drug concentrations, tumor volume, endothelial junctional expression and survival. We found that ibrutinib, in a dose-dependent manner, decreased brain endothelial cell-cell adhesion over 24 h, without affecting endothelial cell viability (p < 0.005). Expression of tight junction gene and protein expression was decreased maximally 4 h after administration, along with inhibition of efflux transporter, ABCB1, activity. We demonstrated an additive effect of ibrutinib with doxil on rat glioma cells, as seen by a significant reduction in cell viability (p < 0.001) and increased CNS doxil concentration in the brain (56 ng/mL doxil alone vs. 74.6 ng/mL combination, p < 0.05). Finally, Ibrutinib, combined with doxil, prolonged median survival in rodent glioma models (27 vs. 16 days, p < 0.0001) with brain imaging showing a - 53% versus - 75% volume change with doxil alone versus combination therapy (p < 0.05). These findings indicate ibrutinib's ability to increase brain endothelial permeability via junctional disruption and efflux inhibition, to increase BTB drug entry and prolong rodent glioma model survival. Our results motivate the need to identify other BTB modifiers, all with the intent of improving survival and reducing systemic toxicities.

Comparison of INSM1 immunostaining with established neuroendocrine markers synaptophysin and chromogranin A in over 14,000 neuroendocrine and non-neuroendocrine tumors

INSM1 is a transcription factor protein which is increasingly used as an immunohistochemical marker for neuroendocrine differentiation. To determine the prevalence of INSM1 expression in tumors and its expression pattern in normal tissues, tissue microarrays containing 14,908 samples from 117 different tumor types/subtypes as well as 76 different normal tissues were analyzed by immunohistochemistry. INSM1 was positive in 89.2% of 471 neuroendocrine neoplasms (NEN) and in 3.5% of 11,815 non-neuroendocrine neoplasms that were successfully analyzed. At least an occasional weak INSM1 positivity was observed in 59 different non-neuroendocrine tumor entities, of which 15 entities contained at least one case with strong INSM1 staining. A comparison with synaptophysin and chromogranin A staining revealed that in NEN, synaptophysin showed the highest sensitivity (93.3%), followed by INSM1 (89.2%) and chromogranin A (87.5%). In neuroendocrine carcinomas (NEC), sensitivity was highest for INSM1 (88.0%), followed by synaptophysin (86.5%) and chromogranin A (66.4%). If INSM1 was used as an additional marker, the sensitivity for detecting neuroendocrine differentiation in NEN increased from 96.6% (synaptophysin and chromogranin A) to 97.2% (synaptophysin, chromogranin A and INSM1). Our study shows that INSM1 is a useful additional marker for neuroendocrine differentiation with high sensitivity, particularly in NEC.

Diagnostic Utility of Immunohistochemical Detection of MEOX2, SOX11, INSM1 and EGFR in Gliomas

Histological identification of dispersed glioma cells in small biopsies can be challenging, especially in tumours lacking the IDH1 R132H mutation or alterations in TP53. We postulated that immunohistochemical detection of proteins expressed preferentially in gliomas (EGFR, MEOX2, CD34) or during embryonal development (SOX11, INSM1) can be used to distinguish reactive gliosis from glioma. Tissue microarrays of 46 reactive glioses, 81 glioblastomas, 34 IDH1-mutant diffuse gliomas, and 23 gliomas of other types were analysed. Glial neoplasms were significantly more often (p < 0.001, χ2) positive for EGFR (34.1% vs. 0%), MEOX2 (49.3% vs. 2.3%), SOX11 (70.5% vs. 20.4%), and INSM1 (65.4% vs. 2.3%). In 94.3% (66/70) of the glioblastomas, the expression of at least two markers was observed, while no reactive gliosis showed coexpression of any of the proteins. Compared to IDH1-mutant tumours, glioblastomas showed significantly higher expression of EGFR, MEOX2, and CD34 and significantly lower positivity for SOX11. Non-diffuse gliomas were only rarely positive for any of the five markers tested. Our results indicate that immunohistochemical detection of EGFR, MEOX2, SOX11, and INSM1 can be useful for detection of glioblastoma cells in limited histological samples, especially when used in combination.

INSM1, a Novel Biomarker for Detection of Neuroendocrine Neoplasms: Cytopathologists’ View

Background: Insulinoma-associated protein 1 (INSM1) has been considered as a novel immunostain for neuroendocrine tumors (NETs) and is hypothesized to be more reliable than first-generation NET biomarkers, such as CGA (chromogranin A), SYP (synaptophysin) and CD56 (neural cell adhesion molecule). In this review, we summarize existing literature on INSM1′s reliability as an immunostain for detection of various NETs, its results in comparison to first-generation NET biomarkers, and its expression in both non-NETs and benign tissues/cells on cytology specimens (cell blocks/smears).

Pituitary neuroendocrine tumors: a model for neuroendocrine tumor classification

The classification of adenohypophysial neoplasms as "pituitary neuroendocrine tumors" (PitNETs) was proposed in 2017 to reflect their characteristics as epithelial neuroendocrine neoplasms with a spectrum of clinical behaviors ranging from small indolent lesions to large, locally invasive, unresectable tumors. Tumor growth and hormone hypersecretion cause significant morbidity and mortality in a subset of patients. The proposal was endorsed by a WHO working group that sought to provide a unified approach to neuroendocrine neoplasia in all body sites. We review the features that are characteristic of neuroendocrine cells, the epidemiology and prognosis of these tumors, as well as further refinements in terms used for other pituitary tumors to ensure consistency with the WHO framework. The intense study of PitNETs has provided information about the importance of cellular differentiation in tumor prognosis as a model for neuroendocrine tumors in different locations.

Insulinoma-associated Protein 1 Expression and Its Diagnostic Significance in Female Genital Tract Neuroendocrine Carcinomas

Neuroendocrine carcinomas (NECs) are rare, but aggressive malignant tumors of the female genital tract, especially in the uterine the cervix. Beside histologic morphology, positivity of neuroendocrine markers with immunohistochemistry plays an important role in diagnosis of NECs. Insulinoma-associated protein 1 (INSM1) is a novel marker reported to be widely expressed in a variety of neuroendocrine tumors. A previous study also suggested INSM1 has superior performance to conventional neuroendocrine markers in cervical NECs. In our present study, comparison between immunomarkers was performed in female genital tract NECs. Forty-nine patients with gynecologic NECs (4 vagina, 39 cervix, 5 endometrium, 1 ovary) were included from 1993 to 2019 at our center. Immunohistochemistry was performed with INSM1, CD56, synaptophysin (SYN), chromogranin-A (CgA), and thyroid transcription factor 1 (TTF1). The results show INSM1 has superior sensitivity and intensity compared with CD56, SYN, CgA, and TTF1 in cervical small cell NECs, but not in large cell NECs. In contrast to cervical NECs, INSM1 immunohistochemistry shows only focal and weak staining in endometrial NECs. Our result suggested INSM1 is a sensitive marker which can be used as first-line test in histologic suspicious cervical cases, especially small cell NECs. However, negative INSM1 stain does not exclude the possibility of NECs. In endometrial NECs, conventional panel with CD56, SYN, CgA has better diagnostic performance than INSM1 alone.

INSM1 Expression in Chordomas

OBJECTIVES

Chordomas are rare malignant tumors with a broad differential diagnosis, including chondrosarcomas and metastatic carcinomas. Recently, insulinoma-associated protein 1 (INSM1) has gained great interest regarding the diagnosis of neuroendocrine tumors but also extraskeletal myxoid chondrosarcomas. However, its expression in chordomas remains largely unknown.

METHODS

We retrospectively examined 57 chordomas for INSM1 expression.

RESULTS

INSM1 expression was found in only 5% of tumors.

CONCLUSIONS

This marker is rarely expressed in this type of tumor, raising questions about neuroendocrine differentiation.

Insulinoma-associated Protein 1 (INSM1) in Thoracic Tumors is Less Sensitive but More Specific Compared With Synaptophysin, Chromogranin A, and CD56

OBJECTIVE

Recognition of neuroendocrine differentiation is important for tumor classification and treatment stratification. To detect and confirm neuroendocrine differentiation, a combination of morphology and immunohistochemistry is often required. In this regard, synaptophysin, chromogranin A, and CD56 are established immunohistochemical markers. Insulinoma-associated protein 1 (INSM1) has been suggested as a novel stand-alone marker with the potential to replace the current standard panel. In this study, we compared the sensitivity and specificity of INSM1 and established markers.

MATERIALS AND METHODS

A cohort of 493 lung tumors including 112 typical, 39 atypical carcinoids, 77 large cell neuroendocrine carcinomas, 144 small cell lung cancers, 30 thoracic paragangliomas, 47 adenocarcinomas, and 44 squamous cell carcinomas were selected and tissue microarrays were constructed. Synaptophysin, chromogranin A, CD56, and INSM1 were stained on all cases and evaluated manually as well as with an analysis software. Positivity was defined as ≥1% stained tumor cells in at least 1 of 2 cores per patient.

RESULTS

INSM1 was positive in 305 of 402 tumors with expected neuroendocrine differentiation (typical and atypical carcinoids, large cell neuroendocrine carcinomas, small cell lung cancers, and paraganglioma; sensitivity: 76%). INSM1 was negative in all but 1 of 91 analyzed non-neuroendocrine tumors (adenocarcinomas, squamous cell carcinomas; specificity: 99%). All conventional markers, as well as their combination, had a higher sensitivity (97%) and a lower specificity (78%) for neuroendocrine differentiation compared with INSM1.

CONCLUSIONS

Although INSM1 might be a meaningful adjunct in the differential diagnosis of neuroendocrine neoplasias, a general uncritical vote for replacing the traditional markers by INSM1 may not be justified.

Transcriptomic analysis identifies a tumor subtype mRNA classifier for invasive non-functioning pituitary neuroendocrine tumor diagnostics

Rationale: The invasive behavior of non-functioning pituitary neuroendocrine tumors (NF-PitNEts) presents obstacles for complete surgical resection and is indicative of poor prognosis. Therefore, developing reliable diagnostic tools for identifying invasive PitNEts would be helpful in guiding surgical decisions and, in particular, the follow-up treatment.

Methods: We analyzed differential gene expression profiles between 39 non-invasive and 22 invasive NF-PitNEts by high-throughput sequencing, gene co-expression, and functional annotation. Twenty-one transcripts were further validated by Taqman-qPCR in another 143 NF-PitNEt samples. The histological expression and serum-exosomal mRNA of three candidate genes were examined by tissue microarray and droplet digital PCR.

Results: Non-invasive and invasive NF-PitNEts were clustered into distinct groups with a few outliers because of their gonadotroph, corticotroph, or null cell lineages. The gene signature with strong invasive potential was enriched in 'Pathways in cancers' and 'MAPK pathway', with significantly higher in situ INSM1 and HSPA2 protein expression in invasive NF-PitNEts. Further integration of the 20 qPCR-validated differentially expressed genes and pituitary cell lineages provided a gene-subtype panel that performed 80.00-90.24% diagnostic accuracy for the invasiveness of NF-PitNEts.

Conclusion: Our approach defined new characteristics in the core molecular network for patients at risk for invasive NF-PitNEt, representing a significant clinical advance in invasive PitNEt diagnostics.

Increased Tau Expression Correlates With IDH Mutation in Infiltrating Gliomas and Impairs Cell Migration

Although the microtubule-associated protein tau is well studied in human neurodegeneration, the role of tau in neoplastic brain diseases is not well understood. Recently, studies have shown tau mRNA expression is associated with improved survival in human infiltrating gliomas. However, the biologic basis of this association is largely unexplored. Using 2 independent publicly available mRNA databases, we show that high tau mRNA expression is associated with improved patient survival in infiltrating gliomas. Higher tau protein expression is also associated with improved patient prognosis in infiltrating gliomas by immunohistochemical staining of tissue microarrays. This prognostic association is in part due to higher tau mRNA and protein expression in IDH-mutant infiltrating astrocytomas. Expression of tau in an IDH-wildtype glioblastoma cell line selectively impairs cell migration in assays designed to mimic tumor invasion. These findings suggest that tau expression is not only associated with IDH mutation status but also may contribute to improved patient outcomes by impairing tumor invasion.

Recurrent DICER1 Hotspot Mutations in Malignant Thyroid Gland Teratomas: Molecular Characterization and Proposal for a Separate Classification

Thyroid gland teratomas are rare tumors that span a wide clinicopathologic spectrum. Although benign and immature teratomas arise in infants and young children and generally have good outcomes, malignant teratomas affect adults and follow an aggressive course. This divergent behavior raises the possibility that benign/immature and malignant teratomas are separate entities rather than different grades of a single tumor. However, the histogenesis and molecular underpinnings of thyroid gland teratomas are poorly understood regardless of grade. In this study, we performed next-generation sequencing on 8 thyroid gland teratomas, including 4 malignant, 3 benign, and 1 immature. We identified DICER1 hotspot mutations in all 4 malignant cases (100%) but not in any benign/immature cases (0%). No clinically significant mutations in other genes were found in either group. We also performed immunohistochemistry to characterize the primitive components of malignant teratomas. Not only did all cases consistently contain immature neural elements (synaptophysin and INSM1 positive), but also spindled cells with rhabdomyoblastic differentiation (desmin and myogenin positive) and bland epithelial proliferations of thyroid follicular origin (TTF-1 and PAX8 positive). Although DICER1 mutations have previously been implicated in multinodular hyperplasia and well-differentiated thyroid carcinomas, these findings demonstrate the first recurrent role for DICER1 in primitive thyroid tumors. The combined neural, rhabdomyoblastic, and homologous epithelial elements highlighted in this series of malignant thyroid gland teratomas parallel the components of DICER1-mutated tumors in other organs. Overall, these molecular findings further expand the differences between benign/immature teratomas and malignant teratomas, supporting the classification of these tumors as separate entities.

A promoter-driven assay for INSM1-associated signaling pathway in neuroblastoma

Aggressive form of neuroblastoma (NB) is a malignant childhood cancer derived from granule neuron precursors and sympatho-adrenal lineage with N-MYC amplification. An insulinoma associated-1 (INSM1) transcription factor has emerged as a NB biomarker that plays critical role in facilitating tumor cell growth and transformation. N-myc activates INSM1 in NB was discovered. In order to elucidate the signaling pathways associated with INSM1 expression and NB tumor cell growth, we developed an INSM1 promoter-driven luciferase assay for new drug discovery. Promoter-driven luciferase assay demonstrated high Z' factor (>0.7). Performance measures using signal-to-noise ratio, signal window, and Z' factor confirmed this assay is a robust screening method. A panel of FDA-approved oncology drugs set (147 compounds) was subjected to the INSM1 promoter-driven luciferase assay. The positive-hit compounds were validated for effects on cell viability and INSM1 expression. Screening a FDA-approved oncology drugs set revealed multiple inhibitors against various signaling pathways via suppression of INSM1 promoter activity. The positive-hit compounds consist of 9 signaling pathway inhibitors negatively regulates INSM1 expression and cell viability in NB. These inhibitors target DNA/RNA/protein synthesis, tubulin assembly, and histone deacetylase signaling pathways. The outcome of this assay indicates that the newly identified pathways could be critical for NB growth and transformation. This technology and the positive-hits of multiple pathways represent a promising option of identifying re-purposed FDA-approved drugs valuable for NB treatment in the context of a NB-specific marker, INSM1.

Insulinoma-associated protein 1 is a sensitive and specific marker for lung neuroendocrine tumors in cytologic and surgical specimens

INTRODUCTION

Insulinoma-associated protein 1 (INSM1) is an immunohistochemical marker for neuroendocrine differentiation with potentially superior sensitivity and specificity. INSM1 performance in pulmonary cytology cell block material (CB) has not been well established, and large series demonstrating its performance have been few.

MATERIALS AND METHODS

Typical and atypical carcinoid, small cell lung carcinoma, and large cell neuroendocrine carcinoma, squamous cell carcinoma, and adenocarcinoma CBs and 563 surgical specimens comprising 17 typical carcinoid, 14 atypical carcinoid, 8 small cell lung carcinoma, 10 large cell neuroendocrine carcinoma, 58 squamous cell carcinoma, 415 adenocarcinoma, and 17 large cell carcinoma cases and 24 other tumor types were immunostained with INSM1, CD56, synaptophysin, and chromogranin A.

RESULTS

The INSM1 sensitivity, specificity, positive predictive value, and negative predictive value were 92.3%, 100%, 78.9%, and 99% in the CBs and 89.8%, 98.1%, 81.5%, and 99% in the surgical specimens, respectively, with 86.2% concordance. The sensitivity, specificity, positive predictive value, and negative predictive value for the other neuroendocrine markers were 97.4%, 93.3%, 97.4%, and 93.3% in the CBs and 93.9%, 93.6%, 58.2%, and 99.4% in the surgical specimens for CD56; 89.7%, 100%, 100%, and 75% in the CBs and 93.4%, 91.2%, 50.5%, and 99.4% in the surgical specimens for synaptophysin; 66.7%, 100%, 100%, and 53.6% in the CBs and 75.5%, 98.6%, 84.1%, and 97.7% in the surgical specimens for chromogranin A, respectively. Finally, INSM1, together with CD56, maximized the sensitivity to 100% with 93.3% specificity in the CBs.

CONCLUSIONS

The results from our study have further established the high sensitivity and specificity of INSM1 in the largest pulmonary cytologic and surgical cohorts to date. INSM1 either matched or outperformed the performance of existing neuroendocrine markers, and its combination with CD56 appeared to maximize test performance.

INSM1 Expression in Peripheral Neuroblastic Tumors and Other Embryonal Neoplasms

Insulinoma-associated protein 1 (INSM1) is a transcription factor that functions in neuroepithelial tissue development and shows expression in neuroendocrine neoplasms. Given the role of INSM1 in controlling differentiation of the sympatho-adrenal lineage, we hypothesized that INSM1 expression would define a subset of neuroblastic tumors. This study aimed to characterize the immunohistochemical profile of INSM1 in a cohort of peripheral neuroblastic tumors and compare INSM1 expression in these tumors to that seen in other embryonal neoplasms, using both tissue microarrays and whole-slide histologic sections. INSM1 showed nuclear expression in 39/50 (78%) peripheral neuroblastic tumors, including 27/32 (84%) neuroblastomas, 9/9 (100%) ganglioneuroblastomas, and 3/9 (33%) ganglioneuromas. Altogether, 70% of peripheral neuroblastic tumors showed anti-INSM1 immunoreactivity in more than 20% of tumor nuclei. Although no non-neuroblastic tumors in this study exhibited INSM1 expression in more than 20% of nuclei, focal or patchy staining was identified in 7/14 (50%) rhabdomyosarcomas, 7/22 (32%) nephroblastomas, and 4/20 (20%) Ewing sarcomas. The absence of INSM1 expression in peripheral neuroblastic tumors was restricted to undifferentiated and poorly differentiated neuroblastomas, as well as mature ganglioneuromas, mimicking the transient INSM1 expression seen in sympatho-adrenal differentiation during normal development. No significant association between MYCN amplification status and INSM1 expression was observed. We found that all 3 INSM1-negative neuroblastoma patients with available follow-up were alive at a median of 15 years, in comparison to 9 of 13 INSM1-positive neuroblastoma patients living at a median of 5 years. Additional studies are needed to determine whether INSM1 expression is indicative of a clinically significant differentiation state in neuroblastoma.

Insulinoma-Associated-1: From Neuroendocrine Tumor Marker to Cancer Therapeutics

Insulinoma-associated-1 (IA-1 or INSM1) encodes a zinc-finger transcription factor, which was isolated from a human insulinoma subtraction library, with specific expression patterns, predominantly in developing neuroendocrine tissues and tumors. INSM1 is key in early pancreatic endocrine, sympatho-adrenal lineage, and pan-neurogenic precursor development. Insm1 gene ablation results in impairment of pancreatic β cells, catecholamine biosynthesis, and basal progenitor development during mammalian neocortex maturation. Recently, INSM1 has emerged as a superior, sensitive, and specific biomarker for neuroendocrine tumors. INSM1 regulates downstream target genes and exhibits extranuclear activities associated with multiple signaling pathways, including Sonic Hedgehog, PI3K/AKT, MEK/ERK^1/2, ADK, p53, Wnt, histone acetylation, LSD1, cyclin D1, Ascl1, and N-myc. Novel strategies targeting INSM1-associated signaling pathways facilitate the suppression of neuroendocrine tumor growth. In addition, INSM1 promoter-driven reporter assay and/or suicide gene therapy are promising effective therapeutic approaches for targeted specific neuroendocrine tumor therapy. In this review, the current knowledge of the biological role of INSM1 as a neuroendocrine tumor biomarker is summarized, and novel strategies targeting multiple signaling pathways in the context of INSM1 expression in neuroendocrine tumors are further explored. IMPLICATIONS: Neuroendocrine transcription factor (INSM1) may serve as a neuroendocrine biomarker for the development of novel cancer therapeutics against neuroendocrine tumors.

Insulinoma-associated protein 1 (INSM1) is a sensitive and highly specific marker of neuroendocrine differentiation in primary lung neoplasms: an immunohistochemical study of 345 cases, including 292 whole-tissue sections

Recent evidence suggests a role for the nuclear marker INSM1 in the diagnosis of neuroendocrine lung neoplasms. The aim of this study was to determine the utility of INSM1 as a marker of neuroendocrine differentiation using a large series of whole-tissue sections of primary lung neoplasms. We stained 345 primary lung neoplasms with INSM1, including 292 whole-tissue sections. Most cases were also stained with synaptophysin, chromogranin, and CD56. The tumors included 64 small cell lung carcinomas, 24 large cell neuroendocrine carcinomas, 64 carcinoid tumors (48 typical, 16 atypical), 130 adenocarcinomas, and 33 squamous cell carcinomas. For small cell lung carcinoma, the sensitivity of INSM1 (98%) was similar to synaptophysin (100%) and CD56 (95%) but considerably higher than chromogranin (83%). For large cell neuroendocrine carcinoma, CD56 (92%) and synaptophysin (88%) were more sensitive than INSM1 (75%), while chromogranin was less sensitive (46%). All markers stained 100% of carcinoid tumors, except one atypical carcinoid tumor, which was negative for INSM1. The sensitivity of INSM1 for neuroendocrine lung neoplasms as a group (95%) was similar to synaptophysin (98%) and CD56 (97%), but higher than chromogranin (84%). The specificity of INSM1 for neuroendocrine lung neoplasms (97%) was similar to chromogranin (98%) but higher than synaptophysin (90%) and CD56 (87%). INSM1 staining was concordant in primary tumors and matched metastases. In conclusion, INSM1 is a reliable marker of neuroendocrine differentiation in primary lung neoplasms, with sensitivity similar to synaptophysin and CD56, and specificity similar to chromogranin.