Sonic hedgehog signaling pathway promotes INSM1 transcription factor in neuroendocrine lung cancer

Therapeutic potential of hedgehog signaling in advanced cancer types

In this chapter, we have made an attempt to elucidate the relevance of hedgehog signaling pathway in tumorigenesis. Here, we have described different types of hedgehog signaling (canonical and non-canonical) with emphasis on the different mechanisms (mutation-driven, autocrine, paracrine and reverse paracrine) it adopts during tumorigenesis. We have discussed the role of hedgehog signaling in regulating cell proliferation, invasion and epithelial-to-mesenchymal transition in both local and advanced cancer types, as reported in different studies based on preclinical and clinical models. We have specifically addressed the role of hedgehog signaling in aggressive neuroendocrine tumors as well. We have also elaborated on the studies showing therapeutic relevance of the inhibitors of hedgehog signaling in cancer. Evidence of the crosstalk of hedgehog signaling components with other signaling pathways and treatment resistance due to tumor heterogeneity have also been briefly discussed. Together, we have tried to put forward a compilation of the studies on therapeutic potential of hedgehog signaling in various cancers, specifically aggressive tumor types with a perspective into what is lacking and demands further investigation.

Genomic Profiling of Metastatic Castration-Resistant Prostate Cancer Samples Resistant to Androgen Receptor Pathway Inhibitors

PURPOSE

The androgen receptor axis inhibitors (ARPI; e.g., enzalutamide, abiraterone acetate) are administered in daily practice for men with metastatic castration-resistant prostate cancer (mCRPC). However, not all patients respond, and mechanisms of both primary and acquired resistance remain largely unknown.

EXPERIMENTAL DESIGN

In the prospective trial MATCH-R (NCT02517892), 59 patients with mCRPC underwent whole-exome sequencing (WES) and/or RNA sequencing (RNA-seq) of samples collected before starting ARPI. Also, 18 patients with mCRPC underwent biopsy at time of resistance. The objectives were to identify genomic alterations associated with resistance to ARPIs as well as to describe clonal evolution. Associations of genomic and transcriptomic alterations with primary resistance were determined using Wilcoxon and Fisher exact tests.

RESULTS

WES analysis indicated that no single-gene genomic alterations were strongly associated with primary resistance. RNA-seq analysis showed that androgen receptor (AR) gene alterations and expression levels were similar between responders and nonresponders. RNA-based pathway analysis found that patients with primary resistance had a higher Hedgehog pathway score, a lower AR pathway score and a lower NOTCH pathway score than patients with a response. Subclonal evolution and acquisition of new alterations in AR-related genes or neuroendocrine differentiation are associated with acquired resistance. ARPIs do not induce significant changes in the tumor transcriptome of most patients; however, programs associated with cell proliferation are enriched in resistant samples.

CONCLUSIONS

Low AR activity, activation of stemness programs, and Hedgehog pathway were associated with primary ARPIs' resistance, whereas most acquired resistance was associated with subclonal evolution, AR-related events, and neuroendocrine differentiation. See related commentary by Slovin, p. 4323.

Repurposing a plant alkaloid homoharringtonine targets insulinoma associated-1 in N-Myc-activated neuroblastoma

High-risk neuroblastoma (NB) is a heterogeneous and malignant childhood cancer that is frequently characterized by MYCN proto-oncogene amplification or elevated N-Myc protein (N-Myc) expression. An N-Myc downstream target gene, insulinoma associated-1 (INSM1) has emerged as a biomarker that plays a critical role in facilitating NB tumor cell growth and transformation. N-Myc activates endogenous INSM1 gene expression through binding to the E2-box of the INSM1 proximal promoter in NB. We identified a plant alkaloid, homoharringtonine (HHT), from a chemical library screening showing potent inhibition of INSM1 promoter activity. This positive-hit plant alkaloid exemplifies an effective screening approach for repurposed compound targeting INSM1 expression in NB cancer therapy. The elevated N-Myc and INSM1 expression in NB constitutes a positive-loop through INSM1 activation that promotes N-Myc stability. In the present study, the biological effects and anti-tumor properties of HHT against NB were examined. HHT either down regulates and/or interferes with the binding of N-Myc to the E2-box of the INSM1 promoter and the inhibition of PI3K/AKT-mediated N-Myc stability could lead to the NB cell apoptosis. HHT inhibition of NB cell proliferation is consistent with the INSM1 expression as higher level of INSM1 exhibits a more sensitive IC50 value. The combination treatment of HHT and A674563 provides a better option of increasing potency and reducing cellular cytotoxicity than HHT or A674563 treatment alone. Taken together, the suppression of the INSM1-associated signaling pathway axis promotes the inhibition of NB tumor cell growth. This study developed a feasible approach for repurposing an effective anti-NB drug.

Exploration of an Prognostic Signature Related to Endoplasmic Reticulum Stress in Colorectal Adenocarcinoma and Their Response Targeting Immunotherapy

Background: Endoplasmic reticulum (ER) stress plays a pro-apoptotic role in colorectal adenocarcinoma (COAD). This study aimed to develop a novel ER-stress-related prognostic risk model for COAD and provide support for COAD cohorts with different risk score responses to immune checkpoint inhibitor therapies. Methods: TCGA-COAD and GSE39582 were included in this prospective study. Univariate and multivariate Cox analyses were performed to identify prognostic ER stress-related genes (ERSGs). Accordingly, the immune infiltration landscape and immunotherapy response in different risk groups were assessed. Finally, the expression of prognostic genes in 10 normal and 10 COAD tissue samples was verified using reverse transcription-quantitative polymerase chain reaction. Results: Eight prognostic genes were selected to establish an ERSG-based signature in the training set of the TCGA-COAD cohort. The accuracy of this was confirmed using a testing set of TCGA-COAD and GSE39582 cohorts. Gene set variation analysis indicated that differential functionality in high-low-risk groups was related to immune-related pathways. Corresponding to this, CD36, TIMP1, and PTGIS were significantly associated with 19 immune cells with distinct proportions between the different risk groups, such as central memory CD4T cells and central memory CD8T cells. Moreover, the risk score was considered effective for predicting the clinical response to immunotherapy, and the immunotherapy response was significantly and negatively correlated with the risk score of individuals with COAD. Furthermore, the immune checkpoint inhibitor treatment was less effective in the high-risk group, where the expression levels of PD-L1 and tumor immune dysfunction and exclusion scores in the high-risk group were significantly increased. Finally, the experimental results demonstrated that the expression trends of prognostic genes in clinical samples were consistent with the results from public databases. Conclusion: Our study established a novel risk signature to predict the COAD prognosis of patients and provide theoretical support for the clinical treatment of COAD.

Targeting CSC-related transcription factors by E3 ubiquitin ligases for cancer therapy

Evidence has revealed that transcription factors play essential roles in regulation of multiple cellular processes, including cell proliferation, metastasis, EMT, cancer stem cells and chemoresistance. Dysregulated expression levels of transcription factors contribute to tumorigenesis and malignant progression. The expression of transcription factors is tightly governed by several signaling pathways, noncoding RNAs and E3 ubiquitin ligases. Cancer stem cells (CSCs) have been validated in regulation of tumor metastasis, reoccurrence and chemoresistance in human cancer. Transcription factors have been verified to participate in regulation of CSC formation, including Oct4, SOX2, KLF4, c-Myc, Nanog, GATA, SALL4, Bmi-1, OLIG2, POU3F2 and FOX proteins. In this review article, we will describe the critical role of CSC-related transcription factors. We will further discuss which E3 ligases regulate the degradation of these CSC-related transcription factors and their underlying mechanisms. We also mentioned the functions and mechanisms of EMT-associated transcription factors such as ZEB1, ZEB2, Snail, Slug, Twist1 and Twist2. Furthermore, we highlight the therapeutic potential via targeting E3 ubiquitin ligases for modulation of these transcription factors.

Insm1 promotes differentiation of retinal progenitor cells toward photoreceptor cells in the developing retina through up-regulation of SHH

This article investigated the effect of Insm1 on RPC differentiation in mice and the underlying mechanism. The retinal tissues of mouse embryo at 12.5 days (E12.5) and postnatal 14 days (P14) were collected, following by the detection of Insm1 and corresponding markers by immunofluorescent staining. RPCs isolated from retinal tissues at P1 were cultured in culture medium for 7 days. The differentiation of photoreceptor and glial cells was assessed after RPCs transferred to the differentiation medium for 20 days. Next, the effect of Insm1 overexpression on the differentiation of RPCs toward rod photoreceptor and glial cells were assessed. Insm1 was highly expressed in RPCs of retinal tissues and decline in photoreceptor cells, while hardly expressed in glial cells. Based on the results of Pax-6 positive immunofluorescent staining and flow cytometry detection, RPCs were successfully isolated from retinal tissues. After the culture in differentiation medium, RPCs showed positive staining of Rhodopsin and glial fibrillary acidic protein (GFAP). Further results showed that overexpression of Insm1 significantly increased the percentage of Rhodopsin positive cells, and up-regulated Sonic Hedgehog (SHH), hairy and enhancer of split homolog-1(Hes1), S-opsin and Rhodopsin levels, while decreased the percentage of Glutamine synthetase positive cells, and reduced Glutamine synthetase and GFAP levels. Whereas, the effect of Insm1 overexpression on these protein levels were partly abolished by the knockdown of SHH or Hes1. We conclude that Insm1 promotes the differentiation of RPCs into photoreceptor cells in the developing retina through up-regulation of SHH.

Molecular Subtypes of Extra-pulmonary Neuroendocrine Carcinomas Identified by the Expression of Neuroendocrine Lineage-Specific Transcription Factors

Extra-pulmonary neuroendocrine carcinomas (EPNEC) represent a group of rare and heterogenous neoplasms with adverse clinical outcome. Their molecular profile is largely unexplored. Our aim was to investigate if the major transcriptional drivers recently described in high-grade pulmonary neuroendocrine carcinomas characterize distinct molecular and clinical subgroups of EPNEC. Gene expression of ASCL1, NEUROD1, DLL3, NOTCH1, INSM1, MYCL1, POU2F3, and YAP1 was investigated in a series of 54 EPNEC (including 10 cases with mixed components analyzed separately) and in a group of 48 pulmonary large cell neuroendocrine carcinomas (P-LCNEC). Unsupervised hierarchical cluster analysis classified the whole series into four major clusters. P-LCNEC were classified into two major clusters, the first ASCL1/DLL3/INSM1-high and the second (including four EPNEC) ASCL1/DLL3-low but INSM1-high. The remaining EPNEC cases were sub-classified into two other clusters. The first showed INSM1-high and alternative ASCL1/DLL3 or NEUROD1 high expression. The second was characterized mainly by MYCL1 and YAP1 overexpression. In the ten cases with mixed histology, ASCL1, DLL3, INSM1, and NEUROD1 genes were significantly upregulated in the neuroendocrine component. Higher gene-expression levels of NOTCH1 and INSM1 were associated with lower pT stage and negative nodal status. Low INSM1 gene expression was associated with shorter overall survival in the entire case series (p = 0.0017) and with a trend towards significance in EPNEC, only (p = 0.06). In conclusion, our results show that EPNEC possess distinct neuroendocrine-lineage-specific transcriptional profiles; moreover, low INSM1 gene expression represents a novel potential unfavorable prognostic marker in high-grade NECs including those in extra-pulmonary location.

Insulinoma-Associated Protein 1 (INSM1): Diagnostic, Prognostic, and Therapeutic Use in Small Cell Lung Cancer

Small cell lung carcinoma (SCLC) is an aggressive and difficult to treat cancer. Although immunohistochemistry is not mandatory for a SCLC diagnosis, it might be required, especially in small samples. Insulinoma-associated protein 1 (INSM1) is expressed in endocrine and nervous tissues during embryogenesis, generally absent in adults and re-expressed in SCLC and other neuroendocrine neoplasms. Its high specificity propelled its use as diagnostic biomarker and an attractive therapeutic target. Herein, we aim to provide a systematic and critical review on the use of INSM1 for diagnosis, prognostication and the treatment of SCLC. An extensive bibliographic search was conducted in PubMed® focusing on articles published since 2015. According to the literature, INSM1 is a highly sensitive (75–100%) and specific (82–100%) neuroendocrine immunohistochemical marker for SCLC diagnosis. It can be used in histological and cytological samples. Although advantageous, its standalone use is currently not recommended. Studies correlating INSM1 expression and prognosis have disclosed contrasting results, although the expression seemed to entail a worse survival. Targeting INSM1 effectively suppressed SCLC growth either as a suicide gene therapy regulator or as an indirect target of molecular-targeted therapy. INSM1 represents a valuable biomarker for a SCLC diagnosis that additionally offers vast opportunities for the development of new prognostic and therapeutic strategies.

Molecular Mechanisms Involving the Sonic Hedgehog Pathway in Lung Cancer Therapy: Recent Advances

According to the latest statistics from the International Agency for Research on Cancer (IARC), lung cancer is one of the most lethal malignancies in the world, accounting for approximately 18% of all cancer-associated deaths. Yet, even with aggressive interventions for advanced lung cancer, the five-year survival rate remains low, at around 15%. The hedgehog signaling pathway is highly conserved during embryonic development and is involved in tissue homeostasis as well as organ development. However, studies have documented an increasing prevalence of aberrant activation of HH signaling in lung cancer patients, promoting malignant lung cancer progression with poor prognostic outcomes. Inhibitors targeting the HH pathway have been widely used in tumor therapy, however, they still cannot avoid the occurrence of drug resistance. Interestingly, natural products, either alone or in combination with chemotherapy, have greatly improved overall survival outcomes for lung cancer patients by acting on the HH signaling pathway because of its unique and excellent pharmacological properties. In this review, we elucidate on the underlying molecular mechanisms through which the HH pathway promotes malignant biological behaviors in lung cancer, as well as the potential of inhibitors or natural compounds in targeting HH signaling for clinical applications in lung cancer therapy.

Ultrastructural changes associated to the neuroendocrine transdifferentiation of the lung adenocarcinoma cell line A549

The neuroendocrine transdifferentiation has been found in many cancer cell types, such as prostate, lung and gastrointestinal cells and is accompanied by a lower patient life expectancy. The transdifferentiation process has been induced in vitro by the exposure to different stimuli in human lung adenocarcinoma. The aim of this work was to identify the morphological characteristics of the neuroendocrine phenotype in a human lung cancer cell line, induced by two cAMP elevating agents (IBMX and FSK). Our results showed two phenotypes, one produced by IBMX with higher volume, cell size and increased number of secondary projections, and the other produced by FSK with higher area, roughness of the membrane, cell neurite percentage, number of outgrowths per cell and increased number of primary projections. In conclusion, we describe some morphological and ultrastructural characteristics of the neuroendocrine phenotype in A549 human lung cancer cell line promoted by IBMX and FSK to contribute to the understanding of the autocrine or paracrine signaling within the tumor microenvironment.

The synergy of BET inhibitors with aurora A kinase inhibitors in MYCN-amplified neuroblastoma is heightened with functional TP53

Amplification of MYCN is a poor prognostic feature in neuroblastoma (NBL) indicating aggressive disease. We and others have shown BET bromodomain inhibitors (BETi) target MYCN indirectly by downregulating its transcription. Here we sought to identify agents that synergize with BETi and to identify biomarkers of resistance. We previously performed a viability screen of ∼1,900 oncology-focused compounds combined with BET bromodomain inhibitors against MYCN-amplified NBL cell lines. Reanalysis of our screening results prominently identified inhibitors of aurora kinase A (AURKAi) to be highly synergistic with BETi. We confirmed the anti-proliferative effects of several BETi+AURKAi combinations in MYCN-amplified NBL cell lines. Compared to single agents, these combinations cooperated to decrease levels of N-myc. We treated both TP53-wild type and mutant, MYCN-amplified cell lines with the BETi JQ1 and the AURKAi Alisertib. The combination had improved efficacy in the TP53-WT context, notably driving apoptosis in both genetic backgrounds. JQ1+Alisertib combination treatment of a MYCN-amplified, TP53-null or TP53-restored genetically engineered mouse model of NBL prolonged survival better than either single agent. This was most profound with TP53 restored, with marked tumor shrinkage and apoptosis induction in response to combination JQ1+Alisertib. BETi+AURKAi in MYCN-amplified NBL, particularly in the context of functional TP53, provided anti-tumor benefits in preclinical models. This combination should be studied more closely in a pediatric clinical trial.

Differentially Expressed mRNAs and Their Long Noncoding RNA Regulatory Network with Helicobacter pylori-Associated Diseases including Atrophic Gastritis and Gastric Cancer

Background

Helicobacter pylori (Hp) infection is the strongest risk factor for gastric cancer (GC). However, the mechanisms of Hp-associated GC remain to be explored.

Methods

The gene expression profiling (GSE111762) data were downloaded from the GEO database. Differentially expressed genes (DEGs) between normal samples (NO) and Hp-atrophic gastritis (GA) or Hp-GA and Hp-GC were identified by GEO2R. Gene Ontology and pathway enrichment analysis were performed using the DAVID database. lncRNA-TF-mRNA and ceRNA regulation networks were constructed using Cytoscape. The cross-networks were obtained by overlapping molecules of the above two networks. GSE27411 and GSE116312 datasets were employed for validation.

Results

DEGs between NO and Hp-GA are linked to the activity of inward rectifying potassium channels, digestion, etc. DEGs between Hp-GA and Hp-GC were associated with digestion, positive regulation of cell proliferation, etc. According to the lncRNA-TF-mRNA network, 63 lncRNAs, 12 TFs, and 209 mRNAs were involved in Hp-GA while 16 lncRNAs, 11 TFs, and 92 mRNAs were contained in the Hp-GC network. In terms of the ceRNA network, 120 mRNAs, 18 miRNAs, and 27 lncRNAs were shown in Hp-GA while 72 mRNAs, 8 miRNAs, and 1 lncRNA were included in the Hp-GC network. In the cross-network, we found that immune regulation and differentiation regulation were important in the process of NO-GA. Neuroendocrine regulation was mainly related to the process of GA-GC. In the end, we verified that CDX2 plays an important role in the pathological process of NO to Hp-GA. Comparing Hp-GA with Hp-GC, DEGs (FPR1, TFF2, GAST, SST, FUT9, and SHH), TF, and GATA5 were of great significance.

Conclusions

We identified the DEGs, and their lncRNA regulatory network of Hp-associated diseases might provide insights into the mechanism between Hp infection and GC. Furthermore, in-depth studies of the molecules might be useful to explore the multistep process of gastric diseases.

The Role of Hedgehog Pathway in Female Cancers

Background:

The hedgehog pathway (HH) is one of the key regulators involved in many biological events. Malfunction of this pathway is associated with a variety of diseases including several types of cancers.

Methods:

We collected data from public databases and conducted a comprehensive search linking the HH pathway with female cancers. In addition, we overviewed clinical trials of targeting HH pathway in female cancers.

Results:

The activation of HH pathway and its role in female cancers, including breast cancer, ovarian cancer, cervical cancer, endometrial cancer, and uterine leiomyosarcoma were summarized. Treatment options targeting SMO and GLI in HH pathway were reviewed and discussed.

Conclusions:

The hedgehog pathway was shown to be activated in several types of female cancers. Therefore, targeting HH pathway may be considered as a therapeutic option to be acknowledged in the treatment of female cancers.

INSM1 expression in a subset of thoracic malignancies and small round cell tumors: rare potential pitfalls for small cell carcinoma

INSM1 is a diagnostic marker for neuroendocrine tumors originating in multiple anatomic sites. In the lung, INSM1 shows 76-97% sensitivity for neuroendocrine tumors overall. Our aim was to characterize INSM1 as a diagnostic marker for small cell carcinoma in the context of its epithelial, lymphoid, and mesenchymal morphologic mimics. Immunohistochemistry was performed on 231 tumors, including lung neuroendocrine tumors, nonneuroendocrine carcinomas of the thoracic cavity, diffuse large B-cell lymphomas, and small round cell sarcomas, using an anti-INSM1 mouse monoclonal antibody. Extent (0-100%) and intensity (1-3+) of nuclear INSM1 staining was multiplied in each case to calculate an H-score. Demographic and clinical information was obtained from the medical record. INSM1 had an overall sensitivity and specificity of 81.5% and 82.7% for small cell carcinoma, respectively, using a threshold established with a receiver operating characteristic curve. 40/48 (82.7%) small cell carcinomas were positive for INSM1, including 19/24 (79%) small cell carcinomas that were negative for chromogranin and synaptophysin. 5/5 carcinoids and 21/28 (75%) large cell neuroendocrine carcinomas showed INSM1 expression. Among nonneuroendocrine tumors, 7/38 (18%) lung adenocarcinomas, 2/17 (12%) lung squamous cell carcinomas, 4/10 (40%) thymic carcinomas, 4/12 (33%) adenoid cystic carcinomas, 1/19 (5%) diffuse large B-cell lymphomas, 4/11 (36%) alveolar rhabdomyosarcomas, and 4/23 (17%) Ewing sarcomas were positive for INSM1. No synovial sarcomas or desmoplastic small round cell tumors were positive. Weak, focal INSM1 expression alone is insufficient as a diagnostic marker for small cell carcinoma, but is sensitive and specific, easy to interpret in small biopsies, and makes a valuable addition to a diagnostic panel.

Curcumin Affects Gastric Cancer Cell Migration, Invasion and Cytoskeletal Remodeling Through Gli1-β-Catenin

Purpose

The function of curcumin on the gastric cancer cell line, SGC-7901 is unknown. The present study aimed to observe the effects of curcumin on gastric cancer cells through the Shh and Wnt signaling pathways.

Methods

SGC-7901 cells were transfected with si-Gli1 and si-β-catenin siRNA, then cells were stimulated with curcumin and its effects on cell migration, invasion, cytoskeleton remodeling, EMT, apoptosis and cell cycle were investigated by transwell assays, immunofluorescence and flow cytometry assays. The interaction between Gli1 and β-catenin was observed by co-immunoprecipitation.

Results

We show that curcumin suppressed the expression of Shh, Gli1 and Foxm1 in the Shh signaling pathway, and the expression of β-catenin in the Wnt signaling pathway in SGC-7901 cells, both in mRNA and protein. As a result, cellular migration, invasion and cytoskeletal remodeling ability decreased. Our results revealed that when stimulated with curcumin, cells showed decreased cellular migration and invasion, while enhanced apoptosis. In addition, curcumin induced cytoskeletal remodeling and S phase cell cycle arrest. The inhibition of Shh and Wnt signaling pathway and the addition of curcumin also inhibited the epithelial–mesenchymal transition process. Furthermore, a physical interaction was observed between Gli1 of the Shh signaling and β-catenin of the Wnt signaling in these cells, but curcumin inhibited the interaction of these two proteins.

Conclusion

The present study indicated that curcumin plays an anti-tumor role through Gli1-β-catenin pathway in gastric cancer SGC-7901 cells.

Insulinoma-associated protein 1 (INSM1): a potential biomarker and therapeutic target for neuroendocrine tumors

BACKGROUND

Insulinoma-associated protein 1 (INSM1), a transcriptional regulator with a zinc-finger DNA-binding domain, has been validated as a cytoplasmic marker for neuroendocrine differentiation of tumor cells. Next to its abundant expression in the fetal pancreas, it is expressed in brain tumors, pheochromocytomas, medullary thyroid carcinomas, insulinomas and pituitary and small-cell lung carcinomas. INSM1 is not expressed in normal adult tissues and/or most non-neuroendocrine tumors. It regulates various downstream signaling pathways, including the Sonic Hedgehog, PI3K/AKT, MEK/ERK1/2, ADK, p53, Wnt, histone acetylation, LSD1, cyclin D1, Ascl1 and N-Myc pathways. Although INSM1 appears to be a subtle and specific biomarker for neuroendocrine tumors, its role in tumor development has remained unclear.

CONCLUSIONS

Here, we highlight INSMI expression, as well as its diagnostic significance and use as a therapeutic target in various neuroendocrine tumors. Targeting signaling pathways or gene expression alterations associated with INSM1 expression may be instrumental for the design of novel therapeutic strategies for neuroendocrine tumors.

The MEK5-ERK5 Kinase Axis Controls Lipid Metabolism in Small-Cell Lung Cancer

Small-cell lung cancer (SCLC) is an aggressive form of lung cancer with dismal survival rates. While kinases often play key roles driving tumorigenesis, there are strikingly few kinases known to promote the development of SCLC. Here, we investigated the contribution of the MAPK module MEK5-ERK5 to SCLC growth. MEK5 and ERK5 were required for optimal survival and expansion of SCLC cell lines in vitro and in vivo. Transcriptomics analyses identified a role for the MEK5-ERK5 axis in the metabolism of SCLC cells, including lipid metabolism. In-depth lipidomics analyses showed that loss of MEK5/ERK5 perturbs several lipid metabolism pathways, including the mevalonate pathway that controls cholesterol synthesis. Notably, depletion of MEK5/ERK5 sensitized SCLC cells to pharmacologic inhibition of the mevalonate pathway by statins. These data identify a new MEK5-ERK5-lipid metabolism axis that promotes the growth of SCLC. SIGNIFICANCE: This study is the first to investigate MEK5 and ERK5 in SCLC, linking the activity of these two kinases to the control of cell survival and lipid metabolism.

General mechanism of JQ1 in inhibiting various types of cancer

Bromodomain-containing 4 (BRD4) is a histone modification reader and transcriptional regulator that has been reported to interact with acetylated lysine histone motifs transcription factors (TFs), transcription co-activators and RNA polymerase II. The selective small molecule inhibitor JQ1, which binds competitively to bromodomains, has been reported to exhibit anti-proliferative effects in various types of cancer. Previous studies on the mechanism of action of JQ1 mostly focused on a specific tumor type or disease; however, the general mechanism through which JQ1 affects various tumors remains to be determined. In the present study, chromatin immunoprecipitation sequencing data for BRD4 and its expression profiles in six cancer cell lines were integrated and analyzed systematically. The results indicated that BRD4 binds to enhancers with histone H3 acetylated at lysine 27 (H3K27Ac) and mediator complex subunit 1 in a cell type-specific manner, as well as binds to promoter regions with the oncogenic TFs MYC and E2F1 in a cell type-common manner. The cell type-common sites across the six cell types investigated were found to be functionally important for tumorigenesis, whereas the cell type-specific sites were functionally enriched with the cell identity, all of which were sensitive to JQ1 treatment. Furthermore, a core set of JQ1-regulated BRD4 binding genes were obtained, which were significantly inhibited by JQ1 in various cancer cell lines and contributed to hallmarks of cancer. These results implied a common mechanism underlying the therapeutic effects of JQ1 and suggested its potential suitability as an anti-cancer drug targeting BRD4-mediated transcriptional regulation.

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.

Expression of Insulinoma-Associated Protein 1 (INSM1) and Orthopedia Homeobox (OTP) in Tumors with Neuroendocrine Differentiation at Rare Sites

Insulinoma-associated protein 1 (INSM1) and orthopedia homeobox (OTP) are transcription factors that play a critical role in neuroendocrine (NE) and neuroepithelial cell development. INSM1 has been identified in multiple tumors of NE or neuroepithelial origin, whereas OTP expression has been mainly studied in NE tumors of pulmonary origin. Expression of OTP appears to correlate with poorer prognosis in pulmonary carcinoids; however, its expression patterns in other NE/neuroepithelial tumors need further investigation. Here, we assessed the diagnostic utility of INSM1 and OTP in tumors with NE differentiation at relatively uncommon sites including prostate, breast, and tumors of gynecologic origin. Thirty-two formalin-fixed, paraffin-embedded cases were used to construct a tissue microarray. Immunohistochemistry for INSM1 and OTP was performed and scored semi-quantitatively. INSM1 was diffusely expressed in 60% of gynecologic tumors, 71.4% of mammary carcinoma, and 25% of prostate adenocarcinoma with NE differentiation. Diffuse expression of OTP was detected in 50% of prostate adenocarcinoma with NE differentiation and 100% neuroendocrine carcinoma of the ovary. Immunostain for achaete-scute homolog 1, chromogranin, synaptophysin, and CD56 supported the NE and/or neuroepithelial differentiation of the tumors. In summary, INSM1 is expressed in most of the tumors with NE and neuroepithelial differentiation in this study, confirming the diagnostic utility of INSM1 as a novel and sensitive marker of NE/neuroepithelial differentiation. The expression of OTP in some NE tumors outside of lung expands the spectrum of tumors that may express this biomarker and should be considered when working up a NE tumor of unknown primary site.

5'-Iodotubercidin represses insulinoma-associated-1 expression, decreases cAMP levels, and suppresses human neuroblastoma cell growth

Insulinoma-associated-1 (INSM1) is a key protein functioning as a transcriptional repressor in neuroendocrine differentiation and is activated by N-Myc in human neuroblastoma (NB). INSM1 modulates the phosphoinositide 3-kinase (PI3K)-AKT Ser/Thr kinase (AKT)-glycogen synthase kinase 3β (GSK3β) signaling pathway through a positive-feedback loop, resulting in N-Myc stabilization. Accordingly, INSM1 has emerged as a critical player closely associated with N-Myc in facilitating NB cell growth. Here, an INSM1 promoter-driven luciferase-based screen revealed that the compound 5'-iodotubercidin suppresses adenosine kinase (ADK), an energy pathway enzyme, and also INSM1 expression and NB tumor growth. Next, we sought to dissect how the ADK pathway contributes to NB tumor cell growth in the context of INSM1 expression. We also found that 5'-iodotubercidin inhibits INSM1 expression and induces an intra- and extracellular adenosine imbalance. The adenosine imbalance, which triggers adenosine receptor-3 signaling that decreases cAMP levels and AKT phosphorylation and enhances GSK3β activity. We further observed that GSK3β then phosphorylates β-catenin and promotes the cytoplasmic proteasomal degradation pathway. 5'-Iodotubercidin treatment and INSM1 inhibition suppressed extracellular signal-regulated kinase 1/2 (ERK1/2) activity and the AKT signaling pathways required for NB cell proliferation. The 5'-iodotubercidin treatment also suppressed β-catenin, lymphoid enhancer-binding factor 1 (LEF-1), cyclin D1, N-Myc, and INSM1 levels, ultimately leading to apoptosis via caspase-3 and p53 activation. The identification of the signaling pathways that control the proliferation of aggressive NB reported here suggests new options for combination treatments of NB patients.

Lung cancer stem cells: origin, features, maintenance mechanisms and therapeutic targeting

Lung cancer remains the leading cause of cancer-related deaths despite recent breakthroughs in immunotherapy. The widely embraced cancer stem cell (CSC) theory has also been applied for lung cancer, postulating that an often small proportion of tumor cells with stem cell properties are responsible for tumor growth, therapeutic resistance and metastasis. The identification of these CSCs and underlying molecular maintenance mechanisms is considered to be absolutely necessary for developing therapies for their riddance, hence achieving remission. In this review, we will critically address the CSC concept in lung cancer and its advancement thus far. We will describe both normal lung stem cells and their malignant counterparts in order to identify common aspects with respect to their emergence and regulation. Subsequently, the importance of CSCs and their molecular features in lung cancers will be discussed in a preclinical and clinical context. We will highlight some examples on how lung CSCs attain stemness through different molecular modifications and cellular assistance from the tumor microenvironment. The exploitation of these mechanistic features for the development of pharmacological therapy will also be discussed. In summary, the validity of the CSC concept has been evidenced by various studies. Ongoing research to identify molecular mechanisms driving lung CSC have revealed potential new cell intrinsic as well as tumor microenvironment-derived therapeutic targets. Although successfully demonstrated in preclinical models, the clinical benefit of lung CSC targeted therapies has thus far not been demonstrated. Therefore, further research to validate the therapeutic value of CSC concept is required.

Targeted deletion of Insm2 in mice result in reduced insulin secretion and glucose intolerance

Background

Neurogenin3 (Ngn3) and neurogenic differentiation 1 (NeuroD1), two crucial transcriptional factors involved in human diabetes (OMIM: 601724) and islet development, have been previously found to directly target to the E-boxes of the insulinoma-associated 2 (Insm2) gene promoter, thereby activating the expression of Insm2 in insulin-secretion cells. However, little is known about the function of Insm2 in pancreatic islets and glucose metabolisms.

Methods

Homozygous Insm2^−/− mice were generated by using the CRISPR-Cas9 method. Glucose-stimulated insulin secretion and islet morphology were analyzed by ELISA and immunostainings. Expression levels of Insm2-associated molecules were measured using quantitative RT-PCR and Western blots.

Results

Fasting blood glucose levels of Insm2^−/− mice were higher than wild-type counterparts. Insm2^−/− mice also showed reduction in glucose tolerance and insulin/C-peptide levels when compared to the wild-type mice. RT-PCR and Western blot analysis revealed that expression of Insm1 was significantly increased in Insm2^−/− mice, suggesting a compensatory response of the homolog gene Insm1. Similarly, transcriptional levels of Ngn3 and NeuroD1 were also increased in Insm2^−/− mice. Moreover, Insm2^−/− female mice showed a significantly decreased reproductive capacity.

Conclusions

Our findings suggest that Insm2 is important in glucose-stimulated insulin secretion and is involved in the development pathway of neuroendocrine tissues which are regulated by the transcription factors Ngn3, NeuroD1 and Insm1.