Neurotensin, a novel target of Wnt/β-catenin pathway, promotes growth of neuroendocrine tumor cells

Navigating Tumour Microenvironment and Wnt Signalling Crosstalk: Implications for Advanced Cancer Therapeutics

Cancer therapeutics face significant challenges due to drug resistance and tumour recurrence. The tumour microenvironment (TME) is a crucial contributor and essential hallmark of cancer. It encompasses various components surrounding the tumour, including intercellular elements, immune system cells, the vascular system, stem cells, and extracellular matrices, all of which play critical roles in tumour progression, epithelial-mesenchymal transition, metastasis, drug resistance, and relapse. These components interact with multiple signalling pathways, positively or negatively influencing cell growth. Abnormal regulation of the Wnt signalling pathway has been observed in tumorigenesis and contributes to tumour growth. A comprehensive understanding and characterisation of how different cells within the TME communicate through signalling pathways is vital. This review aims to explore the intricate and dynamic interactions, expressions, and alterations of TME components and the Wnt signalling pathway, offering valuable insights into the development of therapeutic applications.

Casein Kinase 1α as a Novel Factor Affects Thyrotropin Synthesis via PKC/ERK/CREB Signaling

Casein kinase 1α (CK1α) is present in multiple cellular organelles and plays various roles in regulating neuroendocrine metabolism. Herein, we investigated the underlying function and mechanisms of CK1α-regulated thyrotropin (thyroid-stimulating hormone (TSH)) synthesis in a murine model. Immunohistochemistry and immunofluorescence staining were performed to detect CK1α expression in murine pituitary tissue and its localization to specific cell types. Tshb mRNA expression in anterior pituitary was detected using real-time and radioimmunoassay techniques after CK1α activity was promoted and inhibited in vivo and in vitro. Relationships among TRH/L-T4, CK1α, and TSH were analyzed with TRH and L-T4 treatment, as well as thyroidectomy, in vivo. In mice, CK1α was expressed at higher levels in the pituitary gland tissue than in the thyroid, adrenal gland, or liver. However, inhibiting endogenous CK1α activity in the anterior pituitary and primary pituitary cells significantly increased TSH expression and attenuated the inhibitory effect of L-T4 on TSH. In contrast, CK1α activation weakened TSH stimulation by thyrotropin-releasing hormone (TRH) by suppressing protein kinase C (PKC)/extracellular signal-regulated kinase (ERK)/cAMP response element binding (CREB) signaling. CK1α, as a negative regulator, mediates TRH and L-T4 upstream signaling by targeting PKC, thus affecting TSH expression and downregulating ERK1/2 phosphorylation and CREB transcriptional activity.

Novel therapeutic approaches in GEP-NETs based on genetic and epigenetic alterations

Gastroenteropancreatic neuroendocrine tumors (GEP-NETs) are heterogeneous malignancies with distinct prognosis based on primary tumor localization, grade, stage and functionality. Surgery remains the only curative option in localized tumors, but systemic therapy is the mainstay of treatment for patients with advanced disease. For decades, the therapeutic landscape of GEP-NETs was limited to chemotherapy regimens with low response rates. The arrival of novel agents such as somatostatin analogues, peptide receptor radionuclide therapy, tyrosine kinase inhibitors or mTOR-targeted drugs, has changed the therapeutic paradigm of GEP-NETs. However, the efficacy of these agents is limited in time and there is scarce knowledge of optimal treatment sequencing. In recent years, massive parallel sequencing techniques have started to unravel the genomic intricacies of these tumors, allowing us to better understand the mechanisms of resistance to current treatments and to develop new targeted agents that will hopefully start an era for personalized treatment in NETs. In this review we aim to summarize the most relevant genomic aberrations and signaling pathways underlying GEP-NET tumorigenesis and potential therapeutic strategies derived from them.

Aberrant transcription factors in the cancers of the pancreas

Transcription factors (TFs) are essential for proper activation of gene set during the process of organogenesis, differentiation, lineage specificity. Reactivation or dysregulation of TFs regulatory networks could lead to deformation of organs, diseases including various malignancies. Currently, understanding the mechanism of oncogenesis became necessity for the development of targeted therapeutic strategy for different cancer types. It is evident that many TFs go awry in cancers of the pancreas such as pancreatic ductal adenocarcinoma (PDAC) and pancreatic neuroendocrine neoplasms (PanNENs). These mutated or dysregulated TFs abnormally controls various signaling pathways in PDAC and PanNENs including RTK, PI3K-PTEN-AKT-mTOR, JNK, TGF-β/SMAD, WNT/β-catenin, SHH, NOTCH and VEGF which in turn regulate different hallmarks of cancer. Aberrant regulation of such pathways have been linked to the initiation, progression, metastasis, and resistance in pancreatic cancer. As of today, a number of TFs has been identified as crucial regulators of pancreatic cancer and a handful of them shown to have potential as therapeutic targets in pre-clinical and clinical settings. In this review, we have summarized the current knowledge on the role and therapeutic usefulness of TFs in PDAC and PanNENs.

Gut neuroendocrine signaling regulates synaptic assembly in C. elegans

Synaptic connections are essential to build a functional brain. How synapses are formed during development is a fundamental question in neuroscience. Recent studies provided evidence that the gut plays an important role in neuronal development through processing signals derived from gut microbes or nutrients. Defects in gut-brain communication can lead to various neurological disorders. Although the roles of the gut in communicating signals from its internal environment to the brain are well known, it remains unclear whether the gut plays a genetically encoded role in neuronal development. Using C. elegans as a model, we uncover that a Wnt-endocrine signaling pathway in the gut regulates synaptic development in the brain. A canonical Wnt signaling pathway promotes synapse formation through regulating the expression of the neuropeptides encoding gene nlp-40 in the gut, which functions through the neuronally expressed GPCR/AEX-2 receptor during development. Wnt-NLP-40-AEX-2 signaling likely acts to modulate neuronal activity. Our study reveals a genetic role of the gut in synaptic development and identifies a novel contribution of the gut-brain axis.

Pancreatic Neuroendocrine Tumors: Molecular Mechanisms and Therapeutic Targets

Pancreatic neuroendocrine tumors (pNETs) are unique, slow-growing malignancies whose molecular pathogenesis is incompletely understood. With rising incidence of pNETs over the last four decades, larger and more comprehensive 'omic' analyses of patient tumors have led to a clearer picture of the pNET genomic landscape and transcriptional profiles for both primary and metastatic lesions. In pNET patients with advanced disease, those insights have guided the use of targeted therapies that inhibit activated mTOR and receptor tyrosine kinase (RTK) pathways or stimulate somatostatin receptor signaling. Such treatments have significantly benefited patients, but intrinsic or acquired drug resistance in the tumors remains a major problem that leaves few to no effective treatment options for advanced cases. This demands a better understanding of essential molecular and biological events underlying pNET growth, metastasis, and drug resistance. This review examines the known molecular alterations associated with pNET pathogenesis, identifying which changes may be drivers of the disease and, as such, relevant therapeutic targets. We also highlight areas that warrant further investigation at the biological level and discuss available model systems for pNET research. The paucity of pNET models has hampered research efforts over the years, although recently developed cell line, animal, patient-derived xenograft, and patient-derived organoid models have significantly expanded the available platforms for pNET investigations. Advancements in pNET research and understanding are expected to guide improved patient treatments.

Neurotensin Regulates Proliferation and Stem Cell Function in the Small Intestine in a Nutrient-Dependent Manner

BACKGROUND & AIMS

Intestinal stem cells (ISCs) are sensitive to dietary alterations and nutrient availability. Neurotensin (NT), a gut peptide localized predominantly to the small bowel and released by fat ingestion, stimulates the growth of intestinal mucosa under basal conditions and during periods of nutrient deprivation, suggesting a possible role for NT on ISC function.

METHODS

Leucine-rich repeat-containing G-protein coupled receptor 5-Enhanced Green Fluorescent Protein (Lgr5-EGFP) NT wild type (Nt^+/+) and Lgr5-EGFP NT knockout (Nt^-/-) mice were fed ad libitum or fasted for 48 hours. Small intestine tissue and crypts were examined by gene expression analyses, fluorescence-activated cell sorting, Western blot, immunohistochemistry, and crypt-derived organoid culture. Drosophila expressing NT in midgut enteroendocrine cells were fed a standard diet or low-energy diet and esg-green fluorescent protein⁺ ISCs were quantified via immunofluorescence.

RESULTS

Loss of NT impaired crypt cell proliferation and ISC function in a manner dependent on nutrient status. Under nutrient-rich conditions, NT stimulated extracellular signal-regulated kinases 1 and 2 signaling and the expression of genes that promote cell-cycle progression, leading to crypt cell proliferation. Under conditions of nutrient depletion, NT stimulated WNT/β-catenin signaling and promoted an ISC gene signature, leading to enhanced ISC function. NT was required for the induction of WNT/β-catenin signaling and ISC-specific gene expression during nutrient depletion, and loss of NT reduced crypt cell proliferation and impaired ISC function and Lgr5 expression in the intestine during fasting. Conversely, the expression of NT in midgut enteroendocrine cells of Drosophila prevented loss of ISCs during nutrient depletion.

CONCLUSIONS

Collectively, our findings establish an evolutionarily conserved role for NT in ISC maintenance during nutritional stress. GSE182828.

Molecular Pathology of Well-Differentiated Gastro-entero-pancreatic Neuroendocrine Tumors

Well differentiated neuroendocrine tumors (NETs) arising in the gastrointestinal and pancreaticobiliary system are the most common neuroendocrine neoplasms. Studies of the molecular basis of these lesions have identified genetic mutations that predispose to familial endocrine neoplasia syndromes and occur both as germline events and in sporadic tumors. The mutations often involve epigenetic regulators rather than the oncogenes and tumor suppressors that are affected in other malignancies. Somatic copy number alterations and miRNAs have also been implicated in the development and progression of some of these tumors. The molecular profiles differ by location, but many are shared by tumors in other sites, including those outside the gastroenteropancreatic system. The approach to therapy relies on both the neuroendocrine nature of these tumors and the identification of specific alterations that can serve as targets for precision oncologic approaches.

Transcriptional Profiling Reveals the Regulatory Role of DNER in Promoting Pancreatic Neuroendocrine Neoplasms

Wnt/β-catenin and NOTCH signaling contribute to the pathogenesis and growth of (PanNENs). The wnt and Notch signaling pathways form an integrated signaling device termed "wntch" and regulate stochastic cell fate decisions, suggesting the essentiality of Wnt/Notch interactions in disease progression. However, the function of Wnt/Notch interactions in PanNENs is unclear. We analyzed RNA sequencing (RNA-seq) data to identify differentially expressed lncRNAs, mRNAs and pathways according to enriched Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways associated with PanNENs. RNA-seq analysis revealed that the levels of the lncRNA XLOC_221242 and the mRNA encoding Delta/Notch-like epidermal growth factor (EGF)-related receptor (DNER) were significantly increased in tumor tissues compared with normal tissues (n = 3). Protein-protein interaction (PPI) prediction combined with transcriptional profiling data analysis revealed that DNER expression levels were positively correlated with those of DNA-binding factor (RBPJ), S phase kinase-associated protein 1 (Skp1), CTNNB1 and Cadherin-2 (CDH2), which promote PanNEN tumorigenesis and progression. These results were consistent with those of immunohistochemical analysis of DNER, RBPJ, SKP1, CTNNB1, and CDH2 expression (n = 15). These findings provide compelling clinical and molecular evidence supporting the conclusion that DNER and the related RBPJ, SKP1, CTNNB1, and CDH2 signaling contribute to PanNEN tumorigenesis and progression by activating wnt/Notch interactions.

Long non-coding RNAs in lung cancer: implications for lineage plasticity-mediated TKI resistance

The efficacy of targeted therapy in non-small-cell lung cancer (NSCLC) has been impeded by various mechanisms of resistance. Besides the mutations in targeted oncogenes, reversible lineage plasticity has recently considered to play a role in the development of tyrosine kinase inhibitors (TKI) resistance in NSCLC. Lineage plasticity enables cells to transfer from one committed developmental pathway to another, and has been a trigger of tumor adaptation to adverse microenvironment conditions including exposure to various therapies. More importantly, besides somatic mutation, lineage plasticity has also been proposed as another source of intratumoural heterogeneity. Lineage plasticity can drive NSCLC cells to a new cell identity which no longer depends on the drug-targeted pathway. Histological transformation and epithelial–mesenchymal transition are two well-known pathways of lineage plasticity-mediated TKI resistance in NSCLC. In the last decade, increased re-biopsy practice upon disease recurrence has increased the recognition of lineage plasticity induced resistance in NSCLC and has improved our understanding of the underlying biology. Long non-coding RNAs (lncRNAs), the dark matter of the genome, are capable of regulating variant malignant processes of NSCLC like the invisible hands. Recent evidence suggests that lncRNAs are involved in TKI resistance in NSCLC, particularly in lineage plasticity-mediated resistance. In this review, we summarize the mechanisms of lncRNAs in regulating lineage plasticity and TKI resistance in NSCLC. We also discuss how understanding these themes can alter therapeutic strategies, including combination therapy approaches to overcome TKI resistance.

Inhibition of Fatty Acid Synthase Upregulates Expression of CD36 to Sustain Proliferation of Colorectal Cancer Cells

Fatty acid synthase, a key enzyme of de novo lipogenesis, is an attractive therapeutic target in cancer. The novel fatty acid synthase inhibitor, TVB-3664, shows anti-cancer activity in multiple cancers including colorectal cancer; however, it is unclear whether uptake of exogeneous fatty acids can compensate for the effect of fatty acid synthase inhibition. This study demonstrates that inhibition of fatty acid synthase selectively upregulates fatty acid translocase (CD36), a fatty acid transporter, in multiple colorectal cancer models including colorectal cancer cells with shRNA mediated knockdown of fatty acid synthase and genetically modified mouse tissues with heterozygous and homozygous deletion of fatty acid synthase. Furthermore, human colorectal cancer tissues treated with TVB-3664 show a significant and selective upregulation of CD36 mRNA. shRNA-mediated knockdown of CD36 and inhibition of CD36 via sulfosuccinimidyl oleate, a chemical inhibitor of CD36, decreased cell proliferation in vitro and reduced tumor growth in subcutaneous xenograft models. Isogenic cell populations established from patient derived xenografts and expressing high levels of CD36 show a significantly increased ability to grow tumors in vivo. The tumor-promoting effect of CD36 is associated with an increase in the levels of pAkt and survivin. Importantly, combinatorial treatment of primary and established colorectal cancer cells with TVB-3664 and sulfosuccinimidyl oleate shows a synergistic effect on cell proliferation. In summary, our study demonstrates that upregulation of CD36 expression is a potential compensatory mechanism for fatty acid synthase inhibition and that inhibition of CD36 can improve the efficacy of fatty acid synthase-targeted therapy.

Inhibition of Wnt/β-Catenin Signaling in Neuroendocrine Tumors in vitro: Antitumoral Effects

Background and aims: Inhibition of Wnt/β-catenin signaling by specific inhibitors is currently being investigated as an antitumoral strategy for various cancers. The role of Wnt/β-catenin signaling in neuroendocrine tumors still needs to be further investigated. Methods: This study investigated the antitumor activity of the porcupine (PORCN) inhibitor WNT974 and the β-catenin inhibitor PRI-724 in human neuroendocrine tumor (NET) cell lines BON1, QGP-1, and NCI-H727 in vitro. NET cells were treated with WNT974, PRI-724, or small interfering ribonucleic acids against β-catenin, and subsequent analyses included cell viability assays, flow cytometric cell cycle analysis, caspase3/7 assays and Western blot analysis. Results: Treatment of NET cells with WNT974 significantly reduced NET cell viability in a dose- and time-dependent manner by inducing NET cell cycle arrest at the G1 and G2/M phases without inducing apoptosis. WNT974 primarily blocked Wnt/β-catenin signaling by the dose- and time-dependent downregulation of low-density lipoprotein receptor-related protein 6 (LRP6) phosphorylation and non-phosphorylated β-catenin and total β-catenin, as well as the genes targeting the latter (c-Myc and cyclinD1). Furthermore, the WNT974-induced reduction of NET cell viability occurred through the inhibition of GSK-3-dependent or independent signaling (including pAKT/mTOR, pEGFR and pIGFR signaling). Similarly, treatment of NET cells with the β-catenin inhibitor PRI-724 caused significant growth inhibition, while the knockdown of β-catenin expression by siRNA reduced NET tumor cell viability of BON1 cells but not of NCI-H727 cells. Conclusions: The PORCN inhibitor WNT974 possesses antitumor properties in NET cell lines by inhibiting Wnt and related signaling. In addition, the β-catenin inhibitor PRI-724 possesses antitumor properties in NET cell lines. Future studies are needed to determine the role of Wnt/β-catenin signaling in NET as a potential therapeutic target.

Ca2+ Channel Toolkit in Neuroendocrine Tumors

Neuroendocrine tumors (NET) constitute a heterogeneous group of malignancies with various clinical presentations and growth rates but a common origin in neuroendocrine cells located all over the body. NET are a relatively low-frequency disease mostly represented by gastroenteropancreatic (GEP) and bronchopulmonary tumors (pNET); on the other hand, an increasing frequency and prevalence have been associated with NET. Despite great efforts in recent years, the management of NET is still a critical unmet need due to the lack of knowledge of the biology of the disease, the lack of adequate biomarkers, late presentation, the relative insensitivity of imaging modalities, and a paucity of predictably effective treatment options. In this context Ca2+ signals, being pivotal molecular devices in sensing and integrating signals from the microenvironment, are emerging to be particularly relevant in cancer, where they mediate interactions between tumor cells and the tumor microenvironment to drive different aspects of neoplastic progression (e.g., cell proliferation and survival, cell invasiveness, and proangiogenetic programs). Indeed, ion channels represent good potential pharmacological targets due to their location on the plasma membrane, where they can be easily accessed by drugs. The present review aims to provide a critical and up-to-date overview of NET development integrating Ca2+ signal involvement. In this perspective, we first give an introduction to NET and Ca2+ channels and then describe the different families of Ca2+ channels implicated in NET, i.e., ionotropic receptors, voltage-dependent Ca2+ channels, and transient receptor potential channels, as well as intracellular Ca2+ channels and their signaling molecules.

Regulation of Ketogenic Enzyme HMGCS2 by Wnt/β-catenin/PPARγ Pathway in Intestinal Cells

The Wnt/β-catenin pathway plays a crucial role in development and renewal of the intestinal epithelium. Mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2), a rate-limiting ketogenic enzyme in the synthesis of ketone body β-hydroxybutyrate (βHB), contributes to the regulation of intestinal cell differentiation. Here, we have shown that HMGCS2 is a novel target of Wnt/β-catenin/PPARγ signaling in intestinal epithelial cancer cell lines and normal intestinal organoids. Inhibition of the Wnt/β-catenin pathway resulted in increased protein and mRNA expression of HMGCS2 and βHB production in human colon cancer cell lines LS174T and Caco2. In addition, Wnt inhibition increased expression of PPARγ and its target genes, FABP2 and PLIN2, in these cells. Conversely, activation of Wnt/β-catenin signaling decreased protein and mRNA levels of HMGCS2, βHB production, and expression of PPARγ and its target genes in LS174T and Caco2 cells and mouse intestinal organoids. Moreover, inhibition of PPARγ reduced HMGCS2 expression and βHB production, while activation of PPARγ increased HMGCS2 expression and βHB synthesis. Furthermore, PPARγ bound the promoter of HMGCS2 and this binding was enhanced by β-catenin knockdown. Finally, we showed that HMGCS2 inhibited, while Wnt/β-catenin stimulated, glycolysis, which contributed to regulation of intestinal cell differentiation. Our results identified HMGCS2 as a downstream target of Wnt/β-catenin/PPARγ signaling in intestinal epithelial cells. Moreover, our findings suggest that Wnt/β-catenin/PPARγ signaling regulates intestinal cell differentiation, at least in part, through regulation of ketogenesis.

Mechanism of combined use of vitamin D and puerarin in anti-hepatic fibrosis by regulating the Wnt/β-catenin signalling pathway

AIM

To reveal the protective mechanism of the combined use of vitamin D and puerarin in the progression of hepatic fibrosis induced by carbon tetrachloride (CCl₄).

METHODS

Eight-week-old male Wistar rats were randomly divided into a normal control group (C group), a CCl₄ group (CCl₄ group), a vitamin D group (V group), a puerarin group (P group), and a combined group of vitamin D and puerarin (V + P group), each of which contained ten rats. In this way, we built a rat model of CCl₄-induced hepatic fibrosis with intervention by vitamin D, puerarin, or a combination of the two. After eight weeks, the mice were sacrificed to collect serum and liver specimens. Blood was collected to detect the hyaluronic acid (HA). We also measured hydroxyproline (Hyp) and prepared paraffin sections of liver. After Sirius red staining, the liver specimens were observed under a microscope. RT-PCR and western blot analysis were adopted to detect the mRNA and the protein levels of Collagen I, Collagen III, Wnt1, and β-catenin in the liver tissues, respectively.

RESULTS

Hepatic fibrosis was observed in the CCl₄ group. In comparison, hepatic fibrosis was attenuated in the V, P, and V + P groups: the HA level in blood and the Hyp level in liver were reduced, and the mRNA levels of Collagen I, Collagen III, Wnt, and β-catenin in liver were also decreased, as well as the protein levels of Wnt1 and β-catenin. Among these groups, the V + P group demonstrated the greatest amelioration of hepatic fibrosis.

CONCLUSION

The combined application of vitamin D and puerarin is capable of alleviating CCl₄-induced hepatic fibrosis of rats. As to the mechanism, it is probably because the combined use is able to silence the Wnt1/β-catenin pathway, suppress the activation of hepatic stellate cells, and reduce the secretion of collagen fibers, therefore improving the anti-hepatic fibrosis effect.

Targeted therapy of gastroenteropancreatic neuroendocrine tumours: preclinical strategies and future targets

Molecular targeted therapy of advanced neuroendocrine tumours (NETs) of the gastroenteropancreatic (GEP) system currently encompasses approved therapy with the mammalian target of rapamycin (mTOR) inhibitor everolimus and the multi-tyrosinkinase inhibitor sunitinib. However, clinical efficacy of these treatment strategies is limited by low objective response rates and limited progression-free survival due to tumour resistance. Further novel strategies for molecular targeted therapy of NETs of the GEP system are needed. This paper reviews preclinical research models and signalling pathways in NETs of the GEP system. Preclinical and early clinical data on putative novel targets for molecular targeted therapy of NETs of the GEP system are discussed, including PI3K, Akt, mTORC1/mTORC2, GSK3, c-Met, Ras-Raf-MEK-ERK, embryogenic pathways (Hedgehog, Notch, Wnt/beta-catenin, TGF-beta signalling and SMAD proteins), tumour suppressors and cell cycle regulators (p53, cyclin-dependent kinases (CDKs) CDK4/6, CDK inhibitor p27, retinoblastoma protein (Rb)), heat shock protein HSP90, Aurora kinase, Src kinase family, focal adhesion kinase and epigenetic modulation by histone deacetylase inhibitors.

Neurotensin Receptor 3/Sortilin Contributes to Tumorigenesis of Neuroendocrine Tumors Through Augmentation of Cell Adhesion and Migration

Neurotensin (NTS), a 13–amino acid peptide which is distributed predominantly along gastrointestinal tract, has multiple physiologic and pathologic functions, and its effects are mediated by three distinct NTS receptors (NTSRs). Overexpression and activation of NTS signaling components, especially NTS and/or NTSR1, are closely linked with cancer progression and metastasis in various types of cancers including neuroendocrine tumors (NETs). Although deregulation of NTSR3/sortilin has been implicated in a variety of human diseases, the expression and role of NTSR3/sortilin in NETs have not been elucidated. In this study, we investigated the expression and oncogenic effect of NTSR3/sortilin in NETs. Increased protein levels of NTSR3/sortilin were noted in the majority of human clinical NETs (n = 21) by immunohistochemical analyses compared with normal tissues (n = 12). Expression of NTS and NTSR3/sortilin was also noted in all tested NET cell lines. In addition, small interfering RNA–mediated knockdown of NTSR3/sortilin decreased cell number without alteration of cell cycle progression and apoptosis induction in NET cell lines BON and QGP-1. Moreover, silencing of NTSR3/sortilin significantly suppressed cell adhesion and cell migration with inhibition of focal adhesion kinase and Src phosphorylation in the NET cells. Our results demonstrate increased expression of NTSR3/sortilin in NET patient tissues and a critical role of NTSR3/sortilin on NET cell adhesion and migration suggesting that NTSR3/sortilin contributes to NET tumorigenesis.

Inhibition of neurotensin receptor 1 induces intrinsic apoptosis via let-7a-3p/Bcl-w axis in glioblastoma

Backgroud:

Glioblastoma is a kind of highly malignant and aggressive tumours in the central nervous system. Previously, we found that neurotensin (NTS) and its high-affinity receptor 1 (NTSR1) had essential roles in cell proliferation and invasiveness of glioblastoma. Unexpectedly, cell death also appeared by inhibition of NTSR1 except for cell cycle arrest. However, the mechanisms were remained to be further explored.

Methods:

Cells treated with SR48692, a selective antagonist of NTSR1, or NTSR1 shRNA were stained with Annexin V-FITC/PI and the apoptosis was assessed by flow cytometry. Cytochrome c release was detected by using immunofluorescence. Mitochondrial membrane potential (MMP, ΔΨm) loss was stained by JC-1 and detected by immunofluorescence or flow cytometry. Apoptosis antibody array and microRNA microarray were performed to seek the potential regulators of NTSR1 inhibition-induced apoptosis. Interaction between let-7a-3p and Bcl-w 3′UTR was evaluated by using luciferase assay.

Results:

SR48692 induced massive apoptosis, which was related to mitochondrial cytochrome c release and MMP loss. Knockdown of NTSR1 induced slight apoptosis and significant MMP loss. In addition, NTSR1 inhibition sensitised glioblastoma cells to actinomycin D or doxorubicin-induced apoptosis. Consistently, NTSR1 inhibition-induced mitochondrial apoptosis was accompanied by downregulation of Bcl-w and Bcl-2. Restoration of Bcl-w partly rescued NTSR1 deficiency-induced apoptosis. In addition, NTSR1 deficiency promoted higher let-7a-3p expression and inhibition let-7a-3p partly rescued NTSR1 inhibition-induced apoptosis. In addition, let-7a-3p inhibition promoted 3′UTR activities of Bcl-w and the expression of c-Myc and LIN28, which were the upstream of let-7a-3p, decreased after NTSR1 inhibition.

Conclusions:

NTSR1 had an important role in protecting glioblastoma from intrinsic apoptosis via c-Myc/LIN28/let-7a-3p/Bcl-w axis.

Diverse expression patterns and tumorigenic role of neurotensin signaling components in colorectal cancer cells

Colorectal cancer (CRC), which is one of the most common malignancies worldwide, results from an accumulation of genetic and epigenetic modifications including DNA methylation. Neurotensin (NTS), a hormone localized to the gut and central nervous system, mediates its physiological and pathological effects, including growth stimulation for a variety of cancers, through three distinct NTS receptors (NTSRs). Most NTS functions are mediated through the high-affinity receptor NTSR1, and expression of NTSR1 is increased in many cancers including CRC. In this study, we investigated the expression profiles and cellular functions of the NTSRs, especially NTSR1, in CRC cells. We showed that expression levels for NTS and NTSR1 varied, that NTSR2 expression was not detectable and that NTSR3 was consistently expressed in all CRC cell lines examined. Treatment with the demethylating agent, 5-aza-2'-deoxycytidine, augmented levels of NTSR1/2 in Caco2 and DLD1 cells, which have little or no transcripts for NTSR1/2 suggesting that DNA methylation suppresses NTSR1/2 expression. In addition, we demonstrated that knockdown of NTSR1 decreased cell growth and migration in HCT116 and HT29 cells. Finally, we showed that treatment with SR48692, an antagonist of NTSR1, also inhibited cell proliferation and migration in the CRC cells. Our findings identify promoter methylation as an important process regulating the differential expression or silencing of NTSR1/2 in CRC cells. Moreover, inhibition of NTSR1 repressed tumorigenic effects in CRC cells, suggesting that NTSR1 may be used as a therapeutic target for CRC.

Differential expression and tumorigenic function of neurotensin receptor 1 in neuroendocrine tumor cells

Neurotensin (NTS), localized predominantly to the small bowel, stimulates the growth of a variety of cancers, including neuroendocrine tumors (NETs), mainly through its interaction with the high-affinity NTS receptor 1 (NTSR1). Here, we observed increased expression of NTSR1 in almost all tested clinical NET samples, but not in normal tissues. Through RT-PCR analysis, we found that the expression of NTSR1 and NTSR2 was either variable (NTSR1) or absent (NTSR2) in human NET cell lines. In contrast, NTSR3 and NTS were expressed in all NET cells. Treatment with 5-aza-2′-deoxycytidine, a demethylating agent, increased levels of NTSR1 and NTSR2 suggesting that DNA methylation contributes to NTSR1/2 expression patterns, which was confirmed by methylation analyses. In addition, we found that knockdown of NTSR1 decreased proliferation, expression levels of growth-related proteins, and anchorage-independent growth of BON human carcinoid cells. Moreover, stable silencing of NTSR1 suppressed BON cell growth, adhesion, migration and invasion. Our results show that high expression of NTSR1 is found in clinical NETs and that promoter methylation is an important mechanism controlling the differential expression of NTSR1 and silencing of NTSR2 in NET cells. Furthermore, knockdown of NTSR1 in BON cells suppressed oncogenic functions suggesting that NTSR1 contributes to NET tumorigenesis.

Epidemiology of Lung Cancer in Korea: Recent Trends

Lung cancer causes the most cancer deaths in Korea. Although the smoking rate has begun to decrease, the prevalence of lung cancer is still increasing. We reviewed the national lung cancer registry data and the data published about lung cancer in Korea. In 2012, the crude incidence rate of lung cancer was 43.9 per 100,000. The age-standardized mortality rate of lung cancer was 19.8 per 100,000. The 5-year relative survival rate for lung cancer was 11.3% from 1993 to 1995 and increased to 21.9% in the period from 2008 to 2012. Lung cancer occurring in never-smokers was estimated to increase in Korea. Adenocarcinoma is steadily increasing in both women and men and has replaced squamous cell carcinoma as the most common type of lung cancer in Korea. In patients with adenocarcinoma, the frequency of EGFR mutations was 43% (range, 20%–56%), while that of the EMK4-ALK gene was less than 5%.

Roles of miR-186 and PTTG1 in colorectal neuroendocrine tumors

OBJECTIVES

This work aims to investigate the expression of miRNA-186 in patients with colorectal cancer tissues, blood and feces and its roles in regulating the infiltration and invasion in colorectal cancer.

METHODS

Totally 39 patients with surgical resection were included from August 2012 to February 2015 in Jilin Province People's Hospital as the Colorectal Neuroendocrine tumor (CNET). Peripheral blood, stool, and resected tumor tissues with adjacent normal of each patient was collected. In the same period, the blood and stool from 25 patients with hemorrhoids or other non-neoplastic diseases were collected and these samples used as clinical control group. MiR-186 expression and PTTG1 (pituitary tumor-transforming 1) expression were detected by quantitative Real-Time PCR (qRT-PCR). The PTTG1 protein expression in tumor samples were detected by Western Blot, while its expression in blood and stool were detected by Elisa.

RESULTS

Compared with the control group, the expression of PTTG1 mRNA and protein was significantly up-regulated in tumor samples, blood, and stool of patients with CNET, while the expression of miR-186 was down-regulated (P < 0.05).

CONCLUSION

PTTG1 expression was significantly up-regulated in patients with CNET, which was induced by the down-regulated miR-186. MiR-186 may participate in the regulation of infiltration and invasion in CNET patients through targeting PTTG1 expression.

The potential of neurotensin secreted from neuroendocrine tumor cells to promote gelsolin-mediated invasiveness of prostate adenocarcinoma cells

Neuroendocrine (NE) cells in prostate cancer have been shown to be associated with the progression of prostate cancer. However, little is known about the molecular basis of this association. We have previously demonstrated that NE cells promote metastasis of a human prostate cancer cell line (LNCaP) with overexpression of the gelsolin gene. The purpose of this study was to investigate the interactions between NE cells and LNCaP cells and the involvement of gelsolin in contributing to the invasive potential of LNCaP cells. In addition, we examined whether neurotensin induced gelsolin-mediated invasion. We used the NE cell line NE-CS that was established from the prostate of the LPB-Tag 12T-10 transgenic mouse. Small interfering RNA (siRNA) targeting gelsolin or not targeting it was transfected into LNCaP cells. Cell invasion was assessed by Matrigel invasion assay. The supernatant of NE-CS cells and neurotensin induced the transformation of LNCaP cells. Neurotensin was observed in the supernatant of NE-CS cells but not in LNCaP cells. The siRNA targeting of gelsolin resulted in inhibition of invasion of LNCaP cells in the culture medium with neurotensin added, and in the supernatant of NE-CS cells with epidermal growth factor. The invasive potential of LNCaP cells enhanced by neurotensin or the supernatant of NE-CS cells through neurotensin receptor 1 (NTSR1) was blocked by a phospholipase Cγ inhibitor and an intracellular calcium chelator, with concomitant gelsolin suppression. This study indicates that NE cells and neurotensin induce gelsolin-mediated invasion of LNCaP cells through NTSR1 activation.

New targeted therapies for breast cancer: A focus on tumor microenvironmental signals and chemoresistant breast cancers

Breast cancer is the most frequent female malignancy worldwide. Current strategies in breast cancer therapy, including classical chemotherapy, hormone therapy, and targeted therapies, are usually associated with chemoresistance and serious adverse effects. Advances in our understanding of changes affecting the interactome in advanced and chemoresistant breast tumors have provided novel therapeutic targets, including, cyclin dependent kinases, mammalian target of rapamycin, Notch, Wnt and Shh. Inhibitors of these molecules recently entered clinical trials in mono- and combination therapy in metastatic and chemo-resistant breast cancers. Anticancer epigenetic drugs, mainly histone deacetylase inhibitors and DNA methyltransferase inhibitors, also entered clinical trials. Because of the complexity and heterogeneity of breast cancer, the future in therapy lies in the application of individualized tailored regimens. Emerging therapeutic targets and the implications for personalized-based therapy development in breast cancer are herein discussed.