Altered LKB1/CREB-regulated transcription co-activator (CRTC) signaling axis promotes esophageal cancer cell migration and invasion. Oncogene. 2012;31:469-479. [PMID: 21706049 DOI: 10.1038/onc.2011.247]

Pancreatic cancer tumor organoids exhibit subtype-specific differences in metabolic profiles

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive disease characterized by complex metabolic rewiring that enables growth in changing nutrient availability and oxygen conditions. Transcriptome-based prognostic PDAC tumor subtypes, known as 'basal-like' and 'classical' subtypes are associated with differences in metabolic gene expression including genes involved in glycolysis. Tumor subtype-specific metabolism phenotypes may provide new targets for treatment development in PDAC, but their functional relevance has not been fully elucidated. We aimed to investigate differences in metabolic profiles and transcriptomes in tumor models derived from patients with basal-like and classical tumors.

METHODS

Patient-derived organoids (PDOs) were established from tumor biopsies collected from patients with metastatic PDAC, including three PDOs from basal-like and five PDOs from classical tumors. Metabolic analyses included assessment of differences in metabolic activity using Seahorse Glycolysis and Mito Stress tests and 13C-glucose metabolites tracing analysis. In order to investigate the influence of mitochondrial pyruvate transport on metabolic differences, PDOs were treated with the mitochondrial pyruvate carrier 1 (MPC1) inhibitor UK-5099. Prognostic relevance of MPC1 was determined using a tumor tissue microarray (TMA) in resectable, and proteomics profiling in metastatic PDAC datasets. Whole genome and transcriptome sequencing, differential gene expression and gene set enrichment analyses were performed in PDOs.

RESULTS

Metastatic PDAC PDOs showed subtype-specific differences in glycolysis and oxidative phosphorylation (OXPHOS). Basal-like tumor-derived PDOs had a lower baseline extracellular acidification rate, but higher glycolytic reserves and oxygen consumption rate (OCR) than classical tumor-derived PDOs. OCR difference was eliminated following treatment with UK-5099. In the 13C-glucose metabolites tracing experiment, a basal-like tumor PDO showed lower fractions of some M + 2 metabolites but higher sensitivity to UK-5099 mediated reduction in M + 2 metabolites than a classical tumor PDO. Protein level analyses revealed lower MPC1 protein levels in basal-like PDAC cases and association of low MPC1 levels with clinicopathologic parameters of tumor aggressiveness in PDAC. PDO differential gene expression analyses identified additional subtype-specific cellular pathways and potential disease outcome biomarkers.

CONCLUSIONS

Our findings point to distinct metabolic profiles in PDAC subtypes with basal-like tumor PDOs showing higher OXPHOS and sensitivity to MPC1 inhibition. Subtypes-specific metabolic vulnerabilities may be exploited for selective therapeutic targeting.

Transcriptional co-activators: emerging roles in signaling pathways and potential therapeutic targets for diseases

Specific cell states in metazoans are established by the symphony of gene expression programs that necessitate intricate synergic interactions between transcription factors and the co-activators. Deregulation of these regulatory molecules is associated with cell state transitions, which in turn is accountable for diverse maladies, including developmental disorders, metabolic disorders, and most significantly, cancer. A decade back most transcription factors, the key enablers of disease development, were historically viewed as 'undruggable'; however, in the intervening years, a wealth of literature validated that they can be targeted indirectly through transcriptional co-activators, their confederates in various physiological and molecular processes. These co-activators, along with transcription factors, have the ability to initiate and modulate transcription of diverse genes necessary for normal physiological functions, whereby, deregulation of such interactions may foster tissue-specific disease phenotype. Hence, it is essential to analyze how these co-activators modulate specific multilateral processes in coordination with other factors. The proposed review attempts to elaborate an in-depth account of the transcription co-activators, their involvement in transcription regulation, and context-specific contributions to pathophysiological conditions. This review also addresses an issue that has not been dealt with in a comprehensive manner and hopes to direct attention towards future research that will encompass patient-friendly therapeutic strategies, where drugs targeting co-activators will have enhanced benefits and reduced side effects. Additional insights into currently available therapeutic interventions and the associated constraints will eventually reveal multitudes of advanced therapeutic targets aiming for disease amelioration and good patient prognosis.

Activation of the CREB Coactivator CRTC2 by Aberrant Mitogen Signaling promotes oncogenic functions in HPV16 positive head and neck cancer

Head and neck squamous cell carcinoma (HNSCC) is the 6th most common cancer worldwide and incidence rates are continuing to rise globally. Patients often present with locally advanced disease and a staggering 50% chance of relapse following treatment. Aberrant activation of adaptive response signaling pathways, such as the cAMP/PKA pathway, induce an array of genes associated with known cancer pathways that promote tumorigenesis and drug resistance. We identified the cAMP Regulated Transcription Coactivator 2 (CRTC2) to be overexpressed and constitutively activated in HNSCCs and this confers poor prognosis. CRTCs are regulated through their subcellular localization and we show that CRTC2 is exclusively nuclear in HPV(+) HNSCC, thus constitutively active, due to non-canonical Mitogen-Activated Kinase Kinase 1 (MEKK1)-mediated activation via a MEKK1-p38 signaling axis. Loss-of-function and pharmacologic inhibition experiments decreased CRTC2/CREB transcriptional activity by reducing nuclear CRTC2 via nuclear import inhibition and/or by eviction of CRTC2 from the nucleus. This shift in localization was associated with decreased proliferation, migration, and invasion. Our results suggest that small molecules that inhibit nuclear CRTC2 and p38 activity may provide therapeutic benefit to patients with HPV(+) HNSCC.

Cutaneous melanocytic tumor with CRTC1::TRIM11 fusion and prominent epidermal involvement: A case report

Cutaneous melanocytic tumor with CRTC1::TRIM11 fusion (CMCT) is a recently described entity with only 13 cases reported in the literature. Histopathologically, the neoplasm consists of atypical epithelioid to spindled cells that form a well-circumscribed nodule confined to the dermis and subcutis with cytological features including large vesicular nuclei with prominent nucleoli and abundant eosinophilic cytoplasm. Immunohistochemistry shows variable expressivity of melanocytic markers. Currently, there is limited data regarding long-term outcomes of this newly described entity. Most cases have done well, but there is one case reported with an adverse event. Hence, further studies are needed to accurately classify this tumor. Definitive diagnosis is made by laboratory evidence of CRTC1::TRIM11 fusion. Herein, we report the first case of CMCT with epidermal involvement in the youngest patient known to be affected to date.

Esophageal cancer: Epidemiology, risk factors and screening

More than 600,000 people are diagnosed with esophageal cancer (EC) every year globally, and the five-year survival rate of EC is less than 20%. Two common histological subtypes of EC, esophageal squamous cell carcinoma (ESCC) and esophageal adenocarcinoma (EAC), have great geographical variations in incidence rates. About half of the world's EC was diagnosed in China and a majority of which belong to ESCC. Globally, the overall incidence rate of EC is decreasing. In some high-risk Asian regions, such as China, the incidence rate of ESCC has generally declined, potentially due to economic growth and improvement of diet habits. In some European high-income countries and the United States, the decline is mainly attributed to the decrease in smoking and drinking. The risk factors of EC are not well understood, and the importance of environmental and genetic factors in the pathogenesis is also unclear. The incidence and mortality of advanced EC can be reduced through early diagnosis and screening. White light endoscopy is still the gold standard in the current screening technology. This article reviews the epidemiology, risk factors, and screening strategies of EC in recent years to help researchers determine the most effective management strategies to reduce the risk of EC.

Prioritization and functional analysis of GWAS risk loci for Barrett's esophagus and esophageal adenocarcinoma

Genome-wide association studies (GWAS) have identified ~ 20 genetic susceptibility loci for esophageal adenocarcinoma (EAC), and its precursor, Barrett's esophagus (BE). Despite such advances, functional/causal variants and gene targets at these loci remain undefined, hindering clinical translation. A key challenge is that most causal variants map to non-coding regulatory regions such as enhancers, and typically, numerous potential candidate variants at GWAS loci require testing. We developed a systematic informatics pipeline for prioritizing candidate functional variants via integrative functional potential scores consolidated from multi-omics annotations, and used this pipeline to identify two high-scoring variants for experimental interrogation: chr9q22.32/rs11789015 and chr19p13.11/rs10423674. Minimal candidate enhancer regions spanning these variants were evaluated using luciferase reporter assays in two EAC cell lines. One of the two variants tested (rs10423674) exhibited allele-specific enhancer activity. CRISPR-mediated deletion of the putative enhancer region in EAC cell lines correlated with reduced expression of two genes-CREB-regulated transcription coactivator 1 (CRTC1) and Cartilage oligomeric matrix protein (COMP); expression of five other genes remained unchanged (CRLF1, KLHL26, TMEM59L, UBA52, RFXANK). Expression quantitative trait locus (eQTL) mapping indicated that rs10423674 genotype correlated with CRTC1 and COMP expression in normal esophagus. This study represents the first experimental effort to bridge GWAS associations to biology in BE/EAC, and supports the utility of functional potential scores to guide variant prioritization. Our findings reveal a functional variant and candidate risk enhancer at chr19p13.11, and implicate CRTC1 and COMP as putative gene targets, suggesting that altered expression of these genes may underlie the BE/EAC risk association.

Attacking the PI3K/Akt/mTOR signaling pathway for targeted therapeutic treatment in human cancer

Cancer is the second leading cause of human death globally. PI3K/Akt/mTOR signaling is one of the most frequently dysregulated signaling pathways observed in cancer patients that plays crucial roles in promoting tumor initiation, progression and therapy responses. This is largely due to that PI3K/Akt/mTOR signaling is indispensable for many cellular biological processes, including cell growth, metastasis, survival, metabolism, and others. As such, small molecule inhibitors targeting major kinase components of the PI3K/Akt/mTOR signaling pathway have drawn extensive attention and been developed and evaluated in preclinical models and clinical trials. Targeting a single kinase component within this signaling usually causes growth arrest rather than apoptosis associated with toxicity-induced adverse effects in patients. Combination therapies including PI3K/Akt/mTOR inhibitors show improved patient response and clinical outcome, albeit developed resistance has been reported. In this review, we focus on revealing the mechanisms leading to the hyperactivation of PI3K/Akt/mTOR signaling in cancer and summarizing efforts for developing PI3K/Akt/mTOR inhibitors as either mono-therapy or combination therapy in different cancer settings. We hope that this review will facilitate further understanding of the regulatory mechanisms governing dysregulation of PI3K/Akt/mTOR oncogenic signaling in cancer and provide insights into possible future directions for targeted therapeutic regimen for cancer treatment, by developing new agents, drug delivery systems, or combination regimen to target the PI3K/Akt/mTOR signaling pathway. This information will also provide effective patient stratification strategy to improve the patient response and clinical outcome for cancer patients with deregulated PI3K/Akt/mTOR signaling.

Dependency of human and murine LKB1-inactivated lung cancer on aberrant CRTC-CREB activation

Lung cancer with loss-of-function of the LKB1 tumor suppressor is a common aggressive subgroup with no effective therapies. LKB1-deficiency induces constitutive activation of cAMP/CREB-mediated transcription by a family of three CREB-regulated transcription coactivators (CRTC1-3). However, the significance and mechanism of CRTC activation in promoting the aggressive phenotype of LKB1-null cancer remain poorly characterized. Here, we observed overlapping CRTC expression patterns and mild growth phenotypes of individual CRTC-knockouts in lung cancer, suggesting functional redundancy of CRTC1-3. We consequently designed a dominant-negative mutant (dnCRTC) to block all three CRTCs to bind and co-activate CREB. Expression of dnCRTC efficiently inhibited the aberrantly activated cAMP/CREB-mediated oncogenic transcriptional program induced by LKB1-deficiency, and specifically blocked the growth of human and murine LKB1-inactivated lung cancer. Collectively, this study provides direct proof for an essential role of the CRTC-CREB activation in promoting the malignant phenotypes of LKB1-null lung cancer and proposes the CRTC-CREB interaction interface as a novel therapeutic target.

Visceral Obesity, Metabolic Syndrome, and Esophageal Adenocarcinoma

Esophageal adenocarcinoma (EAC) represents an exemplar of obesity-associated carcinogenesis, with a progressive increase in EAC risk with increased body mass index. In this context, there is increased focus on visceral adipose tissue and associated metabolic dysfunction, including hypertension, diabetes mellitus and hyperlipidemia, or combinations of these in the metabolic syndrome. Visceral obesity (VO) may promote EAC via both directly impacting on gastro-esophageal reflux disease and Barrett's esophagus, as well as via reflux-independent effects, involving adipokines, growth factors, insulin resistance, and the microbiome. In this review these pathways are explored, including the impact of VO on the tumor microenvironment, and on cancer outcomes. The current evidence-based literature regarding the role of dietary, lifestyle, pharmacologic and surgical interventions to modulate the risk of EAC is explored.

LINC00473: A novel oncogenic long noncoding RNA in human cancers

Long noncoding RNAs (lncRNAs) have been found to play essential roles in the occurrence and development of multiple human cancers. Accumulating evidence has shown that LINC00473, an oncogenic lncRNA, is upregulated in various human malignancies and related to poor clinical outcomes. Besides, LINC00473 overexpression can promote cell proliferation, migration, and invasion through multiple potential mechanisms, indicating that it may serve as a novel prognostic biomarker and therapeutic target for human cancers. Here, we reviewed the biological functions, molecular mechanisms, and clinical implications of LINC00473 in human cancers.

What turns CREB on? And off? And why does it matter?

Altered expression and function of the transcription factor cyclic AMP response-binding protein (CREB) has been identified to play an important role in cancer and is associated with the overall survival and therapy response of tumor patients. This review focuses on the expression and activation of CREB under physiologic conditions and in tumors of distinct origin as well as the underlying mechanisms of CREB regulation by diverse stimuli and inhibitors. In addition, the clinical relevance of CREB is summarized, including its use as a prognostic and/or predictive marker as well as a therapeutic target.

Role of INSL4 Signaling in Sustaining the Growth and Viability of LKB1-Inactivated Lung Cancer

BACKGROUND

The LKB1 tumor suppressor gene is commonly inactivated in non-small cell lung carcinomas (NSCLC), a major form of lung cancer. Targeted therapies for LKB1-inactivated lung cancer are currently unavailable. Identification of critical signaling components downstream of LKB1 inactivation has the potential to uncover rational therapeutic targets. Here we investigated the role of INSL4, a member of the insulin/IGF/relaxin superfamily, in LKB1-inactivated NSCLCs.

METHODS

INSL4 expression was analyzed using global transcriptome profiling, quantitative reverse transcription PCR, western blotting, enzyme-linked immunosorbent assay, and RNA in situ hybridization in human NSCLC cell lines and tumor specimens. INSL4 gene expression and clinical data from The Cancer Genome Atlas lung adenocarcinomas (n = 515) were analyzed using log-rank and Fisher exact tests. INSL4 functions were studied using short hairpin RNA (shRNA) knockdown, overexpression, transcriptome profiling, cell growth, and survival assays in vitro and in vivo. All statistical tests were two-sided.

RESULTS

INSL4 was identified as a novel downstream target of LKB1 deficiency and its expression was induced through aberrant CRTC-CREB activation. INSL4 was highly induced in LKB1-deficient NSCLC cells (up to 543-fold) and 9 of 41 primary tumors, although undetectable in all normal tissues except the placenta. Lung adenocarcinomas from The Cancer Genome Atlas with high and low INSL4 expression (with the top 10th percentile as cutoff) showed statistically significant differences for advanced tumor stage (P < .001), lymph node metastasis (P = .001), and tumor size (P = .01). The INSL4-high group showed worse survival than the INSL4-low group (P < .001). Sustained INSL4 expression was required for the growth and viability of LKB1-inactivated NSCLC cells in vitro and in a mouse xenograft model (n = 5 mice per group). Expression profiling revealed INSL4 as a critical regulator of cell cycle, growth, and survival.

CONCLUSIONS

LKB1 deficiency induces an autocrine INSL4 signaling that critically supports the growth and survival of lung cancer cells. Therefore, aberrant INSL4 signaling is a promising therapeutic target for LKB1-deficient lung cancers.

CircCBFB-mediated miR-28-5p facilitates abdominal aortic aneurysm via LYPD3 and GRIA4

HEADING AIMS

Abdominal aortic aneurysm (AAA) is featured by the growth impediment and apoptosis surge of VSMCs (vascular smooth muscle cells). MicroRNAs (miRNAs) are suggested to affect cellular behaviors including cell growth and apoptosis. This study concentrated on unraveling the emerging role of miR-28-5p in abdominal aortic aneurysm.

MATERIALS AND METHODS

Previously, miR-28-5p was reported to be highly expressed in AAA. Functional assays were utilized to determine the role of miR-28-5p in VSMC apoptosis. To narrow down the downstream mRNAs, bioinformatics methods were utilized. The interaction between miR-28-5p and GRIA4 (glutamate ionotropic receptor AMPA type subunit 4) or LYPD3 (LY6/PLAUR domain containing 3) was explored. Candidate circRNAs (circular RNAs) of miR-28-5p were identified. Rescue analyses validated function of circCBFB (core-binding factor subunit beta)/miR-28-5p/GRIA4/LYPD3 axis in VSMC apoptosis and growth.

KEY FINDINGS

MiR-28-5p acted as an apoptosis driver while circCBFB, GRIA4 and LYPD3 exerted anti-apoptosis effects in VSMCs. Mechanically, GRIA4 and LYPD3 were suppressed by miR-28-5p. Moreover, circCBFB served as a sponge of miR-28-5p, releasing GRIA4 and LYPD3 from miR-28-5p suppression. Functionally, GRIA4, LYPD3 and miR-28-5p were required in circCBFB-mediated VSMC apoptosis.

SIGNIFICANCE

This work unveiled an innovative axis of circCBFB/miR-28-5p/GRIA4/LYPD3 in VSMC apoptosis, exerting its potential in providing new thoughts in AAA management.

β2-Adrenergic Signalling Promotes Cell Migration by Upregulating Expression of the Metastasis-Associated Molecule LYPD3

Metastasis is associated with poor prognosis in breast cancer. Although some studies suggest beta-blockers increase survival by delaying metastasis, others have been discordant. This study provides both insights into the anomalous findings and identifies potential biomarkers that may be treatment targets. Cell line models of basal-type and oestrogen receptor-positive breast cancer were profiled for basal levels of adrenoceptor gene/protein expression, and β2-adrenoceptor mediated cell behaviour including migration, invasion, adhesion, and survival in response to adrenoceptor agonist/antagonist treatment. Protein profiling and histology identified biomarkers and drug targets. Baseline levels of adrenoceptor gene expression are higher in basal-type rather than oestrogen receptor-positive cancer cells. Norepinephrine (NE) treatment increased invasive capacity in all cell lines but did not increase proliferation/survival. Protein profiling revealed the upregulation of the pro-metastatic gene Ly6/PLAUR Domain-Containing Protein 3 (LYPD3) in norepinephrine-treated MDA-MB-468 cells. Histology confirmed selective LYPD3 expression in primary and metastatic breast tumour samples. These findings demonstrate that basal-type cancer cells show a more aggressive adrenoceptor-β2-activated phenotype in the resting and stimulated state, which is attenuated by adrenoceptor-β2 inhibition. This study also highlights the first association between ADRβ2 signalling and LYPD3; its knockdown significantly reduced the basal and norepinephrine-induced activity of MCF-7 cells in vitro. The regulation of ADRβ2 signalling by LYPD3 and its metastasis promoting activities, reveal LYPD3 as a promising therapeutic target in the treatment of breast and other cancers.

SERPINE2 promotes esophageal squamous cell carcinoma metastasis by activating BMP4

Metastasis is a major lethal cause of esophageal squamous cell carcinoma (ESCC) and confers a poor prognosis. Previous studies demonstrated that serpin family E member 2 (SERPINE2) is involved in tumor metastasis. However, the function and mechanism of SERPINE2 in ESCC metastasis remains unclear. In this study, we found that SERPINE2 was increased in ESCC and associated with tumor metastasis. SERPINE2 knockdown inhibited tumor cell invasion and lymph node and lung metastasis by inducing epithelial-mesenchymal transition (EMT). We identified a total of 410 differentially expressed genes in SERPINE2-knockdown cells by RNA-Seq analysis. Among them, bone morphogenetic protein 4 (BMP4) was significantly downregulated. Conversely, BMP4 was increased in SERPINE2-overexpressing cells. Inhibiting BMP4 could attenuate SERPINE2-induced migration and invasion. Moreover, SERPINE2 was positively correlated with clinical stage, tumor invasion depth and lymph node metastasis in ESCC patients. These findings suggest that SERPINE2 promotes tumor metastasis by activating BMP4 and could serve as a potential therapeutic target for clinical intervention in ESCC.

Genetic variants in Barrett's esophagus and esophageal adenocarcinoma: a literature review

Surveillance of Barrett's esophagus (BE) is a clinical challenge; metaplasia of the distal esophagus increases a patient's risk of esophageal adenocarcinoma (EAC) significantly but the actual percentage of patients who progress is low. The current screening recommendations require frequent endoscopy and biopsy, which has inherent risk, high cost, and operator variation. Identifying BE patients genetically who are at high risk of progressing could deemphasize the role of endoscopic screening and create an opportunity for early therapeutic intervention. Genetic alterations in germline DNA have been identified in other disease processes and allow for early intervention or surveillance well before disease develops. The genetic component of BE remains mostly unknown and only a few genome-wide association studies exist on this topic. This review summarizes the current literature available that examines genetic alterations in BE and EAC with a particular emphasis on clinical implications.

Keratin 14-high subpopulation mediates lung cancer metastasis potentially through Gkn1 upregulation

Metastasis is the leading cause of lung cancer-related death. Elucidating the metastasis process can provide new avenues to inhibit this malignant behavior of cancer cells. Here we found that human lung cancers with high Keratin 14 (K14) expression were associated with nodal metastasis and poor survival. Using the Kras^G12D/Trp53^L/L lung cancer mouse model, we confirmed that K14-high cancer cells harbored increased metastatic potential. Mechanistic investigation revealed that Gastrokine 1 (Gkn1) expression positively correlated with K14 level, cancer metastasis, and poor patient survival. Importantly, ectopic expression of Gkn1 enhanced the metastatic capability of K14-low cells in vitro and in vivo, whereas knockdown of Gkn1 did the opposite, indicating the importance of Gkn1 in mediating the metastasis of K14-high cells. Further study demonstrated that Gkn1 expression conferred K14-high cells resistance to anoikis, which is critical for cancer metastasis. Collectively, our findings demonstrate that K14-high cells contribute to lung cancer metastasis potentially through inhibition of anoikis via upregulation of Gkn1.

PAK4 signaling in health and disease: defining the PAK4-CREB axis

p21-Activated kinase 4 (PAK4), a member of the PAK family, regulates a wide range of cellular functions, including cell adhesion, migration, proliferation, and survival. Dysregulation of its expression and activity thus contributes to the development of diverse pathological conditions. PAK4 plays a pivotal role in cancer progression by accelerating the epithelial–mesenchymal transition, invasion, and metastasis. Therefore, PAK4 is regarded as an attractive therapeutic target in diverse types of cancers, prompting the development of PAK4-specific inhibitors as anticancer drugs; however, these drugs have not yet been successful. PAK4 is essential for embryonic brain development and has a neuroprotective function. A long list of PAK4 effectors has been reported. Recently, the transcription factor CREB has emerged as a novel effector of PAK4. This finding has broad implications for the role of PAK4 in health and disease because CREB-mediated transcriptional reprogramming involves a wide range of genes. In this article, we review the PAK4 signaling pathways involved in prostate cancer, Parkinson’s disease, and melanogenesis, focusing in particular on the PAK4-CREB axis.

An enzyme that regulates an important controller of gene expression may offer a therapeutic target for cancer and other diseases. cAMP response element-binding protein (CREB) interacts with various other proteins to switch a myriad of target genes on and off in different cells. A review by Eung-Gook Kim, Eun-Young Shin and colleagues at Chungbuk National University, Cheongju, South Korea, explores the interplay between CREB and an enzyme called p21-activated kinase 4 (PAK4) in human health and disease. PAK4, for example, has been shown to promote CREB’s gene-activating function in prostate cancer, and PAK4 overexpression is a feature of numerous other tumor types. Disruptions in PAK4-mediated regulation of CREB activity have also been observed in neurons affected by Parkinson’s disease. The authors see strong clinical promise in further exploring the biology of the PAK4-CREB pathway.

Adaptive Transcriptional Responses by CRTC Coactivators in Cancer

Adaptive stress signaling networks directly influence tumor development and progression. These pathways mediate responses that allow cancer cells to cope with both tumor cell-intrinsic and cell-extrinsic insults and develop acquired resistance to therapeutic interventions. This is mediated in part by constant oncogenic rewiring at the transcriptional level by integration of extracellular cues that promote cell survival and malignant transformation. The cAMP-regulated transcriptional coactivators (CRTCs) are a newly discovered family of intracellular signaling integrators that serve as the conduit to the basic transcriptional machinery to regulate a host of adaptive response genes. Thus, somatic alterations that lead to CRTC activation are emerging as key driver events in the development and progression of many tumor subtypes.

ETS1 regulates Twist1 transcription in a KrasG12D/Lkb1-/- metastatic lung tumor model of non-small cell lung cancer

Distinct members of the Ets family of transcription factors act as positive or negative regulators of genes involved in cellular proliferation, development, and tumorigenesis. In human lung cancer, increased ETS1 expression is associated with poor prognosis and metastasis. We tested whether ETS1 contributes to lung tumorigenesis by binding to Twist1, a gene involved in tumor cell motility and dissemination. We used a mouse lung cancer model with metastasis driven by conditionally activated Kras and concurrent tumor suppressor Lkb1 loss (Kras^G12D/ Lkb1^-/- model) and a similar model of lung cancer that does not metastasize, driven by conditionally activated Kras alone (Kras^G12D model). We show that Ets1 and Twist1 gene expression differs between Kras^G12D tumors (low Ets1 and Twist1 expression) and Kras^G12D/Lkb1^-/- tumors (high Ets1 and Twist1 expression). In human lung tumors, ETS1 and TWIST1 expression positively correlates and low combined ETS1 and TWIST1 levels are associated with improved survival compared to high levels. Using mouse cell lines derived from Kras^G12D and Kras^G12D/Lkb1^-/- mouse models and the human lung cancer (A549) cell line, we show that ETS1 regulates Twist1 expression. Chromatin immunoprecipitation assays confirm binding of ETS1 to the Twist1 promoter. Overexpression studies show that ETS1 transactivates Twist1 promoter activity in mouse and human cells. Silencing endogenous Ets1 by siRNA in mouse cell lines decreases Twist1 mRNA levels, decreases invasion, and increases cell growth. Ets1 and Twist1 are at the crossroad of several signaling pathways in cancer. Understanding their regulation may inform the development of therapies to impair lung tumor metastasis.

Super enhancer inhibitors suppress MYC driven transcriptional amplification and tumor progression in osteosarcoma

Osteosarcoma is the most common primary bone sarcoma that mostly occurs in young adults. The causes of osteosarcoma are heterogeneous and still not fully understood. Identification of novel, important oncogenic factors in osteosarcoma and development of better, effective therapeutic approaches are in urgent need for better treatment of osteosarcoma patients. In this study, we uncovered that the oncogene MYC is significantly upregulated in metastastic osteosarcoma samples. In addition, high MYC expression is associated with poor survival of osteosarcoma patients. Analysis of MYC targets in osteosarcoma revealed that most of the osteosarcoma super enhancer genes are bound by MYC. Treatment of osteosarcoma cells with super enhancer inhibitors THZ1 and JQ1 effectively suppresses the proliferation, migration, and invasion of osteosarcoma cells. Mechanistically, THZ1 treatment suppresses a large group of super enhancer containing MYC target genes including CDK6 and TGFB2. These findings revealed that the MYC-driven super enhancer signaling is crucial for the osteosarcoma tumorigenesis and targeting the MYC/super enhancer axis represents as a promising therapeutic strategy for treatment of osteosarcoma patients.

LKB1 inactivation occurs in a subset of esophageal adenocarcinomas and is sufficient to drive tumor cell proliferation

BACKGROUND

The incidence of esophageal adenocarcinoma (EAC) has increased over the last several decades. Apart from mutations in TP53 gene, there are little data on genetic drivers of EAC. Liver kinase B1 (LKB1) has emerged as a multifunctional tumor suppressor regulating cell growth, differentiation, and metabolism. Somatic inactivation of LKB1 has been described in several tumor types; however, whether LKB1 inactivation has a role in EAC is unknown. Here we analyzed patient tumors to assess the prevalence of LKB1 loss in EAC.

METHODS

Chromosomal deletion and expression of LKB1 in EAC were investigated using publicly available genomic data. Protein expression was assessed by immunohistochemistry (IHC) analysis for LKB1 in a tissue microarray (TMA) containing esophageal tumor specimens, including EAC. LKB1 was suppressed in EAC cells to determine the effects on cell growth in vitro.

RESULTS

Analysis of EAC data in The Cancer Genome Atlas dataset revealed significant deletion of chromosome 19p13.3, containing the LKB1 gene locus. Single copy loss (shallow deletion) of LKB1 was present in 58% of EAC samples. Expression of LKB1 was significantly lower in EAC tumors compared with normal esophagus. IHC analysis showed reduced LKB1 protein expression in EAC. Suppression of LKB1 was sufficient to enhance EAC cell growth in vitro.

CONCLUSIONS

Our data suggest that inactivation of LKB1 frequently occurs in EAC. Based on the reported oncogenic effects of LKB1 inactivation, our data indicate that LKB1 loss may play a significant role in EAC tumorigenesis, and point to the need for future studies.

CRTC1-MAML2 fusion-induced lncRNA LINC00473 expression maintains the growth and survival of human mucoepidermoid carcinoma cells

Mucoepidermoid carcinoma (MEC) arises in many glandular tissues and contributes to the most common malignant salivary gland cancers. MEC is specifically associated with a unique t(11;19) translocation and the resulting CRTC1-MAML2 fusion is a major oncogenic driver for MEC initiation and maintenance. However, the molecular basis underlying the CRTC1-MAML2 oncogenic functions remain very limited. Through gene expression profiling analysis, we observed that LINC00473, a long noncoding RNA (lncRNA), was the top down-regulated target in CRTC1-MAML2-depleted human MEC cells. LncRNAs belong to a new class of non-coding RNAs with emerging roles in tumorigenesis and progression, but remain poorly characterized. In this study, we investigated the role of LINC00473 in mediating CRTC1-MAML2 oncogenic activity in human MEC. We found that LINC00473 transcription was significantly induced in human CRTC1-MAML2-positive MEC cell lines and primary MEC tumors, and was tightly correlated with the CRTC1-MAML2 RNA level. LINC00473 induction was dependent on the ability of CRTC1-MAML2 to activate CREB-mediated transcription. Depletion of LINC00473 significantly reduced the proliferation and survival of human MEC cells in vitro and blocked the in vivo tumor growth in a human MEC xenograft model. RNA in situ hybridization analysis demonstrated a predominantly nuclear localization pattern for LINC00473 in human MEC cells. Furthermore, gene expression profiling revealed that LINC00473 depletion resulted in differential expression of genes important in cancer cell growth and survival. LINC00473 likely regulates gene expression in part through its ability to bind to a cAMP signaling pathway component NONO, enhancing the ability of CRTC1-MAML2 to activate CREB-mediated transcription. Our overall results demonstrate that LINC00473 is a downstream target and an important mediator of the CRTC1-MAML2 oncoprotein. Therefore, LINC00473 acts as a promising biomarker and therapeutic target for human CRTC1-MAML2-positive MECs.

Identification of Upstream Kinases by Fluorescence Complementation Mass Spectrometry

Protein kinases and their substrates comprise extensive signaling networks that regulate many diverse cellular functions. However, methods and techniques to systematically identify kinases directly responsible for specific phosphorylation events have remained elusive. Here we describe a novel proteomic strategy termed fluorescence complementation mass spectrometry (FCMS) to identify kinase-substrate pairs in high throughput. The FCMS strategy employs a specific substrate and a kinase library, both of which are fused with fluorescence complemented protein fragments. Transient and weak kinase-substrate interactions in living cells are stabilized by the association of fluorescence protein fragments. These kinase-substrate pairs are then isolated with high specificity and are identified and quantified by LC-MS. FCMS was applied to the identification of both known and novel kinases of the transcription factor, cAMP response element-binding protein (CREB). Novel CREB kinases were validated by in vitro kinase assays, and the phosphorylation sites were unambiguously located. These results uncovered possible new roles for CREB in multiple important signaling pathways and demonstrated the great potential of this new proteomic strategy.

LKB1 as a Tumor Suppressor in Uterine Cancer: Mouse Models and Translational Studies

The LKB1 tumor suppressor was identified in 1998 as the gene mutated in the Peutz-Jeghers Syndrome (PJS), a hereditary cancer predisposition characterized by gastrointestinal polyposis and a high incidence of cancers, particularly carcinomas, at a variety of anatomic sites including the gastrointestinal tract, lung, and female reproductive tract. Women with PJS have a high incidence of carcinomas of the uterine corpus (endometrium) and cervix. The LKB1 gene is also somatically mutated in human cancers arising at these sites. Work in mouse models has highlighted the potency of LKB1 as an endometrial tumor suppressor and its distinctive roles in driving invasive and metastatic growth. These in vivo models represent tractable experimental systems for the discovery of underlying biological principles and molecular processes regulated by LKB1 in the context of tumorigenesis and also serve as useful preclinical model systems for experimental therapeutics. Here we review LKB1's known roles in mTOR signaling, metabolism, and cell polarity, with an emphasis on human pathology and mouse models relevant to uterine carcinogenesis, including cancers of the uterine corpus and cervix.

The Role of NR2B-CREB-miR212/132-CRTC1-CREB Signal Network in Pain Regulation In Vitro and In Vivo

BACKGROUND

Chronic pain is a debilitating threat to human health, and its molecular mechanism remains undefined. Previous studies have illustrated a key role of cAMP response element-binding protein (CREB) in pain regulation; CREB-regulated transcription coactivator 1 (CRTC1) and microRNA212/132 (miR212/132) are also vital in synaptic plasticity. However, little is known about the interaction among these factors in pain condition. We conducted this experiment mainly to determine the crosstalk between CREB, CRTC1, and miR212/132 in vitro. Moreover, we explored the changes in hyperalgesia on chronic constrictive injury (CCI) mouse in vivo when given CREB-related adenovirus vectors, CRTC1-related adenovirus vectors, and miR212/132-locked nucleic acid (LNA).

METHODS

We cultured primary neurons in the spinal cord of mouse embryos. Exogenous glutamate was added to cultured neurons to simulate in vivo pain process. Real-time quantitative polymerase chain reaction was used to determine changes of NR2B, CRTC1, CREB, and miR212/132 at the mRNA level; Western blot was used to detect p-NR2B, p-CREB, and CRTC1 at protein level. Von Frey cilia were used to study mechanical hyperalgesia in a murine model of CCI. CREB-miR (adenovirus vector interfering CREB gene), CREB-AD (adenovirus vector overexpressing CREB gene); CRTC1-miR (adenovirus vector interfering CRTC1 gene), CRTC1-AD (adenovirus vector overexpressing CRTC1 gene), and miR212/132-LNA were injected intrathecally.

RESULTS

In vitro, 100 μmol/L glutamate induced p-CREB and miR212/132-LNA. CRTC1 protein was downregulated by CREB-miR and miR212/132-LNA. CRTC1 mRNA was upregulated by CREB-AD and downregulated by CREB-miR and miR212-LNA. P-CREB was upregulated by CRTC1-AD and downregulated by miR212/132. CREB mRNA was upregulated by CRTC1-AD and downregulated by CRTC1-miR. MiR212/132 was upregulated by CRTC1-AD and CREB-AD; downregulated by CREB-miR. In vivo, CRTC1-miR, CREB-miR, and miR212/132-LNA increased paw withdrawal mechanical threshold in various degrees.

CONCLUSIONS

The NR2B-CREB-miR212/132-CRTC1-CREB signal network plays an important role in the regulation of pain. Intervening with any molecule in this signal network would reduce pain perception.

New Roles of Lkb1 in Regulating Adipose Tissue Development and Thermogenesis

Adipose tissues regulate energy metabolism and reproduction. There are three types of adipocytes (brown, white, and beige adipocytes) in mammals. White adipocytes store energy and are closely associated with obesity and other metabolic diseases. The beige and brown adipocytes have numerous mitochondria and high levels of UCP1 that dissipates lipid to generate heat and defend against obesity. The global epidemic of obesity and its associated metabolic diseases urge an imperative need for understating the regulation of adipogenesis. Liver kinase B1 (Lkb1), also called STK11, is a master kinase of the AMPK subfamily and plays crucial roles in regulating glucose and energy homeostasis in various metabolic tissues. In this review, we focus on the regulatory roles of Lkb1 in regulating preadipocyte differentiation, adipose tissue development, and thermogenesis. J. Cell. Physiol. 232: 2296-2298, 2017. © 2016 Wiley Periodicals, Inc.

Deregulation of CRTCs in Aging and Age-Related Disease Risk

Advances in public health in the past century have seen a sharp increase in human life expectancy. With these changes have come an increased prevalence of age-related pathologies and health burdens in the elderly. Patient age is the biggest risk factor for multiple chronic conditions that often occur simultaneously within a single individual. An alternative to disease-centric therapeutic approaches is that of 'geroscience', which aims to define molecular mechanisms that link age to overall disease risk. One such mechanism is deregulation of CREB-regulated transcriptional coactivators (CRTCs). Initially identified for their role in modulating CREB transcription, the past 5 years has seen an expansion in knowledge of new cellular regulators and roles of CRTCs beyond CREB. CRTCs have been shown to modulate organismal aging in Caenorhabditis elegans and to impact on age-related diseases in humans. We discuss CRTC deregulation as a new driver of aging that integrates the link between age and disease risk.

Common Variants Confer Susceptibility to Barrett's Esophagus: Insights from the First Genome-Wide Association Studies

Eight loci have been identified by the two genome-wide association studies of Barrett's esophagus that have been conducted to date. Esophageal adenocarcinoma cases were included in the second study following evidence that predisposing genetic variants for this cancer overlap with those for Barrett's esophagus. Genes with roles in embryonic development of the foregut are adjacent to 6 of the loci identified (FOXF1, BARX1, FOXP1, GDF7, TBX5, and ALDH1A2). An additional locus maps to a gene with known oncogenic potential (CREB-regulated transcription coactivator 1), but expression quantitative trait data implicates yet another gene involved in esophageal development (PBX4). These results strongly support a model whereby dysregulation of genes involved in esophageal and thoracic development increases susceptibility to Barrett's esophagus and esophageal adenocarcinoma, probably by reducing anatomical antireflux mechanisms. An additional signal at 6p21 in the major histocompatibility complex also reinforces evidence that immune and inflammatory response to reflux is involved in the development of both diseases. All of the variants identified are intronic or intergenic rather than coding and are presumed to be or to mark regulatory variants. As with genome-wide association studies of other diseases, the functional variants at each locus are yet to be identified and the genes affected need confirming. In this chapter as well as discussing the biology behind each genome-wide association signal, we review the requirements for successfully conducting genome-wide association studies and discuss how progress in understanding the genetic variants that contribute to Barrett's esophagus/esophageal adenocarcinoma susceptibility compares to other cancers.

cAMP/CREB-regulated LINC00473 marks LKB1-inactivated lung cancer and mediates tumor growth

The LKB1 tumor suppressor gene is frequently mutated and inactivated in non-small cell lung cancer (NSCLC). Loss of LKB1 promotes cancer progression and influences therapeutic responses in preclinical studies; however, specific targeted therapies for lung cancer with LKB1 inactivation are currently unavailable. Here, we have identified a long noncoding RNA (lncRNA) signature that is associated with the loss of LKB1 function. We discovered that LINC00473 is consistently the most highly induced gene in LKB1-inactivated human primary NSCLC samples and derived cell lines. Elevated LINC00473 expression correlated with poor prognosis, and sustained LINC00473 expression was required for the growth and survival of LKB1-inactivated NSCLC cells. Mechanistically, LINC00473 was induced by LKB1 inactivation and subsequent cyclic AMP-responsive element-binding protein (CREB)/CREB-regulated transcription coactivator (CRTC) activation. We determined that LINC00473 is a nuclear lncRNA and interacts with NONO, a component of the cAMP signaling pathway, thereby facilitating CRTC/CREB-mediated transcription. Collectively, our study demonstrates that LINC00473 expression potentially serves as a robust biomarker for tumor LKB1 functional status that can be integrated into clinical trials for patient selection and treatment evaluation, and implicates LINC00473 as a therapeutic target for LKB1-inactivated NSCLC.

A Sensitive NanoString-Based Assay to Score STK11 (LKB1) Pathway Disruption in Lung Adenocarcinoma

INTRODUCTION

Serine/threonine kinase 11 gene (STK11), better known as liver kinase β1, is a tumor suppressor that is commonly mutated in lung adenocarcinoma (LUAD). Previous work has shown that mutational inactivation of the STK11 pathway may serve as a predictive biomarker for cancer treatments, including phenformin and cyclooxygenase-2 inhibition. Although immunohistochemical (IHC) staining and diagnostic sequencing are used to measure STK11 pathway disruption, there are serious limitations to these methods, thus emphasizing the importance of validating a clinically useful assay.

METHODS

An initial STK11 mutation mRNA signature was generated using cell line data and refined using three large, independent patient databases. The signature was validated as a classifier using The Cancer Genome Atlas (TCGA) LUAD cohort as well as a 442-patient LUAD cohort developed at Moffitt. Finally, the signature was adapted to a NanoString-based format and validated using RNA samples isolated from formalin-fixed, paraffin-embedded tissue blocks corresponding to a cohort of 150 patients with LUAD. For comparison, STK11 IHC staining was also performed.

RESULTS

The STK11 signature was found to correlate with null mutations identified by exon sequencing in multiple cohorts using both microarray and NanoString formats. Although there was a statistically significant correlation between reduced STK11 protein expression by IHC staining and mutation status, the NanoString-based assay showed superior overall performance, with a -0.1588 improvement in area under the curve in receiver-operator characteristic curve analysis (p < 0.012).

CONCLUSION

The described NanoString-based STK11 assay is a sensitive biomarker to study emerging therapeutic modalities in clinical trials.

Chinese herbal medicine Yougui Pill reduces exogenous glucocorticoid-induced apoptosis in anterior pituitary cells

Long-term glucocorticoid use may result in sustained suppression of one or more secreted components from the hypothalamo-pituitary-adrenal axis, and often results in apoptosis. Yougui Pill (YGP), a 10-component traditional Chinese herbal medicine, has been shown to be clinically effective for glucocorticoid-induced suppression of the hypothalamo-pituitary-adrenal axis. However, the pharmacological and molecular mechanisms remain unclear. We hypothesized that YGP would exert an anti-apoptosis effect on dexamethasone-treated anterior pituitary cells. In vivo experiments showed that YGP significantly reduced the number of apoptotic cells, down-regulated mRNA expression of cytochrome c, caspase-3, and caspase-9, and up-regulated mRNA expression of Bcl-2. These findings suggest that YGP reduced glucocorticoid-induced apoptosis in rat anterior pituitary cells by regulating the mitochondria-mediated apoptosis pathway.

Site-Directed Mutagenesis of Surface-Exposed Lysine Residues Leads to Improved Transduction by AAV2, But Not AAV8, Vectors in Murine Hepatocytes In Vivo

The ubiquitin-proteasome pathway plays a critical role in the intracellular trafficking of recombinant adeno-associated virus 2 (AAV2) vectors, which negatively impacts the transduction efficiency of these vectors. Because ubiquitination occurs on lysine (K) residues, we performed site-directed mutagenesis where we replaced each of 10 surface-exposed K residues (K258, K490, K507, K527, K532, K544, K549, K556, K665, and K706) with glutamic acid (E) because of similarity of size and lack of recognition by modifying enzymes. The transduction efficiency of K490E, K544E, K549E, and K556E scAAV2 vectors increased in HeLa cells in vitro up to 5-fold compared with wild-type (WT) AAV2 vectors, with the K556E mutant being the most efficient. Intravenous delivery of WT and K-mutant ssAAV2 vectors further corroborated these results in murine hepatocytes in vivo. Because AAV8 vectors transduce murine hepatocytes exceedingly well, and because some of the surface-exposed K residues are conserved between these serotypes, we generated and tested two single mutants (K547E and K569E), and one double-mutant (K547 + 569E) AAV8 vector. However, no significant increase in the transduction efficiency of any of these mutant AAV8 vectors was observed in murine hepatocytes in vivo. These studies suggest that although targeting the surface-exposed K residues is yet another strategy to improve the transduction efficiency of AAV vectors, phenotypic outcome is serotype specific.

Gene expression profiling analysis of CRTC1-MAML2 fusion oncogene-induced transcriptional program in human mucoepidermoid carcinoma cells

Background

Mucoepidermoid carcinoma (MEC) arises from multiple organs and accounts for the most common types of salivary gland malignancies. Currently, patients with unresectable and metastatic MEC have poor long-term clinical outcomes and no targeted therapies are available. The majority of MEC tumors contain a t(11;19) chromosomal translocation that fuses two genes, CRTC1 and MAML2, to generate the chimeric protein CRTC1-MAML2. CRTC1-MAML2 displays transforming activity in vitro and is required for human MEC cell growth and survival, partially due to its ability to constitutively activate CREB-mediated transcription. Consequently, CRTC1-MAML2 is implicated as a major etiologic molecular event and a therapeutic target for MEC. However, the molecular mechanisms underlying CRTC1-MAML2 oncogenic action in MEC have not yet been systematically analyzed. Elucidation of the CRTC1-MAML2-regulated transcriptional program and its underlying mechanisms will provide important insights into MEC pathogenesis that are essential for the development of targeted therapeutics.

Methods

Transcriptional profiling was performed on human MEC cells with the depletion of endogenous CRTC1-MAML2 fusion or its interacting partner CREB via shRNA-mediated gene knockdown. A subset of target genes was validated via real-time RT-PCR assays. CRTC1-MAML2-perturbed molecular pathways in MEC were identified through pathway analyses. Finally, comparative analysis of CRTC1-MAML2-regulated and CREB-regulated transcriptional profiles was carried out to assess the contribution of CREB in mediating CRTC1-MAML2-induced transcription.

Results

A total of 808 differentially expressed genes were identified in human MEC cells after CRTC1-MAML2 knockdown and a subset of known and novel fusion target genes was confirmed by real-time RT-PCR. Pathway Analysis revealed that CRTC1-MAML2-regulated genes were associated with network functions that are important for cell growth, proliferation, survival, migration, and metabolism. Comparison of CRTC1-MAML2-regulated and CREB-regulated transcriptional profiles revealed common and distinct genes regulated by CRTC1-MAML2 and CREB, respectively.

Conclusion

This study identified a specific CRTC1-MAML2-induced transcriptional program in human MEC cells and demonstrated that CRTC1-MAML2 regulates gene expression in CREB-dependent and independent manners. Our data provide the molecular basis underlying CRTC1-MAML2 oncogenic functions and lay a foundation for further functional investigation of CRTC1-MAML2-induced signaling in MEC initiation and maintenance.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1827-3) contains supplementary material, which is available to authorized users.

Regulation of triple-negative breast cancer cell metastasis by the tumor-suppressor liver kinase B1

Liver kinase B1 (LKB1), also known as serine/threonine kinase 11 (STK11), has been identified as a tumor suppressor in many cancers including breast. Low LKB1 expression has been associated with poor prognosis of breast cancer patients, and we report here a significant association between loss of LKB1 expression and reduced patient survival specifically in the basal subtype of breast cancer. Owing to the aggressive nature of the basal subtype as evidenced by high incidences of metastasis, the purpose of this study was to determine if LKB1 expression could regulate the invasive and metastatic properties of this specific breast cancer subtype. Induction of LKB1 expression in basal-like breast cancer (BLBC)/triple-negative breast cancer cell lines, MDA-MB-231 and BT-549, inhibited invasiveness in vitro and lung metastatic burden in an orthotopic xenograft model. Further analysis of BLBC cells overexpressing LKB1 by unbiased whole transcriptomics (RNA-sequencing) revealed striking regulation of metastasis-associated pathways, including cell adhesion, extracellular matrix remodeling, and epithelial-to-mesenchymal transition (EMT). In addition, LKB1 overexpression inhibited EMT-associated genes (CDH2, Vimentin, Twist) and induced the epithelial cell marker CDH1, indicating reversal of the EMT phenotype in the MDA-MB-231 cells. We further demonstrated marked inhibition of matrix metalloproteinase 1 expression and activity via regulation of c-Jun through inhibition of p38 signaling in LKB1-expressing cells. Taken together, these data support future development of LKB1 inducing therapeutics for the suppression of invasion and metastasis of BLBC.

Obesity and increased risk of esophageal adenocarcinoma

There has been a substantial increase in the incidence of esophageal adenocarcinoma over the past 40 years. Meta-analyses of large prospective cohorts and population-based case-control studies demonstrate consistent associations between obesity and the development of adenocarcinoma of the esophagus and esophago-gastric junction, with an approximate doubling of risk of esophageal adenocarcinoma among patients who are obese, and an almost five-fold increased risk among those with BMI >40 kg/m². The pathologic precursor, specialized intestinal metaplasia in Barrett's esophagus, is also associated with increased adiposity. Epidemiologic evidence suggests that this cancer risk is not solely due to increased gastro-esophageal reflux, and that adipose tissue itself, in particular visceral adipose, may fuel carcinogenesis through the production of adipokines, cytokines, growth factors, and increased inflammation. The robust epidemiologic evidence linking obesity with esophageal adenocarcinoma makes it an exemplar model for investigating the molecular mechanisms underpinning obesity-associated malignant progression, which are discussed in this review.

Dysregulated CRTC1 activity is a novel component of PGE2 signaling that contributes to colon cancer growth

First identified as a dedicated CREB (cAMP response element-binding protein) co-activator, CRTC1 (CREB-regulated transcription co-activator 1) has been widely implicated in various neuronal functions because of its predominant expression in the brain. However, recent evidences converge to indicate that CRTC1 is aberrantly activated in an expanding number of adult malignancies. In this study, we provide strong evidences of enhanced CRTC1 protein content and transcriptional activity in mouse models of sporadic (APC(min/+) mice) or colitis-associated colon cancer azoxymethane/dextran sulfate sodium (AOM/DSS-treated mice), and in human colorectal tumors specimens compared with adjacent normal mucosa. Among signals that could trigger CRTC1 activation during colonic carcinogenesis, we demonstrate that treatment with cyclooxygenase 2 (COX2) inhibitors reduced nuclear CRTC1 active form levels in colonic tumors of APC(min/+) or AOM/DSS mice. In accordance, prostaglandins E2 (PGE2) exposure to human colon cancer cell lines promoted CRTC1 dephosphorylation and parallel nuclear translocation, resulting in enhanced CRTC1 transcriptional activity, through EP1 and EP2 receptors signaling and consecutive calcineurin and protein kinase A activation. In vitro CRTC1 loss of function in colon cancer cell lines was associated with reduced viability and cell division rate as well as enhanced chemotherapy-induced apoptosis on PGE2 treatment. Conversely, CRTC1 stable overexpression significantly increased colonic xenografts tumor growth, therefore demonstrating the role of CRTC1 signaling in colon cancer progression. Identification of the transcriptional program triggered by enhanced CRTC1 expression during colonic carcinogenesis, revealed some notable pro-tumorigenic CRTC1 target genes including NR4A2, COX2, amphiregulin (AREG) and IL-6. Finally, we demonstrate that COX2, AREG and IL-6 promoter activities triggered by CRTC1 are dependent on functional AP1 and CREB transcriptional partners. Overall, our study establishes CRTC1 as new mediator of PGE2 signaling, unravels the importance of its dysregulation in colon cancer and strengthens its use as a bona fide cancer marker.

Supportive evidence for FOXP1, BARX1, and FOXF1 as genetic risk loci for the development of esophageal adenocarcinoma

The Barrett’s and Esophageal Adenocarcinoma Consortium (BEACON) recently performed a genome-wide association study (GWAS) on esophageal adenocarcinoma (EAC) and Barrett’s esophagus. They identified genome-wide significant association for variants at three genes, namely CRTC1, FOXP1, and BARX1. Furthermore, they replicated an association at the FOXF1 gene that has been previously found in a GWAS on Barrett’s esophagus. We aimed at further replicating the association at these and other loci that showed suggestive association with P <  10⁻⁴ in the BEACON sample. In total, we tested 88 SNPs in an independent sample consisting of 1065 EAC cases and 1019 controls of German descent. We could replicate the association at FOXP1, BARX1, and FOXF1 with nominal significance and thereby confirm that genetic variants at these genes confer EAC risk. In addition, we found association of variants near the genes XRCC2 and GATA6 that were strongly (P < 10⁻⁵) although not genome-wide significantly associated with the BEACON GWAS. Therefore, both variants and corresponding genes represent promising candidates for future EAC association studies on independent samples.

Selective in vivo targeting of human liver tumors by optimized AAV3 vectors in a murine xenograft model

Current challenges for recombinant adeno-associated virus (rAAV) vector-based cancer treatment include the low efficiency and the lack of specificity in vivo. rAAV serotype 3 (rAAV3) vectors have previously been shown to be ineffective in normal mouse tissues following systemic administration. In the present study, we report that rAAV3 vectors can efficiently target and transduce various human liver cancer cells in vivo. Elimination of specific surface-exposed serine and threonine residues on rAAV3 capsids results in further augmentation in the transduction efficiency of these vectors, without any change in the viral tropism and cellular receptor interactions. In addition, we have identified a potential chemotherapy drug, shikonin, as a multifunctional compound to inhibit liver tumor growth as well as to significantly enhance the efficacy of rAAV vector-based gene therapy in vivo. Furthermore, we also document that suppression of tumorigenesis in a human liver cancer xenograft model can be achieved through systemic administration of the optimized rAAV3 vectors carrying a therapeutic gene, and shikonin at a dose that does not lead to liver damage. Our research provides a novel means to achieve not only targeted delivery but also the potential for gene therapy of human liver cancer.

Genes Regulating Epithelial Polarity Are Critical Suppressors of Esophageal Oncogenesis

Esophageal cancer is an aggressive disease featured by early lymphatic and hematogenous dissemination, and is the sixth leading cause of cancer-related deaths worldwide. The proper formation of apicobasal polarity is essential for normal epithelium physiology and tissue homeostasis, while loss of polarity is a hallmark of cancer development including esophageal oncogenesis. In this review, we summarized the stages of esophageal cancer development associated with the loss or deregulation of epithelial cell apicobasal polarity. Loss of epithelial apicobasal polarity exerts an indispensable role in the initiation of esophageal oncogenesis, tumor progression, and the advancement of tumors from benign to malignant. In particular, we reviewed the involvement of several critical genes, including Lkb1, claudin-4, claudin-7, Par3, Lgl1, E-cadherin, and the Scnn1 gene family. Understanding the role of apicobasal regulators may lead to new paradigms for treatment of esophageal tumors, including improvement of prognostication, early diagnosis, and individually tailored therapeutic interventions in esophageal oncology.

Single nucleotide polymorphisms in CRTC1 and BARX1 are associated with esophageal adenocarcinoma

Objective:

Recently, single nucleotide polymorphisms (SNPs) associated with esophageal adenocarcinoma (EAC) and Barrett's esophagus (BE) were identified; rs10419226 (CRTC1), rs11789015 (BARX1), rs2687201 (FOXP1), rs2178146 (FOXF1), rs3111601 (FOXF1), and rs9936833 (FOXF1). These findings indicate that genetic susceptibility could play a role in the initiation of EAC in BE patients. The aim of this study was to validate the association between these previously identified SNPs and the risk of EAC in an independent and large case–control study.

Design:

Six SNPs found to be associated with EAC and BE were genotyped by a multiplex SNaPshot analysis in 1071 EAC patients diagnosed and treated in the Netherlands. Allele frequencies were compared to a control group derived from the Rotterdam Study, a population-based prospective cohort study (n = 6206). Logistic regression analysis and meta-analysis were performed to calculate odds ratios (OR).

Results:

Rs10419226 (CRTC1) showed a significantly increased EAC risk for the minor allele (OR = 1.17, P = 0.001), and rs11789015 (BARX1) showed a significantly decreased risk for the minor allele (OR = 0.85, P = 0.004) in the logistic regression analysis. The meta-analysis of the original GWAS and the current study revealed an improved level of significance for rs10419226 (CRTC1) (OR = 1.18, P = 6.66 × 10^–10) and rs11789015 (BARX1) (OR = 0.83, P = 1.13 × 10^–8).

Conclusions:

This independent and large Dutch case–control study confirms the association of rs10419226 (CRTC1) and rs11789015 (BARX1) with the risk of EAC. These findings suggest a contribution of the patient genetic make-up to the development of EAC and might contribute to gain more insight in the etiology of this cancer.

Cytotoxic genes from traditional Chinese medicine inhibit tumor growth both in vitro and in vivo

OBJECTIVE

Little effort has been made to study the protein-encoding genes isolated from traditional Chinese medicine (TCM) drugs, and the delivery of these genes into malignant cells through recombinant adeno-associated virus (rAAV) vectors has not been attempted.

METHODS

We synthesized the cDNAs of five known cytotoxic proteins isolated from TCM drugs and the FLAG epitope-tagged cDNAs were subcloned into a rAAV plasmid vector. The protein expression was confirmed by Western blot assay. Various cancer cell lines were transfected with the above plasmids and cell growth was monitored both in vitro and in vivo. The best cytotoxic gene was further packaged into rAAV vectors, under the control of a liver cancer-specific promoter. The liver tumor growth was then monitored following intratumor administration of the rAAV vectors.

RESULTS

The expression plasmids, encoding individual potential cytotoxic genes tagged with FLAG epitope, were successfully generated and sequenced. Among these genes, trichosanthin (TCS) gene yielded the most promising results for the inhibition of cancer cell growth in vitro. The over-expressed TCS functioned as a type I ribosome-inactivating protein, followed by inducing apoptosis that is associated with the Bcl-PARP signaling pathway. Furthermore, intratumor injection of rAAV vectors containing the TCS gene significantly inhibited the growth of human hepatocellular carcinoma tumors in a murine xenograft model.

CONCLUSION

Our studies suggest that the use of TCM cytotoxic genes is a useful therapeutic strategy for treating human cancers in general, and liver tumors in particular.

Overexpression of activator of G-protein signaling 3 decreases the proliferation of esophageal squamous cell carcinoma

BACKGROUND

Activator of G-protein Signaling 3 (AGS3, also known as GPSM1), is related to cell cycle progression. We investigated the expression of AGS3 in human esophageal squamous cell carcinoma (ESCC) and the therapeutic effect of chemotherapy drugs.

METHODS

Immunohistochemistry and Western blot analysis were performed for AGS3 in 85ESCC samples. The data were correlated with clinicopathological features. The univariate and multivariate survival analyses were also performed to determine its prognostic significance. The effect of overexpression of AGS3 on proliferation of esophageal carcinoma TE1 cells was analyzed by serum starvation.

RESULTS

AGS3 was down regulated in ESCC as compared with the adjacent normal tissue. Low expression of AGS3 was associated with tumor grade (P=0.002), and AGS3 was negatively correlated with proliferation marker Ki-67 (P<0.01). Univariate analysis showed that AGS3 expression did have a remarkable prediction for poor prognosis (P=0.004), while in vitro, the expression of AGS3 was down regulated with release from serum starvation of TE1 cells.

CONCLUSIONS

This study shows that AGS3 is an important regulator of ESCC proliferation.

Role of LKB1-CRTC1 on glycosylated COX-2 and response to COX-2 inhibition in lung cancer

BACKGROUND

Cyclooxygenase-2 (COX-2) directs the synthesis of prostaglandins including PGE-2 linking inflammation with mitogenic signaling. COX-2 is also an anticancer target, however, treatment strategies have been limited by unreliable expression assays and by inconsistent tumor responses to COX-2 inhibition.

METHODS

We analyzed the TCGA and Director's Challenge lung cancer datasets (n = 188) and also generated an LKB1-null lung cancer gene signature (n = 53) to search the Broad Institute/Connectivity-MAP (C-MAP) dataset. We performed ChIP analyses, real-time polymerase chain reaction, immunoblotting, and drug testing of tumor cell lines (n = 8) and primary lung adenocarcinoma surgical resections (n = 13).

RESULTS

We show that COX-2 is a target of the cAMP/CREB coactivator CRTC1 signaling pathway. In addition, we detected a correlation between LKB1 status, CRTC1 activation, and presence of glycosylated, but not inactive hypoglycosylated COX-2 in primary lung adenocarcinoma. A search of the C-MAP drug database discovered that all high-ranking drugs positively associated with the LKB1-null signature are known CRTC1 activators, including forskolin and six different PGE-2 analogues. Somatic LKB1 mutations are present in 20.0% of lung adenocarcinomas, and we observed growth inhibition with COX-2 inhibitors in LKB1-null lung cancer cells with activated CRTC1 as compared with LKB1-wildtype cells (NS-398, P = .002 and Niflumic acid, P = .006; two-tailed t test).

CONCLUSION

CRTC1 activation is a key event that drives the LKB1-null mRNA signature in lung cancer. We also identified a positive feedback LKB1/CRTC1 signaling loop for COX-2/PGE2 regulation. These data suggest a role for LKB1 status and glycosylated COX-2 as specific biomarkers that provide a framework for selecting patients for COX-2 inhibition studies.

Enhanced transgene expression from recombinant single-stranded D-sequence-substituted adeno-associated virus vectors in human cell lines in vitro and in murine hepatocytes in vivo

We have previously reported that the removal of a 20-nucleotide sequence, termed the D sequence, from both ends of the inverted terminal repeats (ITRs) in the adeno-associated virus serotype 2 (AAV2) genome significantly impairs rescue, replication, and encapsidation of the viral genomes (X. S. Wang, S. Ponnazhagan, and A. Srivastava, J Mol Biol 250:573-580, 1995; X. S. Wang, S. Ponnazhagan, and A. Srivastava, J Virol 70:1668-1677, 1996). Here we describe that replacement of only one D sequence in either ITR restores each of these functions, but DNA strands of only single polarity are encapsidated in mature progeny virions. Since most commonly used recombinant AAV vectors contain a single-stranded DNA (ssDNA), which is transcriptionally inactive, efficient transgene expression from AAV vectors is dependent upon viral second-strand DNA synthesis. We have also identified a transcription suppressor sequence in one of the D sequences, which shares homology with the binding site for the cellular NF-κB-repressing factor (NRF). The removal of this D sequence from, and replacement with a sequence containing putative binding sites for transcription factors in, single-stranded AAV (ssAAV) vectors significantly augments transgene expression both in human cell lines in vitro and in murine hepatocytes in vivo. The development of these genome-modified ssAAV vectors has implications not only for the basic biology of AAV but also for the optimal use of these vectors in human gene therapy.

IMPORTANCE

The results of the studies described here not only have provided novel insights into some of the critical steps in the life cycle of a human virus, the adeno-associated virus (AAV), that causes no known disease but have also led to the development of novel recombinant AAV vectors which are more efficient in allowing increased levels of gene expression. Thus, these studies have significant implications for the potential use of these novel AAV vectors in human gene therapy.

C4.4A as a biomarker in pulmonary adenocarcinoma and squamous cell carcinoma

The high prevalence and mortality of lung cancer, together with a poor 5-year survival of only approximately 15%, emphasize the need for prognostic and predictive factors to improve patient treatment. C4.4A, a member of the Ly6/uPAR family of membrane proteins, qualifies as such a potential informative biomarker in non-small cell lung cancer. Under normal physiological conditions, it is primarily expressed in suprabasal layers of stratified squamous epithelia. Consequently, it is absent from healthy bronchial and alveolar tissue, but nevertheless appears at early stages in the progression to invasive carcinomas of the lung, i.e., in bronchial hyperplasia/metaplasia and atypical adenomatous hyperplasia. In the stages leading to pulmonary squamous cell carcinoma, expression is sustained in dysplasia, carcinoma in situ and invasive carcinomas, and this pertains to the normal presence of C4.4A in squamous epithelium. In pulmonary adenocarcinomas, a fraction of cases is positive for C4.4A, which is surprising, given the origin of these carcinomas from mucin-producing and not squamous epithelium. Interestingly, this correlates with a highly compromised patient survival and a predominant solid tumor growth pattern. Circumstantial evidence suggests an inverse relationship between C4.4A and the tumor suppressor LKB1. This might provide a link to the prognostic impact of C4.4A in patients with adenocarcinomas of the lung and could potentially be exploited for predicting the efficacy of treatment targeting components of the LKB1 pathway.

LKB1 reduces ROS-mediated cell damage via activation of p38

Liver kinase B1 (LKB1, also known as serine/threonine kinase 11, STK11) is a tumor suppressor mutated in Peutz-Jeghers syndrome and in a variety of sporadic cancers. Herein, we demonstrate that LKB1 controls the levels of intracellular reactive oxygen species (ROS) and protects the genome from oxidative damage. Cells lacking LKB1 exhibit markedly increased intracellular ROS levels, excessive oxidation of DNA, increased mutation rates, and accumulation of DNA damage, which are effectively prevented by ectopic expression of LKB1 and by incubation with antioxidant N-acetylcysteine (NAC). The role of LKB1 in suppressing ROS is independent of AMPK, a canonical substrate of LKB1. Instead, under the elevated ROS, LKB1 binds to and maintains the activity of cdc42-PAK1 (p21 activated kinase 1) complex, which triggers the activation of p38 and its downstream signaling targets, such as ATF-2, thereby enhancing the activity of SOD-2 and catalase, two antioxidant enzymes that protect the cells from ROS accumulation, DNA damage, and loss of viability. Our results provide a new paradigm for a non-canonical tumor suppressor function of LKB1 and highlight the importance of targeting ROS signaling as a potential therapeutic strategy for cancer cells lacking LKB1.

CRTC1/MAML2 gain-of-function interactions with MYC create a gene signature predictive of cancers with CREB-MYC involvement

Chimeric oncoproteins created by chromosomal translocations are among the most common genetic mutations associated with tumorigenesis. Malignant mucoepidermoid salivary gland tumors, as well as a growing number of solid epithelial-derived tumors, can arise from a recurrent t (11, 19)(q21;p13.1) translocation that generates an unusual chimeric cAMP response element binding protein (CREB)-regulated transcriptional coactivator 1 (CRTC1)/mastermind-like 2 (MAML2) (C1/M2) oncoprotein comprised of two transcriptional coactivators, the CRTC1 and the NOTCH/RBPJ coactivator MAML2. Accordingly, the C1/M2 oncoprotein induces aberrant expression of CREB and NOTCH target genes. Surprisingly, here we report a gain-of-function activity of the C1/M2 oncoprotein that directs its interactions with myelocytomatosis oncogene (MYC) proteins and the activation of MYC transcription targets, including those involved in cell growth and metabolism, survival, and tumorigenesis. These results were validated in human mucoepidermoid tumor cells that harbor the t (11, 19)(q21;p13.1) translocation and express the C1/M2 oncoprotein. Notably, the C1/M2-MYC interaction is necessary for C1/M2-driven cell transformation, and the C1/M2 transcriptional signature predicts other human malignancies having combined involvement of MYC and CREB. These findings suggest that such gain-of-function properties may also be manifest in other oncoprotein fusions found in human cancer and that agents targeting the C1/M2-MYC interface represent an attractive strategy for the development of effective and safe anticancer therapeutics in tumors harboring the t (11, 19) translocation.

LKB1 loss at transcriptional level promotes tumor malignancy and poor patient outcomes in colorectal cancer

BACKGROUND

Liver kinase B1 (LKB1) loss by gene mutation, loss of heterozygosity, and promoter methylation rarely occurs in colorectal cancer. We wondered whether LKB1 loss could be deregulated at the transcriptional level to promote tumor progression and poor outcome in colorectal cancer.

METHODS

Mechanistic studies were performed in two each of p53 wild-type (HCT116, LoVo) and p53-mutated (SW480, HT29) colon cancer cells to explore whether LKB1 loss could be deregulated by NKX2-1-mediated p53 pathway. LKB1 and NK2 homeobox 1 (NKX2-1) expressions in colorectal tumors were determined by immunohistochemistry, and the prognostic value of both molecules was assessed by Kaplan-Meier test and Cox regression model.

RESULTS

Mechanistically, LKB1 loss at the transcriptional level due to alteration of the NKX2-1-mediated p53 pathway promotes invasiveness in colon cancer cells. The cell invasiveness induced by LKB1 loss was nearly suppressed by mammalian target of rapamycin (mTOR) inhibitor (rapamycin and everolimus) and mTOR/AKT dual inhibitor Palomid 529 (P529). Among patients, low LKB1 tumors exhibited shorter overall survival (OS) and relapse-free survival periods than high LKB1 tumors. The highest hazard ratio value for OS and relapse-free survival was observed in wild-type p53 with low LKB1/low NKX2-1 tumors and in mutated p53 with low LKB1/high NKX2-1 tumors when wild-type p53 with high LKB1/high NKX2-1 and mutated p53 with high LKB1/low NKX2-1 tumors were used as references.

CONCLUSIONS

LKB1 loss at the transcriptional level via alteration of the NKX2-1/p53 axis promotes cell invasion, consequently resulting in poor outcome in colorectal cancer patients.