Hypoxia and miscoupling between reduced energy efficiency and signaling to cell proliferation drive cancer to grow increasingly faster

Decidual stromal cell-derived exosomes deliver miR-22-5p_R-1 to suppress trophoblast metabolic switching from mitochondrial respiration to glycolysis by targeting PDK4 in unexplained recurrent spontaneous abortion

INTRODUCTION

Studies have shown that EMT (epithelial-mesenchymal transition) and energy metabolism influence each other, and it is unclear whether the trophoblast energy metabolism phenotype is dominated by glycolysis or mitochondrial respiration, and the relationship between trophoblast energy metabolism and EMT is still unclear.

METHODS

Exosomes were isolated from the DSC of URSA patients and their miRNA profile was characterized by miRNA sequencing. Wound healing assays and transwell assays were used to assess the invasion and migration ability of trophoblasts. Mitochondrial stress and glycolysis stress test were used to evaluate energy metabolism phenotype of trophoblast. Luciferase reporter assays, qRT-PCR and WB were conducted to uncover the underlying mechanism. Finally, animal experiments were employed to explore the effect of DSC-exos on embryo absorption in mice.

RESULTS

Our results showed that URSA-DSC-exos suppressed trophoblast EMT to reduce their migration and invasion, miR-22-5p_R-1 was the most upregulated miRNAs. URSA-DSC-exos can suppress trophoblast MGS (metabolic switch from mitochondrial respiration to glycolysis) and inhibit trophoblast migration and invasion by transferring miR-22-5p_R-1. Mechanistically, miR-22-5p_R-1 suppress trophoblast MGS and inhibit trophoblast EMT by directly suppressing PDK4 expression at the post-transcriptional level. Furthermore, in vivo experiment suggested that URSA-DSC-exos aggravated embryo absorption in mice. Clinically, PDK4 and EMT molecule were aberrant in villous of URSA patients, and negative correlations were found between miR-22-5p_R-1 and PDK4.

DISCUSSION

Our findings indicated that URSA-DSC-exos induced MGS obstacle playing an important role in intercellular communication between trophoblast and DSC, illuminating a novel mechanism in DSC regulation of trophoblasts and their role in URSA.

Identification of an energy metabolism-related six-gene signature for distinguishing and forecasting the prognosis of low-grade gliomas

Background

Low-grade gliomas (LGG) account for 20-25% of all gliomas. In this study, we assessed whether metabolic status was correlated with clinical outcomes in LGG patients using data from The Cancer Genome Atlas (TCGA).

Methods

LGG patient data were collected from TCGA, and the Molecular Signature Database was used to extract gene sets related to energy metabolism. After performing a consensus-clustering algorithm, the LGG patients were divided into four clusters. We then compared the tumor prognosis, function, immune cell infiltration, checkpoint proteins, chemo-resistance, and cancer stem cells (CSC) between the two groups with the greatest prognostic difference. Using least absolute shrinkage and selection operator (LASSO) analysis, an energy metabolism-related signature was further developed.

Results

Energy metabolism-related signatures were applied to identify four clusters (C1, C2, C3, and C4) using a consensus-clustering algorithm. C1 LGG patients were more related to the synapse and had higher CSC scores, more chemo-resistance, and a better prognosis. C4 LGG was observed to have more immune-related pathways and better immunity. We then identified six energy metabolism-related genes (PYGL, HS3ST3B, NNMT, FMOD, CHST6, and B3GNT7) that can accurately predict LGG prognosis not only as a whole but also based on the independent predictions of each of these six genes.

Conclusions

The energy metabolism-related subtypes of LGG were identified, which were strongly related to the immune microenvironment, immune checkpoint proteins, CSCs, chemo-resistance, prognosis, and LGG advancement. A signature of genes involved in energy metabolism could help to distinguish and predict the prognosis of LGG patients, and a promising method to discover patients that may benefit from LGG therapy.

The Mystery of Cancer Resistance: A Revelation Within Nature

Cancer, a disease due to uncontrolled cell proliferation is as ancient as multicellular organisms. A 255-million-years-old fossilized forerunner mammal gorgonopsian is probably the oldest evidence of cancer, to date. Cancer seems to have evolved by adapting to the microenvironment occupied by immune sentinel, modulating the cellular behavior from cytotoxic to regulatory, acquiring resistance to chemotherapy and surviving hypoxia. The interaction of genes with environmental carcinogens is central to cancer onset, seen as a spectrum of cancer susceptibility among human population. Cancer occurs in life forms other than human also, although their exposure to environmental carcinogens can be different. Role of genetic etiology in cancer in multiple species can be interesting with regard to not only cancer susceptibility, but also genetic conservation and adaptation in speciation. The widely used model organisms for cancer research are mouse and rat which are short-lived and reproduce rapidly. Research in these cancer prone animal models has been valuable as these have led to cancer therapy. However, another rewarding area of cancer research can be the cancer-resistant animal species. The Peto's paradox and G-value paradox are evident when natural cancer resistance is observed in large mammals, like elephant and whale, small rodents viz. Naked Mole Rat and Blind Mole Rat, and Bat. The cancer resistance remains to be explored in other small or large and long-living animals like giraffe, camel, rhinoceros, water buffalo, Indian bison, Shire horse, polar bear, manatee, elephant seal, walrus, hippopotamus, turtle and tortoise, sloth, and squirrel. Indeed, understanding the molecular mechanisms of avoiding neoplastic transformation across various life forms can be potentially having translational value for human cancer management. Adapted and Modified from (Hanahan and Weinberg 2011).

Modelling reoxygenation effects in non-small cell lung cancer cell lines and showing epithelial-mesenchymal transition

Purpose

Circulating tumour cells (CTCs) are a rare cell subpopulation regulated by the tumour microenvironment. In hypoxic conditions, CTCs are able to invade the lymphatic and circulatory systems leading to metastasis at distant sites.

Methods

To mimic in vivo oxygen variations and effects on CTCs, we have cultured five non-small cell lung cancer (NSCLC) cell lines under normoxic and hypoxic conditions, followed by a pulse of reoxygenation for 4 h.

Results

Proliferation, spheroid-formation and colony formation ability under varying O₂ levels were investigated. Proliferation rate was not altered when cells were cultured in 2D models under hypoxic conditions. However, we observed that hypoxia enhanced in vitro formation of tumour-spheres and accelerated clonogenicity of NSCLC cell lines. In addition, cells exposed to hypoxia and reoxygenation conditions showed altered expression of epithelial-mesenchymal transition (EMT) related genes in NSCLC cell lines both at mRNA (AKT1, CAMK2NH1, DESI1, VIM, MAP1B, EGFR, ZEB1, HIF1α) and protein levels (Vimentin, Pan-cytokeratin).

Conclusion

Our data suggest that when investigating CTCs as a prognostic biomarker in NSCLC, it is also essential to take into consideration EMT status to obtain a comprehensive overview of CTCs in circulation.

The Impact of Hypoxia in Early Pregnancy on Placental Cells

Oxygen levels in the placental microenvironment throughout gestation are not constant, with severe hypoxic conditions present during the first trimester. This hypoxic phase overlaps with the most critical stages of placental development, i.e., blastocyst implantation, cytotrophoblast invasion, and spiral artery remodeling initiation. Dysregulation of any of these steps in early gestation can result in pregnancy loss and/or adverse pregnancy outcomes. Hypoxia has been shown to regulate not only the self-renewal, proliferation, and differentiation of trophoblast stem cells and progenitor cells, but also the recruitment, phenotype, and function of maternal immune cells. In this review, we will summarize how oxygen levels in early placental development determine the survival, fate, and function of several important cell types, e.g., trophoblast stem cells, extravillous trophoblasts, syncytiotrophoblasts, uterine natural killer cells, Hofbauer cells, and decidual macrophages. We will also discuss the cellular mechanisms used to cope with low oxygen tensions, such as the induction of hypoxia-inducible factor (HIF) or mammalian target of rapamycin (mTOR) signals, regulation of the metabolic pathway, and adaptation to autophagy. Understanding the beneficial roles of hypoxia in early placental development will provide insights into the root cause(s) of some pregnancy disorders, such as spontaneous abortion, preeclampsia, and intrauterine growth restriction.

Clinical development of photodynamic agents and therapeutic applications

Background

Photodynamic therapy (PDT) is photo-treatment of malignant or benign diseases using photosensitizing agents, light, and oxygen which generates cytotoxic reactive oxygens and induces tumour regressions. Several photodynamic treatments have been extensively studied and the photosensitizers (PS) are key to their biological efficacy, while laser and oxygen allow to appropriate and flexible delivery for treatment of diseases.

Introduction

In presence of oxygen and the specific light triggering, PS is activated from its ground state into an excited singlet state, generates reactive oxygen species (ROS) and induces apoptosis of cancer tissues. Those PS can be divided by its specific efficiency of ROS generation, absorption wavelength and chemical structure.

Main body

Up to dates, several PS were approved for clinical applications or under clinical trials. Photofrin® is the first clinically approved photosensitizer for the treatment of cancer. The second generation of PS, Porfimer sodium (Photofrin®), Temoporfin (Foscan®), Motexafin lutetium, Palladium bacteriopheophorbide, Purlytin®, Verteporfin (Visudyne®), Talaporfin (Laserphyrin®) are clinically approved or under-clinical trials. Now, third generation of PS, which can dramatically improve cancer-targeting efficiency by chemical modification, nano-delivery system or antibody conjugation, are extensively studied for clinical development.

Conclusion

Here, we discuss up-to-date information on FDA-approved photodynamic agents, the clinical benefits of these agents. However, PDT is still dearth for the treatment of diseases in specifically deep tissue cancer. Next generation PS will be addressed in the future for PDT. We also provide clinical unmet need for the design of new photosensitizers.

The 150 most important questions in cancer research and clinical oncology series: questions 57-66 : Edited by Chinese Journal of Cancer

Since the beginning of 2017, Chinese Journal of Cancer has published a series of important questions in cancer research and clinical oncology, which sparkle diverse thoughts, interesting communications, and potential collaborations among researchers all over the world. In this article, 10 more questions are presented as followed. Question 57. What are the major stresses that drive the formation, progression, and metastasis of a cancer? Question 58. What is the mechanism responsible for altering an acidic intracellular pH and a basic extracellular pH in normal tissue cells to a basic intracellular pH and an acidic extracellular pH in cancer cells, a fundamental and yet largely ignored phenomenon? Question 59. Where are the tumor-associated plasma microRNAs from in cancer patients? Question 60. Can we identify mechanisms employed by tumor subpopulations to evade standard therapies and seed relapse/metastatic tumors before treatment? Question 61. Why are mutation rates in epidermal growth factor receptor (EGFR) and erb-b2 receptor tyrosine kinase 2 (ERBB2) higher in lung cancer from never smokers than that from smokers? Question 62. Does tumor vasculogenic mimicry contribute to the resistance against antiangiogenic therapy in renal cancer? Question 63. What molecular targeted drugs would be effective for non-clear cell renal cell carcinoma (RCC), especially metastatic papillary RCC and chromophobe RCC? Question 64. Can it be more effective by targeting both the vascular endothelial growth factor receptor (VEGFR) and MET signaling pathways in sporadic metastatic papillary renal cell carcinoma (RCC)? Question 65. What are the predictive biomarkers that may be used to identify the renal cell carcinoma (RCC) patients who can benefit from immune checkpoint inhibitor treatment? Question 66. How do we identify predictive molecular biomarkers to stratify clear cell renal cell carcinoma patients for targeted therapies?

Genetic Alterations in Gastric Cancer Associated with Helicobacter pylori Infection

Gastric cancer is a world health problem and depicts the fourth leading mortality cause from malignancy in Mexico. Causation of gastric cancer is not only due to the combined effects of environmental factors and genetic variants. Recent molecular studies have transgressed a number of genes involved in gastric carcinogenesis. The aim of this review is to understand the recent basics of gene expression in the development of the process of gastric carcinogenesis. Genetic variants, polymorphisms, desoxyribonucleic acid methylation, and genes involved in mediating inflammation have been associated with the development of gastric carcinogenesis. Recently, these genes (interleukin 10, Il-17, mucin 1, β-catenin, CDX1, SMAD4, SERPINE1, hypoxia-inducible factor 1 subunit alpha, GSK3β, CDH17, matrix metalloproteinase 7, RUNX3, RASSF1A, TFF1, HAI-2, and COX-2) have been studied in association with oncogenic activation or inactivation of tumor suppressor genes. All these mechanisms have been investigated to elucidate the process of gastric carcinogenesis, as well as their potential use as biomarkers and/or molecular targets to treatment of disease.

Oncogenic Sox2 regulates and cooperates with VRK1 in cell cycle progression and differentiation

Sox2 is a pluripotency transcription factor that as an oncogene can also regulate cell proliferation. Therefore, genes implicated in several different aspects of cell proliferation, such as the VRK1 chromatin-kinase, are candidates to be targets of Sox2. Sox 2 and VRK1 colocalize in nuclei of proliferating cells forming a stable complex. Sox2 knockdown abrogates VRK1 gene expression. Depletion of either Sox2 or VRK1 caused a reduction of cell proliferation. Sox2 up-regulates VRK1 expression and both proteins cooperate in the activation of CCND1. The accumulation of VRK1 protein downregulates SOX2 expression and both proteins are lost in terminally differentiated cells. Induction of neural differentiation with retinoic acid resulted in downregulation of Sox2 and VRK1 that inversely correlated with the expression of differentiation markers such as N-cadherin, Pax6, mH2A1.2 and mH2A2. Differentiation-associated macro histones mH2A1.2and mH2A2 inhibit CCND1 and VRK1 expression and also block the activation of the VRK1 promoter by Sox2. VRK1 is a downstream target of Sox2 and both form an autoregulatory loop in epithelial cell differentiation.

Roles of SHARP1 in thyroid cancer

SHARP1 is a basic helix‑loop‑helix transcription factor involved in various cellular processes, including proliferation and differentiation. The present study assessed the role of SHARP1 in the progression and invasion of thyroid cancer. PCR and western blot analysis demonstrated that in thyroid cancer tissues, SHARP1 was significantly downregulated at the mRNA and protein level compared with that in normal tissues. Furthermore, SHARP1 was downregulated in the TT and TPC‑1 thyroid cancer cell lines compared with a normal thyroid cell line, while it was upregulated in other thyroid cancer cell lines. Overexpression of SHARP1 in TT and TPC‑1 cells significantly inhibited the cell viability, migration and invasion in vitro. Furthermore, the protein and mRNA levels of HIF‑1α were found to be decreased in TT and TPC‑1 cells following forced overexpression of SHARP1. In addition, silencing of HIF‑1α reduced the viability, migration and invasion of TT and TPC-1 cells. In conclusion, the present study indicated that SHARP1 acts as a tumor suppressor in thyroid cancer and that its downregulation may contribute to the proliferation, migration and invasion of thyroid cancer cells through mechanisms possibly involving HIF‑1α, suggesting that SHARP1 may be an important therapeutic target for the treatment of thyroid cancer.

Comprehensive characterization of the genomic alterations in human gastric cancer

Gastric cancer is one of the most prevalent and aggressive cancers worldwide, and its molecular mechanism remains largely elusive. Here we report the genomic landscape in primary gastric adenocarcinoma of human, based on the complete genome sequences of five pairs of cancer and matching normal samples. In total, 103,464 somatic point mutations, including 407 nonsynonymous ones, were identified and the most recurrent mutations were harbored by Mucins (MUC3A and MUC12) and transcription factors (ZNF717, ZNF595 and TP53). 679 genomic rearrangements were detected, which affect 355 protein-coding genes; and 76 genes show copy number changes. Through mapping the boundaries of the rearranged regions to the folded three-dimensional structure of human chromosomes, we determined that 79.6% of the chromosomal rearrangements happen among DNA fragments in close spatial proximity, especially when two endpoints stay in a similar replication phase. We demonstrated evidences that microhomology-mediated break-induced replication was utilized as a mechanism in inducing ∼40.9% of the identified genomic changes in gastric tumor. Our data analyses revealed potential integrations of Helicobacter pylori DNA into the gastric cancer genomes. Overall a large set of novel genomic variations were detected in these gastric cancer genomes, which may be essential to the study of the genetic basis and molecular mechanism of the gastric tumorigenesis.

Inhibition of protein phosphatase 2A sensitizes pancreatic cancer to chemotherapy by increasing drug perfusion via HIF-1α-VEGF mediated angiogenesis

Pancreatic cancer is a malignant disease without efficient treatment. Improved treatments are urgently needed to enhance or replace chemotherapy. Here we used a small molecular compound LB-100 to assess the effect of pharmacological inhibition of protein phosphatase 2A (PP2A) in combination with doxorubicin on the proliferation of pancreatic cancer in cell lines and a xenograft model. LB-100 moderately reduced PP2A activity and the growth of the cell lines but did not show chemosensitization in vitro. In vivo, however, LB-100 synergistically enhanced the activity of doxorubicin. This effect was associated with increased microvessel density, blood perfusion, and doxorubicin concentrations within the xenografts. Mechanically, LB-100 induced expression of hypoxia-induced factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF). In an umbilical vein endothelial cell monolayer model for measuring changes in vascular permeability, increased VEGF secretion following exposure to LB-100 and doxorubicin was accompanied by increased amounts of doxorubicin penetrating the endothelial barrier. In conclusion, PP2A inhibition by LB-100 enhanced the cytotoxicity of doxorubicin in vivo but not in vitro potentially via HIF-1α-VEGF mediated angiogenesis. Combining inhibition of PP2A with chemotherapeutic regimens may enhance their effectiveness against pancreatic cancer.

Production of reactive oxygen and nitrogen species by light irradiation of a nitrosyl phthalocyanine ruthenium complex as a strategy for cancer treatment

Production of reactive oxygen species has been used in clinical therapy for cancer treatment in a technique known as Photodynamic Therapy (PDT). The success of this therapy depends on oxygen concentration since hypoxia limits the formation of reactive oxygen species with consequent clinical failure of PDT. Herein, a possible synergistic effect between singlet oxygen and nitric oxide (NO) is examined since this scenario may display increased tumoricidal activity. To this end, the trinuclear species [Ru(pc)(pz)2{Ru(bpy)2(NO)}2](PF6)6 (pc = phthalocyanine; pz = pyrazine; bpy = bipyridine) was synthesized to be a combined NO and singlet oxygen photogenerator. Photobiological assays using at 4 × 10(-6) M in the B16F10 cell line result in the decrease of cell viability to 21.78 ± 0.29% of normal under light irradiation at 660 nm. However, in the dark and at the same concentration of compound , viability was 91.82 ± 0.37% of normal. The potential application of a system like in clinical therapy against cancer may be as an upgrade to normal photodynamic therapy.

Regulatory effect of merlin-1 on adhesion/metastasis and cytoskeleton remodeling in gastric cancer cells under hypoxia

AIM: To investigate the regulatory effect of merlin-1 on cell proliferation, adhesion/metastasis and cytoskeleton remodeling in gastric cancer cells under hypoxia from Qinghai Han-, Hui- and Tibetan-ethnic patients, and to study if the function of merlin-1 in different ethnic groups is related to ethnic specificity under normoxic or hypoxic conditions.

METHODS: MTT assay was used to analyze the influence of merlin-1 on the cell proliferation, adhesion/metastasis and motility, and immunofluorescence staining was performed to detect cytoskeleton remodeling, morphological changes, and the distribution of microvilli on the surface of gastric cancer cells from Han-, Hui- and Tibetan-ethnic patients. In addition, we explored whether the function of merlin-1 in different ethnic groups is correlated with ethnic specificity under normoxic or hypoxic conditions.

RESULTS: The proliferation of gastric cancer cells from Han-, Hui- and Tibetan-ethnic groups was inhibited by merlin-1 under both normoxic and conditions (P_normoxic = 0.00, 0.00, 0.00; P_hypoxic = 0.00, 0.00, 0.00), and the influence of merlin-1 on cancer cell proliferation was not related to ethnic specificity (P_normoxic ≥ 0.05; P_hypoxic ≥ 0.05). The results of adhesion/metastasis analysis showed that merlin-1 inhibited the adhesion/metastasis ability of gastric cancer cells from Han-, Hui- and Tibetan-ethnic groups under both normoxic and hypoxic conditions (P_normoxic = 0.00, 0.00, 0.00; P_hypoxic = 0.00, 0.00, 0.00), and the inhibitory effect of merlin-1 in three ethnic groups showed no significant differences [P_normoxic = 0.51 (3 h), 0.07 (48 h); P_hypoxic = 0.47 (3 h), 0.17 (48 h)]. By detection of cytoskeleton remodeling, morphological change and microvilli distribution, it was found that merlin-1 enhanced cytoskeleton remodeling under hypoxic conditions compared with normoxic conditions.

CONCLUSION: Merlin-1 can inhibit the proliferation and adhesion/metastasis of gastric cancer cells under both hypoxic and normoxic conditions, which is independent on the ethnicity of patients from whom gastric cancer cells are obtained. However, merlin-1 enhances cytoskeleton remodeling under hypoxic conditions.

KLF5 promotes hypoxia-induced survival and inhibits apoptosis in non-small cell lung cancer cells via HIF-1α

Transcription factor Krüppel-like factors 5 (KLF5) is overexpressed in a wide range of tumor tissues and acts as a prognostic factor in cancer. However, the role of KLF5 in non-small cell lung cancer is not clear. Hypoxia plays a vital part in the development of cancer via hypoxia-inducible factor 1 (HIF-1). Our study showed that hypoxia (1% O2) increased cell viability, clonality and proliferation and inhibited cell apoptosis in A549 cells. The expression of HIF-1α and KLF5 was increased time-dependently in hypoxia. Using small interfering RNA (siRNA) targeting KLF5 or HIF-1α, we demonstrated that KLF5 or HIF-1α knockdown inhibited hypoxia-induced cell survival and promoted cell apoptosis by actively downregulating cyclin B1, survivin and upregulating caspase-3. Given the similar effect of KLF5 and HIF-1α on cell survival, an attempt was made to investigate the putative interaction of them in hypoxia. KLF5 was revealed to co-immunoprecipitate with HIF-1α and hypoxia increased the amount of KLF5 and HIF-1α complex. Moreover, silencing of KLF5 decreased HIF-1α expression while KLF5 was not affected by HIF-1α inhibition in hypoxia, confirming the effect of KLF5 on upregulation of HIF-1α. In conclusion, this study identified hypoxia as a tumor promoter by triggering KLF5 → HIF-1α → cyclin B1/survivin/caspase-3 in lung cancer cells.

Altered expression of hypoxia-inducible factor-1α (HIF-1α) and its regulatory genes in gastric cancer tissues

Tissue hypoxia induces reprogramming of cell metabolism and may result in normal cell transformation and cancer progression. Hypoxia-inducible factor 1-alpha (HIF-1α), the key transcription factor, plays an important role in gastric cancer development and progression. This study aimed to investigate the underlying regulatory signaling pathway in gastric cancer using gastric cancer tissue specimens. The integration of gene expression profile and transcriptional regulatory element database (TRED) was pursued to identify HIF-1α ↔ NFκB1 → BRCA1 → STAT3 ← STAT1 gene pathways and their regulated genes. The data showed that there were 82 differentially expressed genes that could be regulated by these five transcription factors in gastric cancer tissues and these genes formed 95 regulation modes, among which seven genes (MMP1, TIMP1, TLR2, FCGR3A, IRF1, FAS, and TFF3) were hub molecules that are regulated at least by two of these five transcription factors simultaneously and were associated with hypoxia, inflammation, and immune disorder. Real-Time PCR and western blot showed increasing of HIF-1α in mRNA and protein levels as well as TIMP1, TFF3 in mRNA levels in gastric cancer tissues. The data are the first study to demonstrate HIF-1α-regulated transcription factors and their corresponding network genes in gastric cancer. Further study with a larger sample size and more functional experiments is needed to confirm these data and then translate into clinical biomarker discovery and treatment strategy for gastric cancer.

[Energy metabolism pathway related genes and adaptive evolution of tumor cells]

The proliferation of tumor cells is an extremely energy-consuming process. However, different from normal cells, tumor cells generate energy via glycolysis even under aerobic conditions, which is one of the ten hallmarks of tumor cells. The switch of energy metabolism results in a series of physiological changes in tumor cells, including rapid generation of ATP and abundant biomass for cell proliferation, which form the basis of tumor cells to successfully adapt to their extreme microenvironment (e.g. lack of oxygen). In this review, we will introduce recent progress in studying somatic mutations on the energy metabolism related genes in tumors, with special focus on the potential factors involving in the "switch" and to decipher the genetic adaptive footprint of the "switch" from the angle of molecular evolution.

MicroRNAs in the imprinted DLK1-DIO3 region repress the epithelial-to-mesenchymal transition by targeting the TWIST1 protein signaling network

Development of metastatic disease accounts for the vast majority of cancer-related deaths. Nevertheless, few treatments exist that are designed to specifically inhibit processes that drive tumor metastasis. The imprinted DLK1-DIO3 region contains tumor-suppressing miRNAs, but their identity and function remain indeterminate. In this study we identify seven miRNAs in the imprinted DLK1-DIO3 region that function cooperatively to repress the epithelial-to-mesenchymal transition, a critical step that drives tumor metastasis, as well as proliferation of carcinoma cells. These seven miRNAs (miRs 300, 382, 494, 495, 539, 543, and 544) repress a signaling network comprising TWIST1, BMI1, ZEB1/2, and miR-200 family miRNAs and silencing of the cluster, which occurs via hypermethylation of upstream CpG islands in human ductal carcinomas, confers morphological, molecular, and function changes consistent with an epithelial-to-mesenchymal transition. Moreover, ectopic expression of miR-544 independently inhibited proliferation of numerous tumor cell lines by inducing the ATM cell cycle checkpoint pathway. These results establish the DLKI-DIO3 miRNA cluster as a critical checkpoint regulating tumor growth and metastasis and implicate epigenetic modification of the cluster in driving tumor progression. These results also suggest that promoter methylation status and miRNA expression levels represent new diagnostic tools and therapeutic targets to predict and inhibit, respectively, tumor metastasis in carcinoma patients.

Cell type specificity of signaling: view from membrane receptors distribution and their downstream transduction networks

Studies on cell signaling pay more attention to spatial dynamics and how such diverse organization can relate to high order of cellular capabilities. To overview the specificity of cell signaling, we integrated human receptome data with proteome spatial expression profiles to systematically investigate the specificity of receptors and receptor-triggered transduction networks across 62 normal cell types and 14 cancer types. Six percent receptors showed cell-type-specific expression, and 4% signaling networks presented enriched cell-specific proteins induced by the receptors. We introduced a concept of "response context" to annotate the cell-type dependent signaling networks. We found that most cells respond similarly to the same stimulus, as the "response contexts" presented high functional similarity. Despite this, the subtle spatial diversity can be observed from the difference in network architectures. The architecture of the signaling networks in nerve cells displayed less completeness than that in glandular cells, which indicated cellular-context dependent signaling patterns are elaborately spatially organized. Likewise, in cancer cells most signaling networks were generally dysfunctional and less complete than that in normal cells. However, glioma emerged hyper-activated transduction mechanism in malignant state. Receptor ATP6AP2 and TNFRSF21 induced rennin-angiotensin and apoptosis signaling were found likely to explain the glioma-specific mechanism. This work represents an effort to decipher context-specific signaling network from spatial dimension. Our results indicated that although a majority of cells engage general signaling response with subtle differences, the spatial dynamics of cell signaling can not only deepen our insights into different signaling mechanisms, but also help understand cell signaling in disease.