Speckle-type POZ protein is negatively associated with malignancies and inhibits cell proliferation and migration in liver cancer

Speckle-type POZ protein (SPOP) is an E3 ubiquitin ligase adaptor that is frequently mutated in human cancers. Our previous findings have indicated that SPOP is mutated and functions as a novel tumor suppressor in hepatoblastoma (HB). However, the biological roles and clinical significance of this SPOP in hepatocellular carcinoma (HCC) remain unknown. In this study, we found that the expression level of SPOP was downregulated in HCC primary tumors by quantitative real-time PCR and the protein level of SPOP was also reduced in 72 pairs of HCC tissue microarrays by immunohistochemical analyses. Moreover, SPOP expression was observed to negatively correlate with the tumor grade and intrahepatic metastasis of HCC patients. Furthermore, we revealed that SPOP not only inhibits cell proliferation but also inhibits the motility of liver cancer cells. Finally, we discovered that one of the mechanisms through which SPOP inhibits liver cancer cell migration involves the disruption of ZEB2 expression and the associated epithelial-mesenchymal transition program. Together, our findings emphasize the critical role of SPOP in the regulation of proliferation and migration in liver cancer.

Optineurin: The autophagy connection

Optineurin is a cytosolic protein encoded by the OPTN gene. Mutations of OPTN are associated with normal tension glaucoma and amyotrophic lateral sclerosis. Autophagy is an intracellular degradation system that delivers cytoplasmic components to the lysosomes. It plays a wide variety of physiological and pathophysiological roles. The optineurin protein is a selective autophagy receptor (or adaptor), containing an ubiquitin binding domain with the ability to bind polyubiquitinated cargoes and bring them to autophagosomes via its microtubule-associated protein 1 light chain 3-interacting domain. It is involved in xenophagy, mitophagy, aggrephagy, and tumor suppression. Optineurin can also mediate the removal of protein aggregates through an ubiquitin-independent mechanism. This protein in addition can induce autophagy upon overexpression or mutation. When overexpressed or mutated, the optineurin protein also serves as a substrate for autophagic degradation. In the present review, the multiple connections of optineurin to autophagy are highlighted.

miR-181a promotes G1/S transition and cell proliferation in pediatric acute myeloid leukemia by targeting ATM

PURPOSE

Abnormal expression of miRNAs is intimately related to a variety of human cancers. The purpose of this study is to confirm the expression of miR-181a and elucidate its physiological function and mechanism in pediatric acute myeloid leukemia (AML).

METHODS

Pediatric AML patients and healthy controls were enrolled, and the expression of miR-181a and ataxia telangiectasia mutated (ATM) in tissues were examined using quantitative PCR. Moreover, cell proliferation and cell cycle were evaluated in several cell lines (HL60, NB4 and K562) by using flow cytometry after transfected with miR-181a mimics and inhibitors, or ATM siRNA and control siRNA. Finally, ATM as the potential target protein of miR-181a was examined.

RESULTS

We found that miR-181a was significantly increased in pediatric AML, which showed an inverse association with ATM expression. Overexpressed miR-181a in cell lines significantly enhanced cell proliferation, as well as increased the ratio of S-phase cells by miR-181a mimics transfection in vitro. Luciferase activity of the reporter construct identified ATM as the direct molecular target of miR-181a. ATM siRNA transfection significantly enhanced cell proliferation and increased the ratio of S-phase cells in vitro.

CONCLUSION

The results revealed novel mechanism through which miR-181a regulates G1/S transition and cell proliferation in pediatric AML by regulating the tumor suppressor ATM, providing insights into the molecular mechanism in pediatric AML.

Downregulation of TRIM21 contributes to hepatocellular carcinoma carcinogenesis and indicates poor prognosis of cancers

The aim of our work is to clarify the clinical implication and functional role of tripartite motif 21 (TRIM21) in hepatocellular carcinoma (HCC). We validated that TRIM21 was downregulated in liver cancer samples by immunohistochemical (IHC) staining. We also demonstrated that its downregulation was associated with several clinicopathologic features such as tumor numbers, T stage, Barcelona Clinic Liver Cancer (BCLC) stage, and Cancer of the Liver Italian Program (CLIP) stage of HCC patients. Importantly, the expression of TRIM21 in tumor samples is significantly correlated with the prognosis of the patients. We further silenced TRIM21 in HCC cell HepG2 and LM3 and confirmed that TRIM21 silencing will promote cancer cell proliferation (CCK-8 assay), colony forming (plate colony-forming assay), migration (transwell assay), and the ability of antiapoptosis (annexin V-FITC/PI staining) in vitro. Then, we predicted gene sets influenced by TRIM21 by using bioinformatic tools. For the first time, we prove that TRIM21 is a potential tumor suppressor in HCC and its low expression indicates poor prognosis. Our findings provide useful insight into the mechanism of HCC origin and progression and offer clues to novel HCC therapies.

SIRT1 is a regulator of autophagy: Implications in gastric cancer progression and treatment

Silent mating type information regulation 1 (SIRT1) is implicated in tumorigenesis through its effect on autophagy. In gastric cancer (GC), SIRT1 is a marker for prognosis and is involved in cell invasion, proliferation, epithelial-mesenchymal transition (EMT) and drug resistance. Autophagy can function as a cell-survival mechanism or lead to cell death during the genesis and treatment of GC. This functionality is determined by factors including the stage of the tumor, cellular context and stress levels. Interestingly, SIRT1 can regulate autophagy through the deacetylation of autophagy-related genes (ATGs) and mediators of autophagy. Taken together, these findings support the need for continued research efforts to understand the mechanisms mediating the development of gastric cancer and unveil new strategies to eradicate this disease.

TRIM26 functions as a novel tumor suppressor of hepatocellular carcinoma and its downregulation contributes to worse prognosis

Hepatocellular carcinoma (HCC) is the one of the most common malignancies worldwide and its prognosis is extremely poor. Tripartite motif (TRIM) proteins play crucial roles in cancer cell biology but the function of tripartite motif 26 (TRIM26) has not been investigated. We demonstrated that low expression level of TRIM26 in tumor samples was significantly correlated with worse prognosis in HCC patients. We also demonstrated its expression level was associated with several clinicopathologic features such as AFP level and T stage of HCC patients. Furthermore, we validated that TRIM26 was significantly downregulated in HCC tissue compared with normal liver tissue. To further clarify the functional role of TRIM26 in HCC, We confirmed that TRIM26 silencing can promote cancer cell proliferation, colony forming, migration and invasion in vitro with HCC cell lines HepG2 and Bel-7402. Then we utilized bioinformatic tool to predict gene influenced by TRIM26, showing TRIM26 could modulate gene sets about cancer cell metabolism. In conclusion, we proved that TRIM26 is a novel tumor suppressor modulating multiple metabolism-related pathways in HCC. To our best knowledge, this is the first study to investigate the function of TRIM26 in cancer biology. Our findings provide useful insight into the mechanism of HCC origin and progression. Moreover, TRIM26 may represent a novel therapeutic target for HCC.

The metabolic alterations of cancer cells

Cancer cells exhibit profound metabolic alterations, allowing them to fulfill the metabolic needs that come with increased proliferation and additional facets of malignancy. Such a metabolic transformation is orchestrated by the genetic changes that drive tumorigenesis, that is, the activation of oncogenes and/or the loss of oncosuppressor genes, and further shaped by environmental cues, such as oxygen concentration and nutrient availability. Understanding this metabolic rewiring is essential to elucidate the fundamental mechanisms of tumorigenesis as well as to find novel, therapeutically exploitable liabilities of malignant cells. Here, we describe key features of the metabolic transformation of cancer cells, which frequently include the switch to aerobic glycolysis, a profound mitochondrial reprogramming, and the deregulation of lipid metabolism, highlighting the notion that these pathways are not independent but rather cooperate to sustain proliferation. Finally, we hypothesize that only those genetic defects that effectively support anabolism are selected in the course of tumor progression, implying that cancer-associated mutations may undergo a metabolically convergent evolution.

Role of the Wnt/β-catenin pathway in gastric cancer: An in-depth literature review

Gastric cancer remains one of the most common cancers worldwide and one of the leading cause for cancer-related deaths. Gastric adenocarcinoma is a multifactorial disease that is genetically, cytologically and architecturally more heterogeneous than other gastrointestinal carcinomas. The aberrant activation of the Wnt/β-catenin signaling pathway is involved in the development and progression of a significant proportion of gastric cancer cases. This review focuses on the participation of the Wnt/β-catenin pathway in gastric cancer by offering an analysis of the relevant literature published in this field. Indeed, it is discussed the role of key factors in Wnt/β-catenin signaling and their downstream effectors regulating processes involved in tumor initiation, tumor growth, metastasis and resistance to therapy. Available data indicate that constitutive Wnt signalling resulting from Helicobacter pylori infection and inactivation of Wnt inhibitors (mainly by inactivating mutations and promoter hypermethylation) play an important role in gastric cancer. Moreover, a number of recent studies confirmed CTNNB1 and APC as driver genes in gastric cancer. The identification of specific membrane, intracellular, and extracellular components of the Wnt pathway has revealed potential targets for gastric cancer therapy. High-throughput “omics” approaches will help in the search for Wnt pathway antagonist in the near future.

Aneuploidy and chromosomal instability in cancer: a jackpot to chaos

Genomic instability (GIN) is a hallmark of cancer cells that facilitates the acquisition of mutations conferring aggressive or drug-resistant phenotypes during cancer evolution. Chromosomal instability (CIN) is a form of GIN that involves frequent cytogenetic changes leading to changes in chromosome copy number (aneuploidy). While both CIN and aneuploidy are common characteristics of cancer cells, their roles in tumor initiation and progression are unclear. On the one hand, CIN and aneuploidy are known to provide genetic variation to allow cells to adapt in changing environments such as nutrient fluctuations and hypoxia. Patients with constitutive aneuploidies are more susceptible to certain types of cancers, suggesting that changes in chromosome copy number could positively contribute to cancer evolution. On the other hand, chromosomal imbalances have been observed to have detrimental effects on cellular fitness and might trigger cell cycle arrest or apoptosis. Furthermore, mouse models for CIN have led to conflicting results. Taken together these findings suggest that the relationship between CIN, aneuploidy and cancer is more complex than what was previously anticipated. Here we review what is known about this complex ménage à trois, discuss recent evidence suggesting that aneuploidy, CIN and GIN together promote a vicious cycle of genome chaos. Lastly, we propose a working hypothesis to reconcile the conflicting observations regarding the role of aneuploidy and CIN in tumorigenesis.

An unexpected inhibition of antiviral signaling by virus-encoded tumor suppressor p53 in pancreatic cancer cells

Virus-encoded tumor suppressor p53 transgene expression has been successfully used in vesicular stomatitis virus (VSV) and other oncolytic viruses (OVs) to enhance their anticancer activities. However, p53 is also known to inhibit virus replication via enhanced type I interferon (IFN) antiviral responses. To examine whether p53 transgenes enhance antiviral signaling in human pancreatic ductal adenocarcinoma (PDAC) cells, we engineered novel VSV recombinants encoding human p53 or the previously described chimeric p53-CC, which contains the coiled-coil (CC) domain from breakpoint cluster region (BCR) protein and evades the dominant-negative activities of endogenously expressed mutant p53. Contrary to an expected enhancement of antiviral signaling by p53, our global analysis of gene expression in PDAC cells showed that both p53 and p53-CC dramatically inhibited type I IFN responses. Our data suggest that this occurs through p53-mediated inhibition of the NF-κB pathway. Importantly, VSV-encoded p53 or p53-CC did not inhibit antiviral signaling in non-malignant human pancreatic ductal cells, which retained their resistance to all tested VSV recombinants. To the best of our knowledge, this is the first report of p53-mediated inhibition of antiviral signaling, and it suggests that OV-encoded p53 can simultaneously produce anticancer activities while assisting, rather than inhibiting, virus replication in cancer cells.

miR-203 downregulates Yes-1 and suppresses oncogenic activity in human oral cancer cells

The purpose of this study was to elucidate the molecular mechanisms of microRNA-203 (miR-203) as a tumor suppressor in KB human oral cancer cells. MicroRNA microarray results showed that the expression of miR-203 was significantly down-regulated in KB cells compared with normal human oral keratinocytes. The viability of KB cells was decreased by miR-203 in the time- and dose-dependent manners. In addition, over-expressed miR-203 not only increased the nuclear condensation but also significantly increased the apoptotic population of KB cells. These results indicated that the over-expression of miR-203 induced apoptosis of KB cells. Furthermore, the target gene array analyses revealed that the expression of Yes-1, a member of the Src family kinases (SFKs), was significantly down-regulated by miR-203 in KB cells. Moreover, both the mRNA and protein levels of Yes-1 were strongly reduced in KB cells transfected with miR-203. Therefore, these results indicated that Yes-1 is predicted to be a potential target gene of miR-203. Through a luciferase activity assay, miR-203 was confirmed to directly targets the Yes-1 3' untranslated region (UTR) to suppress gene expression. Therefore, our findings indicate that miR-203 induces the apoptosis of KB cells by directly targeting Yes-1, suggesting its application in anti-cancer therapeutics.

OPCML is frequently methylated in human colorectal cancer and its restored expression reverses EMT via downregulation of smad signaling

Emerging evidence has indicated that the expression of OPCML gene is frequently altered in a variety of cancers. We previously demonstrated that the OPCML gene is a target of epigenetic inactivation and its gene product exhibits tumor-suppressive properties. However, little is known regarding the effects and mechanisms of OPCML in colon cancer. We show that the loss or downregulation of OPCML is associated with its promoter hypermethylation. Methylation of the OPCML promoter was detected in all tumors and tumor-adjacent tissues, but lower methylation in normal colon tissues. The drug-induced release of epigenetic silencing was able to restore OPCML expression and the re-expression led to the suppression of cell growth. Furthermore, the increase in OPCML expression reversed a partial epithelial-to-mesenchymal (EMT)-like transition. Cell migration and invasiveness were also inhibited in response to OPCML upregulation. These actions were mediated through the inactivation of TGFβ-Smad signaling pathways. In addition, OPCML expression was associated with two upstream nuclear receptors (ERRa and RORa). Altogether, our study reveals OPCML as a potential tumor suppressor gene epigenetically silenced in colon cancer. Our study will help to elucidate the anti-invasive mechanisms of OPCML and establish new chemotherapeutic strategies for human colon cancer.

Structural and functional characterization of tumor suppressors TIG3 and H-REV107

H-REV107-like family proteins TIG3 and H-REV107 are class II tumor suppressors. Here we report that the C-terminal domains (CTDs) of TIG3 and H-REV107 can induce HeLa cell death independently. The N-terminal domain (NTD) of TIG3 enhances the cell death inducing ability of CTD, while NTD of H-REV107 plays an inhibitory role. The solution structure of TIG3 NTD is very similar to that of H-REV107 in overall fold. However, the CTD binding regions on NTD are different between TIG3 and H-REV107, which may explain their functional difference. As a result, the flexible main loop of H-REV107, but not that of TIG3, is critical for its NTD to modulate its CTD in inducing cell death.

Two for the Price of One: G Protein-Dependent and -Independent Functions of RGS6 In Vivo

Regulator of G protein signaling 6 (RGS6) is unique among the members of the RGS protein family as it remains the only protein with the demonstrated capacity to control G protein-dependent and -independent signaling cascades in vivo. RGS6 inhibits signaling mediated by γ-aminobutyric acid B receptors, serotonin 1A receptors, μ opioid receptors, and muscarinic acetylcholine 2 receptors. RGS6 deletion triggers distinct behavioral phenotypes resulting from potentiated signaling by these G protein-coupled receptors namely ataxia, a reduction in anxiety and depression, enhanced analgesia, and increased parasympathetic tone, respectively. In addition, RGS6 possesses potent proapoptotic and growth suppressive actions. In heart, RGS6-dependent reactive oxygen species (ROS) production promotes doxorubicin (Dox)-induced cardiomyopathy, while in cancer cells RGS6/ROS signaling is necessary for activation of the ataxia telangiectasia mutated/p53/apoptosis pathway required for the chemotherapeutic efficacy of Dox. Further, by facilitating Tip60 (trans-acting regulator protein of HIV type 1-interacting protein 60 kDa)-dependent DNA methyltransferase 1 degradation, RGS6 suppresses cellular transformation in response to oncogenic Ras. The culmination of these G protein-independent actions results in potent tumor suppressor actions of RGS6 in the murine mammary epithelium. This work summarizes evidence from human genetic studies and model animals implicating RGS6 in normal physiology, disease, and the pharmacological actions of multiple drugs. Though efforts by multiple laboratories have contributed to the ever-growing RGS6 oeuvre, the pleiotropic nature of this gene will likely lead to additional work detailing the importance of RGS6 in neuropsychiatric disorders, cardiovascular disease, and cancer.

Reduced expression and growth inhibitory activity of the aging suppressor klotho in epithelial ovarian cancer

Klotho is an anti-aging transmembrane protein, which can be shed and function as a hormone. Accumulating data indicate klotho as a tumor suppressor in a wide array of malignancies, and we identified klotho as an inhibitor of the insulin-like growth factor (IGF-1) pathway in cancer cells. As this pathway is significant in the development of epithelial ovarian cancer (EOC) we studied klotho expression and activity in this tumor. Klotho mRNA levels were reduced in 16 of 19 EOC cell lines and immunohistochemistry analysis revealed high expression in normal ovaries, and reduced expression in 100 of 241 high grade papillary-serous adenocarcinoma of the ovaries, fallopian tubes and peritoneum. Reduced expression was associated with wild-type BRCA status. Klotho reduced EOC cell viability, enhanced cisplatin sensitivity, and reduced expression of mesenchymal markers. Finally, klotho inhibited IGF-1 pathway activation and inhibited transcriptional activity of the estrogen receptor. In conclusion, klotho is silenced in a substantial subset of the tumors and restoring its expression slows growth of EOC cells and inhibits major signaling pathways. As klotho is a hormone, treatment with klotho may serve as a novel treatment for EOC.

Tumor suppressive microRNA-200a inhibits renal cell carcinoma development by directly targeting TGFB2

A large body of evidence indicates that microRNAs play a critical role in tumor initiation and progression by negatively regulating oncogenes or tumor suppressor genes. Here, we report that the expression of miR-200a was notably downregulated in 45 renal cell carcinoma (RCC) samples. Restoration of miR-200a suppressed cell proliferation, migration, and invasion in two RCC cell lines. Furthermore, we used an epithelial-to-mesenchymal transition PCR array to explore the putative target genes of miR-200a. By performing quantitative real-time PCR, ELISA, and luciferase reporter assays, transforming growth factor beta2 (TGFB2) was validated as a direct target gene of miR-200a. Moreover, siRNA-mediated knockdown of TGFB2 partially phenocopied the effect of miR-200a overexpression. These results suggest that miR-200a suppresses RCC development via directly targeting TGFB2, indicating that miR-200a may present a novel target for diagnostic and therapeutic strategies in RCC.

Tumor suppressor role of miR-133a in gastric cancer by repressing IGF1R

AIM: To investigate the function and mechanism of miR-133a in gastric cancer (GC) and its relationship with clinicopathological characteristics of GC.

METHODS: A total of 105 GC patients who underwent surgical resection as primary treatment were selected for this study. Real-time quantitative reverse transcriptase polymerase chain (qRT-PCR) was used to examine the expression levels of miR-133a in human GC and adjacent non-tumor tissues, as well as in GC cell lines (SGC-7901, BGC-823, MGC-803, and AGS) and a human gastric mucosal epithelial cell line (GES-1). The biological role of miRNA (miR)-133a was assessed in the GC cell lines using MTT, apoptosis, migration and invasion, and colony formation assays, and xenograft tumorigenesis. qRT-PCR and western blot analyses were used to evaluate the potential target gene expression of miR-133a. Pearson’s correlation was calculated to evaluate the correlation between miR-133a and insulin-like growth factor 1 receptor (IGF1R) expression. The regulation of IGF1R by miR-133a was verified using the luciferase reporter assay.

RESULTS: In 80% of the 105 GC patients, the mean expression of miR-133a was significantly downregulated in tumor tissues compared with adjacent normal tissues (1.215 ± 0.1477 vs 3.093 ± 0.4104, P < 0.0001). Downregulation of miR-133a was significantly correlated with the degree of differentiation (P = 0.01), local invasion (P = 0.001) and TNM stage (P = 0.02) in GC patients. Compared with a control construct, forced expression of miR-133a in GC cell lines inhibited proliferation (0.4787 ± 0.0219 vs 0.7050 ± 0.0147, P = 0.0013 in SGC-7901 cells; and 0.5448 ± 0.0085 vs 0.7270 ± 0.0084, P = 0.001 in MGC-803 cells); migration (0.6333 ± 0.0233 vs 1.037 ± 0.0584, P = 0.003 in SGC-7901 cells; 0.6126 ± 0.0311 vs 1.024 ± 0.0456, P = 0.0017 in MGC-803 cells); and invasion (0.613 ± 0.0399 vs 1.033 ± 0.0278, P = 0.0013 in SGC-7901 cells; 0.7433 ± 0.0221 vs 1.017 ± 0.0311, P = 0.002 in MGC-803 cells). It also induced apoptosis (18.19% ± 0.2483% vs 5.887% ± 0.3837%, P < 0.0001 in SGC-7901 cells; 22.69% ± 0.7846% vs 9.347% ± 0.3012%, P < 0.0001 in MGC-803 cells). Furthermore, miR-133a inhibited tumor growth and xenograft tumorigenesis of SGC -7901 cells in vivo. In addition, we identified IGF1R as a regulatory target of miR-133a in GC.

CONCLUSION: This study suggests that miR-133a is downregulated in GC and functions as a tumor suppressor in vitro and in vivo partly by repressing IGF1R.

Decaprenyl diphosphate synthase subunit 2 as a prognosis factor in hepatocellular carcinoma

AIM: To investigate the involvement of decaprenyl diphosphate synthase subunit 2 (PDSS2) in development and progression of human hepatocellular carcinoma (HCC).

METHODS: PDSS2 protein expression was examined in well- and poorly differentiated HCC tumor samples. The levels of PDSS2 expression were compared with clinical features and prognosis of HCC patients. The effects of PDSS2 on cell proliferation, cell cycle, apoptosis, cell migration, and invasion in HCC HepG2 cells were also investigated.

RESULTS: PDSS2 was downregulated in poorly differentiated cancer samples compared with well-differentiated tumor samples, and the expression level was markedly lower in HCC tissues than in histologically normal tissue adjacent to the cancer. Reduced protein expression was negatively associated with the status of HCC progression. In addition, overexpression of PDSS2 dramatically suppressed cell proliferation and colony formation, and induced apoptosis in HepG2 cells by inducing G1-phase cell-cycle arrest. The migration and invasion capabilities of HepG2 cells were significantly decreased following PDSS2 overexpression.

CONCLUSION: Decreased PDSS2 expression is an unfavorable prognostic factor for HCC, and PDSS2 has potent anticancer activity in HCC tissues and HepG2 cells.

ING3 protein expression profiling in normal human tissues suggest its role in cellular growth and self-renewal

Members of the INhibitor of Growth (ING) family of proteins act as readers of the epigenetic code through specific recognition of the trimethylated form of lysine 4 of histone H3 (H3K4Me3) by their plant homeodomains. The founding member of the family, ING1, was initially identified as a tumor suppressor with altered regulation in a variety of cancer types. While alterations in ING1 and ING4 levels have been reported in a variety of cancer types, little is known regarding ING3 protein levels in normal or transformed cells due to a lack of reliable immunological tools. In this study we present the characterization of a new monoclonal antibody we have developed against ING3 that specifically recognizes human and mouse ING3. The antibody works in western blots, immunofluorescence, immunoprecipitation and immunohistochemistry. Using this antibody we show that ING3 is most highly expressed in small intestine, bone marrow and epidermis, tissues in which cells undergo rapid proliferation and renewal. Consistent with this observation, we show that ING3 is expressed at significantly higher levels in proliferating versus quiescent epithelial cells. These data suggest that ING3 levels may serve as a surrogate for growth rate, and suggest possible roles for ING3 in growth and self renewal and related diseases such as cancer.

Evasion of anti-growth signaling: A key step in tumorigenesis and potential target for treatment and prophylaxis by natural compounds

The evasion of anti-growth signaling is an important characteristic of cancer cells. In order to continue to proliferate, cancer cells must somehow uncouple themselves from the many signals that exist to slow down cell growth. Here, we define the anti-growth signaling process, and review several important pathways involved in growth signaling: p53, phosphatase and tensin homolog (PTEN), retinoblastoma protein (Rb), Hippo, growth differentiation factor 15 (GDF15), AT-rich interactive domain 1A (ARID1A), Notch, insulin-like growth factor (IGF), and Krüppel-like factor 5 (KLF5) pathways. Aberrations in these processes in cancer cells involve mutations and thus the suppression of genes that prevent growth, as well as mutation and activation of genes involved in driving cell growth. Using these pathways as examples, we prioritize molecular targets that might be leveraged to promote anti-growth signaling in cancer cells. Interestingly, naturally occurring phytochemicals found in human diets (either singly or as mixtures) may promote anti-growth signaling, and do so without the potentially adverse effects associated with synthetic chemicals. We review examples of naturally occurring phytochemicals that may be applied to prevent cancer by antagonizing growth signaling, and propose one phytochemical for each pathway. These are: epigallocatechin-3-gallate (EGCG) for the Rb pathway, luteolin for p53, curcumin for PTEN, porphyrins for Hippo, genistein for GDF15, resveratrol for ARID1A, withaferin A for Notch and diguelin for the IGF1-receptor pathway. The coordination of anti-growth signaling and natural compound studies will provide insight into the future application of these compounds in the clinical setting.

DLEC1 is not silenced solely by promoter methylation in head and neck squamous cell carcinoma

Different types of genetic and epigenetic changes are associated with HNSCC. The molecular mechanisms of HNSCC carcinogenesis are still undergoing intensive investigation. The Deleted in lung and esophageal cancer 1 (DLEC1) gene is frequently silenced by methylation in various kinds of cancer. However, there is no data in the literature investigating the DLEC1 gene in the HNSCC. Tumor tissues from 97 patients were analyzed by real-time quantitative RT-PCR and DLEC1 expression levels were correlated with the methylation of the DLEC1 gene promoter. A statistically significant down-regulation was observed in tumors compared to non-cancerous tissue samples (p = 0.00). However, this down-regulation was not directly associated with hypermethylation of the promoter (p ≥ 0.05). Our results indicate that the DLEC1 gene may play an important role in the development of HNSCC. However, its down-regulation is not associated with the clinicopathological parameters and is not solely under the control of promoter methylation.

Re-expression of LKB1 in LKB1-mutant EKVX cells leads to resistance to paclitaxel through the up-regulation of MDR1 expression

OBJECTIVES

The tumor suppressor LKB1 has recently been shown to be involved in the regulation of microtubule dynamics, thus cancer cells with inactivated LKB1 may have developed a means to overcome dysregulated microtubule functions, making them intrinsically resistant to microtubule targeting agents. Here, we generated isogenic LKB1-wild type and mutant non-small cell lung cancer (NSCLC) cell lines to evaluate the role of LKB1 in paclitaxel resistance.

MATERIALS AND METHODS

SRB, flow cytometry and immunoblotting were used to assess cell proliferation and apoptosis in NSCLC cell lines after paclitaxel treatment. Expression of LKB1 was restored in LKB1-null cells by retrovirus infection and was reduced in LKB1-wild type cells by shRNA knock down.

RESULTS AND CONCLUSION

The restoration of LKB1 in LKB1-null cells failed to promote paclitaxel-induced apoptosis in both p53-wild type and p53-mutant backgrounds, indicating that LKB1 was not required for paclitaxel-induced apoptosis. Interestingly, the re-establishment of LKB1 expression led to the up-regulation of class III beta-tubulin and MDR1 in EKVX cells. The up-regulation of MDR1 protein and transcripts in EKVX cells was specifically associated with the expression of wild-type LKB1 and mainly responsible for the increased cellular resistance to paclitaxel. However, the presence of LKB1 protein was not required to maintain this increased MDR1 expression even though there was no genetic amplification or promoter de-methylation of the ABCB1 locus in EKVX-LKB1-WT cells. These data suggest that LKB1 does not promote paclitaxel-induced apoptosis in most NSCLC cell lines. In contrast, in some NSCLC, the presence of LKB1 may facilitate increases in either MDR1 or class III beta-tubulin expression which can lead to paclitaxel resistance.

Biallelic inactivation of protoporphyrinogen oxidase and hydroxymethylbilane synthase is associated with liver cancer in acute porphyrias

Variegate porphyria (VP) and acute intermittent porphyria (AIP), the two most common types of acute porphyrias (AHPs), result from a partial deficiency of protoporphyrinogen oxidase (PPOX) and hydroxymethylbilane synthase (HMBS), respectively. A rare but serious complication in the AHPs is hepatocellular carcinoma (HCC). However, the underlying pathomechanisms are yet unknown. We performed DNA sequence analysis in cancerous and non-cancerous liver tissue of a VP and an AIP patient, both with HCC. In samples of both cancerous and non-cancerous liver tissues from the patients, we identified the underlying PPOX and HMBS germline mutations, c.1082dupC and p.G111R, respectively. Additionally, we detected a second somatic mutation, only in the cancer tissue i.e., p.L416X in the PPOX gene of the VP patient and p.L220X in the HMBS gene of the AIP patient, both located in trans to the respective germline mutations. Both somatic mutations were not detected in 10 non-porphyria-associated HCCs. Our data demonstrate that in the hepatic cancer tissue of AHP patients, somatic second-hit mutations result in nearly complete inactivation of the enzymes catalyzing major steps in the heme biosynthetic pathway. Both PPOX and HMBS, which might act as tumor suppressors, play a crucial role in the development of HCC in these individuals.

The Rho-specific GAP protein DLC3 coordinates endocytic membrane trafficking

Membrane trafficking is known to be coordinated by small GTPases, but the identity of their regulators, the guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs) that ensure balanced GTPase activation at different subcellular sites is largely elusive. Here, we show in living cells that deleted in liver cancer 3 (DLC3, also known as STARD8) is a functional Rho-specific GAP protein, the loss of which enhances perinuclear RhoA activity. DLC3 is recruited to Rab8-positive membrane tubules and is required for the integrity of the Rab8 and Golgi compartments. Depletion of DLC3 impairs the transport of internalized transferrin to the endocytic recycling compartment (ERC), which is restored by the simultaneous downregulation of RhoA and RhoB. We further demonstrate that DLC3 loss interferes with epidermal growth factor receptor (EGFR) degradation associated with prolonged receptor signaling. Taken together, these findings identify DLC3 as a novel component of the endocytic trafficking machinery, wherein it maintains organelle integrity and regulates membrane transport through the control of Rho activity.

Regulation of cell signaling and apoptosis by tumor suppressor WWOX

Human fragile WWOX gene encodes a tumor suppressor WW domain-containing oxidoreductase (named WWOX, FOR, or WOX1). Functional suppression of WWOX prevents apoptotic cell death induced by a variety of stress stimuli, such as tumor necrosis factor, UV radiation, and chemotherapeutic drug treatment. Loss of WWOX gene expression due to gene deletions, loss of heterozygosity, chromosomal translocations, or epigenetic silencing is frequently observed in human malignant cancer cells. Acquisition of chemoresistance in squamous cell carcinoma, osteosarcoma, and breast cancer cells is associated with WWOX deficiency. WWOX protein physically interacts with many signaling molecules and exerts its regulatory effects on gene transcription and protein stability and subcellular localization to control cell survival, proliferation, differentiation, autophagy, and metabolism. In this review, we provide an overview of the recent advances in understanding the molecular mechanisms by which WWOX regulates cellular functions and stress responses. A potential scenario is that activation of WWOX by anticancer drugs is needed to overcome chemoresistance and trigger cancer cell death, suggesting that WWOX can be regarded as a prognostic marker and a candidate molecule for targeted cancer therapies.

p53 mutations in colorectal cancer- molecular pathogenesis and pharmacological reactivation

Colorectal cancer (CRC) is one of the most common malignancies with high prevalence and low 5-year survival. CRC is a heterogeneous disease with a complex, genetic and biochemical background. It is now generally accepted that a few important intracellular signaling pathways, including Wnt/β-catenin signaling, Ras signaling, and p53 signaling are frequently dysregulated in CRC. Patients with mutant p53 gene are often resistant to current therapies, conferring poor prognosis. Tumor suppressor p53 protein is a transcription factor inducing cell cycle arrest, senescence, and apoptosis under cellular stress. Emerging evidence from laboratories and clinical trials shows that some small molecule inhibitors exert anti-cancer effect via reactivation and restoration of p53 function. In this review, we summarize the p53 function and characterize its mutations in CRC. The involvement of p53 mutations in pathogenesis of CRC and their clinical impacts will be highlighted. Moreover, we also describe the current achievements of using p53 modulators to reactivate this pathway in CRC, which may have great potential as novel anti-cancer therapy.

Downregulated TIPE2 is associated with poor prognosis and promotes cell proliferation in non-small cell lung cancer

The present study aims to investigate the expression pattern of TIPE2 protein and its clinical significance in human non-small cell lung cancer (NSCLC). We investigated the expression levels of TIPE2 in 96 NSCLC tumor samples by immunohistochemistry and then analyzed its clinical significance. Furthermore, the role of TIPE2 on the biological properties of the NSCLC cell line H1299 and A549 was experimentally tested in vitro and in vivo. We found that the expression level of TIPE2 was significantly higher in normal lung tissues compared with NSCLC tissues (P<0.001), and TIPE2 downregulation was significantly correlated with advanced TNM stage (P=0.006). TIPE2 expression was lower in lung cancer cell lines than normal bronchial cell line HBE. Transfection of TIPE2 plasmid was performed in H1299 and A549 cells. TIPE2 overexpression inhibited lung cancer cell proliferation, colony formation and cell invasive in vitro, and prevented lung tumor growth in vivo. In addition, TIPE2 transfection reduced the anti-apoptotic Bcl-XL protein and mesenchymal marker N-cadherin expression. Taken together, our results demonstrate that TIPE2 might serve as a tumor suppressor in NSCLC progression.

MicroRNAs in colorectal cancer: small molecules with big functions

Colorectal cancer (CRC) is the third most lethal malignancy, with pathogenesis intricately dependent upon microRNAs (miRNAs). miRNAs are short, non-protein coding RNAs, targeting the 3'-untranslated regions (3'-UTR) of certain mRNAs. They usually serve as tumor suppressors or oncogenes, and participate in tumor phenotype maintenance. Therefore, miRNAs consequently regulate CRC carcinogenesis and other biological functions, including apoptosis, development, angiogenesis, migration, and proliferation. Due to its differential expression and distinct stability, miRNAs are regarded as molecular biomarkers (for diagnosis/prognosis) and therapeutic targets for CRC. Recently, a remarkable number of miRNAs have been discovered with implications via incompletely understood mechanisms in CRC. As further study of relevant miRNAs continues, it is hopeful that novel miRNA-based therapeutic strategies may be available for CRC patients in the future.

C. elegans as a model to study PTEN's regulation and function

PTEN (phosphatase and tensin homolog deleted on chromosome 10) has important roles in tumor suppression, metabolism, and development, yet its regulators, effectors, and functions are not fully understood. DAF-18 is the PTEN ortholog in Caenorhabditis elegans. DAF-18's role is highly conserved to human PTEN, and can be functionally replaced by human PTEN. Thus C. elegans provides a valuable model to study PTEN. This review assesses current and emerging methods to study DAF-18's regulators and functions in C. elegans. We propose genetic modify screens to identify genes that interact with daf-18/PTEN. These genes are potential targets for anticancer drug therapies. We also provide a review on the roles DAF-18/PTEN has during C. elegans development and how studying these physiological roles can provide mechanistic insight on DAF-18/PTEN function.

RNA activation: promise as a new weapon against cancer

RNA activation (RNAa) is a novel mechanism in which short RNA duplexes, referred to as small activating RNAs (saRNAs), enable sequence-specific gene activation capable of lasting up to 2 weeks. RNAa was named in contrast to RNA interference (RNAi). Although many mysteries remain, increasing evidence demonstrates that RNAa not only provides a novel mechanism for the study of gene function and regulation, but also holds exciting potential for clinical translation to therapeutic modality against cancers. In this review, we will focus on the potential applications of RNAa in cancer studies and therapeutics.

Role of BC040587 as a predictor of poor outcome in breast cancer

Background

Accumulating studies have focused on the oncogenic and tumor suppressive roles of the newly identified lncRNAs. A novel lncRNA BC040587 in 3q13.31 locus which exists frequent copy number alterations was found to be associated with poor survival of osteosarcoma patients. However, its role in breast cancer (BC) remains unknown. The aim of this study was to examine the expression pattern of BC040587 in BC and to evaluate its biological role and clinical significance in prediction of prognosis.

Methods

Expression of BC040587 was analyzed in 20 pairs of BC cancer tissues and adjacent noncancerous tissues (ANCT), also in 151 BC tissues, 9 BC cell lines and one normal breast cell line by quantitative reverse-transcription polymerase chain reaction (qRT-PCR). Differences between groups were tested for significance using Student’s t-test (two-tailed). Then we analyzed the potential relationship between BC040587 expression and clinic pathological features of BC patients. The correlation was analyzed by SPSS software.

Results

It showed that BC040587 expression was down regulated both in BC samples and in BC cell lines compared with corresponding normal control. BC040587 expression was correlated with menopausal status (p = 0.040) and tumor differentiation (p = 0.035). The Kaplan-Meier survival curves indicated that the overall survival (OS) was significantly poor in low BC040587 expression BC patients (p = 0.023). Furthermore, expression of BC040587 was significantly associated with worse prognosis and was shown to be an independent prognostic marker breast cancer (p = 0.032). Our studies indicate that BC040587 may represent a new marker of prognosis in breast cancer.

Conclusion

Our studies indicate that BC040587 is significantly down-regulated in BC tissues and BC cell lines. BC040587 may represent a new marker of prognosis in breast cancer.

Epigenetic silencing of microRNA-373 to epithelial-mesenchymal transition in non-small cell lung cancer through IRAK2 and LAMP1 axes

The role of microRNAs (miRNAs) in carcinogenesis as tumor suppressors or oncogenes has been widely reported. Epigenetic change is one of the mechanisms of transcriptional silencing of miRNAs in cancer. To identify lung cancer-related miRNAs that are mediated by histone modification, we conducted microarray analysis in the Calu-6 non-small cell lung cancer (NSCLC) cell line after treatment with suberoylanilide hydroxamic acid (SAHA), a histone deacetylase (HDAC) inhibitor. The expression level of miR-373 was enhanced by SAHA treatment in this cell line by microarray and the following quantitative RT-PCR analyses. Treatment with another HDAC inhibitor, Trichostatin A, restored the levels of miR-373 expression in A549 and Calu-6 cells, while demethylation drug treatment did not. Importantly, miR-373 was found to be down-regulated in NSCLC tissues and cell lines. Transfection of miR-373 into A549 and Calu-6 cells attenuated cell proliferation, migration, and invasion and reduced the expression of mesenchymal markers. Additional microarray analysis of miR-373-transfected cells and computational predictions identified IRAK2 and LAMP1 as targets of miR-373. Knockdown of these two genes showed similar biological effects to those of miR-373 overexpression. In clinical samples, overexpression of IRAK2 correlated with decreased disease-free survival of patients with non-adenocarcinoma. In conclusion, we found that miR-373 is silenced by histone modification in lung cancer cells and identified its function as a tumor suppressor and negative regulator of the mesenchymal phenotype through downstream IRAK2 and LAMP1 target genes.

PTEN hamartoma tumor syndrome: clinical risk assessment and management protocol

The tumor suppressor phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is an important phosphatase that counteracts one of the most critical cancer pathways: the phosphatidylinositol 3-kinase (PI3K)/AKT signaling pathways. Clinically, deregulation of PTEN function resulting in reduced PTEN expression and activity is implicated in human diseases. Cowden syndrome (CS) is an autosomal dominant disorder characterized by benign and malignant tumors. CS-related individual features occur commonly in the general population. Approximately 25% of patients diagnosed with CS have pathogenic germline PTEN mutations, which increase lifetime risks of breast, thyroid, uterine, renal and other cancers. PTEN testing and intensive cancer surveillance allow for early detection and treatment of these cancers for mutation positive patients and their relatives. In this review, we highlight our current knowledge of germline PTEN mutations in relation to human disease. We review current clinical diagnosis and management recommendations for PHTS including recent discoveries in understanding PTEN function regulation and how this can be exploited therapeutically.

MiR-132 prohibits proliferation, invasion, migration, and metastasis in breast cancer by targeting HN1

Accumulating evidence indicates that miRNAs play critical roles in tumorigenesis and cancer progression. This study aims to investigate the role and the underlying mechanism of miR-132 in breast cancer. Here, we report that miR-132 is significantly down-regulated in breast cancer tissues and cancer cell lines. Additional study identifies HN1 as a novel direct target of miR-132. MiR-132 down-regulates HN1 expression by binding to the 3' UTR of HN1 transcript, thereby, suppressing multiple oncogenic traits such as cancer cell proliferation, invasion, migration and metastasis in vivo and in vitro. Overexpression of HN1 restores miR-132-suppressed malignancy. Importantly, higher HN1 expression is significantly associated with worse overall survival of breast cancer patients. Taken together, our data demonstrate a critical role of miR-132 in prohibiting cell proliferation, invasion, migration and metastasis in breast cancer through direct suppression of HN1, supporting the potential utility of miR-132 as a novel therapeutic strategy against breast cancer.

Gene therapy in pancreatic cancer

Pancreatic cancer (PC) is a highly lethal disease and notoriously difficult to treat. Only a small proportion of PC patients are eligible for surgical resection, whilst conventional chemoradiotherapy only has a modest effect with substantial toxicity. Gene therapy has become a new widely investigated therapeutic approach for PC. This article reviews the basic rationale, gene delivery methods, therapeutic targets and developments of laboratory research and clinical trials in gene therapy of PC by searching the literature published in English using the PubMed database and analyzing clinical trials registered on the Gene Therapy Clinical Trials Worldwide website (http://www. wiley.co.uk/genmed/ clinical). Viral vectors are main gene delivery tools in gene therapy of cancer, and especially, oncolytic virus shows brighter prospect due to its tumor-targeting property. Efficient therapeutic targets for gene therapy include tumor suppressor gene p53, mutant oncogene K-ras, anti-angiogenesis gene VEGFR, suicide gene HSK-TK, cytosine deaminase and cytochrome p450, multiple cytokine genes and so on. Combining different targets or combination strategies with traditional chemoradiotherapy may be a more effective approach to improve the efficacy of cancer gene therapy. Cancer gene therapy is not yet applied in clinical practice, but basic and clinical studies have demonstrated its safety and clinical benefits. Gene therapy will be a new and promising field for the treatment of PC.

Negative regulation of RelA phosphorylation: emerging players and their roles in cancer

NF-κB signaling contributes to human disease processes, notably inflammatory diseases and cancer. Many advances have been made in understanding mechanisms responsible for abnormal NF-κB activation with RelA post-translational modification, particularly phosphorylation, proven to be critical for RelA function. While the majority of studies have focused on identifying kinases responsible for NF-κB phosphorylation and pathway activation, recently progress has also been made in understanding the negative regulators important for restraining RelA activity. Here we summarize negative regulators of RelA phosphorylation, their targeting sites in RelA and biological functions through negative regulation of RelA activation. Finally, we emphasize the tumor suppressor-like roles that these negative regulators can assume in human cancers.

DNA damage induced activation of Cygb stabilizes p53 and mediates G1 arrest

Cytoglobin (Cygb) is an emerging tumor suppressor gene silenced by promoter hypermethylation in many human tumors. So far, the precise molecular mechanism underlying its tumor suppressive function remains poorly understood. Here, we identified Cygb as a genotoxic stress-responsive hemoprotein upregulated upon sensing cellular DNA damage. Our studies demonstrated that Cygb physically associates with and stabilizes p53, a key cellular DNA damage signaling factor. We provide evidence that Cygb extends the half-life of p53 by blocking its ubiquitination and subsequent degradation. We show that, upon DNA damage, cells overexpressing Cygb displayed proliferation defect by rapid accumulation of p53 and its target gene p21, while Cygb knockdown cells failed to efficiently arrest in G1 phase in response to DNA insult. These results suggest a possible involvement of Cygb in mediating cellular response to DNA damage and thereby contributing in the maintenance of genomic integrity. Our study thus presents a novel insight into the mechanistic role of Cygb in tumor suppression.

The cytoplasmic and nuclear populations of the eukaryote tRNA-isopentenyl transferase have distinct functions with implications in human cancer

Mod5 is the yeast tRNA isopentenyl transferase, an enzyme that is conserved from bacteria to humans. Mod5 is primarily cytoplasmic where it modifies the A37 position of a few tRNAs, and the yeast enzyme has been shown capable of forming heritable, amyloid-like aggregates that confer a selective advantage in the presence of specific antifungal agents. A subpopulation of Mod5 is also found associated with nuclear tRNA genes, where it contributes tRNA-gene mediated (tgm) silencing of local transcription by RNA polymerase II. The tgm-silencing function of Mod5 has been observed in yeast and a Mod5-deletion in yeast can be complemented by the plant and human tRNA isopentenyl transferases, but not the bacterial enzymes, possibly due to the lack of an extended C-terminal domain found in eukaryotes. In light of this additional nuclear role for Mod5 we discuss the proposed role of the human homologue of Mod5, TRIT1, as a tumor suppressor protein.

TRIM13 regulates ubiquitination and turnover of NEMO to suppress TNF induced NF-κB activation

The NF-κB family of transcription factors is activated in response to various intracellular or extracellular stimuli and its dysregulation leads to pathological conditions like infection, cancer, neurodegenerative disorders. The post-translational modification by ubiquitination regulates various steps of NF-κB pathway. In the current study, we have described the role of TRIM13, an endoplasmic reticulum (ER) membrane anchored E3 ligase in regulation of NF-κB. The expression of TRIM13 represses TNF induced NF-κB while the knockdown has the opposite effect. The E3 ligase activity and ER localization is essential for NF-κB suppression whereas TRIM13 regulated autophagy is not essential. TRIM13 interacts with NEMO and modulates its ubiquitination and turnover, hence may regulate IKK complex activity. TRIM13 mediated NF-κB repression is essential for negative regulation of clonogenic ability of the cells. This study for the first time demonstrated the role of TRIM13, ER resident RING E3 ligase as a novel regulator of NEMO ubiquitination, negative regulator of NF-κB signaling and its role as a tumor suppressor.

Interferon regulatory factor 8 functions as a tumor suppressor in renal cell carcinoma and its promoter methylation is associated with patient poor prognosis

Interferon regulatory factor 8 (IRF8), as a central element of IFN-γ-signaling, plays a critical role in tumor suppression. However, its expression and underlying molecular mechanism remain elusive in renal cell carcinoma (RCC). Here, we examined IRF8 expression and methylation in RCC cell lines and primary tumors, and further assessed its tumor suppressive functions. We found that IRF8 was widely expressed in human normal tissues including kidney, but frequently downregulated by promoter methylation in RCC cell lines. IRF8 methylation was detected in 25% of primary tumors, but not in adjacent non-malignant renal tissues, and associated with higher tumor nuclear grade of RCC. Ectopic expression of IRF8 inhibited colony formation and migration abilities of RCC cells, through inducing cell cycle G2/M arrest and apoptosis. IFN-γ could induce IRF8 expression in RCC cells, together with increased cleaved-PARP. We further found that IRF8 inhibited expression of oncogenes YAP1 and Survivin, as well as upregulated expression of tumor suppressor genes CASP1, p21 and PTEN. Collectively, our data demonstrate that IRF8 as a functional tumor suppressor is frequently methylated in RCC, and IRF8-mediated interferon signaling is involved in RCC pathogenesis.

Cellular prostatic acid phosphatase, a PTEN-functional homologue in prostate epithelia, functions as a prostate-specific tumor suppressor

The inactivation of tumor suppressor genes (TSGs) plays a vital role in the progression of human cancers. Nevertheless, those ubiquitous TSGs have been shown with limited roles in various stages of diverse carcinogenesis. Investigation on identifying unique TSG, especially for early stage of carcinogenesis, is imperative. As such, the search for organ-specific TSGs has emerged as a major strategy in cancer research. Prostate cancer (PCa) has the highest incidence in solid tumors in US males. Cellular prostatic acid phosphatase (cPAcP) is a prostate-specific differentiation antigen. Despite intensive studies over the past several decades on PAcP as a PCa biomarker, the role of cPAcP as a PCa-specific tumor suppressor has only recently been emerged and validated. The mechanism underlying the pivotal role of cPAcP as a prostate-specific TSG is, in part, due to its function as a protein tyrosine phosphatase (PTP) as well as a phosphoinositide phosphatase (PIP), an apparent functional homologue to phosphatase and tensin homolog (PTEN) in PCa cells. This review is focused on discussing the function of this authentic prostate-specific tumor suppressor and the mechanism behind the loss of cPAcP expression leading to prostate carcinogenesis. We review other phosphatases' roles as TSGs which regulate oncogenic PI3K signaling in PCa and discuss the functional similarity between cPAcP and PTEN in prostate carcinogenesis.

The role of tumor suppressor menin in IL-6 regulation in mouse islet tumor cells

Menin is a gene product of multiple endocrine neoplasia type1 (Men1), an inherited familial cancer syndrome characterized by tumors of endocrine tissues. To gain insight about how menin performs an endocrine cell-specific tumor suppressor function, we investigated the possibility that menin was integrated in a cancer-associated inflammatory pathway in a cell type-specific manner. Here, we showed that the expression of IL-6, a proinflammatory cytokine, was specifically elevated in mouse islet tumor cells upon depletion of menin and Men(-/-) MEF cells, but not in hepatocellular carcinoma cells. Histone H3 lysine (K) 9 methylation, but not H3 K27 or K4 methylation, was involved in menin-dependent IL-6 regulation. Menin occupied the IL-6 promoter and recruited SUV39H1 to induce H3 K9 methylation. Our findings provide a molecular insight that menin-dependent induction of H3 K9 methylation in the cancer-associated interleukin gene might be linked to preventing endocrine-specific tumorigenesis.

Drosophila linker histone H1 coordinates STAT-dependent organization of heterochromatin and suppresses tumorigenesis caused by hyperactive JAK-STAT signaling

Background

Within the nucleus of eukaryotic cells, chromatin is organized into compact, silent regions called heterochromatin and more loosely packaged regions of euchromatin where transcription is more active. Although the existence of heterochromatin has been known for many years, the cellular factors responsible for its formation have only recently been identified. Two key factors involved in heterochromatin formation in Drosophila are the H3 lysine 9 methyltransferase Su(var)3-9 and heterochromatin protein 1 (HP1). The linker histone H1 also plays a major role in heterochromatin formation in Drosophila by interacting with Su(var)3-9 and helping to recruit it to heterochromatin. Drosophila STAT (Signal transducer and activator of transcription) (STAT92E) has also been shown to be involved in the maintenance of heterochromatin, but its relationship to the H1-Su(var)3-9 heterochromatin pathway is unknown. STAT92E is also involved in tumor formation in flies. Hyperactive Janus kinase (JAK)-STAT signaling due to a mutation in Drosophila JAK (Hopscotch) causes hematopoietic tumors

Results

We show here that STAT92E is a second partner of H1 in the regulation of heterochromatin structure. H1 physically interacts with STAT92E and regulates its ectopic localization in the chromatin. Mis-localization of STAT92E due to its hyperphosphorylation or H1 depletion disrupts heterochromatin integrity. The contribution of the H1-STAT pathway to heterochromatin formation is mechanistically distinct from that of H1 and Su(var)3-9. The recruitment of STAT92E to chromatin by H1 also plays an important regulatory role in JAK-STAT induced tumors in flies. Depleting the linker histone H1 in flies carrying the oncogenic hopscotch^Tum-l allele enhances tumorigenesis, and H1 overexpression suppresses tumorigenesis.

Conclusions

Our results suggest the existence of two independent pathways for heterochromatin formation in Drosophila, one involving Su(var)3-9 and HP1 and the other involving STAT92E and HP1. The H1 linker histone directs both pathways through physical interactions with Su(var)3-9 and STAT92E, as well with HP1. The physical interaction of H1 and STAT92E confers a regulatory role on H1 in JAK-STAT signaling. H1 serves as a molecular reservoir for STAT92E in chromatin, enabling H1 to act as a tumor suppressor and oppose an oncogenic mutation in the JAK-STAT signaling pathway.

The emerging role of tumor-suppressive microRNA-218 in targeting glioblastoma stemness

Glioblastoma multiforme (GBM) is by far the most common and most aggressive malignant primary tumor in humans and has poor outcomes despite many advances in treatment using combinations of surgery, radiotherapy and chemotherapy. Recent studies demonstrate that GBM contains a subpopulation of cancer cells with stem cell characteristics, including self-renewal and multipotentiality, and that these cancer stem cells contribute to disease progression. MicroRNAs (miRNAs) are small non-coding regulatory RNA molecules that regulate a variety of cellular processes, including stem cell maintenance. An accumulating body of evidence shows that miR-218 may act as a tumor suppressor by inhibiting glioblastoma invasion, migration, proliferation and stemness through its different targets, indicating the great potential and relevance of miR-218 as a novel class of therapeutic target in glioblastoma.

MicroRNA-340 as a modulator of RAS-RAF-MAPK signaling in melanoma

microRNA (miRNA)-dependent regulation of gene expression is increasingly linked to development and progression of melanoma. In this study we evaluated the functions of miR-340 in human melanoma cells. Here, we show that miR-340 inhibits the tumorigenic phenotype of melanoma cells. We also found that miR-340 regulates RAS-RAF-Mitogen Activated Protein Kinase (MAPK) signaling by modulating the expression of multiple components of this pathway. Given the importance of MAPK signaling in melanoma, these results provide further insight into the pathogenesis of melanoma.

PALB2: the hub of a network of tumor suppressors involved in DNA damage responses

PALB2 was first identified as a partner of BRCA2 that mediates its recruitment to sites of DNA damage. PALB2 was subsequently found as a tumor suppressor gene. Inherited heterozygosity for this gene is associated with an increased risk of cancer of the breast and other sites. Additionally, biallelic mutation of PALB2 is linked to Fanconi anemia, which also has an increased risk of developing malignant disease. Recent work has identified numerous interactions of PALB2, suggesting that it functions in a network of proteins encoded by tumor suppressors. Notably, many of these tumor suppressors are related to the cellular response to DNA damage. The recruitment of PALB2 to DNA double-strand breaks at the head of this network is via a ubiquitin-dependent signaling pathway that involves the RAP80, Abraxas and BRCA1 tumor suppressors. Next, PALB2 interacts with BRCA2, which is a tumor suppressor, and with the RAD51 recombinase. These interactions promote DNA repair by homologous recombination (HR). More recently, PALB2 has been found to bind the RAD51 paralog, RAD51C, as well as the translesion polymerase pol η, both of which are tumor suppressors with functions in HR. Further, an interaction with MRG15, which is related to chromatin regulation, may facilitate DNA repair in damaged chromatin. Finally, PALB2 interacts with KEAP1, a regulator of the response to oxidative stress. The PALB2 network appears to mediate the maintenance of genome stability, may explain the association of many of the corresponding genes with similar spectra of tumors, and could present novel therapeutic opportunities.

p120-catenin in cancer - mechanisms, models and opportunities for intervention

The epithelial adherens junction is an E-cadherin-based complex that controls tissue integrity and is stabilized at the plasma membrane by p120-catenin (p120, also known as CTNND1). Mutational and epigenetic inactivation of E-cadherin has been strongly implicated in the development and progression of cancer. In this setting, p120 translocates to the cytosol where it exerts oncogenic properties through aberrant regulation of Rho GTPases, growth factor receptor signaling and derepression of Kaiso (also known as ZBTB33) target genes. In contrast, indirect inactivation of the adherens junction through conditional knockout of p120 in mice was recently linked to tumor formation, indicating that p120 can also function as a tumor suppressor. Supporting these opposing functions are findings in human cancer, which show that either loss or cytoplasmic localization of p120 is a common feature in the progression of several types of carcinoma. Underlying this dual biological phenomenon might be the context-dependent regulation of Rho GTPases in the cytosol and the derepression of Kaiso target genes. Here, we discuss past and present findings that implicate p120 in the regulation of cancer progression and highlight opportunities for clinical intervention.

NLK, a novel target of miR-199a-3p, functions as a tumor suppressor in colorectal cancer

We previously reported that miR-199a-3p is a newly biomarker for diagnosis and novel prognostic indicator in colorectal cancer. However, the miR-199a-3p regulatory mechanism and its target genes are still unclear. In our present study, we demonstrated miR-199a-3p could directly target 3'-UTR of NLK gene by luciferase reporter assay and western blot analysis. We detected NLK expressions in 92 colorectal cancer cases to evaluate its clinicopathologic characteristics in colorectal cancer. Our results showed that NLK expression was significantly downregulated in cancer tissues than NATs, and NLK low-expression was associated with lymph node metastasis, venous invasion, liver metastasis and the TNM stage (P<0.05). Moreover, Kaplan-Meier analysis showed that low expression of NLK correlated with a shorter overall survival rates of patients with CRC (P<0.05). In vitro, we also found that NLK suppressed the biological behaviors of colorectal cancer cells, including the abilities of cell proliferation, clone formation, wound healing, migration and invasion (P<0.05), while overexpression of NLK increased the apoptotic rate of colorectal cancer cells. All these results suggested that NLK was an identified miR-199a-3p target gene and functioned as a tumor suppressor gene in colorectal cancer. NLK could be a novel direction for developing diagnostic and therapeutic approaches in colorectal cancer.

microRNA-7: a tumor suppressor miRNA with therapeutic potential. Int J Biochem Cell Biol. 2014;54:312-317. [PMID: 24907395 DOI: 10.1016/j.biocel.2014.05.040]

microRNAs are a family of endogenous, short, non-coding RNAs that play critical roles in regulating gene expression for key cellular processes in normal and abnormal physiology. microRNA-7 is a 23 nucleotide miRNA whose expression is tightly regulated and restricted predominantly to the brain, spleen and pancreas. Reduced levels of miR-7 have been linked to the development of cancer and metastasis. As a tumor suppressor, miR-7 functions to co-ordinately downregulate a number of direct (e.g. the epidermal growth factor receptor) and indirect (e.g. phospho-Akt) growth promoting targets to decrease tumor growth in vitro and in vivo. In addition, miR-7 can increase the sensitivity of treatment-resistant cancer cells to therapeutics and inhibit metastasis. These data suggest that replacement of miR-7 ('miRNA replacement therapy') for specific human cancers could represent a new treatment approach. This article is part of a Directed Issue entitled: The Non-coding RNA Revolution.

Micro-RNAs as clinical biomarkers and therapeutic targets in breast cancer: Quo vadis?

Breast cancer (BC) is the most frequent type of non skin cancer among women and a major leading cause of cancer-related deaths in Western countries. It is substantial to discover novel biomarkers with diagnostic, prognostic or predictive usefulness as well as therapeutic value for BC. Micro-RNAs (miRNAs) belong to a novel class of endogenous interfering RNAs that play a crucial role in post transcriptional gene silencing through mRNA targeting and, thus, are involved in many biological processes encompassing apoptosis, cell-cycle control, cell proliferation, DNA repair, immunity, metabolism, stress, aging, etc. MiRNAs exert their action mainly in a tumor suppressive or oncogenic manner. The specific aberrant expression patterns of miRNAs in BC that are detected with the use of high-throughput technologies reflect their key role in cancer initiation, progression, migration, invasion and metastasis. The detection of circulating extracellular miRNAs in plasma of BC patients may provide novel, non-invasive biomarkers in favor of BC diagnosis and prognosis and, at the same time, accumulating evidence has underscored the possible contribution of miRNAs as valuable biomarkers to predict response to chemotherapy or radiotherapy. Data from in vitro and in vivo studies on BC have revealed promising therapeutic approaches via miRNA delivery and miRNA inhibition. The purpose of this review is to explore the ontological role of miRNAs in BC etiopathogenesis as well as to highlight their potential, not only as non-invasive circulating biomarkers with diagnostic and prognostic significance, but also as treatment response predictors and therapeutic targets aiding BC management.