Inhibition of STAT5 induces G1 cell cycle arrest and reduces tumor cell invasion in human colorectal cancer cells

MYCN Amplifications and Metabolic Rewiring in Neuroblastoma

Cancer is a disease caused by (epi)genomic and gene expression abnormalities and characterized by metabolic phenotypes that are substantially different from the normal phenotypes of the tissues of origin. Metabolic reprogramming is one of the key features of tumors, including those established in the human nervous system. In this work, we emphasize a well-known cancerous genomic alteration: the amplification of MYCN and its downstream effects in neuroblastoma phenotype evolution. Herein, we extend our previous computational biology investigations by conducting an integrative workflow applied to published genomics datasets and comprehensively assess the impact of MYCN amplification in the upregulation of metabolism-related transcription factor (TF)-encoding genes in neuroblastoma cells. The results obtained first emphasized overexpressed TFs, and subsequently those committed in metabolic cellular processes, as validated by gene ontology analyses (GOs) and literature curation. Several genes encoding for those TFs were investigated at the mechanistic and regulatory levels by conducting further omics-based computational biology assessments applied on published ChIP-seq datasets retrieved from MYCN-amplified- and MYCN-enforced-overexpression within in vivo systems of study. Hence, we approached the mechanistic interrelationship between amplified MYCN and overexpression of metabolism-related TFs in neuroblastoma and showed that many are direct targets of MYCN in an amplification-inducible fashion. These results illuminate how MYCN executes its regulatory underpinnings on metabolic processes in neuroblastoma.

Lung cancer treatment potential and limits associated with the STAT family of transcription factors

Lung cancer is one of the mortal cancers and the leading cause of cancer-related mortality, with a cancer survival rate of fewer than 5% in developing nations. This low survival rate can be linked to things like late-stage detection, quick postoperative recurrences in patients receiving therapy, and chemoresistance developing against various lung cancer treatments. Signal transducer and activator of transcription (STAT) family of transcription factors are involved in lung cancer cell proliferation, metastasis, immunological control, and treatment resistance. By interacting with specific DNA sequences, STAT proteins trigger the production of particular genes, which in turn result in adaptive and incredibly specific biological responses. In the human genome, seven STAT proteins have been discovered (STAT1 to STAT6, including STAT5a and STAT5b). Many external signaling proteins can activate unphosphorylated STATs (uSTATs), which are found inactively in the cytoplasm. When STAT proteins are activated, they can increase the transcription of several target genes, which leads to unchecked cellular proliferation, anti-apoptotic reactions, and angiogenesis. The effects of STAT transcription factors on lung cancer are variable; some are either pro- or anti-tumorigenic, while others maintain dual, context-dependent activities. Here, we give a succinct summary of the various functions that each member of the STAT family plays in lung cancer and go into more detail about the advantages and disadvantages of pharmacologically targeting STAT proteins and their upstream activators in the context of lung cancer treatment.

The complex network of transcription factors, immune checkpoint inhibitors and stemness features in colorectal cancer: A recent update

Cancer immunity is regulated by several mechanisms that include co-stimulatory and/or co-inhibitory molecules known as immune checkpoints expressed by the immune cells. In colorectal cancer (CRC), CTLA-4, LAG3, TIM-3 and PD-1 are the major co-inhibitory checkpoints involved in tumor development and progression. On the other hand, the deregulation of transcription factors and cancer stem cells activity plays a major role in the development of drug resistance and in the spread of metastatic disease in CRC. In this review, we describe how the modulation of such transcription factors affects the response of CRC to therapies. We also focus on the role of cancer stem cells in tumor metastasis and chemoresistance and discuss both preclinical and clinical approaches for targeting stem cells to prevent their tumorigenic effect. Finally, we provide an update on the clinical applications of immune checkpoint inhibitors in CRC and discuss the regulatory effects of transcription factors on the expression of the immune inhibitory checkpoints with specific focus on the PD-1 and PD-L1 molecules.

JAK/STAT pathway: Extracellular signals, diseases, immunity, and therapeutic regimens

Janus kinase/signal transduction and transcription activation (JAK/STAT) pathways were originally thought to be intracellular signaling pathways that mediate cytokine signals in mammals. Existing studies show that the JAK/STAT pathway regulates the downstream signaling of numerous membrane proteins such as such as G-protein-associated receptors, integrins and so on. Mounting evidence shows that the JAK/STAT pathways play an important role in human disease pathology and pharmacological mechanism. The JAK/STAT pathways are related to aspects of all aspects of the immune system function, such as fighting infection, maintaining immune tolerance, strengthening barrier function, and cancer prevention, which are all important factors involved in immune response. In addition, the JAK/STAT pathways play an important role in extracellular mechanistic signaling and might be an important mediator of mechanistic signals that influence disease progression, immune environment. Therefore, it is important to understand the mechanism of the JAK/STAT pathways, which provides ideas for us to design more drugs targeting diseases based on the JAK/STAT pathway. In this review, we discuss the role of the JAK/STAT pathway in mechanistic signaling, disease progression, immune environment, and therapeutic targets.

STK11 Prevents Invasion through Signal Transducer and Activator of Transcription 3/5 and FAK Repression in Cutaneous Melanoma

The STK11/LKB1 is a tumor suppressor involved in metabolism and cell motility. In BRAFV600E melanoma, STK11 is inactivated by extracellular signal‒regulated kinase and RSK, preventing it from binding and activating adenosine monophosphate-activated protein kinase and promoting melanoma cell proliferation. Although STK11 mutations occur in 5‒10% of cutaneous melanoma, few functional studies have been performed. By knocking out STK11 with CRISPR/Cas9 in two human BRAF-mutant melanoma cell lines, we found that STK11 loss reduced the sensitivity to a BRAF inhibitor. More strikingly, STK11 loss led to an increased invasive phenotype in both three-dimensional spheroids and in vivo zebrafish xenograft models. STK11 overexpression consistently reversed the invasive phenotype. Interestingly, STK11 knockout increased invasion also in an NRAS-mutant melanoma cell line. Furthermore, although STK11 was expressed in primary human melanoma tumors, its expression significantly decreased in melanoma metastases, especially in brain metastases. In the STK11-knockout cells, we observed increased activating phosphorylation of signal transducer and activator of transcription 3/5 and FAK. Using inhibitors of signal transducer and activator of transcription 3/5 and FAK, we reversed the invasive phenotype in both BRAF- and NRAS-mutated cells. Our findings confirm an increased invasive phenotype on STK11 inactivation in BRAF- and NRAS-mutant cutaneous melanoma that can be targeted by signal transducer and activator of transcription 3/5 and FAK inhibition.

Transcription factors in colorectal cancer: molecular mechanism and therapeutic implications

Colorectal cancer (CRC) is a major cause of cancer mortality worldwide, however, the molecular mechanisms underlying the pathogenesis of CRC remain largely unclear. Recent studies have revealed crucial roles of transcription factors in CRC development. Transcription factors essential for the regulation of gene expression by interacting with transcription corepressor/enhancer complexes and they orchestrate downstream signal transduction. Deregulation of transcription factors is a frequent occurrence in CRC, and the accompanying drastic changes in gene expression profiles play fundamental roles in multistep process of tumorigenesis, from cellular transformation, disease progression to metastatic disease. Herein, we summarized current and emerging key transcription factors that participate in CRC tumorigenesis, and highlighted their oncogenic or tumor suppressive functions. Moreover, we presented critical transcription factors of CRC, emphasized the major molecular mechanisms underlying their effect on signal cascades associated with tumorigenesis, and summarized of their potential as molecular biomarkers for CRC prognosis therapeutic response, as well as drug targets for CRC treatment. A better understanding of transcription factors involved in the development of CRC will provide new insights into the pathological mechanisms and reveal novel prognostic biomarkers and therapeutic strategies for CRC.

Transcriptome analysis reveals modulation of the STAT family in PEDV-infected IPEC-J2 cells

BACKGROUND

Porcine epidemic diarrhea virus (PEDV) is a causative agent of serious viral enteric disease in suckling pigs. Such diseases cause considerable economic losses in the global swine industry. Enhancing our knowledge of PEDV-induced transcriptomic responses in host cells is imperative to understanding the molecular mechanisms involved in the immune response. Here, we analyzed the transcriptomic profile of intestinal porcine epithelial cell line J2 (IPEC-J2) after infection with a classical strain of PEDV to explore the host response.

RESULTS

In total, 854 genes were significantly differentially expressed after PEDV infection, including 716 upregulated and 138 downregulated genes. Functional annotation analysis revealed that the differentially expressed genes were mainly enriched in the influenza A, TNF signaling, inflammatory response, cytokine receptor interaction, and other immune-related pathways. Next, the putative promoter regions of the 854 differentially expressed genes were examined for the presence of transcription factor binding sites using the MEME tool. As a result, 504 sequences (59.02%) were identified as possessing at least one binding site of signal transducer and activator of transcription (STAT), and five STAT transcription factors were significantly induced by PEDV infection. Furthermore, we revealed the regulatory network induced by STAT members in the process of PEDV infection.

CONCLUSION

Our transcriptomic analysis described the host genetic response to PEDV infection in detail in IPEC-J2 cells, and suggested that STAT transcription factors may serve as key regulators in the response to PEDV infection. These results further our understanding of the pathogenesis of PEDV.

Role of the JAK/STAT Pathway in Cervical Cancer: Its Relationship with HPV E6/E7 Oncoproteins

The janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathway is associated with the regulation of essential cellular mechanisms, such as proliferation, invasion, survival, inflammation, and immunity. Aberrant JAK/STAT signaling contributes to cancer progression and metastatic development. STAT proteins play an essential role in the development of cervical cancer, and the inhibition of the JAK/STAT pathway may be essential for enhancing tumor cell death. Persistent activation of different STATs is present in a variety of cancers, including cervical cancer, and their overactivation may be associated with a poor prognosis and poor overall survival. The oncoproteins E6 and E7 play a critical role in the progression of cervical cancer and may mediate the activation of the JAK/STAT pathway. Inhibition of STAT proteins appears to show promise for establishing new targets in cancer treatment. The present review summarizes the knowledge about the participation of the different components of the JAK/STAT pathway and the participation of the human papillomavirus (HPV) associated with the process of cellular malignancy.

Involvement of STAT5 in Oncogenesis

Signal transducer and activator of transcription (STAT) proteins, and in particular STAT3, have been established as heavily implicated in cancer. Recently, the involvement of STAT5 signalling in the pathology of cancer has been shown to be of increasing importance. STAT5 plays a crucial role in the development of the mammary gland and the homeostasis of the immune system. However, in various cancers, aberrant STAT5 signalling promotes the expression of target genes, such as cyclin D, Bcl-2 and MMP-2, that result in increased cell proliferation, survival and metastasis. To target constitutive STAT5 signalling in cancers, there are several STAT5 inhibitors that can prevent STAT5 phosphorylation, dimerisation, or its transcriptional activity. Tyrosine kinase inhibitors (TKIs) that target molecules upstream of STAT5 could also be utilised. Consequently, since STAT5 contributes to tumour aggressiveness and cancer progression, inhibiting STAT5 constitutive activation in cancers that rely on its signalling makes for a promising targeted treatment option.

Essential role of STAT5a in DCIS formation and invasion following estrogen treatment

Ductal carcinoma in situ (DCIS) is one of the earliest stages of breast cancer (BCa). The mechanisms by which DCIS lesions progress to an invasive state while others remain indolent are yet to be fully characterized and both diagnosis and treatment of this pre-invasive disease could benefit from better understanding the pathways involved. While a decreased expression of Caveolin-1 (Cav-1) in the tumor microenvironment of patients with DCIS breast cancer was linked to progression to invasive breast cancer (IBC), the downstream effector(s) contributing to this process remain elusive. The current report shows elevated expression of Signal Transducer and Activator of Transcription 5a (STAT5a) within the DCIS-like lesions in Cav-1 KO mice following estrogen treatment and inhibition of STAT5a expression prevented the formation of these mammary lesions. In addition, STAT5a overexpression in a human DCIS cell line (MCF10DCIS.com) promoted their invasion, a process accelerated by estrogen treatment and associated with increased levels of the matrix metalloproteinase-9 (MMP-9) precursor. In sum, our results demonstrate a novel regulatory axis (Cav-1♦STAT5a♦MMP-9) in DCIS that is fully activated by the presence of estrogen. Our sudies suggest to further study phosphorylated STAT5a (Y694) as a potential biomarker to guide and predict outcome of DCIS patient population.

STAT signaling in polycystic kidney disease

The most common form of polycystic kidney disease (PKD) in humans is caused by mutations in the PKD1 gene coding for polycystin1 (PC1). Among the many identified or proposed functions of PC1 is its ability to regulate the activity of transcription factors of the STAT family. Most STAT proteins that have been investigated were found to be aberrantly activated in kidneys in PKD, and some have been shown to be drivers of disease progression. In this review, we focus on the role of signal transducer and activator of transcription (STAT) signaling pathways in various renal cell types in healthy kidneys as compared to polycystic kidneys, on the mechanisms of STAT regulation by PC1 and other factors, and on the possibility to target STAT signaling for PKD therapy.

Curcumin inhibits CT26 cells metastasis by decreasing heparanase expression

This study tested the hypothesis that heparanase (HPSE) is related to tumor metastasis and curcumin (CCM) inhibits tumor metastasis by down-regulating HPSE expression. MTT, Transwell assays, and RT-PCR were used to study the effects of CCM on the migration and invasion of CT26 cells and the expression of HPSE. CT26 cells were transfected with lentivirus to establish HPSE-overexpressing cells (OE) and corresponding negative control cells (NC). Signal pathways involved in down-regulating the expression of HPSE and inhibiting the migration and invasion of CT26 cells by CCM were screened by the liquid crystal chip. HPSE promoted CT26 cells migration and invasion, and CCM inhibited the proliferation and metastasis of CT26 cells. The results of RT-PCR indicated that CCM down-regulated HPSE expression. Liquid phase microarray showed that CCM inhibited the phosphorylation of P38 and STAT5 in CT26 cells and NC cells. In contrast, the inhibitory function of CCM was markedly enhanced when HPSE was overexpressed (P < 0.05). In short, HPSE is closely related to metastasis of colon cancer cells. CCM inhibits colon cancer cell migration and invasion by inhibiting HPSE expression, which may be related to P38 MAPK and JAK/STAT5 signal pathways.

Silencing Stat3 inhibits viability and induces apoptosis in BGC-823 human gastric cancer cell line

Gastric cancer (GC) is characterized by infrequent early diagnosis, poor prognosis and high mortality. Signal transducer and activator of transcription 3 (Stat3) and signal transducer and activator of transcription 5b (Stat5b) play multiple roles in the development and progression of many human cancers. We investigated the effects of silencing Stat3 and Stat5b on the viability and apoptosis of the human gastric cancer cell line, BGC-823. We found that Stat3 and Stat5b were expressed in both the nucleus and cytoplasm of BGC-823 cells. Silencing of Stat3 caused significantly decreased viability and increased apoptosis, as well as attenuated B-cell lymphoma-2 (Bcl-2) expression in BGC-823 cells. Silencing of Stat5b, however, had no significant effect on these events. Stat3, but not Stat5b, plays an important role in the viability and apoptosis of human gastric cancer cell line, BGC-823, which suggests that Stat3 is a potential target for gastric cancer therapy.

The Effect of 4'-hydroxy-3,4,5-trimetoxystilbene, the Metabolite of Resveratrol Analogue DMU-212, on Growth, Cell Cycle and Apoptosis in DLD-1 and LOVO Colon Cancer Cell Lines

Resveratrol is a phytoalexin that naturally occurs in grapes, blueberries, cranberries, peanuts and many other plants. Although resveratrol inhibits carcinogenesis in all three stages, its clinical application is restricted due to poor pharmacokinetics. The methylated analogues of resveratrol have been found to have higher bioavailability and cytotoxic activity than that of the prototupe compound. Among the various methoxy derivatives of resveratrol, 3,4,5,4′-tetrametoxystilbene (DMU-212) is suggested to be one of the strongest activators of cytotoxicity and apoptosis. DMU-212 has been shown to exert anti-tumor activity in DLD-1 and LOVO colon cancer cells. Since colorectal cancer is the third most common cause of cancer-related deaths worldwide, the development of new anticancer agents is nowadays of high significance. The aim of the present study was to assess the anticancer activity of 4′-hydroxy-3,4,5-trimetoxystilbene (DMU-281), the metabolite of DMU-212, in DLD-1 and LOVO cell lines. We showed for the first time the cytotoxic activity of DMU-281 triggered via cell cycle arrest at G2/M phase and apoptosis induction accompanied by the activation of caspases-9, -8, -3/7. Furthermore, DMU-281 has been found to change the expression pattern of genes and proteins related to intrinsic as well as extrinsic apoptosis. Since the activation of these pathways of apoptosis is still the most desired strategy in anticancer research, DMU-281 seems to provide a promising approach to the treatment of colon cancer.

Energy Metabolism in Cancer: The Roles of STAT3 and STAT5 in the Regulation of Metabolism-Related Genes

A central characteristic of many types of cancer is altered energy metabolism processes such as enhanced glucose uptake and glycolysis and decreased oxidative metabolism. The regulation of energy metabolism is an elaborate process involving regulatory proteins such as HIF (pro-metastatic protein), which reduces oxidative metabolism, and some other proteins such as tumour suppressors that promote oxidative phosphorylation. In recent years, it has been demonstrated that signal transducer and activator of transcription (STAT) proteins play a pivotal role in metabolism regulation. STAT3 and STAT5 are essential regulators of cytokine- or growth factor-induced cell survival and proliferation, as well as the crosstalk between STAT signalling and oxidative metabolism. Several reports suggest that the constitutive activation of STAT proteins promotes glycolysis through the transcriptional activation of hypoxia-inducible factors and therefore, the alteration of mitochondrial activity. It seems that STAT proteins function as an integrative centre for different growth and survival signals for energy and respiratory metabolism. This review summarises the functions of STAT3 and STAT5 in the regulation of some metabolism-related genes and the importance of oxygen in the tumour microenvironment to regulate cell metabolism, particularly in the metabolic pathways that are involved in energy production in cancer cells.

Balancing STAT Activity as a Therapeutic Strategy

Driven by dysregulated IL-6 family member cytokine signaling in the tumor microenvironment (TME), aberrant signal transducer and activator of transcription (STAT3) and (STAT5) activation have been identified as key contributors to tumorigenesis. Following transformation, persistent STAT3 activation drives the emergence of mesenchymal/cancer-stem cell (CSC) properties, important determinants of metastatic potential and therapy failure. Moreover, STAT3 signaling within tumor-associated macrophages and neutrophils drives secretion of factors that facilitate metastasis and suppress immune cell function. Persistent STAT5 activation is responsible for cancer cell maintenance through suppression of apoptosis and tumor suppressor signaling. Furthermore, STAT5-mediated CD4+/CD25+ regulatory T cells (T_regs) have been implicated in suppression of immunosurveillance. We discuss these roles for STAT3 and STAT5, and weigh the attractiveness of different modes of targeting each cancer therapy. Moreover, we discuss how anti-tumorigenic STATs, including STAT1 and STAT2, may be leveraged to suppress the pro-tumorigenic functions of STAT3/STAT5 signaling.

The Signal Transducer and Activator of Transcription 5B (STAT5B) Gene Promotes Proliferation and Drug Resistance of Human Mantle Cell Lymphoma Cells by Activating the Akt Signaling Pathway

Background

Mantle cell lymphoma (MCL) is a high-grade B-cell lymphoma with poor prognosis. Fludarabine is used alone or in combination for relapsed and advanced-stage MCL. The expression of the signal transducer and activator of transcription 5B (STAT5B) gene is associated with tumorigenesis in solid tumors, but its role in MCL remains unknown. The aims of this study were to investigate the role of STAT5B in GRANTA-519 human mantle cell lymphoma cells and drug resistance.

Material/Methods

GRANTA-519 human mantle cell lymphoma cells were cultured with and without 10 μM fludarabine dephosphorylated 9-β-D-arabinofuranosyl-2-fluoroadenine, (2-F-araA) or 10 μM 4-hydroperoxycyclophosphamide (4-HC). The MTT assay assessed cell proliferation. Flow cytometry was used to investigate the cell cycle in MCL cells treated with the specific inhibitor of the Akt pathway, LY294002, and assessed cell cycle and cell apoptosis. Western blot was used to detect the expression levels of p-Akt/Akt and STAT5B/p-STAT5B. The gene expression profiles of lymph node (LN)-derived MCL cells were compared with peripheral blood (PB)-derived lymphocytes using bioinformatics and hierarchical cluster analysis. Quantitative reverse transcription polymerase chain reaction (RT-qPCR) was performed to determine the expression of the marker of proliferation Ki-67 (MKI67) gene.

Results

STAT5B was significantly upregulated in LN-derived MCL cells compared with PB lymphocytes. Increased expression of STAT5B was associated with increased MCL cell proliferation and reduced cell apoptosis and was associated with drug resistance and activation of Akt.

Conclusions

STAT5B promoted cell proliferation and drug resistance in human MCL cells by activating the Akt signaling pathway.

PEST-containing nuclear protein regulates cell proliferation, migration, and invasion in lung adenocarcinoma

Lung cancer is the leading cause of cancer-related mortality worldwide. PEST-containing nuclear protein (PCNP) has been found in the nucleus of cancer cells. Whether PCNP plays a role in the growth of lung adenocarcinoma is still unknown. In the present study, the results indicated that the level of PCNP in lung adenocarcinoma tissue was significantly higher than that in corresponding adjacent non-tumor tissue. Over-expression of PCNP promoted the proliferation, migration, and invasion of lung adenocarcinoma cells, while down-regulation of PCNP exhibited opposite effects. PCNP over-expression decreased apoptosis through up-regulating the expression levels of phospho (p)-signal transducers and activators of transcription (STAT) 3 and p-STAT5 in lung adenocarcinoma cells, whereas PCNP knockdown showed opposite trends. PCNP overexpression enhanced autophagy by increasing the expression levels of p-phosphatidylinositol 3-kinase (PI3K), p-Akt, and p-mammalian target of rapamycin (mTOR) in lung adenocarcinoma cells, however an opposite trend was observed in the sh-PCNP group. In addition, overexpression of PCNP showed the tumor-promoting effect on xenografted lung adenocarcinoma, while PCNP knockdown reduced the growth of lung adenocarcinoma via regulating angiogenesis. Our study elucidates that PCNP can regulate the procession of human lung adenocarcinoma cells via STAT3/5 and PI3K/Akt/mTOR signaling pathways. PCNP may be considered as a promising biomarker for the diagnosis and prognosis in patients with lung adenocarcinoma. Furthermore, PCNP can be a novel therapeutic target and potent PCNP inhibitors can be designed and developed in the treatment of lung adenocarcinoma.

Signal Transducer and Activator of Transcription (STATs) Proteins in Cancer and Inflammation: Functions and Therapeutic Implication

Signal Transducer and Activator of Transcription (STAT) pathway is connected upstream with Janus kinases (JAK) family protein and capable of integrating inputs from different signaling pathways. Each family member plays unique functions in signal transduction and crucial in mediating cellular responses to different kind of cytokines. STAT family members notably STAT3 and STAT5 have been involved in cancer progression whereas STAT1 plays opposite role by suppressing tumor growth. Persistent STAT3/5 activation is known to promote chronic inflammation, which increases susceptibility of healthy cells to carcinogenesis. Here, we review the role of STATs in cancers and inflammation while discussing current therapeutic implications in different cancers and test models, especially the delivery of STAT3/5 targeting siRNA using nanoparticulate delivery system.

Drosophila Jak/STAT Signaling: Regulation and Relevance in Human Cancer and Metastasis

Over the past three-decades, Janus kinase (Jak) and signal transducer and activator of transcription (STAT) signaling has emerged as a paradigm to understand the involvement of signal transduction in development and disease pathology. At the molecular level, cytokines and interleukins steer Jak/STAT signaling to transcriptional regulation of target genes, which are involved in cell differentiation, migration, and proliferation. Jak/STAT signaling is involved in various types of blood cell disorders and cancers in humans, and its activation is associated with carcinomas that are more invasive or likely to become metastatic. Despite immense information regarding Jak/STAT regulation, the signaling network has numerous missing links, which is slowing the progress towards developing drug therapies. In mammals, many components act in this cascade, with substantial cross-talk with other signaling pathways. In Drosophila, there are fewer pathway components, which has enabled significant discoveries regarding well-conserved regulatory mechanisms. Work across species illustrates the relevance of these regulators in humans. In this review, we showcase fundamental Jak/STAT regulation mechanisms in blood cells, stem cells, and cell motility. We examine the functional relevance of key conserved regulators from Drosophila to human cancer stem cells and metastasis. Finally, we spotlight less characterized regulators of Drosophila Jak/STAT signaling, which stand as promising candidates to be investigated in cancer biology. These comparisons illustrate the value of using Drosophila as a model for uncovering the roles of Jak/STAT signaling and the molecular means by which the pathway is controlled.

The Impact of Coffee and Its Selected Bioactive Compounds on the Development and Progression of Colorectal Cancer In Vivo and In Vitro

Coffee is one of the most popular beverages worldwide. Coffee contains bioactive compounds that affect the human body such as caffeine, caffeic acid, chlorogenic acids, trigonelline, diterpenes, and melanoidins. Some of them have demonstrated potential anticarcinogenic effects in animal models and in human cell cultures, and may play a protective role against colorectal cancer. Colorectal cancer (CRC) is the third leading cause of cancer-related mortality in the USA and other countries. Dietary patterns, as well as the consumption of beverages, may reduce the risk of CRC incidence. In this review, we focus on published epidemiological studies concerning the association of coffee consumption and the risk of development of colorectal cancer, and provide a description of selected biologically active compounds in coffee that have been investigated as potential cancer-combating compounds: Caffeine, caffeic acid (CA), chlorogenic acids (CGAs), and kahweol in relation to colorectal cancer progression in in vitro settings. We review the impact of these substances on proliferation, viability, invasiveness, and metastasis, as well as on susceptibility to chemo- and radiotherapy of colorectal cancer cell lines cultured in vitro.

Reactive Oxygen Species and Oncoprotein Signaling-A Dangerous Liaison

SIGNIFICANCE

There is evidence to implicate reactive oxygen species (ROS) in tumorigenesis and its progression. This has been associated with the interplay between ROS and oncoproteins, resulting in enhanced cellular proliferation and survival. Recent Advances: To date, studies have investigated specific contributions of the crosstalk between ROS and signaling networks in cancer initiation and progression. These investigations have challenged the established dogma of ROS as agents of cell death by demonstrating a secondary function that fuels cell proliferation and survival. Studies have thus identified (onco)proteins (Bcl-2, STAT3/5, RAS, Rac1, and Myc) in manipulating ROS level as well as exploiting an altered redox environment to create a milieu conducive for cancer formation and progression.

CRITICAL ISSUES

Despite these advances, drug resistance and its association with an altered redox metabolism continue to pose a challenge at the mechanistic and clinical levels. Therefore, identifying specific signatures, altered protein expressions, and modifications as well as protein-protein interplay/function could not only enhance our understanding of the redox networks during cancer initiation and progression but will also provide novel targets for designing specific therapeutic strategies.

FUTURE DIRECTIONS

Not only a heightened realization is required to unravel various gene/protein networks associated with cancer formation and progression, particularly from the redox standpoint, but there is also a need for developing more sensitive tools for assessing cancer redox metabolism in clinical settings. This review attempts to summarize our current knowledge of the crosstalk between oncoproteins and ROS in promoting cancer cell survival and proliferation and treatment strategies employed against these oncoproteins. Antioxid. Redox Signal.

A 65‑gene signature for prognostic prediction in colon adenocarcinoma

The aim of the present study was to examine the molecular factors associated with the prognosis of colon cancer. Gene expression datasets were downloaded from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus databases to screen differentially expressed genes (DEGs) between colon cancer samples and normal samples. Survival‑related genes were selected from the DEGs using the Cox regression method. A co‑expression network of survival‑related genes was then constructed, and functional clusters were extracted from this network. The significantly enriched functions and pathways of the genes in the network were identified. Using Bayesian discriminant analysis, a prognostic prediction system was established to distinguish the positive from negative prognostic samples. The discrimination efficacy of the system was validated in the GSE17538 dataset using Kaplan‑Meier survival analysis. A total of 636 and 1,892 DEGs between the colon cancer samples and normal samples were screened from the TCGA and GSE44861 dataset, respectively. There were 155 survival‑related genes selected. The co‑expression network of survival‑related genes included 138 genes, 534 lines (connections) and five functional clusters, including the signaling pathway, cellular response to cAMP, and immune system process functional clusters. The molecular function, cellular components and biological processes were the significantly enriched functions. The peroxisome proliferator‑activated receptor signaling pathway, Wnt signaling pathway, B cell receptor signaling pathway, and cytokine‑cytokine receptor interactions were the significant pathways. A prognostic prediction system based on a 65‑gene signature was established using this co‑expression network. Its discriminatory effect was validated in the TCGA dataset (P=3.56e‑12) and the GSE17538 dataset (P=1.67e‑6). The 65‑gene signature included kallikrein‑related peptidase 6 (KLK6), collagen type XI α1 (COL11A1), cartilage oligomeric matrix protein, wingless‑type MMTV integration site family member 2 (WNT2) and keratin 6B. In conclusion, a 65‑gene signature was screened in the present study, which showed a prognostic prediction effect in colon adenocarcinoma. KLK6, COL11A1, and WNT2 may be suitable prognostic predictors for colon adenocarcinoma.

Identification of a novel fusion gene HMGA2-EGFR in glioblastoma

Glioblastoma is one of the most malignant forms of cancer, for which no effective targeted therapy has been found. Although The Cancer Genome Atlas has provided a list of fusion genes in glioblastoma, their role in progression of glioblastoma remains largely unknown. To search for novel fusion genes, we obtained RNA-seq data from TGS-01 human glioma-initiating cells, and identified a novel fusion gene (HMGA2-EGFR), encoding a protein comprising the N-terminal region of the high-mobility group AT-hook protein 2 (HMGA2) fused to the C-terminal region of epidermal growth factor receptor (EGFR), which retained the transmembrane and kinase domains of the EGFR. This fusion gene product showed transforming potential and a high tumor-forming capacity in cell culture and in vivo. Mechanistically, HMGA2-EGFR constitutively induced a higher level of phosphorylated STAT5B than EGFRvIII, an in-frame exon deletion product of the EGFR gene that is commonly found in primary glioblastoma. Forced expression of HMGA2-EGFR enhanced orthotopic tumor formation of the U87MG human glioma cell line. Furthermore, the EGFR kinase inhibitor erlotinib blocked sphere formation of TGS-01 cells in culture and inhibited tumor formation in vivo. These findings suggest that, in addition to gene amplification and in-frame exon deletion, EGFR signaling can also be activated by gene fusion, suggesting a possible avenue for treatment of glioblastoma.

Cell lineage determinants as regulators of breast cancer metastasis

The mammary epithelium is organized in a hierarchy of mammary stem cells (MaSCs), progenitors, and differentiated cells. The development and homeostasis of mammary gland are tightly controlled by a complex network of cell lineage regulators. These determinants of cellular hierarchy are frequently deregulated in breast tumor cells and closely associated with cancer progression and metastasis. They also contribute to the diversity of breast cancer subtypes and their distinct metastatic patterns. Cell fate regulators that normally promote stem/progenitor activities can serve as drivers for epithelial-mesenchymal transition and metastasis whereas regulators that promote terminal differentiation generally suppress metastasis. In this review, we discuss how some of the key factors function in normal mammary lineage determination and how these processes are hijacked by tumor cells to enhance metastasis. Understanding the molecular connections between normal development and cancer metastasis will enable the development of more specific and effective therapeutic approaches targeting metastatic tumor cells.

Pleiotropic Effects of IL-2 on Cancer: Its Role in Cervical Cancer

IL-2 receptor (IL-2R) signalling is critical for normal lymphocyte proliferation, but its role in cervical cancer is not fully understood. The receptor is composed of three chains: IL-2α, IL-2β, and IL-2γ. Intracellular signalling is initiated by ligand-induced heterodimerization of the IL-2β and IL-2γ chains, resulting in the activation of multiple intracellular kinases. Recently, IL-2R was shown to be expressed on nonhaematopoietic cells, especially on several types of tumour cells. However, the function of this receptor on malignant cells has not been clearly defined. The expression of IL-2R and the production of IL-2 in cervical cancer cells have been documented as well as expression of molecules of the JAK-STAT pathway. In the current review we have highlighted the differences in the responses of molecules downstream from the IL-2R in normal lymphocytes and tumour cells that could explain the presence of tumour cells in an environment in which cytotoxic lymphocytes also exist and compete and also the effect of different concentrations of IL-2 that could activate effector cells of the immune system cells, which favour the elimination of tumour cells, or concentrations that may promote a regulatory microenvironment in which tumour cells can easily grow.

Integrating Immunologic Signaling Networks: The JAK/STAT Pathway in Colitis and Colitis-Associated Cancer

Cytokines are believed to be crucial mediators of chronic intestinal inflammation in inflammatory bowel diseases (IBD) such as Crohn's disease (CD) and ulcerative colitis (UC). Many of these cytokines trigger cellular effects and functions through signaling via janus kinase (JAK) and signal transducer and activator of transcription (STAT) molecules. In this way, JAK/STAT signaling controls important events like cell differentiation, secretion of cytokines or proliferation and apoptosis in IBD in both adaptive and innate immune cells. Moreover, JAK/STAT signaling, especially via the IL-6/STAT3 axis, is believed to be involved in the transition of inflammatory lesions to tumors leading to colitis-associated cancer (CAC). In this review, we will introduce the main cellular players and cytokines that contribute to pathogenesis of IBD by JAK/STAT signaling, and will highlight the integrative function that JAK/STATs exert in this context as well as their divergent role in different cells and processes. Moreover, we will explain current concepts of the implication of JAK/STAT signaling in CAC and finally discuss present and future therapies for IBD that interfere with JAK/STAT signaling.

The combination of methylsulfonylmethane and tamoxifen inhibits the Jak2/STAT5b pathway and synergistically inhibits tumor growth and metastasis in ER-positive breast cancer xenografts

BACKGROUND

Combination therapy, which reduces the dosage intensity of the individual drugs while increasing their efficacy, is not a novel approach for the treatment of cancer. Methylsulfonylmethane (MSM) is an organic sulfur compound shown to act against tumor cells. Tamoxifen is a commercially available therapeutic agent for breast malignancies.

METHODS

In the current study, we analyzed the combinatorial effect of MSM and tamoxifen on the suppression of ER-positive breast cancer xenograft growth and metastasis. Additionally, we also validated the molecular targets by which the drug combination regulated tumor growth and metastasis.

RESULTS

We observed that the combination of MSM and tamoxifen regulated cell viability and migration in vitro. The intragastric administration of MSM and subcutaneous implantation of tamoxifen tablets led to tumor growth suppression and inhibition of the Janus kinase 2 (Jak2)/signal transducer and activator of transcription 5b (STAT5b) pathway. Our study also assessed the regulation of signaling molecules implicated in the growth, progression, differentiation, and migration of cancer cells, such as Jak2, STAT5b, insulin-like growth factor-1Rβ, and their phosphorylation status.

CONCLUSIONS

Study results indicated that this combination therapy inhibited tumor growth and metastasis. Therefore, this drug combination may have a synergistic and powerful anticancer effect against breast cancer.

CD24 mediates gastric carcinogenesis and promotes gastric cancer progression via STAT3 activation

The development of gastric cancer (GC) is a complex multistep process, including numerous genetic and epigenetic changes. CD24 is associated with enhanced invasiveness of GC and a poor prognosis. However, the mechanism by which CD24 induces GC progression remains poorly characterized. Here, we found that the expression of CD24 gradually increased in samples of normal gastric mucosa, non-atrophic chronic gastritis, chronic atrophic gastritis (CAG), CAG with intestinal metaplasia, dysplasia and GC. Moreover, the knockdown of CD24 induced significant levels of apoptosis in GC cells via the mitochondrial apoptotic pathway. CD24 may also promote cellular invasion and regulate the expression of E-cadherin, fibronectin and vitamin D receptor in GC cells. The activation of signal transducer and activator of transcription 3 (STAT3) may mediate CD24-induced GC survival and invasion in vitro. Furthermore, CD24-induced GC progression and STAT3 activation could also be detected in vivo and in clinical GC tissues samples. Taken together, our results indicate that CD24 mediates gastric carcinogenesis and may promote GC progression by suppressing apoptosis and promoting invasion, with the activation of STAT3 playing a critical role.

Functions and regulation of MUC13 mucin in colon cancer cells

BACKGROUND

MUC13 is overexpressed and aberrantly localized in colon cancer tissue; however, the specific functions and regulation of MUC13 expression are unknown.

METHODS

Stable cell lines with either overexpressed or suppressed MUC13 levels were analyzed to determine cell growth, colony formation, cell migration, and cell invasion assays. The molecular mechanisms involved in MUC13 regulation were elucidated via chromatin immunoprecipitation (ChIP) and analysis of interleukin 6 (IL6) treatments. Colon cancer tissues were analyzed by immunohistochemistry (IHC) for the protein levels of MUC13 and P-STAT5 in colon cancer cells.

RESULTS

Overexpression of MUC13 increased cell growth, colony formation, cell migration, and invasion. In concordance, MUC13 silencing decreased these tumorigenic features. Overexpression of MUC13 also modulated various cancer-associated proteins, including telomerase reverse transcriptase, sonic hedgehog, B cell lymphoma murine like site 1, and GATA like transcription factor 1. Additionally, MUC13-overexpressing cells showed increased HER2 and P-ERK expression. ChIP analysis revealed binding of STAT5 to the predicted MUC13 promoter. IL6 treatment of colon cancer cells increased the expression of MUC13 via activation of the JAK2/STAT5 signaling pathway. Suppression of JAK2 and STAT5 signaling by chemical inhibitors abolished IL6-induced MUC13 expression. IHC analysis showed increased expression of both P-STAT5 and MUC13 in colon cancer as compared to adjacent normal tissue.

CONCLUSIONS

The results of this study, for the first time, suggest functional roles of MUC13 in colon cancer progression and provide information regarding the regulation of MUC13 expression via JAK2/STAT5 which may reveal promising therapeutic approaches for colon cancer treatment.

AZD1480, a JAK inhibitor, inhibits cell growth and survival of colorectal cancer via modulating the JAK2/STAT3 signaling pathway

Interleukin (IL)-6 and the downstream Janus kinase (JAK)/signal activator of transcription (STAT) pathway have been found to be important in the development of colorectal cancer (CRC). To develop novel therapies for CRC, we have explored the effects of a novel small-molecule JAK inhibitor (AZD1480) on IL-6/JAK/STAT3 pathway and its potential antitumor activity on the human CRC cell lines (HCT116, HT29 and SW480). The results showed that, AZD1480 effectively prevents constitutive and IL-6-induced JAK2 and STAT-3 phosphorylation and exerted antitumor functional effects by a decrease in proliferation and an increase in apoptosis in CRC cells. The inhibition of tumorigenesis was consistent with the decreased phosphorylated JAK2 and phosphorylated STAT3, and the decreased expression of STAT3‑targeted genes c-Myc, cyclin D2 and IL-6. Thus, AZD1480 is a potential new clinical therapeutic agent for patients with CRC.

Knockdown of prolactin receptors in a pancreatic beta cell line: effects on DNA synthesis, apoptosis, and gene expression

Prolactin (PRL) and placental lactogen stimulate beta cell replication and insulin production in vitro and in vivo. The molecular mechanisms by which lactogens promote beta cell expansion are unclear. We treated rat insulinoma cells with a PRL receptor (PRLR) siRNA to determine if PRLR signaling is required for beta cell DNA synthesis and cell survival and to identify beta cell cycle genes whose expression depends upon lactogen action. Effects of PRLR knockdown were compared with those of PRL treatment. PRLR knockdown (-80 %) reduced DNA synthesis, increased apoptosis, and inhibited expression of cyclins D2 and B2, IRS-2, Tph1, and the anti-apoptotic protein PTTG1; p21 and BCL6 mRNAs increased. Conversely, PRL treatment increased DNA synthesis, reduced apoptosis, and enhanced expression of A, B and D2 cyclins, CDK1, IRS-2, FoxM1, BCLxL, and PTTG1; BCL6 declined. PRLR signaling is required for DNA synthesis and survival of rat insulinoma cells. The effects of lactogens are mediated by down-regulation of cell cycle inhibitors (BCL6, p21) and induction of A, B, and D2 cyclins, IRS-2, Tph1, FoxM1, and the anti-apoptotic proteins BCLxL and PTTG1.

Nucleic acid-based approaches to STAT inhibition

Silencing of abnormally activated genes can be accomplished in a highly specific manner using nucleic acid based approaches. The focus of this review includes the different nucleic acid based inhibition strategies such as antisense oligodeoxynucleotides, small interfering RNA (siRNA), dominant-negative constructs, G-quartet oligonucleotides and decoy oligonucleotides, their mechanism of action and the effectiveness of these approaches to targeting the STAT (signal transducer and activator of transcription) proteins in cancer. Among the STAT proteins, especially STAT3, followed by STAT5, are the most frequently activated oncogenic STATs, which have emerged as plausible therapeutic cancer targets. Both STAT3 and STAT5 have been shown to regulate numerous oncogenic signaling pathways including proliferation, survival, angiogenesis and migration/invasion.

Activation of STAT5 contributes to proliferation in U87 human glioblastoma multiforme cells

Rapid increases in the tyrosine phosphorylation of signal transducers and activators of transcription 5 (STAT5) proteins have been extensively documented in cells stimulated with cytokines and growth factors. However, the mechanisms by which STAT5 translocates to the nucleus and regulates proliferation in human glioblastoma multiforme cells have not been studied in detail. To the best of our knowledge, the present study demonstrated for first time that stimulation of a glioblastoma multiforme (GBM) cell line (U87-MG) with hepatocyte growth factor (HGF) resulted in the phosphorylation of STAT5 at Tyr-694/699 and nuclear translocation of STAT5. In addition, HGF promoted nuclear translocation of STAT5 in a time-dependent manner and increased the proliferation of U87-MG cells. In order to determine the role of STAT5 directly, RNA interference was used to knockdown STAT5 expression in the U87-MG cell line. It was illustrated that small interfering RNA (siRNA) against STAT5 successfully inhibited the protein expression of STAT5 in the U87-MG cell line, leading to a potent suppression of tumor cell proliferation with or without HGF treatment. In order to broaden the investigation and to determine the role of STAT5 in vivo, immunohistochemistry (IHC) was applied to evaluate STAT5 expression in 100 newly diagnosed glioma and 10 non-neoplastic brain tissues. p-STAT5 expression increased according to the histopathological grade of the glioma. However, no p-STAT5 staining was observed in non-neoplastic brain tissues. These findings suggested that inhibition of the STAT5 pathway may be an effective therapeutic strategy for the clinical management of GBM.

A positive feedback loop between STAT3 and cyclooxygenase-2 gene may contribute to Helicobacter pylori-associated human gastric tumorigenesis

Persistent infection with Helicobacter pylori (H. pylori) contributes to gastric diseases including chronic gastritis and gastric cancer. However, the pathogenesis of this carcinogenic bacterium has not been completely elucidated. Here, we report that H. pylori rapidly triggers STAT3 signaling and induces STAT3-dependent COX-2 expression both in vitro and in vivo. STAT3 upregulates COX-2 by binding to and increasing the activity of COX-2 promoter. COX-2 in turn regulates IL-6/STAT3 signaling under basal conditions and during H. pylori infection. These findings suggest that a positive feedback loop between STAT3 and COX-2 exists in the basal condition and H. pylori infectious condition. Immunohistochemical staining revealed that H. pylori-positive gastritis tissues exhibited markedly higher levels of pSTAT3(Tyr705) than H. pylori-negative ones. High pSTAT3(Tyr705) levels are correlated with intestinal metaplasia and dysplasia, suggesting pSTAT3(Tyr705) may be useful in the early detection of gastric tumorigenesis. Additionally, a strong positive correlation between STAT3/pSTAT3(Tyr705) levels and COX-2 expression was identified in gastritis and gastric cancer tissues. Together, these findings provide new evidence for a positive feedback loop between STAT3 signaling and COX-2 in H. pylori pathogenesis and may lead to new approaches for early detection and effective therapy of gastric cancer

The IL-6/JAK/STAT3 pathway: potential therapeutic strategies in treating colorectal cancer (Review)

Among the cytokines linked to inflammation-associated cancer, interleukin (IL)-6 drives many of the cancer 'hallmarks' through downstream activation of the Janus kinase/signal transducer and activator of transcription 3 (JAK/STAT3) signaling pathway. Additionally, dysregulation of the interleukin (IL)-6-mediated JAK/STAT3 signaling pathway is closely related to the development of diverse human solid tumors including colorectal cancer (CRC). On this basis, modulation of the IL-6/JAK/STAT3 signaling pathway is currently being widely explored to develop novel therapies for CRC. The present review details the mechanisms and roles of the IL-6/JAK/STAT3 pathway in CRC, describes current therapeutic strategies, and the search for potential therapeutic approaches to treat CRC.

Oxidative metabolism in cancer: A STAT affair?

STAT3 and STAT5 (STAT3/5) proteins are crucial mediators of cytokine- or growth factor-induced cell survival and proliferation. These transcription factors are frequently overactivated in a variety of solid tumors and hematopoietic neoplasms and are targets of various oncogenes with tyrosine kinase activity. STAT3/5 proteins regulate expression of genes involved in survival and proliferation in the nucleus and interact with signaling pathways in the cytoplasm. Evidences for a cross-talk between STAT3/5 and oxidative metabolism have recently emerged. This review summarizes the current knowledge on the cross-regulation between STAT3/5 and oxidative metabolism in normal and cancer cells.

Combined EGFR and c-Src antisense oligodeoxynucleotides encapsulated with PAMAM Denderimers inhibit HT-29 colon cancer cell proliferation

Colon cancer continues to be one of the most common cancers, and the importance and necessity of new therapies needs to be stressed. The most important proto-oncogen factors for colon cancer appear to be epidermal growth factor receptor, EGFR, and c-Src with high expression and activity leading to tumor growth and ultimately to colon cancer progression. Application of c-Src and EGFR antisense agents simultaneously should theoretically therefore have major benefit. In the present study, anti-EGFR and c-Src specific antisense oligodeoxynucleotides were combined in a formulation using PAMAM dendrimers as a carrier. Nano drug entry into cells was confirmed by flow cytometry and fluorescence microscopy imaging and real time PCR showed gene expression of c-Src and EGFR, as well as downstream STAT5 and MAPK-1 with the tumor suppressor gene P53 to all be downregulated. EGFR and c-Src protein expression was also reduced when assessed by western blotting techniques. The effect of the antisense oligonucleotide on HT29 cell proliferation was determined by MTT assay, reduction beijng observed after 48 hours. In summary, nano-drug, anti-EGFR and c-Src specific antisense oligodeoxynucleotides were effectively transferred into HT-29 cells and inhibited gene expression in target cells. Based on the results of this study it appears that the use of antisense EGFR and c-Src simultaneously might have a significant effect on colon cancer growth by down regulation of EGFR and its downstream genes.

STAT5b as molecular target in pancreatic cancer--inhibition of tumor growth, angiogenesis, and metastases

The prognosis of patients suffering from pancreatic cancer is still poor and novel therapeutic options are urgently needed. Recently, the transcription factor signal transducer and activator of transcription 5b (STAT5b) was associated with tumor progression in human solid cancer. Hence, we assessed whether STAT5b might serve as an anticancer target in ductal pancreatic adenocarcinoma (DPAC). We found that nuclear expression of STAT5b can be detected in approximately 50% of DPAC. Blockade of STAT5b by stable shRNA-mediated knockdown showed no effects on tumor cell growth in vitro. However, inhibition of tumor cell motility was found even in response to stimulation with epidermal growth factor or interleukin-6. These findings were paralleled by a reduction of prometastatic and proangiogenic factors in vitro. Subsequent in vivo experiments revealed a strong growth inhibition on STAT5b blockade in subcutaneous and orthotopic models. These findings were paralleled by impaired tumor angiogenesis in vivo. In contrast to the subcutaneous model, the orthotopic model revealed a strong reduction of tumor cell proliferation that emphasizes the meaning of assessing targets in an appropriate microenvironment. Taken together, our results suggest that STAT5b might be a potential novel target for human DPAC.

c-Src antisense complexed with PAMAM denderimes decreases of c-Src expression and EGFR-dependent downstream genes in the human HT-29 colon cancer cell line

c-Src is one member of non-receptor tyrosine kinase protein family that has over expression and activation in many human cancer cells. It has been shown that c-Src is implicated in various downstream signaling pathways associated with EGFR-dependent signaling such as MAPK and STAT5 pathways. Transactivation of EGFR by c-Src is more effective than EGFR ligands. To inhibit the c-Src expression, we used c-Src antisense oligonucleotide complexed with PAMAM Denderimes. The effect of c-Src antisense oligonucleotide on HT29 cell proliferation was determined by MTT assay. Then, the expression of c-Src, EGFR and the genes related to EGFR-depended signaling with P53 was applied by real time PCR. We used western blot analysis to elucidate the effect of antisense on the level of c-Src protein expression. The results showed, c-Src antisense complexed with PAMAM denderimers has an effective role in decrease of c-Src expression and EGFR-dependent downstream genes.

Rac1 signalling modulates a STAT5/BCL-6 transcriptional switch on cell-cycle-associated target gene promoters

Gene expression depends on binding of transcriptional regulators to gene promoters, a process controlled by signalling pathways. The transcriptional repressor B-cell lymphoma (BCL)-6 downregulates genes involved in cell-cycle progression and becomes inactivated following phosphorylation by the Rac1 GTPase-activated protein kinase PAK1. Interestingly, the DNA motifs recognized by BCL-6 and signal transducers and activators of transcription 5 (STAT5) are similar. Because STAT5 stimulation in epithelial cells can also be triggered by Rac1 signalling, we asked whether both factors have opposing roles in transcriptional regulation and whether Rac1 signalling may coordinate a transcription factor switch. We used chromatin immunoprecipitation to show that active Rac1 promotes release of the repressor BCL-6 while increasing binding of STAT5A to a BCL-6-regulated reporter gene. We further show in colorectal cell lines that the endogenous activation status of the Rac1/PAK1 pathway correlated with the phosphorylation status of BCL-6 and STAT5A. Three cellular genes (cyclin D2, p15^INK4B, small ubiquitin-like modifier 1) were identified to be inversely regulated by BCL-6 and STAT5A and responded to Rac1 signalling with increased expression and corresponding changes in promoter occupancy. Together, our data show that Rac1 signalling controls a group of target genes that are repressed by BCL-6 and activated by STAT5A, providing novel insights into the modulation of gene transcription by GTPase signalling.

STAT5 isoforms regulate colorectal cancer cell apoptosis via reduction of mitochondrial membrane potential and generation of reactive oxygen species

Although the two isoforms of signal transducer and activator of transcription 5 (STAT5) protein, STAT5a and STAT5b, have 94% sequence identity, they are encoded by different genes. Previous studies have been unable to define clearly the roles of the STAT5 genes in colorectal cancer (CRC). To investigate the role of STAT5 isoforms in CRC oncogenesis, immunohistochemical staining was performed. Colorectal adenocarcinomas showed higher expression of STAT5a/5b than normal colonic mucosa (P < 0.05), and STAT5b expression was significantly higher than that of STAT5a in colorectal adenocarcinoma tissue (P < 0.05). Furthermore, STAT5b expression was significantly associated with TNM stage. To delineate the roles of STAT5a/5b in CRC carcinogenesis, we studied CRC cells depleted of each isoform by treating the cells with small interfering RNA. Both STAT5a and STAT5b were found to be involved in cell growth, cell cycle progression, and apoptosis of CRC cells, and exerted their effects via the regulation of downstream targets of the STAT genes. However, STAT5b influenced CRC cell apoptosis more than STAT5a (P < 0.05), reducing mitochondrial membrane potential and generating reactive oxygen species. In conclusion, both isoforms of STAT5 are involved in the growth and cell cycle progression of CRC cells, STAT5b could play a more important role than STAT5a in the clinicopathological characteristics of CRC and CRC cell apoptosis.

Inducible and repressable oncogene-addicted hepatocellular carcinoma in Tet-on xmrk transgenic zebrafish

BACKGROUND & AIMS

Liver cancer, mainly hepatocellular carcinoma, is a major malignancy and currently there are no effective treatment protocols due to insufficient understanding of hepatocarcinogenesis. As a potentially high-throughput and cost-effective experimental model, the zebrafish is increasingly recognized for disease studies. Here, we aim at using the zebrafish to generate a convenient hepatocellular carcinoma model.

METHODS

Using the Tet-on system for liver-specific expression of fish oncogene xmrk, a hyperactive version of epidermal growth factor receptor homolog, we have generated transgenic zebrafish with inducible development of liver cancer.

RESULTS

Liver tumors were rapidly induced with 100% penetrance in both juvenile and adult xmrk transgenic fish. Histological examination indicated that they all showed features of hepatocellular carcinoma. The induced liver tumors regressed rapidly upon inducer withdrawal. During the tumor induction stage, we detected increased cell proliferation and activation of Xmrk downstream targets Erk and Stat5, which were important for liver tumorigenesis as proved by inhibition experiments. When tumors regressed, there were decreased phosphorylated Erk and Stat5 accompanied with an increase in apoptosis.

CONCLUSIONS

Our zebrafish model demonstrates the potential of a hyperactivated epidermal growth factor receptor pathway in initiating heptocarcinogenesis. It provides clear evidence for the requirement of only a single oncogene for HCC initiation and maintenance and is thus a convenient model for further investigation of oncogene addiction and future anti-cancer drug screening.

Nanoparticle delivery of a peptide targeting EGFR signaling

EGFR serves as an important therapeutic target because of its over-expression in many cancers. In this study, we investigated a peptide-based therapy aimed at blocking intracellular protein-protein interactions during EGFR signaling and evaluated a targetable lipid carrier system that can deliver peptides to intracellular targets in human cancer cells. EEEEpYFELV (EV), a nonapeptide mimicking the Y845 site of EGFR which is responsible for STAT5b phosphorylation, was designed to block EGFR downstream signaling. EV was loaded onto LPH nanoparticles that are comprised of a membrane/core structure including a surface-grafted polyethylene glycol (PEG) used to evade the reticuloendothelial system (RES) and anisamide (AA) for targeting the sigma receptor over-expressed in H460 human lung cancer cells. EV formulated with PEGylated and targeted LPH (LPH-PEG-AA) was taken up by the tumor cells and trafficked to the cytoplasm with high efficiency. Using this approach, EV acted as a dominant negative inhibitor of STAT5b phosphorylation, arrested cell proliferation, and induced massive apoptosis. Intravenous administration of EV loaded in LPH-PEG-AA led to efficient EV peptide delivery to the tumor in a xenograft mouse model, and multiple injections inhibited tumor growth in a dose-dependent manner. Our findings offer proof-of-concept for an intracellular peptide-mediated cancer therapy that is delivered by carefully designed nanoparticles.

Cyclin-dependent kinase inhibitor 3 (CDKN3) novel cell cycle computational network between human non-malignancy associated hepatitis/cirrhosis and hepatocellular carcinoma (HCC) transformation

The relationship of cyclin-dependent kinase inhibitor 3 (CDKN3) with tumours has previously been presented in a number of publications. However, the molecular network and interpretation of CDKN3 through the cell cycle between non-malignancy associated hepatitis/cirrhosis and hepatocellular carcinoma (HCC) have remained to be elucidated. Here, we have constructed and analysed significant high expression gene CDKN3 activated and inhibited cell cycle networks from 25 HCC versus 25 non-malignancy associated hepatitis/cirrhosis patients (viral infection HCV or HBV) in GEO Dataset GSE10140-10141, by combination of a gene regulatory network inference method based on linear programming, and decomposition procedure using CapitalBio MAS 3.0 software, based on integration of public databases including Gene Ontology, KEGG, BioCarta, GenMapp, Intact, UniGene, OMIM, and others. Comparing the same and differently activated and inhibited CDKN3 networks with GO analysis, between non-malignancy associated hepatitis/cirrhosis and HCC, our results suggest a CDKN3 cell cycle network (i) with stronger DNA replication and with weaker ubiquitin-dependent protein catabolism as common characteristics in both non-malignancy associated hepatitis/cirrhosis and HCC; (ii) with more cell division and weaker mitotic G2 checkpoint in non-malignancy associated hepatitis/cirrhosis; (iii) with stronger cell cycle and weaker cytokinesis, as a result forming multinucleate cells in HCC. Thus, it is useful to identify CDKN3 cell cycle networks for comprehension of molecular mechanism between non-malignancy associated hepatitis/cirrhosis and HCC transformation.

Trichostatin A, a histone deacetylase inhibitor, suppresses JAK2/STAT3 signaling via inducing the promoter-associated histone acetylation of SOCS1 and SOCS3 in human colorectal cancer cells

Aberrant janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling is involved in the oncogenesis of several cancers. Suppressors of cytokine signaling (SOCS) genes and SH2-containing protein tyrosine phosphatase 1 (SHP1) proteins, which are negative regulators of JAK/STAT signaling, have been reported to have tumor suppressor functions. However, in colorectal cancer (CRC) cells, the mechanisms that regulate SOCS and SHP1 genes, and the cause of abnormalities in the JAK/STAT signaling pathway, remain largely unknown. The present study shows that trichostatin A (TSA), a histone deacetylase (HDAC) inhibitor, leads to the hyperacetylation of histones associated with the SOCS1 and SOCS3 promoters, but not the SHP1 promoter in CRC cells. This indicates that histone modifications are involved in the regulation of SOCS1 and SOCS3. Moreover, upregulation of SOCS1 and SOCS3 expression was achieved using TSA, which also significantly downregulated JAK2/STAT3 signaling in CRC cells. We also demonstrate that TSA suppresses the growth of CRC cells, and induces G1 cell cycle arrest and apoptosis through the regulation of downstream targets of JAK2/STAT3 signaling, including Bcl-2, survivin and p16(ink4a) . Therefore, our data demonstrate that TSA may induce SOCS1 and SOCS3 expression by inducing histone modifications and consequently inhibits JAK2/STAT3 signaling in CRC cells. These results also establish a mechanistic link between the inhibition of JAK2/STAT3 signaling and the anticancer action of TSA in CRC cells.