Nucleolus and Nucleolar Stress: From Cell Fate Decision to Disease Development.

Besides the canonical function in ribosome biogenesis, there have been significant recent advances towards the fascinating roles of the nucleolus in stress response, cell destiny decision and disease progression. Nucleolar stress, an emerging concept describing aberrant nucleolar structure and function as a result of impaired rRNA synthesis and ribosome biogenesis under stress conditions, has been linked to a variety of signaling transductions, including but not limited to Mdm2-p53, NF-κB and HIF-1α pathways. Studies have uncovered that nucleolus is a stress sensor and signaling hub when cells encounter various stress conditions, such as nutrient deprivation, DNA damage and oxidative and thermal stress. Consequently, nucleolar stress plays a pivotal role in the determination of cell fate, such as apoptosis, senescence, autophagy and differentiation, in response to stress-induced damage. Nucleolar homeostasis has been involved in the pathogenesis of various chronic diseases, particularly tumorigenesis, neurodegenerative diseases and metabolic disorders. Mechanistic insights have revealed the indispensable role of nucleolus-initiated signaling in the progression of these diseases. Accordingly, the intervention of nucleolar stress may pave the path for developing novel therapies against these diseases. In this review, we systemically summarize recent findings linking the nucleolus to stress responses, signaling transduction and cell-fate decision, set the spotlight on the mechanisms by which nucleolar stress drives disease progression, and highlight the merit of the intervening nucleolus in disease treatment.

Emerging Roles of the Nervous System in Gastrointestinal Cancer Development.

Our understanding of the fascinating connection between nervous system and gastrointestinal (GI) tumorigenesis has expanded greatly in recent years. Recent studies revealed that neurogenesis plays an active part in GI tumor initiation and progression. Tumor-driven neurogenesis, as well as neurite outgrowth of the pre-existing peripheral nervous system (PNS), may fuel GI tumor progression via facilitating cancer cell proliferation, chemoresistance, invasion and immune escape. Neurotransmitters and neuropeptides drive the activation of various oncogenic pathways downstream of neural receptors within cancer cells, underscoring the importance of neural signaling pathways in GI tumor malignancy. In addition, neural infiltration also plays an integral role in tumor microenvironments, and contributes to an environment in favor of tumor angiogenesis, immune evasion and invasion. Blockade of tumor innervation via denervation or pharmacological agents may serve as a promising therapeutic strategy against GI tumors. In this review, we summarize recent findings linking the nervous system to GI tumor progression, set the spotlight on the molecular mechanisms by which neural signaling fuels cancer aggressiveness, and highlight the importance of targeting neural mechanisms in GI tumor therapy.

Perfluorooctane sulfonate aggravates CCl4-induced hepatic fibrosis via HMGB1/TLR4/Smad signaling.

Perfluorooctane sulfonate (PFOS) is a widespread environmental pollutant and may cause a variety of adverse health effects. The hepatotoxicity of PFOS has attracted particular attention, given the fact that the liver has one of the highest PFOS accumulations among human tissues. In this study, we revealed that subchronic PFOS exposure may exacerbate carbon tetrachloride (CCl4 )-induced liver fibrosis in animal models. Administration with 1 mg/kg PFOS every other day for 56 days dramatically enhanced CCl4 -mediated liver injury and hepatic stellate cell (HSC) activation. Furthermore, PFOS exposure may promote the activation of high-mobility group box 1 (HMGB1)/toll-like receptor 4 (TLR4) signaling pathway through inducing the secretion of HMGB1 from hepatocytes. PFOS exposure induced the translocation of HMGB1 from the nucleus into the cytoplasm of hepatocytes and cultured BRL-3A cells at a starting concentration of 50 µM. This process is accompanied with concurrent flux of calcium, suggesting a link between calcium signaling and HMGB1 release following PFOS exposure. Finally, we showed that PFOS-exposed conditional medium (PFOS-CM) of hepatocytes may induce the translocation of Smad2/3 in HSCs in a TLR4-dependent manner. Taken together, subchronic PFOS exposure might play a pro-fibrotic role via a HMGB1/TLR4-dependent Smad signaling in HSCs. Our findings for the first time uncovered an involvement of PFOS exposure in liver fibrosis via HMGB1/TLR4/Smad signaling.

PFOS facilitates liver inflammation and steatosis: An involvement of NLRP3 inflammasome-mediated hepatocyte pyroptosis.

Perfluorooctane sulfonate (PFOS) is a fluorinated organic pollutant with substantial accumulation in mammalian liver tissues. However, the impact of chronic PFOS exposure on liver disease progression and the underlying molecular mechanisms remain elusive. Herein, we for the first time revealed that micromolar range of PFOS exposure initiates the activation of NLR pyrin domain containing 3 (NLRP3) inflammasome to drive hepatocyte pyroptosis. We showed that 5 mg/kg/day PFOS exposure may exacerbated liver inflammation and steatosis in high-fat diet (HFD)-fed mice with concurrently elevated expression of NLRP3 and caspase-1. PFOS exposure resulted in viability impairment and LDH release in BRL-3A rat liver cells. 25-100 µM concentrations of PFOS exposure activated the NLRP3 inflammasome, leading to consequent GSDMD cleavage, IL-1ß release and the initiation of pyroptosis in a dose-dependent manner, whereas treatment with 10 µM NLRP3 inhibitor MCC950 abrogated this effect. Moreover, pretreatment of 5 mM ROS scavenger N-acetyl-L-cysteine (NAC) ameliorated PFOS-induced NLRP3 inflammasome activation and pyroptosis. Collectively, our data highlight a pivotal role of pyroptotic death in PFOS-mediated liver inflammation and metabolic disorder.

MED12 and BRD4 cooperate to sustain cancer growth upon loss of mediator kinase.

Mediator kinases (CDK8/19) are transcriptional regulators broadly implicated in cancer. Despite their central role in fine-tuning gene-expression programs, we find complete loss of CDK8/19 is tolerated in colorectal cancer (CRC) cells. Using orthogonal functional genomic and pharmacological screens, we identify BET protein inhibition as a distinct vulnerability in CDK8/19-depleted cells. Combined CDK8/19 and BET inhibition led to synergistic growth retardation in human and mouse models of CRC. Strikingly, depletion of CDK8/19 in these cells led to global repression of RNA polymerase II (Pol II) promoter occupancy and transcription. Concurrently, loss of Mediator kinase led to a profound increase in MED12 and BRD4 co-occupancy at enhancer elements and increased dependence on BET proteins for the transcriptional output of cell-essential genes. In total, this work demonstrates a synthetic lethal interaction between Mediator kinase and BET proteins and exposes a therapeutic vulnerability that can be targeted using combination therapies.

Genome-scale CRISPR-Cas9 screen of Wnt/ß-catenin signaling identifies therapeutic targets for colorectal cancer.

Aberrant activation of Wnt/ß-catenin pathway is a key driver of colorectal cancer (CRC) growth and of great therapeutic importance. In this study, we performed comprehensive CRISPR screens to interrogate the regulatory network of Wnt/ß-catenin signaling in CRC cells. We found marked discrepancies between the artificial TOP reporter activity and ß-catenin-mediated endogenous transcription and redundant roles of T cell factor/lymphoid enhancer factor transcription factors in transducing ß-catenin signaling. Compiled functional genomic screens and network analysis revealed unique epigenetic regulators of ß-catenin transcriptional output, including the histone lysine methyltransferase 2A oncoprotein (KMT2A/Mll1). Using an integrative epigenomic and transcriptional profiling approach, we show that KMT2A loss diminishes the binding of ß-catenin to consensus DNA motifs and the transcription of ß-catenin targets in CRC. These results suggest that KMT2A may be a promising target for CRCs and highlight the broader potential for exploiting epigenetic modulation as a therapeutic strategy for ß-catenin-driven malignancies.

Severe Zinc Deficiency Causes the Loss and Apoptosis of Olfactory Ensheathing Cells (OECs) and Olfactory Deficit.

Dietary zinc deficiency may lead to olfactory deficits, whose mechanism remains largely elusive. Olfactory ensheathing cells (OECs), a type of glial cells that support the function and neurogenesis in the olfactory bulb (OB), may play a pivotal role in the maintenance of the olfactory system. In the present study, we established a rat model of dietary zinc deficiency and found that severe zinc deficiency, but not marginal zinc deficiency, caused significantly reduced food intake, growth retardation, and apparent olfactory deficit in growing rats. We showed that severe zinc deficiency resulted in the loss of OECs in the olfactory nerve layer (ONL) of the olfactory bulb. In addition, we revealed that the number of TUNEL-positive cells increased markedly in the region, suggesting an involvement of apoptotic cell death in zinc deficiency-induced loss of OECs. Moreover, we found that treatment with zinc chelator N,N,N'N',-tetrakis (2-pyridylmethyl)ethylenediamine (TPEN) triggered the apoptosis of in vitro-cultured primary OECs. The apoptosis of OECs was correlated with significantly elevated expression of p53. Importantly, TUNEL and CCK-8 assays both demonstrated that treatment with p53 antagonist pifithrin-α (PFT-α) markedly attenuated TPEN-induced OEC apoptosis. These findings implicated that p53-triggered apoptosis of OECs might play an integral role in zinc deficiency-induced olfactory malfunction.

A novel ß2-AR/YB-1/ß-catenin axis mediates chronic stress-associated metastasis in hepatocellular carcinoma.

ß-Adrenergic receptor (ß-AR) signalling is strongly associated with tumour progression by the coupling of ß-ARs with either a G protein or ß-arrestin; however, the related mechanism underlying hepatocellular carcinoma (HCC) metastasis is not clear. Here, we reveal that the transcription factor Y-box binding protein 1 (YB-1) interacts with ß2-adrenergic receptor (ß2-AR) following stimulation with the agonist isoproterenol (ISO). Clinicopathological analysis demonstrated that ß2-AR is significantly correlated with YB-1, which favours the progression of HCC. The binding of YB-1 with ß2-AR resulted in YB-1 phosphorylation at serine 102 (S102) via the ß-arrestin-1-dependent activation of the PI3K/AKT pathway, followed by the translocation of YB-1 to the nucleus to carry out its tumour-related function. ß2-AR-mediated activation of YB-1 facilitated epithelial-to-mesenchymal transition (EMT) and HCC metastasis. The interference of YB-1 expression significantly attenuated liver tumour metastasis induced by chronic stress. Analysis of the transcriptional profile and chromatin immunoprecipitation (ChIP) identified ß-catenin as a crucial target of YB-1. Our results unveiled a novel ß2-AR-mediated regulatory axis in HCC metastasis that might be helpful for the development of HCC therapeutics.

Transcriptional Regulation of Wnt/ß-Catenin Pathway in Colorectal Cancer.

The Wnt/ß-catenin signaling pathway exerts integral roles in embryogenesis and adult homeostasis. Aberrant activation of the pathway is implicated in growth-associated diseases and cancers, especially as a key driver in the initiation and progression of colorectal cancer (CRC). Loss or inactivation of Adenomatous polyposis coli (APC) results in constitutive activation of Wnt/ß-catenin signaling, which is considered as an initiating event in the development of CRC. Increased Wnt/ß-catenin signaling is observed in virtually all CRC patients, underscoring the importance of this pathway for therapeutic intervention. Prior studies have deciphered the regulatory networks required for the cytoplasmic stabilisation or degradation of the Wnt pathway effector, ß-catenin. However, the mechanism whereby nuclear ß-catenin drives or inhibits expression of Wnt target genes is more diverse and less well characterised. Here, we describe a brief synopsis of the core canonical Wnt pathway components, set the spotlight on nuclear mediators and highlight the emerging role of chromatin regulators as modulators of ß-catenin-dependent transcription activity and oncogenic output.

Nicotine triggers islet ß cell senescence to facilitate the progression of type 2 diabetes.

Cigarette smoking is a well-recognized risk factor for type 2 diabetes (T2DM), and may result in islet ß cell damage and impaired insulin secretion. However, the underlying mechanisms remain largely elusive. In the present study, we demonstrated that nicotine induced premature senescence of pancreatic ß cells in vitro and in vivo. The senescence-associated ß-galactosidase (SA-ß-Gal) assay showed that nicotine exposure induced apparent senescence phenotype of ß-TC-6 cells at an initiating dose of 100 µM and starting from 12 h. In addition, 100 and 500 µM of nicotine exposure altered the expression of senescence marker proteins, such as p16, p19 and p21. Furthermore, we uncovered that the levels of intracellular Ca2+ and reactive oxygen species (ROS) were significantly elevated in ß-TC-6 cells following exposure to 100 and 500 µM nicotine, while calcium channel blocker can reverse this effect. Furthermore, the senescence-inducing phenotype was confirmed in rat insulinoma INS-1 cells at a similar dose range, whereas blockade of nAChRs, calcium and ROS led to apparent impairment of senescence. Finally, we found that administration with 100 and 200 µg/mL nicotine in drinking water for 28 days significantly exacerbated aberrant glucose homeostasis in a mouse model of fat-induced T2DM. Of great intrigue, pancreatic ß cells exhibited significantly enhanced senescence following nicotine administration. Taken together, this study suggests that premature senescence plays a pivotal role in nicotine-triggered ß cell destruction and glucose intolerance, providing a theoretical basis for targeted prevention and treatment of smoking-induced T2DM.

Efficacy of 125I seed implantation combined with intermittent hormonal therapy on moderate- and high-risk non-metastatic prostate cancer.

PURPOSE: Long non-coding RNA (lncRNA) plasmacytoma variant translocation 1-214 transcript (PVT1-214) is a notable lncRNA involved in gastric cancer and colorectal cancer (CRC) so far. Nowadays, the biological function of PVT1-214 on the response of CRC to chemotherapy is still unclear. We aimed to explore the molecular mechanism of PVT1-214 and its regulatory mechanism in advanced CRC. METHODS: The levels of PVT1-214, microRNA (miR)-128, and interferon regulatory factor-1 (IRF-1) in CRC tissues and cell lines were evaluated by quantitative real-time polymerase chain reaction (qRT-PCR). Log-rank test was applied to evaluate the role of high PVT1-214 levels in shortening the overall survival of CRC patients. Chi-square test was to assess the relation between PVT1-214 expression and clinicopathological features of CRC patients. CCK8 assays tested the cell proliferation of oxaliplatin-resistant CRC cells (HCT116/Oxa and SW480/Oxa) with PVT1-214 knockdown. The underlying regulatory mechanism between PVT1-214 and miR-128 was predicted by bioinformatics and verified by RNA transfection, qRT-PCR and western blotting. Chromatin immunoprecipitation (ChIP) assay was done to examine the relationship between or IRF-1 and the PVT1-214 gene. RESULTS: High levels of PVT1-214 expression were more likely to be present in patients with late-stage (IV), chemotherapy resistance, and inferior overall survival. PVT1-214 was aberrantly elevated in oxaliplatin-resistant CRC tissues and cell lines (HCT116/Oxa and SW480/Oxa). PVT1-214 knockdown reduced cell proliferation, migration and invasion of oxaliplatin-resistant CRC cells in vitro. Moreover, IRF-1 was found to be a negative transcription regulator of PVT1-214 and decreased PVT1-214 levels in oxaliplatin-resistant CRC cells. Besides, PVT1-214 repressed miR-128 function by binding to the complementary sites of miR-128. CONCLUSIONS: IRF-1/PVT1-214 may markedly boost the oxaliplatin-resistance of CRC, resulting in the late TNM stage and poor survival. These findings suggest that the IRF-1/PVT1-214 axis may be a helpful target for intervention in CRC.

MiR-539-5p alleviates sepsis-induced acute lung injury by targeting ROCK1.

INTRODUCTION: Sepsis-induced acute lung injury (ALI) is an inflammatory process involved with simultaneous production of inflammatory cytokines and chemokines. In this study, we investigated the regulatory role of miR-539-5p in sepsis-induced ALI using a mouse model of cecal ligation puncture (CLP) and an in vitro model of primary murine pulmonary microvascular endothelial cells (MPVECs). MATERIAL AND METHODS: Adult male C57BL/6 mice were intravenously injected with or without miR-539-5p agomir or scrambled control one week before CLP operation. MPVECs were transfected with miR-539-5p mimics or control mimics, followed by lipopolysaccharide (LPS) stimulation. ROCK1 was predicted and confirmed as a direct target of miR-539-5p using dual-luciferase reporter assay. In rescue experiment, MPVECs were co-transfected with lentiviral vector expressing ROCK1 (or empty vector) and miR-539-5p mimics 24 h before LPS treatment. The transcriptional activity of caspase-3, the apoptosis ratio, the levels of miR-539-5p, interleukin-1b (IL-1b), interleukin-6 (IL-6), and ROCK1 were assessed. RESULTS: Compared to sham group, mice following CLP showed pulmonary morphological abnormalities, elevated production of IL-1b and IL-6, and increased caspase-3 activity and apoptosis ratio in the lung. In MPVECs, LPS stimulation resulted in a significant induction of inflammatory cytokine levels and apoptosis compared to untreated cells. The overexpression of miR-539-5p in septic mice alleviated sepsis-induced pulmonary injury, apoptosis, and inflammation. MiR-539-5p also demonstrated anti-apoptotic and anti-inflammatory effect in LPS-treated MPVECs. The upregulation of ROCK1 in MPVECs recovered miR-539-5p-suppressed caspase-3 activity and proinflammatory cytokine production. CONCLUSION: In conclusion, miR-539-5p alleviated sepsis-induced ALI via suppressing its downstream target ROCK1, suggesting a therapeutic potential of miR-539-5p for the management of sepsis-induced ALI.

Nrf2 Signaling Elicits a Neuroprotective Role Against PFOS-mediated Oxidative Damage and Apoptosis.

Perfluorooctanesulfonate (PFOS) may cause neurotoxicity through the initiation of oxidative stress. In the current study, we investigated the role of anti-oxidant nuclear factor erythroid 2-related factor 2 (Nrf2) pathway in PFOS-induced neurotoxicity. We found that human neuroblastoma SH-SY5Y cells exhibited significant apoptotic cell death following PFOS exposure, and this process was accompanied with apparent accumulation of reactive oxidative species (ROS). In addition, we revealed that PFOS exposure caused marked activation of Nrf2 pathway and the expression of Nrf2 transcription target heme oxygenase-1. We further found that pre-treatment with ROS scavenger N-acetyl-L-cysteine (NAC) dramatically ameliorated PFOS-induced ROS production and Nrf2 signaling. In keeping with these findings, western blot and Cell Counter Kit-8 analyses revealed that pre-incubation with NAC suppressed PFOS-induced expression of pro-apoptotic proteins and impairment of neuronal viability. Moreover, antagonizing Nrf2 pathway with Nrf2 inhibitor brusatol resulted in increased ROS production and enhanced PFOS-induced expression of apoptosis related proteins. Finally, we showed that PFOS exposure altered mitochondrial transmembrane potential and disrupted normal mitochondrial morphology in SH-SY5Y cells. Whereas treatment with NAC ameliorated PFOS-induced mitochondrial disorders, co-incubation with brusatol augmented PFOS-induced mitochondrial deficits, consequently contributing to neuronal apoptosis. These results manifest that Nrf2 pathway plays a protective role in PFOS-induced neurotoxicity, providing new insights into the prevention and treatment of PFOS-related toxicities.

α7nAChR-mediated recruitment of PP1γ promotes TRAF6/NF-κB cascade to facilitate the progression of Hepatocellular Carcinoma.

The cholinergic signaling pathways have been recently implicated in the development of various human cancers. However, the underlying molecular mechanism remains largely unclear. In the present study, we reported that α7 nicotinic acetylcholine receptor (α7nAChR), an important member of nicotinic acetylcholine receptors, interacts with Protein Phosphatase-1γ (PP1γ) in human Hepatocellular Carcinoma (HCC) tissues. In addition, we found that α7nAChR facilitates the ubiquitination and activation of TRAF6 in a PP1γ-dependent manner in HCC cells. Furthermore, we showed that ligand-bounded α7nAChR induces the degradation of IκBα, leading to resultant phosphorylation and nuclear accumulation of NF-κB p65. Accordingly, acetylcholine triggers the expression of critical NF-κB target genes, such as Cyclin D1 and PCNA, as well as the proliferation of HCC cells in a PP1γ- and α7nAChR-dependent manner. Furthermore, we revealed that nicotine-triggered α7nAChR activation promotes oncosphere formation and in vivo tumor growth of HCC cells. Moreover, we showed that the protein levels of both α7nAChR and PP1γ are significantly upregulated in human HCC specimens compared with adjacent non-cancerous ones, and that upregulated expression of the two proteins predict significantly worsened prognosis in HCC patients. These findings together indicate that the cholinergic receptor α7nAChR exerts a facilitating role in HCC development through PP1γ-dependent TRAF6/NF-κB signaling.

CBX7 regulates stem cell-like properties of gastric cancer cells via p16 and AKT-NF-κB-miR-21 pathways.

BACKGROUND: Chromobox protein homolog 7 (CBX7), a member of the polycomb group (PcG) family of proteins, is involved in the regulation of cell proliferation and cancer progression. PcG family members, such as BMI, Mel-18, and EZH2, are integral constituents of the polycomb repressive complexes (PRCs) and have been known to regulate cancer stem cell (CSC) phenotype. However, the role of other PRCs' constituents such as CBX7 in the regulation of CSC phenotype remains largely elusive. This study was to investigate the role of CBX7 in regulating stem cell-like properties of gastric cancer and the underlying mechanisms. METHODS: Firstly, the role of CBX7 in regulating stem cell-like properties of gastric cancer was investigated using sphere formation, Western blot, and xenograft tumor assays. Next, RNA interference and ectopic CBX7 expression were employed to determine the impact of CBX7 on the expression of CSC marker proteins and CSC characteristics. The expression of CBX7, its downstream targets, and stem cell markers were analyzed in gastric stem cell spheres, common cancer cells, and gastric cancer tissues. Finally, the pathways by which CBX7 regulates stem cell-like properties of gastric cancer were explored. RESULTS: We found that CBX7, a constituent of the polycomb repressive complex 1 (PRC1), plays an important role in maintaining stem cell-like characteristics of gastric cancer cells via the activation of AKT pathway and the downregulation of p16. Spearman rank correlation analysis showed positive correlations among the expression of CBX7 and phospho-AKT (pAKT), stem cell markers OCT-4, and CD133 in gastric cancer tissues. In addition, CBX7 was found to upregulate microRNA-21 (miR-21) via the activation of AKT-NF-κB pathway, and miR-21 contributes to CBX7-mediated CSC characteristics. CONCLUSIONS: CBX7 positively regulates stem cell-like characteristics of gastric cancer cells by inhibiting p16 and activating AKT-NF-κB-miR-21 pathway.

Nucleostemin/GNL3 promotes nucleolar polyubiquitylation of p27kip1 to drive hepatocellular carcinoma progression.

p27kip, as a cyclin dependent kinase inhibitor (CDKI), plays a pivotal role in the regulation of cell cycle progression and hepatocarcinogenesis. Herein, we revealed that p27 exhibited apparent nucleolar distribution and interacted with nucleolar protein nucleostemin (NS) in Hepatocellular carcinoma (HCC) cells. Furthermore, subcellular fractionation experiments demonstrated that nucleolar p27 had significantly higher level of polyubiquitylation, compared with nucleoplasmic fraction. Depletion of NS inhibited nucleolar polyubiquitylation of p27, indicating an involvement of NS in triggering p27 ubiquitylation and inactivation during HCC development. Moreover, we found that knockdown of NS promoted p27 to bind to CDK2-Cyclin E complex and inhibited the activity of CDK2, resulting in consequent cell cycle arrest in HCC cells. Furthermore, silencing NS expression reduced in vitro colony formation and in vivo tumor growth of HCC cells. Finally, we found that NS was upregulated in HCC tissues, compared with adjacent non-tumorous tissues. Kaplan-Meier analysis indicated patients with high expression of NS and low expression of p27 had significantly worsened prognosis. Our results suggested NS mediated p27-dependent cell cycle control via inducing nucleolar sequestration and polyubiquitylation of p27 in HCC. These findings help gain an insightful view into the mechanism underlying aberrant cell cycle progression during hepatocarcinogenesis, and thus benefit the development of molecular-targeted therapies in HCC.

CBX7 suppresses cell proliferation, migration, and invasion through the inhibition of PTEN/Akt signaling in pancreatic cancer.

Chromobox protein homolog 7 (CBX7), one of the polycomb group (PcG) proteins, is a transcriptional repressor involved in the regulation of cell proliferation and senescence. In the present study, we showed that CBX7 negatively regulates the proliferation, viability, chemoresistance, and migration of pancreatic cancer cells. Overexpression of CBX7 significantly inhibited the proliferation of pancreatic cancer cells in vitro and in vivo. Depletion of CBX7 facilitated their growth. CBX7 also impaired the viability and chemoresistance of pancreatic cancer cells. Transwell assays showed that CBX7 reduces the migratory capacity of pancreatic cancer cells. Of note, CBX7 reduced PTEN/Akt signaling in pancreatic cancer cells by increasing PTEN transcription, suggesting involvement of PTEN/Akt pathway in the tumor suppressive activity of CBX7. In addition, immunohistochemical analysis the CBX7 and PTEN expression in 74 surgically resected pancreatic ductal adenocarcinoma (PDAC) specimens revealed that CBX7 expression is significantly downregulated in pancreatic ductal adenocarcinoma, compared to normal pancreatic tissues. Reduced expression of CBX7 and PTEN was associated with increased malignancy grade in pancreatic adenocarcinoma, whereas maintenance of CBX7 and PTEN expression showed a trend toward a longer survival. These findings suggest CBX7 is an important tumor suppressor that negatively modulates PTEN/Akt signaling during pancreatic tumorigenesis.

Overexpression of Protein Phosphatase 1γ (PP1γ) Is Associated with Enhanced Cell Proliferation and Poor Prognosis in Hepatocellular Carcinoma.

BACKGROUND: Protein phosphatase 1γ (PP1γ), as a member of the protein phosphatase 1 family, may be involved in regulation of multiple cellular processes, such as mitosis, cell survival, and apoptosis. However, little is known about the underlying mechanisms by which PP1γ regulates hepatocellular carcinoma development. AIM: We investigated the expression profile of PP1γ in hepatocellular carcinoma (HCC) cell lines and human HCC specimens, as well as its potential prognostic significance in HCC. METHODS: PP1γ expression profile was detected in 94 HCC specimens using immunohistochemistry. PP1γ levels in HCC cells were downregulated by small interfering RNA (siRNA) transfection. Cell cycle progression and proliferation status of HCC cells and the effectiveness of doxorubicin were evaluated by flow cytometry and CCK-8 assay. The levels of PP1γ, CyclinD1, PCNA, Mdmx, p53, p21, and active caspase-3 were evaluated by Western blot analysis. RESULTS: PP1γ was upregulated in tumorous specimens, compared with adjacent nontumorous tissues. Univariate and multivariate survival analyses were conducted to determine the prognostic significance of PP1γ in HCC. The expression pattern of PP1γ was positively correlated with tumor size, histological grade, Ki-67 expression, and poor prognosis in HCC. In addition, depletion of PP1γ by siRNA could inhibit cell proliferation, resulted in G1 phase arrest, and attenuated resistance to doxorubicin in Huh7 cells. CONCLUSIONS: PP1γ is upregulated in HCC cell lines and HCC specimens, promotes cancer cell proliferation through regulation of p53, and may be a potential target for treatment of HCC.

RACK1 overexpression associates with pancreatic ductal adenocarcinoma growth and poor prognosis.

OBJECTIVES: The receptor for activated protein kinase C (RACK1) is a scaffold protein involved in multiple intracellular signal pathways. Previous studies have shown that RACK1 is associated with the progression of multiple cancer types, including hepatocellular carcinoma and gastric cancer. However, the role of RACK1 in human pancreatic ductal adenocarcinoma (PDAC) remains unclear. METHODS: In this study, the expression of RACK1 was evaluated by Western blot analysis in 8 paired fresh PDAC tissues and immunohistochemistry on 179 paraffin-embedded slices. Then, we used Fisher exact test to analyze the correlation between RACK1 expression and clinicopathological characteristics. Starvation and re-feeding assay was used to assess cell cycle. Western blot, CCK8, flow cytometry assays, and colony formation analyses demonstrated that RACK1 played an essential role in PDAC development. Annexin-V/PI apoptotic assay and western blot showed that RACK1 was involved in regulating the apoptosis of PDAC cells. RESULTS: RACK1 was highly expressed in PDAC tissues and cell lines and was significantly associated with multiple clinicopathological factors. Univariate and multivariate analyses showed that high RACK1 expression was identified to be an independent prognostic factor for PDAC patients' survival. In vitro, serum starvation-refeeding experiment suggested that RACK1 was upregulated in proliferating PDAC cells, together with the percentage of cells at the S phase, and was correlated with the expression of Cyclin D1. Moreover, Overexpression of RACK1 facilitated the proliferation and cell cycle progression of PDAC cells, while downregulation of RACK1 induced growth impairment, G1/S cell cycle arrest and apoptosis in PDAC cells. Silencing RACK1 decreased bcl-2 expression, increased cleaved caspase3 expression level and induced the apoptosis of PDAC cells. CONCLUSIONS: Our results suggest that RACK1 could play an important role in the tumorigenesis of PDAC and serve as a potential therapeutical target in PDAC treatment.