Liwei Dong

LPS-induced down-regulation of signal regulatory protein α contributes to innate immune activation in macrophages

Activation of the mitogen-activated protein kinases (MAPKs) and nuclear factor κB (NF-κB) cascades after Toll-like receptor (TLR) stimulation contributes to innate immune responses. Signal regulatory protein (SIRP) α, a member of the SIRP family that is abundantly expressed in macrophages, has been implicated in regulating MAPK and NF-κB signaling pathways. In addition, SIRPα can negatively regulate the phagocytosis of host cells by macrophages, indicating an inhibitory role of SIRPα in innate immunity. We provide evidences that SIRPα is an essential endogenous regulator of the innate immune activation upon lipopolysaccharide (LPS) exposure. SIRPα expression was promptly reduced in macrophages after LPS stimulation. The decrease in SIRPα expression levels was required for initiation of LPS-induced innate immune responses because overexpression of SIRPα reduced macrophage responses to LPS. Knockdown of SIRPα caused prolonged activation of MAPKs and NF-κB pathways and augmented production of proinflammatory cytokines and type I interferon (IFN). Mice transferred with SIRPα-depleted macrophages were highly susceptible to endotoxic shock, developing multiple organ failure and exhibiting a remarkable increase in mortality. SIRPα may accomplish this mainly through its association and sequestration of the LPS signal transducer SHP-2. Thus, SIRPα functions as a biologically important modulator of TLR signaling and innate immunity.

Development of Glycoprotein Capture-Based Label-Free Method for the High-throughput Screening of Differential Glycoproteins in Hepatocellular Carcinoma

A robust, reproducible, and high throughput method was developed for the relative quantitative analysis of glycoprotein abundances in human serum. Instead of quantifying glycoproteins by glycopeptides in conventional quantitative glycoproteomics, glycoproteins were quantified by nonglycosylated peptides derived from the glycoprotein digest, which consists of the capture of glycoproteins in serum samples and the release of nonglycopeptides by trypsin digestion of captured glycoproteins followed by two-dimensional liquid chromatography-tandem MS analysis of released peptides. Protein quantification was achieved by comparing the spectrum counts of identified nonglycosylated peptides of glycoproteins between different samples. This method was demonstrated to have almost the same specificity and sensitivity in glycoproteins quantification as capture at glycopeptides level. The differential abundance of proteins present at as low as nanogram per milliliter levels was quantified with high confidence. The established method was applied to the analysis of human serum samples from healthy people and patients with hepatocellular carcinoma (HCC) to screen differential glycoproteins in HCC. Thirty eight glycoproteins were found with substantial concentration changes between normal and HCC serum samples, including α-fetoprotein, the only clinically used marker for HCC diagnosis. The abundance changes of three glycoproteins, i.e. galectin-3 binding protein, insulin-like growth factor binding protein 3, and thrombospondin 1, which were associated with the development of HCC, were further confirmed by enzyme-linked immunosorbent assay. In conclusion, the developed method was an effective approach to quantitatively analyze glycoproteins in human serum and could be further applied in the biomarker discovery for HCC and other cancers.

Prognostic significance of Beclin 1 in intrahepatic cholangiocellular carcinoma.

Autophagy enables cells to recycle long-lived proteins or damaged organelles. Beclin 1 plays important roles in autophagy, differentiation, apoptosis and the development and progression of cancer, but the expression of Beclin 1 and its possible role in primary intrahepatic cholangiocarcinoma (ICC) has not been reported yet. This study aimed to investigate Beclin 1 expression and its prognostic significance in ICC. First, we assessed the expression levels of Becn1 by real-time PCR in 50 ICC samples and found Becn1 mRNA expression was markedly increased in 78% (39 of 50) samples compared with normal bile duct epithelium. Beclin 1 protein expression in 108 tumor specimens from patients diagnosed with ICC was examined by immunohistochemistry and the correlation between Beclin 1 expression and clinicopathological factors were investigated. Immunopositivity for Beclin 1 was found in 72.2% (78 of 108) samples and low Beclin 1 expression was significantly associated with lymph node metastasis. The correlation between Beclin 1 expression and metastasis was validated in 46 ICC samples with lymph node metastasis. In survival analysis, low Beclin 1 expression was associated with worse overall survival (OS; p = 0.025) and disease-free survival (DFS; p = 0.027). In multivariate analysis, Beclin 1 expression, intrahepatic metastasis, lymph node metastasis and tumor size were found to be independent prognostic factors of OS. Thus, our results suggested the expression of Beclin 1 was correlated with progression and metastasis of ICC and it might serve as a novel prognostic marker for patients with ICC.

Signal regulatory protein α negatively regulates both TLR3 and cytoplasmic pathways in type I interferon induction

Recognition of double-stranded RNA (dsRNA) activates interferon-regulatory factor 3 (IRF3)-dependent expression of anti-viral factors. The innate immune system recognizes viral dsRNA through two distinct pathways. First, the Toll-like receptor 3 (TLR3) detects dsRNA phagocytosed in endosomes. In addition, the helicases retinoic acid induced protein I (RIG-I)/melanoma differentiation associated gene 5 (MDA5) binds cytoplasmic dsRNA generated during viral replication. Both RIG-I/MDA5 and TLR3 can bind polyriboinosinic:polyribocytidylic acid (poly(I:C)), the synthetic analog of viral dsRNA, and mediate type I IFN production. Here we show that signal regulatory protein (SIRP) alpha negatively regulates both TLR3- and RIG-1/MDA5-dependent anti-viral pathways. Suppression of SIRPalpha expression by RNA interference results in enhanced activation of IRF3 and MAPK pathways after poly(I:C) treatment, coupled with the up-regulation of IFN-beta and IFN-beta-inducible gene transcriptional activation. The requirement of phosphoinositide 3-kinase (PI3K) activity for the induction of IFN-beta and IFN-beta-inducible genes by dsRNA is supported by the observation that a PI3K inhibitor failed to activate IFN-beta and IFN-beta-inducible gene expression. PI3K, whose activity is essential for activation of IRF3, is recruited to the phosphorylated tyrosine residues of SIRPalpha upon poly(I:C) stimulation, which lead to a reduction in the activity of the downstream kinase AKT. Thus SIRPalpha may accomplish its inhibitory function in type I IFN induction, in part, through its association and sequestration of the signal transducer PI3K.

Gankyrin‐mediated dedifferentiation facilitates the tumorigenicity of rat hepatocytes and hepatoma cells

Gankyrin is a critical oncoprotein overexpressed in human hepatocellular carcinoma (HCC). However, the mechanism underlying gankyrin‐mediated hepatocarcinogenesis remains elusive. Herein, we provide evidence that gankyrin expression was progressively elevated in liver fibrosis, cirrhosis, and HCC. Levels of gankyrin expression were closely associated with the dedifferentiation status of hepatoma in patients. Decrease of hepatocyte characteristic markers and increase of cholangiocyte‐specific markers were observed in rat primary hepatocytes with enforced gankyrin expression and diethylnitrosamine (DEN)‐triggered rat hepatocarcinogenesis. Overexpression of gankyrin also attenuated the hepatic function of primary hepatocytes, which further suggests that gankyrin promotes the dedifferentiation of hepatocytes. Moreover, elevated expression of gankyrin closely correlated with the expression of HCC stem/progenitor cell markers in DEN‐triggered hepatocarcinogenesis and human HCCs. Hepatoma cells derived from suspension‐cultured spheroids exhibited a higher gankyrin level, and enforced gankyrin expression in hepatoma cells remarkably enhanced cluster of differentiation (CD)133, CD90, and epithelial cellular adhesion molecule expression, indicating a role of gankyrin in hepatoma cell dedifferentiation and the generation of hepatoma stem/progenitor cells. In contrast, down‐regulation of gankyrin in hepatoma cells by lentivirus‐mediated microRNA delivery significantly improved their differentiation status and attenuated malignancy. Interference of gankyrin expression in hepatoma cells also diminished the proportion of cancer stem/progenitor cells and their self‐renewal capacity. Furthermore, gankyrin was found to bind hepatocyte nuclear factor 4α (HNF4α), which determines hepatocyte differentiation status and enhances proteasome‐dependent HNF4α degradation in hepatoma cells. The inverse correlation of gankyrin and HNF4α was further confirmed in primary hepatocytes, DEN‐induced hepatocarcinogenesis, and human HCCs. Conclusion: Gankyrin‐mediated dedifferentiation of hepatocytes and hepatoma cells via, at least partially, down‐regulation of HNF4α facilitates HCC development, and interference of gankyrin expression could be a novel strategy for HCC prevention and differentiation therapy. (HEPATOLOGY 2011;54:1259–1272)

Inhibition of active autophagy induces apoptosis and increases chemosensitivity in cholangiocarcinoma

Intrahepatic cholangiocellular carcinomas (ICCs) are usually fatal neoplasms originating from bile duct epithelia. However, many cholangiocarcinoma cells are shown to be resistant to chemotherapeutic drugs, which induce cell apoptosis. The role of autophagy and the therapeutic value of autophagy-associated genes are largely unknown in ICC. Here, we showed that autophagy was activated in nutrient starvation and xenograft cholangiocarcinoma cells. Furthermore, expression of autophagic genes and their autophagic activity were higher in clinical ICC specimens than that in normal cholangiocytes separated by laser capture microdissection. Inhibition of autophagy by autophagy inhibitors or siRNA, cholangiocarcinoma cells showed detention of proliferation and increase of apoptosis during nutrient starvation. In addition, autophagy inhibitor treatment or knockdown of beclin 1 suppressed tumor growth and sensitized ICC cells to chemotherapeutic agent-induced cell death. In conclusion, our data showed that autophagy is activated in ICC, and inactivation of autophagy may lead to cell apoptosis and enhance chemotherapy sensitivity.

The Prognostic Significance and Therapeutic Potential of Hedgehog Signaling in Intrahepatic Cholangiocellular Carcinoma

Purpose: The correlation of the hedgehog signaling pathway with the progression, prognosis, and therapeutics of intrahepatic cholangiocellular carcinoma (ICC) has not been well documented. The study aimed to investigate the expression, prognostic significance, and therapeutic value of hedgehog components in ICC. Experimental Design: Two independent cohorts of 200 patients with ICC were enrolled. By real-time PCR and immunohistochemistry assay, hedgehog components expression was evaluated. The prognostic values of hedgehog proteins were identified and verified. Cyclopamine or siRNA-targeting Gli was used to block the hedgehog signaling. Cell proliferation and apoptosis were observed by CCK8, cell cycle, and annexin V staining assays. In vivo murine tumor model was used to evaluate the role of hedgehog in ICC. Results: In ICC tissues, the Gli1 nuclear immune-intensity was associated with intrahepatic metastasis and the expression of Gli2 was associated with intrahepatic metastasis, venous invasion, and Unio Internationale Contra Cancrum (UICC) pT characteristics. In survival analysis, high Gli1 or Gli2 expressers had an unfavorable overall survival (OS) prognosis and a shorter disease-free survival (DFS) than those with low expression. In multivariate analysis, Gli1 expression was found to be an independent prognostic factor of OS, which was validated by another independent cohort. Furthermore, blocking the hedgehog signaling by cyclopamine or siRNA-targeting Gli1 resulted in apoptosis and growth inhibition in ICC cells. Conclusions: This study shows, for the first time, activation of hedgehog pathway associated with the progression and metastasis in ICC, which may provide prognostic and therapeutic values for this tumor. Clin Cancer Res; 19(8); 2014–24. ©2013 AACR.

The oncoprotein p28GANK establishes a positive feedback loop in β-catenin signaling.

p28GANK (also known as PSMD10 or gankyrin) is a novel oncoprotein that is highly expressed in hepatocellular carcinoma (HCC). Through its interaction with various proteins, p28GANK mediates the degradation of the tumor suppressor proteins Rb and p53. Although p53 was reported to downregulate β-catenin, whether p28GANK is involved in the regulation of β-catenin remains uncertain. Here we report that both growth factors and Ras upregulate p28GANK expression through the activation of the phosphoinositide 3-kinase-AKT pathway. Upregulation of p28GANK expression subsequently enhanced the transcription activity of β-catenin. This effect was observed in p53-deficient cells, suggesting a p53-independent mechanism for the p28GANK-mediated activation of β-catenin. p28GANK overexpression also reduced E-cadherin protein levels, leading to increased release of free β-catenin into the cytoplasm from the cadherin-bound pool. Interestingly, exogenous expression of p28GANK resulted in elevated expression of the endogenous protein. We also observed that both β-catenin and c-Myc were transcriptional activators of p28GANK, and a correlation between p28GANK overexpression and c-Myc, cyclin D1 and β-catenin activation in primary human HCC. Together, these results suggest that p28GANK expression is regulated by a positive feedback loop involving β-catenin, which may play a critical role in tumorigenesis and the progression of HCC.

CD133/Prominin-1-Mediated Autophagy and Glucose Uptake Beneficial for Hepatoma Cell Survival

CD133/Prominin-1 is a pentaspan transmembrane protein that has been frequently used as a biomarker for cancer stem cells, although its biological function is unclear. The aim of our study was to explore the intrinsic functions of CD133 membrane protein in hepatoma cells during autophagy, apoptosis, tumorigenesis and cell survival through expression or downregulation of CD133. In this study, CD133 was found to be dynamically released from plasma membrane into cytoplasm in both of complete medium(CM) and low glucose medium (LGM), and LGM promoted this translocation. Expression of CD133 enhanced autophagic activity in LGM, while silencing CD133 attenuated this activity in HCC LM3 and Huh-7 cells, suggesting that CD133 is associated with autophagy. Immunofluorescence and time-lapsed confocal techniques confirmed that CD133 was associated with autophagy marker, microtubule-associated protein light chain3 (LC3) and lysosome marker during the glucose starvation. We further found that Huh-7 cells with stable expression of shCD133 (Huh-7sh133) impaired the ability of cell proliferation and formation of xenograft tumors in the NOD/SCID mice. Although loss of CD133 did not affect the rates of glucose uptake in Huh-7con and Huh-7sh133 cells under the CM, Huh-7sh133 cells obviously died fast than Huh-7con cells in the LGM and decreased the rate of glucose uptake and ATP production. Furthermore, targeting CD133 by CD133mAb resulted in cell death in HepG2 cells, especially in the LGM, via inhibition of autophagic activity and increase of apoptosis. The results demonstrated that CD133 is involved in cell survival through regulation of autophagy and glucose uptake, which may be necessary for cancer stem cells to survive in tumor microenvironment.

Zinc finger protein ZBTB20 expression is increased in hepatocellular carcinoma and associated with poor prognosis

BackgroundOur previous studies showed that ZBTB20, a new BTB/POZ-domain gene, could negatively regulate α feto-protein and other liver-specific genes, concerning such as bio-transformation, glucose metabolism and the regulation of the somatotropic hormonal axis. The aim of this study is to determine the potential clinical implications of ZBTB20 in hepatocellular carcinoma (HCC).MethodsQuantitative real-time RT-PCR and Western blot analyses were used to detect expression levels of ZBTB20 in 50 paired HCC tumorous and nontumorous tissues and in 20 normal liver tissues. Moreover, expression of ZBTB20 was assessed by immunohistochemistry of paired tumor and peritumoral liver tissue from 102 patients who had undergone hepatectomy for histologically proven HCC. And its relationship with clinicopathological parameters and prognosis was investigated.ResultsBoth messenger RNA and protein expression levels of ZBTB20 were elevated significantly in HCC tissues compared with the paired non-tumor tissues and normal liver tissues. Overexpressed ZBTB20 protein in HCC was significantly associated with vein invasion (P = 0.016). Importantly, the recurrence or metastasis rates of HCCs with higher ZBTB20 expression were markedly greater than those of HCCs with lower expression (P = 0.003, P = 0.00015, respectively). Univariate and multivariate analyses revealed that ZBTB20 overexpression was an independent prognostic factor for HCC. The disease-free survival period and over-all survival period in patients with overexpressed ZBTB20 in HCC was significantly reduced.ConclusionsThe expression of ZBTB20 is increased in HCC and associated with poor prognosis in patients with HCC, implicating ZBTB20 as a candidate prognostic marker in HCC.