Crossed-dipole arrays for asynchronous DS-CDMA systems

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DLC1 (deleted in liver cancer 1)

Review on DLC1 (deleted in liver cancer 1), with data on DNA, on the protein encoded, and where the gene is implicated

Rho GTPase-activating protein deleted in liver cancer suppresses cell proliferation and invasion in hepatocellular carcinoma

Deleted in liver cancer (DLC1) is a candidate tumor suppressor gene recently isolated from human hepatocellular carcinoma. Structurally, DLC1 protein contains a conserved GTPase-activating protein for Rho family protein (RhoGAP) domain, which has been thought to regulate the activity of Rho family proteins. Previous studies indicated that DLC1 was frequently inactivated in cancer cells. In the present study, we aimed to characterize the tumor suppressor roles of DLC1 in hepatocellular carcinoma. We showed that DLC1 significantly inhibited cell proliferation, anchorage-independent growth, and in vivo tumorigenicity when stably expressed in hepatocellular carcinoma cells. Moreover, DLC1 expression greatly reduced the motility and invasiveness of hepatocellular carcinoma cells. With RhoGAP-deficient DLC1 mutant (DLC1-K714E), we showed that the RhoGAP activity was essential for DLC1-mediated tumor suppressor function. Furthermore, the 292- to 648-amino acid region and the steroidogenic acute regulatory related lipid transfer domain played an auxiliary role to RhoGAP and tumor suppressor function of DLC1. Taken together, our findings showed that DLC1 functions as a tumor suppressor in hepatocellular carcinoma and provide the first evidence to support the hypothesis that DLC1 suppresses cancer cell growth by negatively regulating the activity of Rho proteins. ©2005 American Association for Cancer Research.postprin

ANXA3/JNK Signaling Promotes Self-Renewal and Tumor Growth, and Its Blockade Provides a Therapeutic Target for Hepatocellular Carcinoma

Frequent tumor relapse in hepatocellular carcinoma (HCC) has been commonly attributed to the presence of residual cancer stem cells (CSCs) after conventional treatments. We have previously identified and characterized CD133 to mark a specific CSC subset in HCC. In the present study, we found endogenous and secretory annexin A3 (ANXA3) to play pivotal roles in promoting cancer and stem cell-like features in CD133+ liver CSCs through a dysregulated JNK pathway. Blockade of ANXA3 with an anti-ANXA3 monoclonal antibody in vitro as well as in human HCC xenograft models resulted in a significant reduction in tumor growth and self-renewal. Clinically, ANXA3 expression in HCC patient sera closely associated with aggressive clinical features. Our results suggest that ANXA3 can serve as a novel diagnostic biomarker and that the inhibition of ANXA3 may be a viable therapeutic option for the treatment of CD133+ liver-CSC-driven HCC. © 2015 The Authors.published_or_final_versio

C20, a novel binding partner of DLC1 identified by yeast-2-hybrid screening

Hepatocellular carcinoma (HCC) is the fifth most common malignancies worldwide. Although the risk factors are known, the molecular and cellular mechanism of hepatocarcinogenesis is still unclear. Deleted in Liver Cancer 1(DLC1) is a recently identified tumor suppressor gene and the DLC1 gene encodes a RhoGAP protein, switching the active GTP bound form of small monomeric G-protein, Rho, into the inactive GDP bound form. We have previously shown that it is frequently underexpressed in HCC. We have also characterized DLC1 to be a growth suppressor in HCC cell lines and documented its in vitro RhoGAP activity. Our recent findings have also revealed that inhibition of Rho-mediated actin stress fiber formation by DLC1 is associated with its growth suppressive effect. Although DLC1 has multiple domains, the potential molecular targets and binding partners remain unclear. With the employment of yeast-2-hybrid system to screen against the human liver cDNA library, we have identified a yeast clone, namely clone 20 (C20), as a novel binding partner of DLC1. C20 contains a partial, unknown protein encoding DNA sequence of approximately 600 base pairs corresponding to human chromosome 19p13.3. C20 has a high sequence homology to the mouse Gtrgeo22 gene, which encodes a novel transmembrane protein containing dileucine and tyrosine-based motifs. Previous report has pointed out that mutation of Gtrgeo22can cause multiple defects in mice including male sterility. C20 is expressed in human liver and the transcripts are detectable by RT-PCR in all 10 HCC cell lines we have screened. The minimal interacting domain of DLC1 with C20 protein was mapped to the residues 293-647 of DLC1 in SFY526 yeast cells. Our results showed that DLC1 specifically interacted with C20, which is therefore a novel binding partner of DLC1. Further studies will derive new insight into the biological functions of DLC1. (This study was funded in part by the Michael Kadoorie Cancer Genetic Research Program of the Kadoorie Charitable Foundation

Role and significance of focal adhesion proteins in hepatocellular carcinoma

Focal adhesions are structural links between the extracellular matrix and actin cytoskeleton. They are important sites where dynamic alterations of proteins in the focal contacts are involved during cell movement. Focal adhesions are composed of diverse molecules, for instance, receptors, structural proteins, adaptors, GTPase, kinases and phosphatases. These molecules play critical roles in normal physiological events such as cellular adhesion, movement, cytoskeletal structure and intracellular signaling pathways. In cancers, aberrant expression and altered functions of focal adhesion proteins contribute to adverse tumor behavior. It is evident that these proteins do not function alone, but rather associate and work together in the process of tumor development and cancer metastasis. Focal adhesion proteins have been shown to play critical roles in hepatocellular carcinoma. Understanding the molecular interactions and mechanisms of the interconnected focal adhesion proteins is of particular importance in understanding mechanisms underlying hepatocellular carcinoma progression and development of potential effective treatment. © 2009 Journal of Gastroenterology and Hepatology Foundation and Blackwell Publishing Asia Pty Ltd.link_to_subscribed_fulltex

Integrin-linked kinase promotes hepatocellular carcinoma oncogenesis

Poster Session: Molecular BiologyBACKGROUND: Integrin-linked kinase (ILK) was first discovered as an integrin binding protein. It localizes to focal adhesions and facilitates actin polymerization. Accumulating evidences suggest that ILK is a putative oncogene. ILK was over-expressed in various malignancies and its aberrant activation influenced a wide range of cellular functions. In this study, we aimed to elucidate the role of ILK in hepatocarcinogenesis and its clinical significance by assessing ILK expression in human hepatocellular carcinoma (HCC) tissues and functionally characterizing ILK in HCC cell models. MATERIAL AND METHODS: Expression level of ILK in HCC cell lines was examined by Western blotting, while ILK expression in clinical samples was determined by quantitative PCR. ILK knock-down stable clones were established in BEL7402 and HLE using a lentiviral-based short-hairpin knockdown approach. For each cell line, two stable ILK knock-down (shILK) clones and one stable non-target control (shCTL) were established. To functionally characterize ILK in HCC, the knock-down stable clones were subjected to various functional assays including cell proliferation assay, soft agar colony formation assay, cell migration assay, wound-healing assay and cell invasion assay. In vivo tumourigenicity of BEL7402 ILK knock-down stable clones was assessed by subcutaneous injection of the cells into nude mice. RESULTS: Western blotting revealed a higher ILK protein expression in HCC cell lines than in normal liver cell line. In the physiological context, qPCR analysis showed that ILK was over-expressed in 36.9% (21/57) of HCC tissues when compared to the corresponding non-tumourous livers. The overall ILK expression level was significantly higher in tumourous tissues (P = 0.005), with a stepwise increase of expression along tumour stage. Functional characterization of ILK in HCC using the two ILK stable knockdown cell lines showed a reduction in the rate of cell proliferation, migration, invasion and anchorage-independent growth. Knock-down of ILK in BEL7402 also suppressed tumour formation in nude mice, thus decreasing the in vivo tumourigenicity of HCC cells. To probe the underlying mechanism, AKT activity was evaluated in the shILK clones. Western blotting analysis showed a decrease in phospho-AKT(Ser473) level upon ILK silencing. CONCLUSION: Our study suggests that ILK plays a role in the progression of HCC via the activation of the PKB/AKT pathway.The 21st Meeting of the European Association for Cancer Research (EACR), Oslo, Norway, 26-29 June 2010. In European Journal of Cancer Supplements, 2010, v. 8 n. 5, p. 183-184, abstract no. 72

Nuclear targeted Deleted in liver cancer 1 exhibited reduced tumor suppressive function both in vitro and in vivo

Session - Cellular and Molecular Biology: no. 5007The tumor suppressor Deleted in liver cancer 1 (DLC1) protects cell from transformation by catalyzing the GTP hydrolysis of active RhoA. Besides the RhoGAP activity, accumulating evidences have supported that localization at focal adhesions and interaction with tensin protein are key factors guiding the tumor suppressive activity of DLC1. In this study, we provided new evidence that DLC1 was a dynamic protein which shuttles between cytoplasm and nucleus instead of statically staying in the cytoplasm. Subcellular fractionation assay showed that DLC1 protein can be detected in cytoplasmic and nuclear fractions. Treatment of Leptomycin B (LMB), a nuclear export blocker, could lead to the nuclear retention of exogenous and endogenous DLC1 in different human cancer cell lines. Detail examination of relevant DLC1 mutants had shown that the center region of DLC1 was necessary and sufficient for its nuclear localization. We transiently expressed a NLS fusion DLC1 (NLS-DLC1) with preferential nuclear localization in SMMC HCC cells and found that NLS-DLC1 was less potent in suppressing colony formation and actin stress fiber formation. To study the tumor suppressive function of nuclear DLC1 both in vitro and in vivo, we employed retroviral transduction to stably express NLS-DLC1 in a p53−/− RasV12 hepatoblast model. We found that NLS-DLC1 expressing cells proliferated faster in vitro and exhibited increased tumorigenicity upon nude mice injection when compared with the non-nuclear targeted DLC1. Although the function of nuclear DLC1 remains to be answered, our results clearly demonstrated that nuclear localization of DLC1 may serve as a potential mechanism in negatively regulating its tumor suppressive activity.link_to_OA_fulltex