Role of hepatitis B virus X protein in liver cancer

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PTEN underexpression was associated with more aggressive tumor behaviour in hepatocellular carcinoma and PTEN suppressed cell invasion by downregulating NF-κB signaling pathway

Top Scored Posters: P-006postprintThe 3rd Annual Conference of the International Liver Cancer Association (ILCA 2009), Milan, Italy, 4-6 September 2009. In Abstract Book of ILCA 2009, 2009, p. 20, abstract no. P-00

Tensin4 is up-regulated by EGF-induced ERK1/2 activity and promotes cell proliferation and migration in hepatocellular carcinoma

The focal adhesion protein Tensin4, also known as cten (c-terminal tensin like), is structurally distinct from the three other members in the Tensin family. Its expression and potential functions in cancers including hepatocellular carcinoma (HCC) are not well understood. With immunohistochemistry, 43% (13/30) of our human HCC cases showed up-regulation of Tensin4 as compared with their corresponding non-tumorous livers. In HCC cells, treatment with epidermal growth factor (EGF) significantly induced Tensin4 transcript and protein expression, while treatment with pharmacological inhibitors against the MEK1/2 kinases abolished such induction, suggesting that Tensin4 expression was dependent on Ras/MAPK signaling. With immunofluorescence microscopy, the focal adhesion localization of Tensin4 was confirmed in HCC cells. Significantly, detailed examination using a panel of Tensin4 deletion constructs revealed that this specific focal adhesion localization required the N-terminal region together with the C-terminal SH2 domain. Up-regulation of ERK signaling by EGF in the HCC cells resulted in a change to a mesenchymal celllike morphology through modulation of the actin cytoskeleton. Functionally, stable Tensin4 knockdown in SMMC-7721 HCC cells resulted in reduced cell proliferation and migration in vitro. Taken together, our data suggest that Tensin4 may play a pro-oncogenic role in HCC, possibly functioning as a downstream effector of Ras/ MAPK signaling.published_or_final_versio

Rapamycin and CCI-779 inhibit the mammalian target of rapamycin signalling in hepatocellular carcinoma

Background: The mammalian target of rapamycin (mTOR), which phosphorylates p70S6K and 4EBP1 and activates the protein translation process, is upregulated in cancers and its activation may be involved in cancer development. Aims: In this study, we investigated the tumour-suppressive effects of rapamycin and its new analogue CCI-779 on hepatocellular carcinoma (HCC). Methods: Rapamycin and its new analogue CCI-779 were applied to treat HCC cells. Cell proliferation, cell cycle profile and tumorigenicity were analysed. Results: In human HCCs, we observed frequent (67%, 37/55) overexpression of mTOR transcripts using real-time reverse transcriptasepolymerase chain reaction. Upon drug treatment, PLC/PRF/5 showed the greatest reduction in cell proliferation using the colony formation assay, as compared with HepG2, Hep3B and HLE. Rapamycin was a more potent antiproliferative agent than CCI-779 in HCC cell lines. Proliferation assays by cell counting showed that the IC50 value of rapamycin was lower than that of CCI-779 in PLC/PRF/5 cells. Furthermore, flow cytometric analysis showed that both drugs could arrest HCC cells in the G1 phase but did not induce apoptosis of these cells, suggesting that these mTOR inhibitors are cytostatic rather than cytotoxic. Upon rapamycin and CCI-779 treatment, the phosphorylation level of mTOR and p70S6K in HCC cell lines was significantly reduced, indicating that both drugs can suppress mTOR activity in HCC cells. In addition, both drugs significantly inhibited the growth of xenografts of PLC/PRF/5 cells in nude mice. Conclusions: Our findings indicate that rapamycin and its clinical analogue CCI-779 possess tumour-suppressive functions towards HCC cells. © 2009 John Wiley & Sons A/S.postprin

RhoE/ROCK signaling modulates chemoresistance in HCC through IL6/JAK2/STAT3 pathways

Conference Theme: New Horizons in Cancer Research Conference: Harnessing Breakthroughs - Targeting CuresPoster Session B: Tumor Biology: no. B40Liver cancer (hepatocellular carcinoma, HCC) is a major malignancy worldwide and the second commonest fatal cancer in Southeast Asia and China including Hong Kong, due to the high prevalence of hepatitis B viral infection. HCC is highly chemoresistant, limiting treatment options to patients. There is an urgent need to delineate the underlying molecular mechanism of HCC chemoresistance so as to identify novel therapeutic targets for this aggressive cancer. Deregulation of Rho GTPase pathway is demonstrated to play important roles in HCC tumorigenesis. RhoE/Rnd3 belongs to the Rnd subfamily of the Rho GTPase which lacks the intrinsic GTPase activity. In our previous study, we have shown that RhoE is frequently downregulated in human HCCs and acts as a metastasis suppressor, whereas ROCK2 is upregulated in human HCCs. In this study, we aimed to investigate whether RhoE is also involved in the regulation of chemoresistance in HCC. Using short-hairpin RNA and ...published_or_final_versio

C-terminus-truncated hepatitis B virus X protein enhances cell invasiveness in hepatocellular carcinoma

Poster Session 8 - Oncogenic Gene Regulatory Mechanisms: abstract no. 2212Open Access JournalHepatocellular carcinoma (HCC) is the fifth of major malignancies worldwide and chronic hepatitis B virus (HBV) infection is one of its well known risk factors. Random integration of the HBV DNA into host genome is frequent in human HCCs and this leads to truncation of the HBV DNA, particularly at the C-terminal end of the HBV X protein (HBx). In this study, we investigated the frequency of this C-terminal truncation of HBx in human HCCs and its functional significance in HCC cells. In the 51 HBV-positive patients with HCC, full-length HBx was detected in all of the non-tumorous livers. Interestingly, natural COOH-truncated HBx was found in 47% tumours. Upon clinicopathological analysis, presence of natural COOH-truncated HBx significantly correlated with the presence of venous invasion, a hallmark of metastasis (p < 0.01). Doxycycline- inducible stable expression of the full-length HBx and C-terminal truncated forms of HBx in HepG2 cells was employed for in vitro cell invasion assay and cell signalling analysis involved in cell invasiveness. Inducible expression of COOH-truncated HBx protein (with 24 amino acids truncated at C-terminal end) in HepG2 cells enhanced cell invasiveness, and C-Jun transcriptional activity, and increased MMP10 transcription production, as compared with the full-length HBx. The activation of the MMP10 promoter by the COOH-truncated HBx was abolished when the AP-1 binding sites were mutated. Our data suggest that COOH-truncation of HBx may play a significant role in enhancing cell invasiveness and metastasis in HCC, possibly via activation of the MMP10 through C-Jun signaling pathway.link_to_OA_fulltextThe 103rd Annual Meeting of the American Association for Cancer Research (AACR 2012), Chicago, IL., 31 March-4 April 2012

Role of a novel splice variant of mitotic arrest deficient 1 (MAD1), MAD1β, in mitotic checkpoint control in liver cancer

Loss of mitotic checkpoint contributes to chromosomal instability, leading to carcinogenesis. In this study, we identified a novel splicing variant of mitotic arrest deficient 1 (MAD1), designated MAD1β, and investigated its role in mitotic checkpoint control in hepatocellular carcinoma (HCC). The expression levels of human MAD1β were examined in hepatoma cell lines and human HCC samples. The functional roles of MAD1β in relation to the mitotic checkpoint control, chromosomal instability, and binding with MAD2 were assessed in hepatoma cell lines. On sequencing, MAD1β was found to have deletion of exon 4. It was expressed at both mRNA and protein levels in the nine hepatoma cell lines tested and was overexpressed in 12 of 50 (24%) human HCCs. MAD1β localized in the cytoplasm, whereas MAD1α was found in the nucleus. This cytoplasmic localization of MAD1β was due to the absence of a nuclear localization signal in MAD1α. In addition, MAD1β was found to physically interact with MAD2 and sequester it in the cytoplasm. Furthermore, expression of MAD1β induced mitotic checkpoint impairment, chromosome bridge formation, and aberrant chromosome numbers via binding with MAD2. Our data suggest that the novel splicing variant MAD1β may have functions different from those of MAD1α and may play opposing roles to MAD1α in mitotic checkpoint control in hepatocarcinogenesis. ©2008 American Association for Cancer Research.link_to_OA_fulltex

Proline-rich acidic protein 1 (PRAP1), a novel mitotic arrest deficient 1 (MAD1) interacting partner, suppresses mitotic checkpoint signaling in hepatocellular carcinoma

Poster Presentations - Cell Cycle 1: abstract no. 572DNA aneuploidy or chromosomal instability is commonly observed in major types of human cancers, and one of the causes for chromosomal instability is defective mitotic checkpoint signaling in cells. Loss of mitotic checkpoint contributes to chromosomal instability, leading to carcinogenesis. The mitotic checkpoint monitors the status of kinetochore-microtubule attachment and delays the onset of anaphase until all kinetochores have been attached with microtubules. Mitotic arrest deficient 1 (MAD1) is key component in mitotic checkpoint signaling. We previously identified a novel isoform of …link_to_OA_fulltex

Proline-rich acidic protein 1 (PRAP1), a novel mitotic arrest deficient 1 (MAD1) interacting partner, has suppressive role in mitotic checkpoint signaling in hepatocellular carcinoma

Young Investigator Award: Biomedicine: abstract no. A4

Association of MAD2 expression with mitotic checkpoint competence in hepatoma cells

Chromosomal instability (CIN) refers to high rates of chromosomal gains and losses and is a major cause of genomic instability of cells. It is thought that CIN caused by loss of mitotic checkpoint contributes to carcinogenesis. In this study, we evaluated the competence of mitotic checkpoint in hepatoma cells and investigated the cause of mitotic checkpoint defects. We found that 6 (54.5%) of the 11 hepatoma cell lines were defective in mitotic checkpoint control as monitored by mitotic indices and flow-cytometric analysis after treatment with microtubule toxins. Interestingly, all 6 hepatoma cell lines with defective mitotic checkpoint showed significant underexpression of mitotic arrest deficient 2 (MAD2), a key mitotic checkpoint protein. The level of MAD2 underexpression was significantly associated with defective mitotic checkpoint response (p < 0.001). In addition, no mutations were found in the coding sequences of MAD2 in all 11 hepatoma cell lines. Our findings suggest that MAD2 deficiency may cause a mitotic checkpoint defect in hepatoma cells. Copyright © 2004 National Science Council, ROC and S. Karger AG, Basel.link_to_subscribed_fulltex