Small molecule inhibitors of Late SV40 Factor (LSF) abrogate hepatocellular carcinoma (HCC): Evaluation using an endogenous HCC model.

Hepatocellular carcinoma (HCC) is a lethal malignancy with high mortality and poor prognosis. Oncogenic transcription factor Late SV40 Factor (LSF) plays an important role in promoting HCC. A small molecule inhibitor of LSF, Factor Quinolinone Inhibitor 1 (FQI1), significantly inhibited human HCC xenografts in nude mice without harming normal cells. Here we evaluated the efficacy of FQI1 and another inhibitor, FQI2, in inhibiting endogenous hepatocarcinogenesis. HCC was induced in a transgenic mouse with hepatocyte-specific overexpression of c-myc (Alb/c-myc) by injecting N-nitrosodiethylamine (DEN) followed by FQI1 or FQI2 treatment after tumor development. LSF inhibitors markedly decreased tumor burden in Alb/c-myc mice with a corresponding decrease in proliferation and angiogenesis. Interestingly, in vitro treatment of human HCC cells with LSF inhibitors resulted in mitotic arrest with an accompanying increase in CyclinB1. Inhibition of CyclinB1 induction by Cycloheximide or CDK1 activity by Roscovitine significantly prevented FQI-induced mitotic arrest. A significant induction of apoptosis was also observed upon treatment with FQI. These effects of LSF inhibition, mitotic arrest and induction of apoptosis by FQI1s provide multiple avenues by which these inhibitors eliminate HCC cells. LSF inhibitors might be highly potent and effective therapeutics for HCC either alone or in combination with currently existing therapies.

Astrocyte Elevated Gene-1 (AEG-1) Regulates Lipid Homeostasis.

Astrocyte elevated gene-1 (AEG-1), also known as MTDH (metadherin) or LYRIC, is an established oncogene. However, the physiological function of AEG-1 is not known. To address this question, we generated an AEG-1 knock-out mouse (AEG-1KO) and characterized it. Although AEG-1KO mice were viable and fertile, they were significantly leaner with prominently less body fat and lived significantly longer compared with wild type (WT). When fed a high fat and cholesterol diet (HFD), WT mice rapidly gained weight, whereas AEG-1KO mice did not gain weight at all. This phenotype of AEG-1KO mice is due to decreased fat absorption from the intestines, not because of decreased fat synthesis or increased fat consumption. AEG-1 interacts with retinoid X receptor (RXR) and inhibits RXR function. In enterocytes of AEG-1KO mice, we observed increased activity of RXR heterodimer partners, liver X receptor and peroxisome proliferator-activated receptor-α, key inhibitors of intestinal fat absorption. Inhibition of fat absorption in AEG-1KO mice was further augmented when fed an HFD providing ligands to liver X receptor and peroxisome proliferator-activated receptor-α. Our studies reveal a novel role of AEG-1 in regulating nuclear receptors controlling lipid metabolism. AEG-1 may significantly modulate the effects of HFD and thereby function as a unique determinant of obesity.

Combination of Nanoparticle-Delivered siRNA for Astrocyte Elevated Gene-1 (AEG-1) and All-trans Retinoic Acid (ATRA): An Effective Therapeutic Strategy for Hepatocellular Carcinoma (HCC).

Hepatocellular carcinoma (HCC) is a fatal cancer with no effective therapy. Astrocyte elevated gene-1 (AEG-1) plays a pivotal role in hepatocarcinogenesis and inhibits retinoic acid-induced gene expression and cell death. The combination of a lentivirus expressing AEG-1 shRNA and all-trans retinoic acid (ATRA) profoundly and synergistically inhibited subcutaneous human HCC xenografts in nude mice. We have now developed liver-targeted nanoplexes by conjugating poly(amidoamine) (PAMAM) dendrimers with polyethylene glycol (PEG) and lactobionic acid (Gal) (PAMAM-PEG-Gal) which were complexed with AEG-1 siRNA (PAMAM-AEG-1si). The polymer conjugate was characterized by (1)H-NMR, MALDI, and mass spectrometry; and optimal nanoplex formulations were characterized for surface charge, size, and morphology. Orthotopic xenografts of human HCC cell QGY-7703 expressing luciferase (QGY-luc) were established in the livers of athymic nude mice and tumor development was monitored by bioluminescence imaging (BLI). Tumor-bearing mice were treated with PAMAM-siCon, PAMAM-siCon+ATRA, PAMAM-AEG-1si, and PAMAM-AEG-1si+ATRA. In the control group the tumor developed aggressively. ATRA showed little effect due to high AEG-1 levels in QGY-luc cells. PAMAM-AEG-1si showed significant reduction in tumor growth, and the combination of PAMAM-AEG-1si+ATRA showed profound and synergistic inhibition so that the tumors were almost undetectable by BLI. A marked decrease in AEG-1 level was observed in tumor samples treated with PAMAM-AEG-1si. The group treated with PAMAM-AEG-1si+ATRA nanoplexes showed increased necrosis, inhibition of proliferation, and increased apoptosis when compared to other groups. Liver is an ideal organ for RNAi therapy and ATRA is an approved anticancer agent. Our exciting observations suggest that the combinatorial approach might be an effective way to combat HCC.

Astrocyte Elevated Gene-1 (AEG-1) Contributes to Non-thyroidal Illness Syndrome (NTIS) Associated with Hepatocellular Carcinoma (HCC).

Non-thyroidal illness syndrome (NTIS), characterized by low serum 3,5,3'-triiodothyronine (T3) with normal l-thyroxine (T4) levels, is associated with malignancy. Decreased activity of type I 5'-deiodinase (DIO1), which converts T4 to T3, contributes to NTIS. T3 binds to thyroid hormone receptor, which heterodimerizes with retinoid X receptor (RXR) and regulates transcription of target genes, such as DIO1. NF-κB activation by inflammatory cytokines inhibits DIO1 expression. The oncogene astrocyte elevated gene-1 (AEG-1) inhibits RXR-dependent transcription and activates NF-κB. Here, we interrogated the role of AEG-1 in NTIS in the context of hepatocellular carcinoma (HCC). T3-mediated gene regulation was analyzed in human HCC cells, with overexpression or knockdown of AEG-1, and primary hepatocytes from AEG-1 transgenic (Alb/AEG-1) and AEG-1 knock-out (AEG-1KO) mice. Serum T3 and T4 levels were checked in Alb/AEG-1 mice and human HCC patients. AEG-1 and DIO1 levels in human HCC samples were analyzed by immunohistochemistry. AEG-1 inhibited T3-mediated gene regulation in human HCC cells and mouse hepatocytes. AEG-1 overexpression repressed and AEG-1 knockdown induced DIO1 expression. An inverse correlation was observed between AEG-1 and DIO1 levels in human HCC patients. Low T3 with normal T4 was observed in the sera of HCC patients and Alb/AEG-1 mice. Inhibition of co-activator recruitment to RXR and activation of NF-κB were identified to play a role in AEG-1-mediated down-regulation of DIO1. AEG-1 thus might play a role in NTIS associated with HCC and other cancers.

Astrocyte elevated gene-1 and c-Myc cooperate to promote hepatocarcinogenesis in mice.

UNLABELLED: Astrocyte elevated gene-1 (AEG-1) and c-Myc are overexpressed in human hepatocellular carcinoma (HCC) functioning as oncogenes. AEG-1 is transcriptionally regulated by c-Myc, and AEG-1 itself induces c-Myc by activating the Wnt/ß-catenin-signaling pathway. We now document the cooperation of AEG-1 and c-Myc in promoting hepatocarcinogenesis by analyzing hepatocyte-specific transgenic mice expressing either AEG-1 (albumin [Alb]/AEG-1), c-Myc (Alb/c-Myc), or both (Alb/AEG-1/c-Myc). Wild-type and Alb/AEG-1 mice did not develop spontaneous HCC. Alb/c-Myc mice developed spontaneous HCC without distant metastasis, whereas Alb/AEG-1/c-Myc mice developed highly aggressive HCC with frank metastasis to the lungs. Induction of carcinogenesis by N-nitrosodiethylamine significantly accelerated the kinetics of tumor formation in all groups. However, in Alb/AEG-1/c-Myc, the effect was markedly pronounced with lung metastasis. In vitro analysis showed that Alb/AEG-1/c-Myc hepatocytes acquired increased proliferation and transformative potential with sustained activation of prosurvival and epithelial-mesenchymal transition-signaling pathways. RNA-sequencing analysis identified a unique gene signature in livers of Alb/AEG-1/c-Myc mice that was not observed when either AEG-1 or c-Myc was overexpressed. Specifically, Alb/AEG-1/c-Myc mice overexpressed maternally imprinted noncoding RNAs (ncRNAs), such as Rian, Meg-3, and Mirg, which are implicated in hepatocarcinogenesis. Knocking down these ncRNAs significantly inhibited proliferation and invasion by Alb/AEG-1/c-Myc hepatocytes. CONCLUSION: Our studies reveal a novel cooperative oncogenic effect of AEG-1 and c-Myc that might explain the mechanism of aggressive HCC. Alb/AEG-1/c-Myc mice provide a useful model to understand the molecular mechanism of cooperation between these two oncogenes and other molecules involved in hepatocarcinogenesis. This model might also be of use for evaluating novel therapeutic strategies targeting HCC.

Role of the staphylococcal nuclease and tudor domain containing 1 in oncogenesis (review).

The staphylococcal nuclease and tudor domain containing 1 (SND1) is a multifunctional protein overexpressed in breast, prostate, colorectal and hepatocellular carcinomas and malignant glioma. Molecular studies have revealed the multifaceted activities of SND1 involved in regulating gene expression at transcriptional as well as post-transcriptional levels. Early studies identified SND1 as a transcriptional co-activator. SND1 is also a component of RNA-induced silencing complex (RISC) thus mediating RNAi function, a regulator of mRNA splicing, editing and stability, and plays a role in maintenance of cell viability. Such diverse actions allow the SND1 to modulate a complex array of molecular networks, thereby promoting carcinogenesis. Here, we describe the crucial role of SND1 in cancer development and progression, and highlight SND1 as a potential target for therapeutic intervention.

The role of AEG-1 in the development of liver cancer.

AEG-1 is an oncogene that is overexpressed in all cancers, including hepatocellular carcinoma. AEG-1 plays a seminal role in promoting cancer development and progression by augmenting proliferation, invasion, metastasis, angiogenesis and chemoresistance, all hallmarks of aggressive cancer. AEG-1 mediates its oncogenic function predominantly by interacting with various protein complexes. AEG-1 acts as a scaffold protein, activating multiple protumorigenic signal transduction pathways, such as MEK/ERK, PI3K/Akt, NF-κB and Wnt/ß-catenin while regulating gene expression at transcriptional, post-transcriptional and translational levels. Our recent studies document that AEG-1 is fundamentally required for activation of inflammation. A comprehensive and convincing body of data currently points to AEG-1 as an essential component critical to the onset and progression of cancer. The present review describes the current knowledge gleaned from patient and experimental studies as well as transgenic and knockout mouse models, on the impact of AEG-1 on hepatocarcinogenesis.

Genetic deletion of AEG-1 prevents hepatocarcinogenesis.

Activation of the oncogene AEG-1 (MTDH, LYRIC) has been implicated recently in the development of hepatocellular carcinoma (HCC). In mice, HCC can be initiated by exposure to the carcinogen DEN, which has been shown to rely upon activation of NF-κB in liver macrophages. Because AEG-1 is an essential component of NF-κB activation, we interrogated the susceptibility of mice lacking the AEG-1 gene to DEN-induced hepatocarcinogenesis. AEG-1-deficient mice displayed resistance to DEN-induced HCC and lung metastasis. No difference was observed in the response to growth factor signaling or activation of AKT, ERK, and ß-catenin, compared with wild-type control animals. However, AEG-1-deficient hepatocytes and macrophages exhibited a relative defect in NF-κB activation. Mechanistic investigations showed that IL6 production and STAT3 activation, two key mediators of HCC development, were also deficient along with other biologic and epigenetics findings in the tumor microenvironment, confirming that AEG-1 supports an NF-κB-mediated inflammatory state that drives HCC development. Overall, our findings offer in vivo proofs that AEG-1 is essential for NF-κB activation and hepatocarcinogenesis, and they reveal new roles for AEG-1 in shaping the tumor microenvironment for HCC development.

AEG-1 regulates retinoid X receptor and inhibits retinoid signaling.

Retinoid X receptor (RXR) regulates key cellular responses such as cell growth and development, and this regulation is frequently perturbed in various malignancies, including hepatocellular carcinoma (HCC). However, the molecule(s) that physically govern this deregulation are mostly unknown. Here, we identified RXR as an interacting partner of astrocyte-elevated gene-1 (AEG-1)/metadherin (MTDH), an oncogene upregulated in all cancers. Upon interaction, AEG-1 profoundly inhibited RXR/retinoic acid receptor (RAR)-mediated transcriptional activation. Consequently, AEG-1 markedly protected HCC and acute myelogenous leukemia (AML) cells from retinoid- and rexinoid-induced cell death. In nontumorigenic cells and primary hepatocytes, AEG-1/RXR colocalizes in the nucleus in which AEG-1 interferes with recruitment of transcriptional coactivators to RXR, preventing transcription of target genes. In tumor cells and AEG-1 transgenic hepatocytes, overexpressed AEG-1 entraps RXR in cytoplasm, precluding its nuclear translocation. In addition, ERK, activated by AEG-1, phosphorylates RXR that leads to its functional inactivation and attenuation of ligand-dependent transactivation. In nude mice models, combination of all-trans retinoic acid (ATRA) and AEG-1 knockdown synergistically inhibited growth of human HCC xenografts. The present study establishes AEG-1 as a novel homeostatic regulator of RXR and RXR/RAR that might contribute to hepatocarcinogenesis. Targeting AEG-1 could sensitize patients with HCC and AML to retinoid- and rexinoid-based therapeutics.

Staphylococcal nuclease domain containing-1 (SND1) promotes migration and invasion via angiotensin II type 1 receptor (AT1R) and TGFß signaling.

Staphylococcal nuclease domain containing-1 (SND1) is overexpressed in human hepatocellular carcinoma (HCC) patients and promotes tumorigenesis by human HCC cells. We now document that SND1 increases angiotensin II type 1 receptor (AT1R) levels by increasing AT1R mRNA stability. This results in activation of ERK, Smad2 and subsequently the TGFß signaling pathway, promoting epithelial-mesenchymal transition (EMT) and migration and invasion by human HCC cells. A positive correlation was observed between SND1 and AT1R expression levels in human HCC patients. Small molecule inhibitors of SND1, alone or in combination with AT1R blockers, might be an effective therapeutic strategy for late-stage aggressive HCC.

Emerging role of insulin-like growth factor-binding protein 7 in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is a vicious and highly vascular cancer with a dismal prognosis. It is a life-threatening illness worldwide that ranks fifth in terms of cancer prevalence and third in cancer deaths. Most patients are diagnosed at an advanced stage by which time conventional therapies are no longer effective. Targeted molecular therapies, such as the multikinase inhibitor sorafenib, provide a modest increase in survival for advanced HCC patients and display significant toxicity. Thus, there is an immense need to identify novel regulators of HCC that might be targeted effectively. The insulin-like growth factor (IGF) axis is commonly abnormal in HCC. Upon activation, the IGF axis controls metabolism, tissue homeostasis, and survival. Insulin-like growth factor-binding protein 7 (IGFBP7) is a secreted protein of a family of low-affinity IGF-binding proteins termed "IGFBP-related proteins" that have been identified as a potential tumor suppressor in HCC. IGFBP7 has been implicated in regulating cellular proliferation, senescence, and angiogenesis. In this review, we provide a comprehensive discussion of the role of IGFBP7 in HCC and the potential use of IGFBP7 as a novel biomarker for drug resistance and as an effective therapeutic strategy.

Insulin-like growth factor-binding protein-7 (IGFBP7): a promising gene therapeutic for hepatocellular carcinoma (HCC).

Hepatocellular carcinoma (HCC) is a highly fatal disease mandating development of novel, targeted therapies to elicit prolonged survival benefit to the patients. Insulin-like growth factor-binding protein-7 (IGFBP7), a secreted protein belonging to the IGFBP family, functions as a potential tumor suppressor for HCC. In the present study, we evaluated the therapeutic efficacy of a replication-incompetent adenovirus expressing IGFBP7 (Ad.IGFBP7) in human HCC. Ad.IGFBP7 profoundly inhibited viability and induced apoptosis in multiple human HCC cell lines by inducing reactive oxygen species (ROS) and activating a DNA damage response (DDR) and p38 MAPK. In orthotopic xenograft models of human HCC in athymic nude mice, intravenous administration of Ad.IGFBP7 profoundly inhibited primary tumor growth and intrahepatic metastasis. In a nude mice subcutaneous model, xenografts from human HCC cells were established in both flanks and only left-sided tumors received intratumoral injection of Ad.IGFBP7. Growth of both left-sided injected tumors and right-sided uninjected tumors were markedly inhibited by Ad.IGFBP7 with profound suppression of angiogenesis. These findings indicate that Ad.IGFBP7 might be a potent therapeutic eradicating both primary HCC and distant metastasis and might be an effective treatment option for terminal HCC patients.

The transcription factor LSF: a novel oncogene for hepatocellular carcinoma.

The transcription factor LSF (Late SV40 Factor), also known as TFCP2, belongs to the LSF/CP2 family related to Grainyhead family of proteins and is involved in many biological events, including regulation of cellular and viral promoters, cell cycle, DNA synthesis, cell survival and Alzheimer's disease. Our recent studies establish an oncogenic role of LSF in Hepatocellular carcinoma (HCC). LSF overexpression is detected in human HCC cell lines and in more than 90% cases of human HCC patients, compared to normal hepatocytes and liver, and its expression level showed significant correlation with the stages and grades of the disease. Forced overexpression of LSF in less aggressive HCC cells resulted in highly aggressive, angiogenic and multi-organ metastatic tumors in nude mice. Conversely, inhibition of LSF significantly abrogated growth and metastasis of highly aggressive HCC cells in nude mice. Microarray studies revealed that as a transcription factor LSF modulated specific genes regulating invasion, angiogenesis, chemoresistance and senescence. LSF transcriptionally regulates thymidylate synthase (TS) gene, thus contributing to cell cycle regulation and chemoresistance. Our studies identify a network of proteins, including osteopontin (OPN), Matrix metalloproteinase-9 (MMP-9), c-Met and complement factor H (CFH), that are directly regulated by LSF and play important role in LSF-induced hepatocarcinogenesis. A high throughput screening identified small molecule inhibitors of LSF DNA binding and the prototype of these molecules, Factor Quinolinone inhibitor 1 (FQI1), profoundly inhibited cell viability and induced apoptosis in human HCC cells without exerting harmful effects to normal immortal human hepatocytes and primary mouse hepatocytes. In nude mice xenograft studies, FQI1 markedly inhibited growth of human HCC xenografts as well as angiogenesis without exerting any toxicity. These studies establish a key role of LSF in hepatocarcinogenesis and usher in a novel therapeutic avenue for HCC, an invariably fatal disease.

Astrocyte elevated gene-1 promotes hepatocarcinogenesis: novel insights from a mouse model.

UNLABELLED: Astrocyte elevated gene-1 (AEG-1) is a key contributor to hepatocellular carcinoma (HCC) development and progression. To enhance our understanding of the role of AEG-1 in hepatocarcinogenesis, a transgenic mouse with hepatocyte-specific expression of AEG-1 (Alb/AEG1) was developed. Treating Alb/AEG-1, but not wild-type (WT) mice, with N-nitrosodiethylamine resulted in multinodular HCC with steatotic features and associated modulation of expression of genes regulating invasion, metastasis, angiogenesis, and fatty acid synthesis. Hepatocytes isolated from Alb/AEG-1 mice displayed profound resistance to chemotherapeutics and growth factor deprivation with activation of prosurvival signaling pathways. Alb/AEG-1 hepatocytes also exhibited marked resistance toward senescence, which correlated with abrogation of activation of a DNA damage response. Conditioned media from Alb/AEG-1 hepatocytes induced marked angiogenesis with elevation in several coagulation factors. Among these factors, AEG-1 facilitated the association of factor XII (FXII) messenger RNA with polysomes, resulting in increased translation. Short interfering RNA-mediated knockdown of FXII resulted in profound inhibition of AEG-1-induced angiogenesis. CONCLUSION: We uncovered novel aspects of AEG-1 functions, including induction of steatosis, inhibition of senescence, and activation of the coagulation pathway to augment aggressive hepatocarcinogenesis. The Alb/AEG-1 mouse provides an appropriate model to scrutinize the molecular mechanism of hepatocarcinogenesis and to evaluate the efficacy of novel therapeutic strategies targeting HCC.

Multifunction protein staphylococcal nuclease domain containing 1 (SND1) promotes tumor angiogenesis in human hepatocellular carcinoma through novel pathway that involves nuclear factor κB and miR-221.

Staphylococcal nuclease domain-containing 1 (SND1) is a multifunctional protein that is overexpressed in multiple cancers, including hepatocellular carcinoma (HCC). Stable overexpression of SND1 in Hep3B cells expressing a low level of SND1 augments, whereas stable knockdown of SND1 in QGY-7703 cells expressing a high level of SND1 inhibits establishment of xenografts in nude mice, indicating that SND1 promotes an aggressive tumorigenic phenotype. In this study we analyzed the role of SND1 in regulating tumor angiogenesis, a hallmark of cancer. Conditioned medium from Hep3B-SND1 cells stably overexpressing SND1 augmented, whereas that from QGY-SND1si cells stably overexpressing SND1 siRNA significantly inhibited angiogenesis, as analyzed by a chicken chorioallantoic membrane assay and a human umbilical vein endothelial cell differentiation assay. We unraveled a linear pathway in which SND1-induced activation of NF-κB resulted in induction of miR-221 and subsequent induction of angiogenic factors Angiogenin and CXCL16. Inhibition of either of these components resulted in significant inhibition of SND1-induced angiogenesis, thus highlighting the importance of this molecular cascade in regulating SND1 function. Because SND1 regulates NF-κB and miR-221, two important determinants of HCC controlling the aggressive phenotype, SND1 inhibition might be an effective strategy to counteract this fatal malady.

Antiproliferative small-molecule inhibitors of transcription factor LSF reveal oncogene addiction to LSF in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide. Despite the prevalence of HCC, there is no effective, systemic treatment. The transcription factor LSF is a promising protein target for chemotherapy; it is highly expressed in HCC patient samples and cell lines, and promotes oncogenesis in rodent xenograft models of HCC. Here, we identify small molecules that effectively inhibit LSF cellular activity. The lead compound, factor quinolinone inhibitor 1 (FQI1), inhibits LSF DNA-binding activity both in vitro, as determined by electrophoretic mobility shift assays, and in cells, as determined by ChIP. Consistent with such inhibition, FQI1 eliminates transcriptional stimulation of LSF-dependent reporter constructs. FQI1 also exhibits antiproliferative activity in multiple cell lines. In LSF-overexpressing cells, including HCC cells, cell death is rapidly induced; however, primary or immortalized hepatocytes are unaffected by treatment with FQI1. The highly concordant structure-activity relationship of a panel of 23 quinolinones strongly suggests that the growth inhibitory activity is due to a single biological target or family. Coupled with the striking agreement between the concentrations required for antiproliferative activity (GI(50)s) and for inhibition of LSF transactivation (IC(50)s), we conclude that LSF is the specific biological target of FQIs. Based on these in vitro results, we tested the efficacy of FQI1 in inhibiting HCC tumor growth in a mouse xenograft model. As a single agent, tumor growth was dramatically inhibited with no observable general tissue cytotoxicity. These findings support the further development of LSF inhibitors for cancer chemotherapy.

Late SV40 factor (LSF) enhances angiogenesis by transcriptionally up-regulating matrix metalloproteinase-9 (MMP-9).

The transcription factor late SV40 factor (LSF) is overexpressed in human hepatocellular carcinoma (HCC) fostering a highly aggressive and metastatic phenotype. Angiogenesis is an essential component of cancer aggression and metastasis and HCC is a highly aggressive and angiogenic cancer. In the present studies, we analyzed the molecular mechanism of LSF-induced angiogenesis in HCC. Employing human umbilical vein endothelial cells (HUVEC) differentiation assay and chicken chorioallantoic membrane (CAM) assay we document that stable LSF overexpression augments and stable dominant negative inhibition of LSF (LSFdn) abrogates angiogenesis by human HCC cells. A quest for LSF-regulated factors contributing to angiogenesis, by chromatin immunoprecipitation-on-chip (ChIP-on-chip) assay, identified matrix metalloproteinase-9 (MMP-9) as a direct target of LSF. MMP-9 expression and enzymatic activity were higher in LSF-overexpressing cells and lower in LSFdn-expressing cells. Deletion mutation analysis identified the LSF-responsive regions in the MMP-9 promoter and ChIP assay confirmed LSF binding to the MMP-9 promoter. Inhibition of MMP-9 significantly abrogated LSF-induced angiogenesis as well as in vivo tumorigenesis, thus reinforcing the role of MMP-9 in facilitating LSF function. The present findings identify a novel target of LSF contributing to its oncogenic properties.

Insulin-like growth factor-binding protein-7 functions as a potential tumor suppressor in hepatocellular carcinoma.

PURPOSE: Hepatocellular carcinoma (HCC) is a highly virulent malignancy with no effective treatment, thus requiring innovative and effective targeted therapies. The oncogene astrocyte-elevated gene-1 (AEG-1) plays a seminal role in hepatocarcinogenesis and profoundly downregulates insulin-like growth factor-binding protein-7 (IGFBP7). The present study focuses on analyzing potential tumor suppressor functions of IGFBP7 in HCC and the relevance of IGFBP7 downregulation in mediating AEG-1 function. EXPERIMENTAL DESIGN: IGFBP7 expression was detected by immunohistochemistry in HCC tissue microarray and real-time PCR and ELISA in human HCC cell lines. Dual FISH was done to detect LOH at IGFBP7 locus. Stable IGFBP7-overexpressing clones were established in the background of AEG-1-overexpressing human HCC cells and were analyzed for in vitro proliferation and senescence and in vivo tumorigenesis and angiogenesis. RESULTS: IGFBP7 expression is significantly downregulated in human HCC samples and cell lines compared with normal liver and hepatocytes, respectively, and inversely correlates with the stages and grades of HCC. Genomic deletion of IGFBP7 was identified in 26% of patients with HCC. Forced overexpression of IGFBP7 in AEG-1-overexpressing HCC cells inhibited in vitro growth and induced senescence, and profoundly suppressed in vivo growth in nude mice that might be an end result of inhibition of angiogenesis by IGFBP7. CONCLUSION: The present findings provide evidence that IGFBP7 functions as a novel putative tumor suppressor for HCC and establish the corollary that IGFBP7 downregulation can effectively modify AEG-1 function. Accordingly, targeted overexpression of IGFBP7 might be a potential novel therapy for HCC.

c-Met activation through a novel pathway involving osteopontin mediates oncogenesis by the transcription factor LSF.

BACKGROUND & AIMS: Understanding the molecular pathogenesis of hepatocellular carcinoma (HCC) would facilitate development of targeted and effective therapies for this fatal disease. We recently demonstrated that the cellular transcription factor Late SV40 Factor (LSF) is overexpressed in more than 90% of human HCC cases, compared to the normal liver, and plays a seminal role in hepatocarcinogenesis. LSF transcriptionally upregulates osteopontin (OPN) that plays a significant role in mediating the oncogenic function of LSF. The present study aims at a better understanding of LSF function by analyzing the signaling pathway modulated by LSF. METHODS: Phospho-receptor tyrosine kinase (RTK) array was performed to identify which receptor tyrosine kinases are activated by LSF. Immunohistochemical analysis using tissue microarray was performed to establish correlation among LSF, OPN, and phospho-c-Met levels in HCC patients. Co-immunoprecipitation analysis was performed to check OPN-induced CD44 and c-Met interaction. Inhibition studies using chemicals and siRNAs were performed in vitro and in vivo using nude mice xenograft models to establish the importance of c-Met activation in mediating LSF function. RESULTS: Secreted OPN, induced by LSF, activates c-Met via a potential interaction between OPN and its cell surface receptor CD44. A significant correlation was observed among LSF, OPN, and activated c-Met levels in HCC patients. Chemical or genetic inhibition of c-Met resulted in profound abrogation of LSF-mediated tumorigenesis and metastasis in nude mice xenograft studies. CONCLUSIONS: The present findings elucidate a novel pathway of c-Met activation during hepatocarcinogenesis and support the rationale of using c-Met inhibitors as potential HCC therapeutics.