EEF1A2 inactivates p53 by way of PI3K/AKT/mTOR-dependent stabilization of MDM4 in hepatocellular carcinoma

Mouse Double Minute homolog 4 (MDM4) gene up-regulation often occurs in human hepatocellular carcinoma (HCC), but the molecular mechanisms responsible for its induction remain poorly understood. Here we investigated the role of the phosphoinositide-3-kinase/v-akt murine thymoma viral oncogene homolog/mammalian target of rapamycin (PI3K/AKT/mTOR) axis in the regulation of MDM4 levels in HCC. The activity of MDM4 and the PI3K/AKT/mTOR pathway was modulated in human HCC cell lines by way of silencing and overexpression experiments. Expression of main pathway components was analyzed in an AKT mouse model and human HCCs. MDM4 inhibition resulted in growth restraint of HCC cell lines both in vitro and in vivo. Inhibition of the PI3K-AKT and/or mTOR pathways lowered MDM4 protein levels in HCC cells and reactivated p53-dependent transcription. Deubiquitination by ubiquitin-specific protease 2a and AKT-mediated phosphorylation protected MDM4 from proteasomal degradation and increased its protein stability. The eukaryotic elongation factor 1A2 (EEF1A2) was identified as an upstream inducer of PI3K supporting MDM4 stabilization. Also, we detected MDM4 protein up-regulation in an AKT mouse model and a strong correlation between the expression of EEF1A2, activated/phosphorylated AKT, and MDM4 in human HCC (each rho > 0.8, P < 0.001). Noticeably, a strong activation of this cascade was associated with shorter patient survival.

CONCLUSION

The EEF1A2/PI3K/AKT/mTOR axis promotes the protumorigenic stabilization of the MDM4 protooncogene in human HCC by way of a posttranscriptional mechanism. The activation level of the EEF1A2/PI3K/AKT/mTOR/MDM4 axis significantly influences the survival probability of HCC patients in vivo and may thus represent a promising molecular target.

Kidney protein profiling of Wilms' tumor patients by analysis of formalin-fixed paraffin-embedded tissue samples

Wilms' tumor (nephroblastoma, WT) is the most frequent renal cancer in children. However, molecular details leading to WT have not been characterized sufficiently yet. Proteomic studies might provide new insights but are hampered by limited availability of fresh frozen tissue specimen. Therefore, we tested formalin-fixed paraffin-embedded (FFPE) tissue sections routinely collected for pathological inspection for their use in in-depth-proteomic analyses of WT samples in comparison to fresh frozen specimen. The overlap of the proteins identified was over 65%. Thus we used FFPE material from 7 patients for tandem mass spectrometry based comparison of the proteomes of WT and healthy renal tissues. We detected 262 proteins, which were differentially expressed in tumor compared to healthy renal tissue. The majority of these proteins displayed lower levels in the tumor tissue and only 30% higher levels. For selected candidates data were confirmed by immunohistochemical staining. Correlation analysis of blastemal proportions in WT and protein intensities revealed candidates for tumor stratification.

CONCLUSION

This proof of principle proteomic study of FFPE tissue sections from WT patients demonstrates that these archived tissues constitute a valuable resource for larger in-depth proteomic studies to identify markers to follow chemotherapy efficiency or for stratification of tumor subtypes.

Virtual slide telepathology with scanner systems for intraoperative frozen-section consultation

Telepathology provides pathology services over a distance using digital imaging and telecommunication for primary diagnostic practice, including intraoperative frozen sections. Virtual slide technology provides digitizing of histological slides by scanner systems and improved remote assessment substantially. In this retrospective study, diagnostic accuracy of intraoperative frozen sections assessed as virtual slide was determined. Tissue assessment was mainly requested for urological, gynecological and dermatological resections. Issues of time consumption, cost and cost effectiveness of this diagnostic method are discussed. 1204 intraoperative frozen sections were conducted in the course of this study at our department over a period of 2.5 years. 98.59% of all intraoperative frozen sections were accurately diagnosed in the initial telepathological assessment. Tumor affection was present in 15.6% of frozen sections, in 174 instances already assessed in the initial slides (sensitivity 92.6%). Discrepant diagnoses compared to the final diagnosis occurred in 1.41%. Our determined averaged time for virtual slide technology of 10.58±8.19min can be ranged in well. Our study did not allow a full economic assessment, but some preliminary insights are pointed out. The quality of services is highly acceptable and the investment costs and the labor cost of virtual slide technology are lower than those of robotic microscopy.

Autoimmune pancreatitis in MRL/Mp mice is a T cell-mediated disease responsive to cyclosporine A and rapamycin treatment

BACKGROUND

Autoimmune pancreatitis (AIP) in humans invariably responds to steroid treatment, but little is known about the underlying pathogenesis and the benefits of alternative treatments.

OBJECTIVE

To study the pathogenesis, and the efficacy of alternative immunosuppressant agents in the MRL/Mp mouse model of AIP.

DESIGN

MRL/Mp mice were pretreated for 4 weeks with polyinosinic:polycytidylic acid to induce AIP. Pancreatic sections of mice genetically deleted for CTLA-4 were analysed. Blockage of CTLA-4 was achieved by intraperitoneal antibody treatment with 2 μg/g anti-mouse-CD152. Subsequent therapeutic studies were performed for a period of 4 weeks using cyclosporine A (40 μg/g), rapamycin (1 μg/g) or azathioprine (15 μg/g).

RESULTS

Blockage of CTLA-4 in MRL/Mp mice suppressed regulatory T cell (Treg) function and raised the effector T cell (Teff) response with subsequent histomorphological organ destruction, indicating that AIP is a T cell-driven disease. Using an established histopathological score, we found that dexamethasone, cyclosporine A and rapamycin, but less so azathioprine, reduced pancreatic damage. However, the beneficial effects of cyclosporine A and rapamycin were achieved via different mechanisms: cyclosporine A inhibited Teff activation and proliferation whereas rapamycin led to selective expansion of Tregs which subsequently suppressed the Teff response.

CONCLUSIONS

The calcineurin inhibitor cyclosporine A and the mammalian target of rapamycin (mTOR) inhibitor, rapamycin, improve the course of AIP in MRL/Mp mice via different mechanisms. These findings further support the concept of autoreactive T cells as key players in the pathogenesis of AIP and suggest that cyclosporine A and rapamycin should be considered for treatment of AIP in humans.

Deregulation of DNA-dependent protein kinase catalytic subunit contributes to human hepatocarcinogenesis development and has a putative prognostic value

Background:

The DNA-repair gene DNA-dependent kinase catalytic subunit (DNA-PKcs) favours or inhibits carcinogenesis, depending on the cancer type. Its role in human hepatocellular carcinoma (HCC) is unknown.

Methods:

DNA-dependent protein kinase catalytic subuni, H2A histone family member X (H2AFX) and heat shock transcription factor-1 (HSF1) levels were assessed by immunohistochemistry and/or immunoblotting and qRT–PCR in a collection of human HCC. Rates of proliferation, apoptosis, microvessel density and genomic instability were also determined. Heat shock factor-1 cDNA or DNA-PKcs-specific siRNA were used to explore the role of both genes in HCC. Activator protein 1 (AP-1) binding to DNA-PKcs promoter was evaluated by chromatin immunoprecipitation. Kaplan–Meier curves and multivariate Cox model were used to study the impact on clinical outcome.

Results:

Total and phosphorylated DNA-PKcs and H2AFX were upregulated in HCC. Activated DNA-PKcs positively correlated with HCC proliferation, genomic instability and microvessel density, and negatively with apoptosis and patient's survival. Proliferation decline and massive apoptosis followed DNA-PKcs silencing in HCC cell lines. Total and phosphorylated HSF1 protein, mRNA and activity were upregulated in HCC. Mechanistically, we demonstrated that HSF1 induces DNA-PKcs upregulation through the activation of the MAPK/JNK/AP-1 axis.

Conclusion:

DNA-dependent protein kinase catalytic subunit transduces HSF1 effects in HCC cells, and might represent a novel target and prognostic factor in human HCC.

Functional crosstalk between AKT/mTOR and Ras/MAPK pathways in hepatocarcinogenesis: implications for the treatment of human liver cancer

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death worldwide, with limited treatment options. AKT/mTOR and Ras/MAPK pathways are frequently deregulated in human hepatocarcinogenesis. Recently, we generated an animal model characterized by the co-expression of activated forms of AKT and Ras in the mouse liver. We found that concomitant activation of AKT/mTOR and Ras/MAPK cascades leads to rapid liver tumor development in AKT/Ras mice, mainly through mTORC1 induction. To further define the role of mTORC1 cascade in AKT/Ras induced HCC development, the mTORC1 inhibitor Rapamycin was administered to AKT/Ras mice at the time when small tumors started to emerge in the liver. Of note, Rapamycin treatment significantly delayed hepatocarcinogenesis in AKT/Ras mice. However, some microscopic lesions persisted in the livers of AKT/Ras mice despite the treatment and rapidly gave rise to HCC following Rapamycin withdrawal. Mechanistically, Rapamycin inhibited mTORC1 and mTORC2 pathways, lipogenesis and glycolysis, resulting in inhibition of proliferation in the treated livers. However, activated ERK and its downstream effectors, Mnk1 and eIF4E, were strongly upregulated in the residual lesions. Concomitant suppression of AKT/mTOR and Ras/MAPK pathways was highly detrimental for the growth of AKT/Ras cells in vitro. The study indicates the existence of a complex interplay between AKT/mTOR and Ras/MAPK pathways during hepatocarcinogenesis, with important implications for the understanding of HCC pathogenesis as well as for its prevention and treatment.

Yes-associated protein up-regulates Jagged-1 and activates the Notch pathway in human hepatocellular carcinoma

BACKGROUND & AIMS

Cancer cells often lose contact inhibition to undergo anchorage-independent proliferation and become resistant to apoptosis by inactivating the Hippo signaling pathway, resulting in activation of the transcriptional co-activator yes-associated protein (YAP). However, the oncogenic mechanisms of YAP activity are unclear.

METHODS

By using cross-species analysis of expression data, the Notch ligand Jagged-1 (Jag-1) was identified as a downstream target of YAP in hepatocytes and hepatocellular carcinoma (HCC) cells. We analyzed the functions of YAP in HCC cells via overexpression and RNA silencing experiments. We used transgenic mice that overexpressed a constitutively activated form of YAP (YAP(S127A)), and measured protein levels in HCC, colorectal and pancreatic tumor samples from patients.

RESULTS

Human HCC cell lines and mouse hepatocytes that overexpress YAP(S127A) up-regulated Jag-1, leading to activation of the Notch pathway and increased proliferation. Induction of Jag-1, activation of Notch, and cell proliferation required binding of YAP to its transcriptional partner TEA domain family member 4 (TEAD4); TEAD4 binding required the Mst1/2 but not β-catenin signaling. Levels of YAP correlated with Jag-1 expression and Notch signaling in human tumor samples and correlated with shorter survival times of patients with HCC or colorectal cancer.

CONCLUSIONS

The transcriptional regulator YAP up-regulates Jag-1 to activate Notch signaling in HCC cells and mouse hepatocytes. YAP-dependent activity of Jag-1 and Notch correlate in human HCC and colorectal tumor samples with patient survival times, suggesting the use of YAP and Notch inhibitors as therapeutics for gastrointestinal cancer. Transcript profiling: microarray information was deposited at the Gene Expression Omnibus database (http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?token=jxepvsumwosqkve&acc=GSE35004).

Abstract 1880: Role of fatty acid synthase and do novo lipogenesis in liver cancer development in mice

Aberrant metabolism, including increased de novo lipogenesis, is one of the hallmarks of cancer. Fatty Acid Synthase (Fasn) catalyzes the de novo synthesis of long-chain fatty acids from acetyl-CoA and malonyl-CoA. Increased Fasn expression has been reported in multiple tumor types, and inhibition of Fasn expression has been shown to have tumor-suppressing activity. However, how increased de novo lipogenesis contributes to tumor initiation and progression, especially in vivo, remains unknown.

In our previous studies, we showed that overexpression of the activated form of AKT (myr-AKT) induced de novo lipogenesis, hepatocyte proliferation and, eventually, liver cancer formation in mice. The tumorigenesis process could be significantly accelerated via co-expression of activated form of Ras. In the AKTRas tumor model, tumors were predominantly (&gt;80%) hepatocellular carcinoma (HCC), and the remaining (&lt;20%) were intrahepatic cholangiocarcinoma (ICC). The ICCs were induced via hepatocyte-biliary epithelial cell metaplasia in a Notch dependent manner. Intriguingly, fat droplet formation, increased expression of Fasn and other lipogenesis pathway genes were identified in HCC lesions, but not ICC lesions. To define whether Fasn-mediated de novo lipogenesis is a key metabolic event downstream of mTORC1 during AKTRas-induced hepatocarcinogenesis, we utilized Fasn flox/flox mice, and co-expressed AKTRas in the Fasn KO hepatocytes. Of note, we found that ablation of Fasn completely inhibited AKT induced lipogenesis and hepatocyte proliferation in mice. However, loss of Fasn modestly delayed AKTRas-induced liver tumor development. Histological analysis revealed that these tumor lesions were predominantly ICCs. The ICC cells were highly proliferative, and did not express Fasn or any other lipogenic pathway gene. The results suggest that Fasn-mediated de novo lipogenesis is required for AKTRas-induced HCC formation, but this process is dispensable for ICC formation.

In summary, our experiments support a critical role for Fasn as a downstream effector of mTORC1 in HCC pathogenesis. However, Fasn-mediated do novo fatty acid synthesis is not required in all tumor types. It is likely that other sources of fatty acids, presumably including those derived from the diet, can be utilized by cancer cells for membrane synthesis during cell proliferation.

Citation Format: Xin Chen, Lei Li, Chunmei Wang, Matthias Evert, Diego F. Calvisi, Clay F. Semenkovich. Role of fatty acid synthase and do novo lipogenesis in liver cancer development in mice. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1880. doi:10.1158/1538-7445.AM2013-1880

Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.

Abstract 4300: The EEF1A2-PI3K-AKT-mTOR axis supports the protumorigenic function of MDM4 in human hepatocellular carcinoma

Background & Aims: The Mouse Double Minute homolog 4 (MDM4) is one of the main negative p53 regulators in mammalian cells and mutational inactivation of p53 is a rare event in Western hepatocellular carcinomas (HCCs). 1q gains promote the upregulation of MDM4 in HCC, leading to a negative regulation of p53 activity. However, additional mechanisms might be involved that explain the increased MDM4 activity observed in HCCs with balanced MDM4 gene locus. Here we aimed at the identification of post-transcriptional mechanisms involved in the upregulation of MDM4 in HCC.

Methods: To investigate a potential role of PI3K-AKT-mTOR signaling on MDM4 activity, HCC cell lines were treated with small molecule inhibitors and siRNAs and expression changes as well as functional analyses were recorded. Expression changes of central pathway components were investigated in human liver samples (normal liver, peritumorous liver tissue, and HCC). An AKT transgenic mouse model was used to show the involvement of AKT pathway in the regulation of MDM4 in vivo.

Results: The inhibition of both PI3K-AKT and mTOR signaling pathways resulted in reduced MDM4 protein levels in HCC cell lines, which was associated with the transcriptional activation of p53-target genes. Biochemical assays revealed that both AKT-mediated phosphorylation and ubiquitin-specific protease 2a (USP2a)-mediated deubiquitination protected MDM4 from proteasomal in human HCC cell lines. In addition, AKT transgenic mice showed increased MDM4 protein levels indicating that AKT signaling is involved in the stabilization of MDM4 protein in vivo. Furthermore, the Eukaryotic translational Elongation Factor 1 alpha 2 (EEF1A2), which is frequently upregulated in human HCC, sustained the PI3K-AKT-mTOR cascade both in vitro and in vivo. In human HCCs, a strong positive correlation between the overexpression of EEF1A2, pAKT, USP2a, and MDM4 was observed, which was associated with shorter survival of HCC patients.

Conclusions: Our data demonstrate that the EEF1A2/PI3K/AKT/mTOR cascade inactivates wild-type p53 in human HCC through the stabilization of the MDM4 protooncogene via a post-transcriptional mechanism involving an AKT-mediated phosphorylation of MDM4 and USP2a-mediated de-ubiquitination. Since the sustained activation of the EEF1A2/PI3K/AKT/mTOR/MDM4 axis has impact on the survival probability of HCC patients, it may thus represent a promising therapeutic target.

Citation Format: Rossella Pellegrino, Diego F. Calvisi, Olaf Neumann, Xin Chen, Chunmei Wang, Bernhard Radlwimmer, Sara Ladu, Frank Dombrowski, Matthias Evert, Peter Schirmacher, Thomas Longerich. The EEF1A2-PI3K-AKT-mTOR axis supports the protumorigenic function of MDM4 in human hepatocellular carcinoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4300. doi:10.1158/1538-7445.AM2013-4300

Tissue tolerable plasma (TTP) induces apoptosis in pancreatic cancer cells in vitro and in vivo

Background

The rate of microscopic incomplete resections of gastrointestinal cancers including pancreatic cancer has not changed considerably over the past years. Future intra-operative applications of tissue tolerable plasmas (TTP) could help to address this problem. Plasma is generated by feeding energy, like electrical discharges, to gases. The development of non-thermal atmospheric plasmas displaying spectra of temperature within or just above physiological ranges allows biological or medical applications of plasmas.

Methods

We have investigated the effects of tissue tolerable plasmas (TTP) on the human pancreatic cancer cell line Colo-357 and PaTu8988T and the murine cell line 6606PDA in vitro (Annexin-V-FITC/DAPI-Assay and propidium iodide DNA staining assay) as well as in the in vivo tumour chorio-allantoic membrane (TUM-CAM) assay using Colo-357.

Results

TTP of 20 seconds (s) induced a mild elevation of an experimental surface temperature of 23.7 degree Celsius up to 26.63+/−0.40 degree Celsius. In vitro TTP significantly (p=0.0003) decreased cell viability showing the strongest effects after 20s TTP. Also, TTP effects increased over time levelling off after 72 hours (30.1+/−4.4% of dead cells (untreated control) versus 78.0+/−9.6% (20s TTP)). However, analyzing these cells for apoptosis 10s TTP revealed the largest proportion of apoptotic cells (34.8+/−7.2%, p=0.0009 versus 12.3+/−6.6%, 20s TTP) suggesting non-apoptotic cell death in the majority of cells after 20s TTP. Using solid Colo-357 tumours in the TUM-CAM model TUNEL-staining showed TTP-induced apoptosis up to a depth of tissue penetration (DETiP) of 48.8+/−12.3μm (20s TTP, p<0.0001). This was mirrored by a significant (p<0.0001) reduction of Ki-67+ proliferating cells (80.9+/−13.2% versus 37.7+/−14.6%, p<0.0001) in the top cell layers as well as typical changes on HE specimens. The bottom cell layers were not affected by TTP.

Conclusions

Our data suggest possible future intra-operative applications of TTP to reduce microscopic residual disease in pancreatic cancer resections. Further promising applications include other malignancies (central liver/lung tumours) as well as synergistic effects combining TTP with chemotherapies. Yet, adaptations of plasma sources as well as of the composition of effective components of TTP are required to optimize their synergistic apoptotic actions.

Bmi1 is required for hepatic progenitor cell expansion and liver tumor development

Bmi1 is a polycomb group transcriptional repressor and it has been implicated in regulating self-renewal and proliferation of many types of stem or progenitor cells. In addition, Bmi1 has been shown to function as an oncogene in multiple tumor types. In this study, we investigated the functional significance of Bmi1 in regulating hepatic oval cells, the major type of bipotential progenitor cells in adult liver, as well as the role of Bmi1 during hepatocarcinogenesis using Bmi1 knockout mice. We found that loss of Bmi1 significantly restricted chemically induced oval cell expansion in the mouse liver. Concomitant deletion of Ink4a/Arf in Bmi1 deficient mice completely rescued the oval cell expansion phenotype. Furthermore, ablation of Bmi1 delayed hepatocarcinogenesis induced by AKT and Ras co-expression. This antineoplastic effect was accompanied by the loss of hepatic oval cell marker expression in the liver tumor samples. In summary, our data demonstrated that Bmi1 is required for hepatic oval cell expansion via deregulating the Ink4a/Arf locus in mice. Our study also provides the evidence, for the first time, that Bmi1 expression is required for liver cancer development in vivo, thus representing a promising target for innovative treatments against human liver cancer.

Hepatoma cells from mice deficient in glycine N-methyltransferase have increased RAS signaling and activation of liver kinase B1

BACKGROUND & AIMS

Patients with cirrhosis are at high risk for developing hepatocellular carcinoma (HCC), and their liver tissues have abnormal levels of S-adenosylmethionine (SAMe). Glycine N-methyltransferase (GNMT) catabolizes SAMe, but its expression is down-regulated in HCC cells. Mice that lack GNMT develop fibrosis and hepatomas and have alterations in signaling pathways involved in carcinogenesis. We investigated the role of GNMT in human HCC cell lines and in liver carcinogenesis in mice.

METHODS

We studied hepatoma cells from GNMT knockout mice and analyzed the roles of liver kinase B1 (LKB1, STK11) signaling via 5'-adenosine monophosphate-activated protein kinase (AMPK) and Ras in regulating proliferation and transformation.

RESULTS

Hepatoma cells from GNMT mice had defects in LKB1 signaling to AMPK, making them resistant to induction of apoptosis by adenosine 3',5'-cyclic monophosphate activation of protein kinase A and calcium/calmodulin-dependent protein kinase kinase 2. Ras-mediated hyperactivation of LKB1 promoted proliferation of GNMT-deficient hepatoma cells and required mitogen-activated protein kinase 2 (ERK) and ribosomal protein S6 kinase polypeptide 2 (p90RSK). Ras activation of LKB1 required expression of RAS guanyl releasing protein 3 (RASGRP3). Reduced levels of GNMT and phosphorylation of AMPKα at Thr172 and increased levels of Ras, LKB1, and RASGRP3 in HCC samples from patients were associated with shorter survival times.

CONCLUSIONS

Reduced expression of GNMT in mouse hepatoma cells and human HCC cells appears to increase activity of LKB1 and RAS; activation of RAS signaling to LKB1 and RASGRP3, via ERK and p90RSK, might be involved in liver carcinogenesis and be used as a prognostic marker. Reagents that disrupt this pathway might be developed to treat patients with HCC.

Inactivation of Spry2 accelerates AKT-driven hepatocarcinogenesis via activation of MAPK and PKM2 pathways

BACKGROUND & AIMS

Aberrant activation of the AKT oncogenic pathway and downregulation of the Sprouty 2 (Spry2) tumor suppressor gene are frequently observed molecular events in human hepatocarcinogenesis. The goal of the present study was to investigate the eventual biochemical and genetic crosstalk between activated AKT and inactivation of Spry2 during liver cancer development by using in vivo and in vitro approaches.

METHODS

Activated AKT and/or Spry2Y55F, a dominant negative form of Spry2, were overexpressed in the mouse liver via hydrodynamic gene delivery. Histological and biochemical assays were applied to characterize the molecular features of AKT and AKT/Spry2Y55F liver tumors. The human HLE hepatocellular carcinoma (HCC) cell line, stably overexpressing AKT, was transfected with Spry2Y55F to study the molecular mechanisms underlying hepatocarcinogenesis driven by Spry2 loss.

RESULTS

Spry2Y55F overexpression significantly accelerated AKT-induced hepatocarcinogenesis in the mouse. AKT/Spry2Y55F liver lesions had increased proliferation and glycolysis and decreased lipogenesis when compared with AKT corresponding lesions. At the molecular level, AKT/Spry2Y55F HCCs exhibited a significantly stronger induction of activated mitogen-activated protein kinase (MAPK) and pyruvate kinase M2 (PKM2) pathways than in AKT corresponding lesions. This phenotype was reproduced in HLE cells overexpressing AKT following transfection with Spry2Y55F. Furthermore, we found that concomitant suppression of the MAPK cascade and PKM2 strongly inhibited the growth induced by Spry2Y55F in AKT-overexpressing cells.

CONCLUSIONS

Inactivation of Spry2 accelerates AKT-induced hepatocarcinogenesis via activation of MAPK and PKM2 pathways.

Effect of multipeak spectral modeling of fat for liver iron and fat quantification: correlation of biopsy with MR imaging results

PURPOSE

To investigate the effect of the multipeak spectral modeling of fat on R2* values as measures of liver iron and on the quantification of liver fat fraction, with biopsy as the reference standard.

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained. Patients with liver disease (n = 95; 50 men, 45 women; mean age, 57.2 years±14.1 [standard deviation]) underwent a nontargeted liver biopsy, and 97 biopsy samples were reviewed for steatosis and iron grades. MR imaging at 1.5 T was performed 24-72 hours after biopsy by using a three-echo three-dimensional gradient-echo sequence for water and fat separation. Data were reconstructed off-line, correcting for T1 and T2* effects. Fat fraction and R2* maps (1/T2*) were reconstructed and differences in R2* and steatosis grades with and without multipeak modeling of fat were tested by using the Kruskal-Wallis test. Spearman rank correlation coefficient was used to assess fat fractions and steatosis grades. Linear regression analysis was performed to compare the fat fraction for both models.

RESULTS

Mean steatosis grade at biopsy ranged from 0% to 95%. Biopsy specimens in 26 of 97 patients (27%) showed liver iron (15 mild, six moderate, and five severe). In all 71 samples without iron, a strong increase in the apparent R2* was observed with increasing steatosis grade when single-peak modeling of fat was used (P=.001). When multipeak modeling was used, there were no differences in the apparent R2* as a function of steatosis grading (P=.645), and R2* values agreed closely with those reported in the literature. Good correlation between fat fraction and steatosis grade was observed (rS=0.85) both without and with spectral modeling.

CONCLUSION

In the presence of fat, multipeak spectral modeling of fat improves the agreement between R2* and liver iron. Single-peak modeling of fat leads to underestimation of liver fat.

Cholangiocarcinomas can originate from hepatocytes in mice

Intrahepatic cholangiocarcinomas (ICCs) are primary liver tumors with a poor prognosis. The development of effective therapies has been hampered by a limited understanding of the biology of ICCs. Although ICCs exhibit heterogeneity in location, histology, and marker expression, they are currently thought to derive invariably from the cells lining the bile ducts, biliary epithelial cells (BECs), or liver progenitor cells (LPCs). Despite lack of experimental evidence establishing BECs or LPCs as the origin of ICCs, other liver cell types have not been considered. Here we show that ICCs can originate from fully differentiated hepatocytes. Using a mouse model of hepatocyte fate tracing, we found that activated NOTCH and AKT signaling cooperate to convert normal hepatocytes into biliary cells that act as precursors of rapidly progressing, lethal ICCs. Our findings suggest a previously overlooked mechanism of human ICC formation that may be targetable for anti-ICC therapy.

V-AKT murine thymoma viral oncogene homolog/mammalian target of rapamycin activation induces a module of metabolic changes contributing to growth in insulin-induced hepatocarcinogenesis

Mounting epidemiological evidence supports a role for insulin-signaling deregulation and diabetes mellitus in human hepatocarcinogenesis. However, the underlying molecular mechanisms remain unknown. To study the oncogenic effect of chronically elevated insulin on hepatocytes in the presence of mild hyperglycemia, we developed a model of pancreatic islet transplantation into the liver. In this model, islets of a donor rat are transplanted into the liver of a recipient diabetic rat, with resulting local hyperinsulinism that leads to the development of preneoplastic lesions and hepatocellular carcinoma (HCC). Here, we investigated the metabolic and growth properties of the v-akt murine thymoma viral oncogene homolog/mammalian target of rapamycin (AKT/mTOR) pathway, a major downstream effector of insulin signaling, in this model of insulin-induced hepatocarcinogenesis. We found that activation of insulin signaling triggers a strong induction of the AKT/mTOR cascade that is paralleled by increased synthesis of fatty acids, cholesterol, and triglycerides, induction of glycolysis, and decrease of fatty acid oxidation and gluconeogenesis in rat preneoplastic and neoplastic liver lesions, when compared with the healthy liver. AKT/mTOR metabolic effects on hepatocytes, after insulin stimulation, were found to be mTORC1 dependent and independent in human HCC cell lines. In these cells, suppression of lipogenesis, glycolysis, and the pentose phosphate pathway triggered a strong growth restraint, despite insulin administration. Noticeably, metabolic abnormalities and proliferation driven by insulin were effectively reverted using the dual PI3K/mTOR inhibitor, NVP-BEZ235, both in vitro and in vivo.

CONCLUSIONS

The present results indicate that activation of the AKT/mTOR cascade by unconstrained insulin signaling induces a defined module of metabolic alterations in hepatocytes contributing to aberrant cell growth. Thus, inhibition of AKT/mTOR and related metabolic changes might represent a novel preventive and therapeutic approach to effectively inhibit insulin-induced hepatocarcinogenesis.

Abstract 984: High-level expression of YAP induces protumorigenic Notch signalling in human hepatocarcinogenesis

The evolutionary conserved Hippo-pathway negatively regulates organ size control by phosphorylation and cytoplasmic retention of the transcriptional co-activator yes-associated protein (YAP). Recent studies demonstrated that deletion of essential Hippo-pathway constituents (e.g., Mst-1/2 and WW45) or overexpression of YAP lead to the development of liver cancer. However, the underlying molecular tumor-supporting mechanisms in carcinogenesis have not been defined so far. Overexpression and nuclear accumulation of YAP in nearly 70% of all human hepatocellular carcinomas (HCC) significantly correlated with tumor cell proliferation and dedifferentiation. In human HCC cell lines, siRNA-mediated inhibition of YAP significantly reduced tumor cell viability, and migration/invasion. Based on transcriptomic profiling approaches, the Notch ligand Jagged-1 (Jag-1) was identified as YAP-dependent target gene in HCC cells and in primary murine hepatocytes of transgenic animals expressing constitutively active YAPS127A. Inhibition of YAP reduced the protein levels of Jag-1, cleaved Notch receptor (NICD), and Hes-1, while YAP overexpression increased the amounts of all factors. As detected for YAP knock down, transfection of gene-specific siRNA targeting Jag-1 diminished HCC cell viability and migration. Overexpression and concomitant inhibition of Jag-1 abolished Hes-1 expression and YAP-induced HCC cell viability. By applying different mutant isoforms of YAP (e.g., YAPS127A and YAP5SA-delta-C - dominant negative isoform), TEAD4 but not TEAD1 was identified as the transcription factor required for YAP-dependent regulation of Jag-1 and Hes-1. Furthermore, the WNT/beta-catenin pathway, a putative inducer of Jag-1, did not influence the YAP-dependent modulation of Jag-1. Knock down experiments revealed Mst-2 and Lats-2 as negative regulators of YAP activity and Jag-1/Hes-1 expression. The amounts of YAP, Jag-1, and Hes-1 transcripts as well as proteins significantly correlated with each other in human HCC tissues. Most importantly, increased concentrations of all factors significantly associated with poor prognosis of HCC patients. These data demonstrate that high-level expression of YAP in HCC cells induces tumor growth and tumor cell dissemination in part through activation of the Jag-1/Notch pathway in a TEAD4-dependent and beta-catenin-independent manner. This regulatory cross-talk between Hippo- and Notch-signalling defines a group of HCC patients with poor overall survival.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 984. doi:1538-7445.AM2012-984

Abstract 2248: Both rpS6 and 4EBP1 are required for the carcinogenesis induced by coactivation of AKT and Ras

AKT and Ras pathways are frequently concurrently hyperactivated in cancer. We have shown that co-expression of constitutively active forms of AKT (Myr-AKT) and activated Ras (N-RasV12) can rapidly induce liver tumors in mice. mTORC1 is the main downstream effector of AKT. mTORC1 phosphorylates rpS6 and 4EBP1, eukaryotic initiation factor eIF4E binding protein. Rapamycin is a well-characterized drug that partially inhibits mTORC1 activity. It can efficiently inhibit the phosphorylation of rpS6 but not the phosphorylation of 4EBP1. An unphophorylable mutant of 4EBP1, 4EBP1A4, is able to continuously bind to eIF4E and to inhibit eIF4E activity. Whether both of the two downstream effectors of mTORC1, rpS6 and 4EBP1, are required for hepatocarcinogenesis is unknown. The purpose of this study is to investigate the role of these two downstream effectors in hepatocarcinogenesis induced by co-activation of AKT and Ras. To determine the role of rpS6 in AKT/Ras-driven hepatocarcinogenesis, we treated AKT/Ras mice with rapamycin or vehicle daily for 7 weeks. After 7 weeks of vehicle treatment, all of the AKT/RAS/Veh mice developed large liver tumors. Lesions occupied ∼70-80% of the liver parenchyma. Histologically, the lesions consisted of large hepatocellular carcinonas (HCCs) and adenomas (HCAs). Tumor cells showed high proliferative activity, as indicated by Ki-67 staining. By contrast, after 7 weeks of Rapamycin treatment, none of the AKT/RAS/Rapa mice developed tumor. Small clusters of lipid-rich preneoplastic cells occupied 5-15% of the liver tissue. Few hepatocytes and non-parenchymal cells showed proliferative activity. Western blot analysis confirmed that Rapamycin inhibited the activation of rpS6 but had no effect on phosphorylated/inactivated levels of 4EBP1. These result indicated that Rapamycin treatment efficiently inhibited the progression of AKT/RAS induced liver tumor via inhibiting the rpS6 pathway. To determine the role of 4EBP1 in AKT/Ras-driven hepatocarcinogenesis, we overexpressed 4EBP1A4 or 4EBP1WT along with AKT and Ras into the mouse liver. Seven weeks after hydrodynamic injection, AKT/Ras/4EBP1WT mice developed large liver tumors which were equivalent to those developed in AKT/RAS/Veh mice. However, only few very small nodules developed in the livers of AKT/Ras/4EBP1A4 mice. The nodules consisted only of HCA and represented less than 5% of the lesional tissue. Notably, the proliferation in tumor cells of AKT/Ras/4EBP1A4 was more robust than in AKT/RAS/Rapa mice. The AKT/Ras/4EBP1A4 mice finally developed large liver tumors around 20 weeks after hydrodynamic injection. These results indicated that 4EBP1A4 efficiently delayed the AKT/RAS induced liver tumor. Altogether, our result indicates that the two main downstream effectors of mTORC1, rpS6 and 4EBP1, are both required for hepatocarcinogenesis induced by co-activation of AKT and Ras.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2248. doi:1538-7445.AM2012-2248

Rare case of a large mediastinal cyst involved in Hodgkin's lymphoma

We report a case of a mediastinal cystic retrosternal process, discovered by magnetic resonance imaging (MRI) in a 19-year-old male patient, with unusual inhomogenous signals in both T1- and T2-weighted images and contrast-enhancing septation. Macroscopically, the tumor weighed 1330 g, and was constituted by one dominating cyst measuring 14 cm in diameter. Additional small cysts were seen microscopically. The cystic wall was continuously infiltrated by nodular sclerosing Hodgkin's lymphoma, also affecting adjacent lymph-nodes. Age and sex of the patient and the diagnosed subtype of Hodgkin's lymphoma are in line with previously reported rare cases of mediastinal cysts with Hodgkin's lymphoma. The cyst reported here, most likely a secondary thymic cyst, is larger than those reported before. The main reason for the development of these cysts might be the accompanying inflammation of the lymphoma. Little is known about the imaging features of mediastinal cysts caused by lymphoma. Plain thymic cysts are normally homogenous on T1- and T2-weighted images. Hodgkin's lymphoma might be homogenous on T1-weighted images and is mostly inhomogenous on T2-weighted images. In case of inhomogenous cysts with contrast-enhancing septation, one should consider the diagnosis of an associated neoplasm.

Recruitment of histone deacetylases HDAC1 and HDAC2 by the transcriptional repressor ZEB1 downregulates E-cadherin expression in pancreatic cancer

OBJECTIVE

Pancreatic cancer is characterised by invasive tumour spread and early metastasis formation. During epithelial-mesenchymal transition, loss of the cell adhesion molecule E-cadherin is frequent and can be caused by genetic or epigenetic modifications, recruitment of transcriptional activators/repressors or post-translational modifications. A study was undertaken to investigate how E-cadherin expression in human pancreatic adenocarcinoma and pancreatic cancer cell lines is regulated.

METHODS

In 25 human pancreatic cancer resection specimens, the coding region of the E-cadherin gene (CDH1) was sequenced for somatic mutations. The tumour samples and 11 established human pancreatic cancer cell lines were analysed by immunohistochemistry, western blot analysis, chromatin immunoprecipitation and methylation-specific PCR. The role of specific histone deacetylase inhibitors (HDACi) on pancreatic tumour cell migration and proliferation was studied in vitro.

RESULTS

Neither somatic mutations nor CDH1 promoter hypermethylation were found to be responsible for downregulation of E-cadherin in pancreatic cancer. In the transcriptionally active CDH1 promoter, acetylation of histones H3 and H4 was detected whereas HDAC1 and HDAC2 were found attached only to a silent promoter. Expression of ZEB1, a transcription factor known to recruit HDACs, was seen in E-cadherin-deficient cell lines in which ZEB1/HDAC complexes were found attached to the CDH1 promoter. Moreover, knockdown of ZEB1 prevented HDAC from binding to the CDH1 promoter, resulting in histone acetylation and expression of E-cadherin. HDACi treatment attenuated tumour cell migration and proliferation.

CONCLUSIONS

These findings imply an important role for histone deacetylation in the downregulation of E-cadherin in human pancreatic cancer. Recruitment of HDACs to the CDH1 promoter is regulated by the transcription factor ZEB1, and inhibition of HDACs may be a promising antitumour therapy for pancreatic cancer.

AKT (v-akt murine thymoma viral oncogene homolog 1) and N-Ras (neuroblastoma ras viral oncogene homolog) coactivation in the mouse liver promotes rapid carcinogenesis by way of mTOR (mammalian target of rapamycin complex 1), FOXM1 (forkhead box M1)/SKP2, and c-Myc pathways

Activation of v-akt murine thymoma viral oncogene homolog (AKT) and Ras pathways is often implicated in carcinogenesis. However, the oncogenic cooperation between these two cascades in relationship to hepatocellular carcinoma (HCC) development remains undetermined. To investigate this issue, we generated a mouse model characterized by combined overexpression of activated forms of AKT and neuroblastoma Ras viral oncogene homolog (N-Ras) protooncogenes in the liver by way of hydrodynamic gene transfer. The molecular mechanisms underlying crosstalk between AKT and N-Ras were assessed in the mouse model and further evaluated in human and murine HCC cell lines. We found that coexpression of AKT and N-Ras resulted in a dramatic acceleration of liver tumor development when compared with mice overexpressing AKT alone, whereas N-Ras alone did not lead to tumor formation. At the cellular level, concomitant up-regulation of AKT and N-Ras resulted in increased proliferation and microvascularization when compared with AKT-injected mice. Mechanistic studies suggested that accelerated hepatocarcinogenesis driven by AKT and N-Ras resulted from a strong activation of mammalian target of rapamycin complex 1 (mTORC1). Furthermore, elevated expression of FOXM1/SKP2 and c-Myc also contributed to rapid tumor growth in AKT/Ras mice, yet by way of mTORC1-independent mechanisms. The biological effects of coactivation of AKT and N-Ras were then recapitulated in vitro using HCC cell lines, which supports the functional significance of mTORC1, FOXM1/SKP2, and c-Myc signaling cascades in mediating AKT and N-Ras-induced liver tumor development.

CONCLUSION

Our data demonstrate the in vivo crosstalk between the AKT and Ras pathways in promoting liver tumor development, and the pivotal role of mTORC1-dependent and independent pathways in mediating AKT and Ras induced hepatocarcinogenesis.

Reassessment of sst3 somatostatin receptor expression in human normal and neoplastic tissues using the novel rabbit monoclonal antibody UMB-5

BACKGROUND

Among the five somatostatin receptors (sst(1)-sst(5)), the sst(3) receptor displays a distinct pharmacological profile. Like sst(2), the sst(3) receptor efficiently internalizes radiolabeled somatostatin analogs. Unlike sst(2), however, internalized sst(3) receptors are rapidly transferred to lysosomes for degradation. Apart from this, very little is known about the clinical relevance of the sst(3) receptor, which may in part be due to the lack of specific monoclonal sst(3) antibodies.

METHODS

Here, we have extensively characterized the novel rabbit monoclonal anti-human sst(3) antibody UMB-5 using transfected cells and receptor-expressing tissues. UMB-5 was then subjected to immunohistochemical staining of a series of 190 formalin-fixed, paraffin-embedded normal and neoplastic human tissues.

RESULTS

Specificity of UMB-5 was demonstrated by detection of a broad band migrating at a molecular weight of 70,000-85,000 in immunoblots from human pituitary. After enzymatic deglycosylation, the size of this band decreased to a molecular weight of 45,000. Tissue immunostaining was completely abolished by pre-adsorption of UMB-5 with its immunizing peptide. In addition, UMB-5 detected distinct cell populations in human tissues like pancreatic islands, anterior pituitary, adrenal cortex, adrenal medulla, and enteric ganglia, similar to that seen with a rabbit polyclonal antibody generated against a different carboxyl-terminal epitope of the sst(3) receptor. In a comparative immunohistochemical study, UMB-5 yielded predominant plasma membrane staining in the majority of pituitary adenomas, pheochromocytomas, and a subset of neuroendocrine tumors. The sst(3) receptor was also present in many glioblastomas, pancreatic, breast, cervix, and ovarian carcinomas.

CONCLUSION

The rabbit monoclonal antibody UMB-5 may prove of great value in the identification of sst(3)-expressing tumors during routine histopathological examinations. Given its unique trafficking properties, these tumors may be potential candidates for sst(3)-directed receptor radiotherapy.

Activation of v-Myb avian myeloblastosis viral oncogene homolog-like2 (MYBL2)-LIN9 complex contributes to human hepatocarcinogenesis and identifies a subset of hepatocellular carcinoma with mutant p53

Up-regulation of the v-Myb avian myeloblastosis viral oncogene homolog-like2 B-Myb (MYBL2) gene occurs in human hepatocellular carcinoma (HCC) and is associated with faster progression of rodent hepatocarcinogenesis. We evaluated, in distinct human HCC prognostic subtypes (as defined by patient survival length), activation of MYBL2 and MYBL2-related genes, and relationships of p53 status with MYBL2 activity. Highest total and phosphorylated protein levels of MYBL2, E2F1-DP1, inactivated retinoblastoma protein (pRB), and cyclin B1 occurred in HCC with poorer outcome (HCCP), compared to HCC with better outcome (HCCB). In HCCP, highest LIN9-MYBL2 complex (LINC) and lowest inactive LIN9-p130 complex levels occurred. MYBL2 positively correlated with HCC genomic instability, proliferation, and microvessel density, and negatively with apoptosis. Higher MYBL2/LINC activation in HCC with mutated p53 was in contrast with LINC inactivation in HCC harboring wildtype p53. Small interfering RNA (siRNA)-mediated MYBL2/LINC silencing reduced proliferation, induced apoptosis, and DNA damage at similar levels in HCC cell lines, irrespective of p53 status. However, association of MYBL2/LINC silencing with doxorubicin-induced DNA damage caused stronger growth restraint in p53(-/-) Huh7 and Hep3B cells than in p53(+/+) Huh6 and HepG2 cells. Doxorubicin triggered LIN9 dissociation from MYBL2 in p53(+/+) cell lines and increased MYBL2-LIN9 complexes in p53(-/-) cells. Doxorubicin-induced MYBL2 dissociation from LIN9 led to p21(WAF1) up-regulation in p53(+/+) but not in p53(-/-) cell lines. Suppression of p53 or p21(WAF1) genes abolished DNA damage response, enhanced apoptosis, and inhibited growth in doxorubicin-treated cells harboring p53(+/+) .

CONCLUSION

We show that MYBL2 activation is crucial for human HCC progression. In particular, our data indicate that MYBL2-LIN9 complex integrity contributes to survival of DNA damaged p53(-/-) cells. Thus, MYBL2 inhibition could represent a valuable adjuvant for treatments against human HCC with mutated p53.

Increased lipogenesis, induced by AKT-mTORC1-RPS6 signaling, promotes development of human hepatocellular carcinoma

BACKGROUND & AIMS

De novo lipogenesis is believed to be involved in oncogenesis. We investigated the role of aberrant lipid biosynthesis in the pathogenesis of human hepatocellular carcinoma (HCC).

METHODS

We evaluated expression of enzymes that regulate lipogenesis in human normal liver tissues and HCC and surrounding, nontumor, liver tissues from patients using real-time reverse transcription polymerase chain reaction, immunoblotting, immunohistochemistry, and biochemical assays. Effects of lipogenic enzymes on human HCC cell lines were evaluated using inhibitors and overexpression experiments. The lipogenic role of the proto-oncogene AKT was assessed in vitro and in vivo.

RESULTS

In human liver samples, de novo lipogenesis was progressively induced from nontumorous liver tissue toward the HCC. Extent of aberrant lipogenesis correlated with clinical aggressiveness, activation of the AKT-mammalian target of rapamycin signaling pathway, and suppression of adenosine monophosphate-activated protein kinases. In HCC cell lines, the AKT-mammalian target of rapamycin complex 1-ribosomal protein S6 pathway promoted lipogenesis via transcriptional and post-transcriptional mechanisms that included inhibition of fatty acid synthase ubiquitination by the USP2a de-ubiquitinase and disruption of the SREBP1 and SREBP2 degradation complexes. Suppression of the genes adenosine triphosphate citrate lyase, acetyl-CoA carboxylase, fatty acid synthase, stearoyl-CoA desaturase 1, or sterol regulatory element-binding protein 1, which are involved in lipogenesis, reduced proliferation, and survival of HCC cell lines and AKT-dependent cell proliferation. Overexpression of an activated form of AKT in livers of mice induced lipogenesis and tumor development.

CONCLUSIONS

De novo lipogenesis has pathogenic and prognostic significance for HCC. Inhibitors of lipogenic signaling, including those that inhibit the AKT pathway, might be useful as therapeutics for patients with liver cancer.

[Chronic pancreatitis as a risk factor for the development of pancreatic cancer--diagnostic challenges]

Patients with chronic pancreatitis are burdened with an increased risk of developing pancreatic cancer. Strategies or guidelines for the surveillance and early detection of pancreatic adenocarcinoma in patients with chronic pancreatitis are not established, because available clinical, serologic or imaging techniques are still of limited sensitivity and specificity. Despite these limitations do patients with chronic pancreatitis and suspected pancreatic cancer need a careful and sometimes repeated diagnostic work-up. A clear benefit of surveillance programs outside of clinical trials for the early detection of pancreatic cancer has not been demonstrated. A 51-year-old patient with chronic pancreatitis is reported who developed cancer of the pancreatic head while undergoing repeated imaging studies.

Synergistic role of Sprouty2 inactivation and c-Met up-regulation in mouse and human hepatocarcinogenesis

Sprouty2 (Spry2), a negative feedback regulator of the Ras/mitogen-activated protein kinase (MAPK) pathway, is frequently down-regulated in human hepatocellular carcinoma (HCC). We tested the hypothesis that loss of Spry2 cooperates with unconstrained activation of the c-Met protooncogene to induce hepatocarcinogenesis via in vitro and in vivo approaches. We found coordinated down-regulation of Spry2 protein expression and activation of c-Met as well as its downstream effectors extracellular signal-regulated kinase (ERK) and v-akt murine thymoma viral oncogene homolog (AKT) in a subset of human HCC samples with poor outcome. Mechanistic studies revealed that Spry2 function is disrupted in human HCC via multiple mechanisms at both transcriptional and post-transcriptional level, including promoter hypermethylation, loss of heterozygosity, and proteosomal degradation by neural precursor cell expressed, developmentally down-regulated 4 (NEDD4). In HCC cell lines, Spry2 overexpression inhibits c-Met-induced cell proliferation as well as ERK and AKT activation, whereas loss of Spry2 potentiates c-Met signaling. Most importantly, we show that blocking Spry2 activity via a dominant negative form of Spry2 cooperates with c-Met to promote hepatocarcinogenesis in the mouse liver by sustaining proliferation and angiogenesis. The tumors exhibited high levels of activated ERK and AKT, recapitulating the subgroup of human HCC with a clinically aggressive phenotype.

CONCLUSION

The occurrence of frequent genetic, epigenetic, and biochemical events leading to Spry2 inactivation provides solid evidence that Spry2 functions as a tumor suppressor gene in liver cancer. Coordinated deregulation of Spry2 and c-Met signaling may be a pivotal oncogenic mechanism responsible for unrestrained activation of ERK and AKT pathways in human hepatocarcinogenesis.

Abstract B29: Genetic interactions between AKT/mTOR and Ras/MAPK pathways in liver cancer pathogenesis: from animal models to targeted therapy

Introduction: Hepatocellular carcinoma (HCC) and cholangiocellular carcinoma (CCC) are deadly malignant liver tumors lacking of efficient treatment options. Akt/mTOR and Ras/MAPK pathways have been implicated in hepatic carcinogenesis. Our study is to define the genetic interactions between Akt/mTOR and Ras/MAPK pathways in liver carcinogenesis.

Methods: Activation of Akt/mTOR and Ras/MAPK signaling was assayed in 62 human HCC and 25 CCC samples. An activated Akt (myr-Akt) was stably transfected into the mouse liver alone or together with activated N-Ras (RasV12) via hydrodynamic gene delivery. Molecular and biochemical features of liver lesions were analyzed. A primary cell line (Akt/Ras) was isolated from a tumor co-injected with Akt and Ras protooncogenes. Akt/Ras cells and human HCC cell lines were treated with different mTOR inhibitors, including NVP-BEZ235, PP242 and Rapamcyin, as well as the MEK inhibitor AZD6244.

Results: Using human HCC samples, we demonstrated the coordinated activation of Akt/mTOR and Ras/MAPK pathways in subsets of HCC and CCC characterized by poor prognosis. We found that coexpression of myr-Akt with RasV12 synergizes to promote liver tumor development in mice, leading to HCC and CCC formation within 4 to 6 weeks post injection. At cellular level, tumors from Akt/N-Ras co-injection cells are characterized by high proliferation and low apoptotic index, and disrupted expression of genes involved in cell cycle regulation. At the molecular level, liver tumors show high levels of activated Akt/mTOR and Erk cascades. A primary cell line (Akt/Ras) was isolated from a tumor and used to test the response to different mTOR and MEK inhibitors. We found that dual PI3K/mTOR inhibitor NVP-BEZ235 has superior activity inhibiting Akt/Ras cell proliferation with IC50 around 2nM. It also efficiently inhibits phospho-S6, phospho-4EBP1 and cyclin D1 expression in Akt/Ras cells. Furthermore, NVP-BEZ235 synergizes with the MEK inhibitor AZD6244 to dramatically reduce the growth of the Akt/Ras cell line. Equivalent results were obtained in human HCC cell lines with the same inhibitors.

Conclusion: Coordinated activation of Akt/mTOR and Ras/MAPK signaling is the hallmark of aggressive subtypes of human HCC and CCC. Activated Akt cooperates with activated Ras/MAPK to rapidly promote liver tumor formation in mice. The Akt/Ras mouse model is a useful pre-clinical system to test anti-neoplastic therapeutic approaches against HCC and CCC in vivo. In addition, our preliminary studies suggest that the combination of a dual PI3K/mTOR inhibitor with a MEK inhibitor may represent a promising novel targeted therapy for treating human HCC harboring activated Akt/mTOR and Ras/MAPK pathways.

Citation Information: Clin Cancer Res 2010;16(14 Suppl):B29.

Immunohistochemical identification of the PTHR1 parathyroid hormone receptor in normal and neoplastic human tissues

BACKGROUND

Parathyroid hormone (PTH) is a crucial regulator of calcium homoeostasis in humans. Although it is well known that PTH acts primarily on kidney and bone, the precise cellular and subcellular sites of PTH action have not been visualised in human tissues.

METHOD

We developed and characterised a novel anti-peptide antibody to the carboxy-terminal region of the human PTH receptor type 1 (PTHR1). Specificity of the antiserum was demonstrated by i) detection of a broad band migrating at M(r) 85,000-95,000 in western blots of membranes from human kidney and PTHR1-transfected cells; ii) cell surface staining of PTHR1-transfected cells; iii) translocation of PTHR1 receptor immunostaining after agonist exposure; and iv) abolition of tissue immunostaining by preadsorption of the antibody with its immunising peptide. The distribution of PTHR1 receptors was investigated in 320 human tumours and their tissues of origin.

RESULTS

In the kidney, PTHR1 receptors were predominantly detected at the basolateral plasma membrane of epithelial cells in the proximal and distal tubules but not in the thin limbs of Henle, collecting ducts or glomeruli. In bone, PTHR1 receptors were detected as discrete plasma membrane staining of osteocytes and osteoblasts, whereas osteoclasts remained unstained. In addition, PTHR1 was found in the gut and in a number of neoplastic tissues including colorectal carcinoma, prostate cancer, renal cell carcinoma and osteosarcoma.

CONCLUSION

This is the first localisation of PTHR1 receptors in human tissues at the cellular level. The overexpression of PTHR1 receptors may provide a molecular basis for efficient targeting of human tumours with radiolabelled PTH analogues.

Oncogenic and tumor suppressive roles of polo-like kinases in human hepatocellular carcinoma

Polo-like kinase (PLK) proteins play critical roles in the control of cell cycle progression, either favoring or inhibiting cell proliferation, and in DNA damage response. Although either overexpression or down-regulation of PLK proteins occurs frequently in various cancer types, no comprehensive analysis on their function in human hepatocellular carcinoma (HCC) has been performed to date. In the present study, we define roles for PLK1, PLK2, PLK3, and PLK4 during hepatocarcinogenesis. Levels of PLK1, as assessed by means of real-time reverse-transcription PCR and western blot analysis, were progressively increased from nonneoplastic surrounding liver tissues to HCC, reaching the highest expression in tumors with poorer outcome (as defined by the length of patients' survival) compared with normal livers. In sharp contrast, PLK2, PLK3, and PLK4 messenger RNA and protein expression gradually declined from nontumorous liver to HCC, with the lowest levels being detected in HCC with shorter survival. In liver tumors, PLK2-4 down-regulation was paralleled by promoter hypermethylation and/or loss of heterozygosity at the PLK2-4 loci. Subsequent functional studies revealed that PLK1 inhibition led to suppression of cell growth in vitro, whereas opposite effects followed PLK2-4 silencing in HCC cell lines. In particular, suppression of PLK1 resulted in a block in the G2/M phase of the cell cycle and in massive apoptosis of HCC cells in vitro regardless of p53 status.

CONCLUSION

PLK1-4 proteins are aberrantly regulated and possess different roles in human HCC, with PLK1 acting as an oncogene and PLK2-4 being presumably tumor suppressor genes. Thus, therapeutic approaches aimed at inactivating PLK1 and/or reactivating PLK2-4 might be highly useful in the treatment of human liver cancer.

Fatty acid synthase as a novel target for meningioma therapy

High levels of fatty acid synthase (FAS) expression have been reported in hormone receptor-positive tumors, including prostate, breast, and ovarian cancers, and its inhibition reduces tumor growth in vitro and in vivo. Similar to other hormone receptor-positive tumor types, meningiomas are progesterone receptor- and estrogen receptor-immunoreactive brain tumors. To define the role of FAS in human meningioma growth control, we first analyzed the FAS expression using a tissue microarray containing 38 meningiomas and showed increased FAS expression in 70% of atypical WHO grade II and anaplastic WHO grade III meningiomas compared with 10% of benign WHO grade I tumors. We next confirmed this finding by real-time PCR and Western blotting. Second, we demonstrated that treatment with the FAS inhibitor, cerulenin (Cer), significantly decreased meningioma cell survival in vitro. Third, we showed that Cer treatment reduced FAS expression by modulating Akt phosphorylation (activation). Fourth, we demonstrated that Cer treatment of mice bearing meningioma xenografts resulted in significantly reduced tumor volumes associated with increased meningioma cell death. Collectively, our data suggest that the increased FAS expression in human meningiomas represents a novel therapeutic target for the treatment of unresectable or malignant meningioma.

[Conjunctival tumours in elderly patients]

The conjunctiva as a mucous membrane provides a protective barrier to the eye. It represents a small segment of the skin - the largest organ of the body, which has a size of about 1.7 square metres. For this reason conjunctival ageing is affected by equivalent processes as skin ageing. Common causes for these ageing processes are biological and genetic effects as well as environmental conditions and exposure to light. The resulting dysfunction in conjunctival homoeostasis and protective function represent common factors which contribute to increased incidences of tumours and malignant transformations in elderly patients. At the time of tumour manifestation the patient's age is an important parameter for differential diagnosis and regimen strategy. All therapeutic options (surgical incision or excision, cryotherapy, chemo- or radiotherapy, exenteratio orbitae etc.) have to be determined individually depending on clinically relevant findings and previous anamnesis. Due to the patient's age geriatric aspects have to be considered in therapeutic management (tissue fragility, wound healing, multimorbidity, decreased adherence).

[Current diagnosis and treatment of desmoid tumours in patients with familial adenomatous polyposis - the surgical view]

Based on a representative selection of relevant references, the aim of this study was to reflect the change of the algorithm in the surgical management of desmoid tumours (DT) in cases of accompanying familial adenomatous polyposis (FAP). Main focus is concerned with the basics of differential treatment, including additional considerations on epidemiology, diagnosis, outcome and follow-up. DT are rare benign tumours that do not metastasise but tend to invade locally. In contrast to the general population, DT in patients with FAP are more common, show a different pattern of tumour sites and cause considerable morbidity and mortality. Most DT occur in the abdominal cavity and account for the majority of serious problems. Genetic disposition and hormonal factors as well as prior surgical trauma are considered causative for the development of DT. Characteristic symptoms are abdominal pain, nausea and vomiting but DT may also present as acute abdomen. CT scan determines localisation and extension of the tumour. Treatment includes various strategies of medication, surgical resection and radiation. Data concerning diagnostic and therapeutic procedures are based on studies with small case series or case reports only. Therefore data from international multicentre studies are necessary for improving the prognosis and developing reliable and stringent guidelines.

[A rare extra-skeletal myxoid chondrosarcoma of the lower leg - is amputation absolutely necessary]

INTRODUCTION

Sarcomas represent less than 2 % of all malignancies. Special challenges are bone sarcomas in extra-skeletal localisation. The aim of this case report is to show the management of an extraordinary extra-skeletal myxoid chondrosarcoma based on a case report with references from the literature.

CASE REPORT

After a delay in diagnostics for 1.5 years, an MRI scan taken in a 42-year-old male patient with progressive swelling of the left calf showed a soft-tissue tumour in the proximal part of the muscle. Histopathological investigation of a percutaneous biopsy revealed a chondrosarcoma. En-bloc-resection (R 0) of the rear superficial compartment was performed (specimen weight 1 370 g; tumour size 11.5 x 9.5 x 8 cm) leading to the definitive diagnosis of an extra-skeletal myxoid chondrosarcoma. The patient was discharged with a bland wound 8 days after surgery. At 4 weeks postoperatively, the patient received adjuvant radiotherapy with a 56-Gy boost. During the follow-up period of 28 months, there have been neither signs of local tumour recurrence nor distant metastases.

DISCUSSION

The myxoid chondrosarcoma is a rare tumour lesion, and according to the literature, only 2 % occur outside of the skeleton. The accurate diagnostic and therapeutic algorithm allowed a precise preparation for surgery and made amputation obsolete. Compartment resection preserving the main neurovascular bundles as well as enabling an early mobilisation resulted in both sufficient radical resection status and adequate postoperative motor function. Intraoperative clip-marking of the former tumour bed is considered a key point for the focused radiotherapy.

CONCLUSION

Each persistent soft tissue swelling must be appropriately diagnosed using adequate imaging and even biopsy (in case of a doubtful finding), which should be performed with definitive surgery in mind.

[Gastric schwannoma: a "typical" clinical course?]

Intra-abdominal schwannoma is a rare tumor entity. Although often detected incidentally, its diagnosis and surgical planning are difficult-as with all intramural intra-abdominal tumors. Puncturing is often not satisfying due to the inhomogeneous proliferation rates of different regions of the tumor. We describe the procedure using the example of a gastric schwannoma that was found incidentally. The leading symptom was perforation of a peptic stomach ulcer.

[Hepatocellular carcinoma in the non-cirrhotic liver]

Of hepatocellular carcinomas (HCC), 15-20% occur in the non-cirrhotic liver. All factors which cause HCC when liver cirrhosis (LC) is present, can also lead to HCC without LC. On the basis of the relative frequency, HCC can be roughly differentiated into 3 groups: 1) HCC, rarely occurring without cirrhosis (e.g. virus hepatitis, alcohol abuse). 2) HCC, frequently occurring without LC (alpha1-antitrypsin deficiency, hemochromatosis, non-alcoholic fatty liver disease). 3) HCC, consistently occurring without LC (glycogen storage disease type 1, consumption of oral contraceptives/anabolic steroids). In groups 1 and 2 the level of hepatocellular toxicity necessary to reach LC is not yet achieved but the carcinogenic effect is already strong enough to induce HCC, possibly owing to the influence of additional carcinogens or host factors. In group 3, the carcinogenic effect is mediated by a long-standing alteration of the hepatocellular metabolism that is of low toxic effect and does not lead to cell death, but is nevertheless carcinogenic. In these cases, the initial formation of hepatocellular adenomas that subsequently transform into HCC is a common finding (adenoma-carcinoma sequence).

Hepatocarcinogenesis following pancreatic islet transplantation in streptozotocin- and autoimmune-diabetic rats

Epidemiological studies assign a role to insulin signalling deregulation and diabetes mellitus in human hepatocarcinogenesis. The underlying mechanisms, however, remain largely unknown. To unravel the molecular pathogenesis of insulin-induced hepatocarcinogenesis, we generated an experimental animal model: after transplantation of only a low number of isologous pancreatic islets into the livers of diabetic rats, mild diabetes persists and the beta cells are maximally stimulated to permanently secrete insulin. As a consequence, liver acini, draining the hyperinsulinemic blood from islet grafts, show insulin-induced adaptive alterations simultaneously resembling preneoplastic foci of chemically-induced hepatocarcinogenesis models. These lesions progress to hepatocellular tumours within 6 and 24 months. Hepatocarcinogenesis is accompanied by alterations in hepatocytes metabolisms and changes in signal transduction pathways that, in the beginning, can be attributed solely to insulin action. In this review, we summarize our findings that may help understanding the oncogenic potential of diabetes mellitus in the human liver.

Whipple's disease: an endoscopic and histologic study

BACKGROUND/AIM

Primary gastrointestinal tract involvement occurs in one third of patients with Whipple's disease (WD). Nevertheless, there are scant data on the endoscopic appearance of WD. The aim of this study was to provide a detailed endoscopic-pathologic assessment of patients with WD.

METHODS

Four patients with a diagnosis of WD who underwent endoscopic evaluation by a single endoscopist were included. Published information on WD was reviewed in detail, focusing on the endoscopic and histologic features of this disease.

RESULTS

WD had a wide range of endoscopic features, including edema, brown discoloration of the mucosa, erythematous spots, subepithelial hemorrhages, and megaduodenum. Magnification endoscopy revealed engorged and flattened villi, villi filled with white material, and white ring-like structures inside of the villi and multiple yellow spots. The histological features of WD include a coarse granular cytoplasm and foamy macrophages that stain strongly with the period acid-Schiff reagent.

CONCLUSIONS

Gastrointestinal WD has a wide spectrum of endoscopic appearance. Magnification endoscopy enhances the mucosal details. Esophagogastroduodenoscopy with procurement of biopsy specimens from the duodenum was an accurate method for the diagnosis of WD in this case series.

Virtual 3D microscopy using multiplane whole slide images in diagnostic pathology

To reproduce focusing in virtual microscopy, it is necessary to construct 3-dimensional (3D) virtual slides composed of whole slide images with different focuses. As focusing is frequently used for the assessment of Helicobacter pylori colonization in diagnostic pathology, we prepared virtual 3D slides with up to 9 focus planes from 144 gastric biopsy specimens with or without H pylori gastritis. The biopsy specimens were diagnosed in a blinded manner by 3 pathologists according to the updated Sydney classification using conventional microscopy, virtual microscopy with a single focus plane, and virtual 3D microscopy with 5 and 9 focus planes enabling virtual focusing. Regarding the classification of H pylori, we found a positive correlation between the number of focus planes used in virtual microscopy and the number of correct diagnoses as determined by conventional microscopy. Concerning H pylori positivity, the specificity and sensitivity of virtual 3D microscopy using virtual slides with 9 focus planes achieved a minimum of 0.95 each, which was approximately the same as in conventional microscopy. We consider virtual 3D microscopy appropriate for primary diagnosis of H pylori gastritis and equivalent to conventional microscopy.

Thymoquinone reduces mouse colon tumor cell invasion and inhibits tumor growth in murine colon cancer models

We have shown that thymoquinone (TQ) is a potent antitumor agent in human colorectal cancer cells. In this study, we evaluated TQ's therapeutic potential in two different mice colon cancer models [1,2-dimethyl hydrazine (DMH) and xenografts]. We also examined TQ effects on the growth of C26 mouse colorectal carcinoma spheroids and assessed tumor invasion in vitro. Mice were treated with saline, TQ, DMH, or combinations once per week for 30 weeks and the multiplicity, size and distribution of aberrant crypt foci (ACF) and tumors were determined at weeks 10, 20 and 30. TQ injected intraperitoneally (i.p.) significantly reduced the numbers and sizes of ACF at week 10; ACF numbers were reduced by 86%. Tumor multiplicity was reduced at week 20 from 17.8 in the DMH group to 4.2 in mice injected with TQ. This suppression was observed at week 30 and was long-term; tumors did not re-grow even when TQ injection was discontinued for 10 weeks. In a xenograft model of HCT116 colon cancer cells, TQ significantly (P < 0.05) delayed the growth of the tumor cells. Using a matrigel artificial basement membrane invasion assay, we demonstrated that sub-cyto-toxic doses of TQ (40μM) decreased C26 cell invasion by 50% and suppressed growth in three-dimensional spheroids. Apoptotic signs seen morphologically were increased significantly in TQ-treated spheroids. TUNEL staining of xenografts and immunostaining for caspase 3 cleavage in DMH tumors confirmed increased apoptosis in mouse tumors in response to TQ. These data should encourage further in vivo testing and support the potential use of TQ as a therapeutic agent in human colorectal cancer.