Quantifying telomere transcripts as tool to improve risk assessment for genetic instability and genotoxicity

Telomere repeat-containing RNAs (TERRA) are transcribed from telomeres as long non-coding RNAs and are part of the telomere structure with protective function. The genetic stability of cells requires telomeric repeats at the ends of chromosomes. Maintenance of telomere length (TL) is essential for proliferative capacity and chromosomal integrity. In contrast, telomere shortening is a recognized risk factor for carcinogenesis and a biomarker of aging due to the cumulative effects of environmental exposures and life experiences such as trauma or stress. In this context, telomere repeats are lost due to cell proliferation, but are also susceptible to stress factors including reactive oxygen species (ROS) inducing oxidative base damage. Quantitative PCR (qPCR) of genomic DNA is an established method to analyze TL as a tool to detect genotoxic events. That same qPCR method can be applied to RNA converted into cDNA to quantify TERRA as a useful tool to perform high-throughput screenings. This short review summarizes relevant qPCR studies using both TL and TERRA quantification, provides an overall view of the molecular mechanisms of telomere protection against ROS by TERRA, and summarizes the presented studies comparing the results at DNA and RNA levels, which indicate that fluctuations at transcript level might reflect a short-term response. Therefore, we conclude that performing both of these measurements together will improve genotoxicity studies.

Alternative Lengthening of Telomeres Is Rare in Canine Histiocytic Sarcoma

Cancer cells activate telomere maintenance mechanisms (TMMs) to overcome senescence and thus are targets for TMM-specific therapies. Telomerase-independent alternative lengthening of telomeres (ALT) is frequently utilized as a TMM in human sarcoma subtypes. Histiocytic sarcoma (HS) is a rare but aggressive tumor of hematopoietic origin with unknown ALT incidence in humans. ALT has been identified in canine HS, a tumor type comparable to human HS that occurs with high rates in certain canine breeds such as Bernese mountain dogs (BMDs). This retrospective study characterized the frequency of ALT in BMD and non-BMD patients diagnosed with HS as surrogates for humans. Formalin-fixed paraffin-embedded tumor samples from 63 dogs at two centers, including 47 BMDs, were evaluated for their ALT activity and relative telomere content (TC) using a radiolabel C-circle assay (CCA). Known ALT-positive samples served as controls. CCA-positive cases were validated via FISH. Two BMD samples showed ALT activity of 1-14% compared to controls. All other samples were ALT-negative. The TC did not correlate with the CCA results. ALT positivity was validated by the appearance of ultrabright telomere foci. Low ALT activity was present in 4% of BMDs with HS and therefore does not appear to be a common target for therapeutic approaches but can have diagnostic value.

Primary and hTERT-Transduced Mesothelioma-Associated Fibroblasts but Not Primary or hTERT-Transduced Mesothelial Cells Stimulate Growth of Human Mesothelioma Cells

Pleural mesothelioma (PM) is an aggressive malignancy that develops in a unique tumor microenvironment (TME). However, cell models for studying the TME in PM are still limited. Here, we have generated and characterized novel human telomerase reverse transcriptase (hTERT)-transduced mesothelial cell and mesothelioma-associated fibroblast (Meso-CAF) models and investigated their impact on PM cell growth. Pleural mesothelial cells and Meso-CAFs were isolated from tissue of pneumothorax and PM patients, respectively. Stable expression of hTERT was induced by retroviral transduction. Primary and hTERT-transduced cells were compared with respect to doubling times, hTERT expression and activity levels, telomere lengths, proteomes, and the impact of conditioned media (CM) on PM cell growth. All transduced derivatives exhibited elevated hTERT expression and activity, and increased mean telomere lengths. Cell morphology remained unchanged, and the proteomes were similar to the corresponding primary cells. Of note, the CM of primary and hTERT-transduced Meso-CAFs stimulated PM cell growth to the same extent, while CM derived from mesothelial cells had no stimulating effect, irrespective of hTERT expression. In conclusion, all new hTERT-transduced cell models closely resemble their primary counterparts and, hence, represent valuable tools to investigate cellular interactions within the TME of PM.

Signal Transduction as an Assimilation of Signals with Different Origins and Different Intracellular States

Higher organisms, such as humans, are made up of trillions of cells that have to act as a unit in a finely tuned way to ensure the functioning of the living being that is composed of them [...].

Impact of Bariatric Surgery on the Stability of the Genetic Material, Oxidation, and Repair of DNA and Telomere Lengths

Obesity causes genetic instability, which plays a key-role in the etiology of cancer and aging. We investigated the impact of bariatric surgery (BS) on DNA repair, oxidative DNA damage, telomere lengths, alterations of antioxidant enzymes and, selected proteins which reflect inflammation. The study was realized with BS patients (n = 35). DNA damage, base oxidation, BER, and NER were measured before and 1 month and 6 months after surgery with the single-cell gel electrophoresis technique. SOD and GPx were quantified spectrophotometrically, malondealdehyde (MDA) was quantified by HPLC. Telomere lengths were determined with qPCR, and plasma proteome profiling was performed with high-resolution mass spectrophotometry. Six months after the operations, reduction of body weight by 27.5% was observed. DNA damage decreased after this period, this effect was paralleled by reduced formation of oxidized DNA bases, a decline in the MDA levels and of BER and NER, and an increase in the telomere lengths. The activities of antioxidant enzymes were not altered. Clear downregulation of certain proteins (CRP, SAA1) which reflect inflammation and cancer risks was observed. Our findings show that BS causes reduced oxidative damage of DNA bases, possibly as a consequence of reduction of inflammation and lipid peroxidation, and indicate that the surgery has beneficial long-term health effects.

Search for the optimal genotoxicity assay for routine testing of chemicals: Sensitivity and specificity of conventional and new test systems

Many conventional in vitro tests that are currently widely used for routine screening of chemicals have a sensitivity/specificity in the range between 60 % and 80 % for the detection of carcinogens. Most procedures were developed 30-40 years ago. In the last decades several assays became available which are based on the use of metabolically competent cell lines, improvement of the cultivation conditions and development of new endpoints. Validation studies indicate that some of these models may be more reliable for the detection of genotoxicants (i.e. many of them have sensitivity and specificity values between 80 % and 95 %). Therefore, they could replace conventional tests in the future. The bone marrow micronucleus (MN) assay with rodents is at present the most widely used in vivo test. The majority of studies indicate that it detects only 5-6 out of 10 carcinogens while experiments with transgenic rodents and comet assays seem to have a higher predictive value and detect genotoxic carcinogens that are negative in MN experiments. Alternatives to rodent experiments could be MN experiments with hen eggs or their replacement by combinations of new in vitro tests. Examples for promising candidates are ToxTracker, TGx-DDI, multiplex flow cytometry, γH2AX experiments, measurement of p53 activation and MN experiments with metabolically competent human derived liver cells. However, the realization of multicentric collaborative validation studies is mandatory to identify the most reliable tests.

The C-Circle Biomarker Is Secreted by Alternative-Lengthening-of-Telomeres Positive Cancer Cells inside Exosomes and Provides a Blood-Based Diagnostic for ALT Activity

Simple Summary

A clinical test for alternative-lengthening-of-telomeres (ALT) could assist with cancer diagnosis and monitoring of disease progression. ALT-targeted anticancer treatments are being developed; however, there is no appropriate companion ALT diagnostic. The C-Circle biomarker is the only known ALT specific molecule and the C-Circle Assay the only quantitative ALT assay that is amenable to clinical use. We show here that C-Circles are secreted by ALT+ cancer cell lines inside the exosomes and are protected from nucleases. We also show that secreted C-Circles, like intracellular C-Circles, are an ALT-specific biomarker, and in high-risk neuroblastoma, the blood-based C-Circle Assay has the potential to be an accurate diagnostic for ALT cancer activity. Therefore, the secretion of C-Circles by ALT+ cancer cells in the exosomes provides a stable blood-based biomarker and, potentially, a clinical diagnostic for ALT activity, which is required for the development of ALT-targeted therapies as well as for the diagnosis and monitoring of ALT+ cancer.

Abstract

C-Circles, self-primed telomeric C-strand templates for rolling circle amplification, are the only known alternative-lengthening-of-telomeres (ALT)-specific molecule. However, little is known about the biology of C-Circles and if they may be clinically useful. Here we show that C-Circles are secreted by ALT+ cancer cells inside exosomes, and that a blood-based C-Circle Assay (CCA) can provide an accurate diagnostic for ALT activity. Extracellular vesicles were isolated by differential centrifugation from the growth media of lung adenocarcinoma, glioblastoma, neuroblastoma, osteosarcoma, and soft tissue sarcoma cell lines, and C-Circles were detected in the exosome fraction from all eleven ALT+ cancer cell lines and not in any extracellular fraction from the eight matching telomerase positive cancer cell lines or the normal fibroblast strain. The existence of C-Circles in ALT+ exosomes was confirmed with exosomes isolated by iodixanol gradient separation and CD81-immunoprecipitation, and C-Circles in the exosomes were protected from nucleases. On average, 0.4% of the total ALT+ intracellular C-Circles were secreted in the exosomes every 24 h. Comparing the serum-based and tumor-based CCAs in 35 high risk neuroblastoma patients divided randomly into ALT+ threshold derivation and validation groups, we found the serum-based CCA to have 100% sensitivity (6/6), 70% specificity (7/10), and 81% concordance (13/16). We conclude that the secretion of C-Circles by ALT+ cancer cells in the exosomes provides a stable blood-based biomarker and a potential clinical diagnostic for ALT activity.

Targeting fibroblast growth factor receptors to combat aggressive ependymoma

Ependymomas (EPN) are central nervous system tumors comprising both aggressive and more benign molecular subtypes. However, therapy of the high-risk subtypes posterior fossa group A (PF-A) and supratentorial RELA-fusion positive (ST-RELA) is limited to gross total resection and radiotherapy, as effective systemic treatment concepts are still lacking. We have recently described fibroblast growth factor receptors 1 and 3 (FGFR1/FGFR3) as oncogenic drivers of EPN. However, the underlying molecular mechanisms and their potential as therapeutic targets have not yet been investigated in detail. Making use of transcriptomic data across 467 EPN tissues, we found that FGFR1 and FGFR3 were both widely expressed across all molecular groups. FGFR3 mRNA levels were enriched in ST-RELA showing the highest expression among EPN as well as other brain tumors. We further identified high expression levels of fibroblast growth factor 1 and 2 (FGF1, FGF2) across all EPN subtypes while FGF9 was elevated in ST-EPN. Interrogation of our EPN single-cell RNA-sequencing data revealed that FGFR3 was further enriched in cycling and progenitor-like cell populations. Corroboratively, we found FGFR3 to be predominantly expressed in radial glia cells in both mouse embryonal and human brain datasets. Moreover, we detected alternative splicing of the FGFR1/3-IIIc variant, which is known to enhance ligand affinity and FGFR signaling. Dominant-negative interruption of FGFR1/3 activation in PF-A and ST-RELA cell models demonstrated inhibition of key oncogenic pathways leading to reduced cell growth and stem cell characteristics. To explore the feasibility of therapeutically targeting FGFR, we tested a panel of FGFR inhibitors in 12 patient-derived EPN cell models revealing sensitivity in the low-micromolar to nano-molar range. Finally, we gain the first clinical evidence for the activity of the FGFR inhibitor nintedanib in the treatment of a patient with recurrent ST-RELA. Together, these preclinical and clinical data suggest FGFR inhibition as a novel and feasible approach to combat aggressive EPN.

Micronucleus assays with the human derived liver cell line (Huh6): A promising approach to reduce the use of laboratory animals in genetic toxicology

The inadequate representation of enzymes which catalyze the activation/detoxification of xenobiotics in cells that are currently used in genotoxicity testing of chemicals leads to a high number of false positive results and the number of follow up studies with rodents could be reduced by use of more reliable in vitro models. We found earlier that several xenobiotic drug metabolizing enzymes are represented in the human derived liver cell line Huh6 and developed a protocol for micronucleus (MN) experiments which is in agreement with the current OECD guideline. This protocol was used to test 23 genotoxic and non-genotoxic reference chemicals; based on these results and of earlier findings (with 9 chemicals) we calculated the predictive value of the assay for the detection of genotoxic carcinogens. We found a sensitivity of 80% and a specificity of 94% for a total number of 32 chemicals; comparisons with results obtained with other in vitro assays show that the validity of MN tests with Huh6 is higher as that of other experimental models. These results are promising and indicate that the use of Huh6 cells in genetic toxicology may contribute to the reduction of the use of laboratory rodents; further experimental work to confirm this assumption is warranted.

Prevalence and potentially prognostic value of C-circles associated with alternative lengthening of telomeres in canine appendicular osteosarcoma

Alternative lengthening of telomeres (ALT) is a telomerase‐independent telomere maintenance mechanism (TMM) with high prevalence in human osteosarcomas but remains unknown in canine osteosarcomas. The aim of this study was to evaluate the prevalence of ALT by detection of extra‐chromosomal circles of telomeric DNA and to assess clinical outcome in canine patients with spontaneous occurring appendicular osteosarcoma. Fifty dogs with histopathological confirmed osteosarcomas were included into this study. Medical records were retrospectively analysed for patient characteristics, oncologic therapy and survival. DNA was isolated from archived FFPE tumour tissue specimens and applied for C‐ and G‐circle assay (CCA and GCA) and for telomeric content (TC) measurement with radiolabeled probes. ALT activity was detected for 10 of 50 (20%) cases by CCA. Four CCA positive cases were detected even with input DNA below 1 ng and demonstrated the high sensitivity of CCA for canine tumours. G‐circles and TC were not suitable to distinguish CCA positive and negative cases. CCA‐status showed an association with male gender and Rottweiler breed. Dogs with CCA positive osteosarcomas had shorter overall survival times than patients with CCA‐tumours and CCA‐status was a significant prognostic factor besides treatment in the Cox proportional hazard model. These findings make canine osteosarcomas an interesting model for comparative TMM research, but future studies are warranted to investigate if CCA‐status can serve as novel prognostic marker.

Interaction of FGF9 with FGFR3-IIIb/IIIc, a putative driver of growth and aggressive behaviour of hepatocellular carcinoma

BACKGROUND & AIMS

Recently, overexpression of the fibroblast growth factor receptor 3 (FGFR3) splice variants FGFR3-IIIb and FGFR3-IIIc was found in ~50% of hepatocellular carcinoma (HCC). Here, we aim to identify FGFR3-IIIb/IIIc ligands, which drive the progression of HCC.

METHODS

FACS, MTT assay and/or growth curves served to identify the FGFR3-IIIb/IIIc ligand being most effective to induce growth of hepatoma/hepatocarcinoma cell lines, established from human HCC. The most potent FGF was characterized regarding the expression levels in epithelial and stromal cells of liver and HCC and impact on neoangiogenesis, clonogenicity and invasive growth of hepatoma/hepatocarcinoma cells.

RESULTS

Among all FGFR3-IIIb/IIIc ligands tested, FGF9 was the most potent growth factor for hepatoma/hepatocarcinoma cells. Replication and/or sprouting of blood/lymphendothelial cells was stimulated as well. FGF9 occurred mainly in stromal cells of unaltered liver but in epithelial cells of HCC. Every fifth HCC exhibited overexpressed FGF9 and frequent co-upregulation of FGFR3-IIIb/IIIc. In hepatoma/hepatocarcinoma cells FGF9 enhanced the capability for clonogenicity and disintegration of the blood and lymphatic endothelium, being most pronounced in cells overexpressing FGFR3-IIIb or FGFR3-IIIc, respectively. Any of the FGF9 effects in hepatoma/hepatocarcinoma cells was blocked completely by applying the FGFR1-3-specific tyrosine kinase inhibitor BGJ398 or siFGFR3, while siFGFR1/2/4 were mostly ineffective.

CONCLUSIONS

FGF9 acts via FGFR3-IIIb/IIIc to enhance growth and aggressiveness of HCC cells. Accordingly, blockade of the FGF9-FGFR3-IIIb/IIIc axis may be an efficient therapeutic option for HCC patients.

Rapamycin-based graft-versus-host disease prophylaxis increases the immunosuppressivity of myeloid-derived suppressor cells without affecting T cells and anti-tumor cytotoxicity

The immunosuppressant rapamycin (RAPA) inhibits mammalian target of rapamycin (mTOR) functions and is applied after allogeneic bone marrow transplantation (BMT) to attenuate the development of graft‐versus‐host disease (GVHD), although the cellular targets of RAPA treatment are not well defined. Allogeneic T cells are the main drivers of GVHD, while immunoregulatory myeloid‐derived suppressor cells (MDSCs) were recently identified as potent disease inhibitors. In this study, we analyzed whether RAPA prevents the deleterious effects of allogeneic T cells or supports the immunosuppressive functions of MDSCs in a BMT model with major histocompatibility complex (MHC) classes I and II disparities. RAPA treatment efficiently attenuated clinical and histological GVHD and strongly decreased disease‐induced mortality. Although splenocyte numbers increased during RAPA treatment, the ratio of effector T cells to MDSCs was unaltered. However, RAPA treatment induced massive changes in the genomic landscape of MDSCs preferentially up‐regulating genes responsible for uptake or signal transduction of lipopeptides and lipoproteins. Most importantly, MDSCs from RAPA‐treated mice exhibited increased immunosuppressive potential, which was primarily inducible nitric oxide synthase (iNOS)‐dependent. Surprisingly, RAPA treatment had no impact on the genomic landscape of T cells, which was reflected by unchanged expression of activation and exhaustion markers and cytokine profiles in T cells from RAPA‐treated and untreated mice. Similarly, T cell cytotoxicity and the graft‐versus‐tumor effect were maintained as co‐transplanted tumor cells were efficiently eradicated, indicating that the immunosuppressant RAPA might be an attractive approach to strengthen the immunosuppressive function of MDSCs without affecting T cell immunity.

Hot Spot TERT Promoter Mutations Are Rare in Sporadic Pancreatic Neuroendocrine Neoplasms and Associated with Telomere Length and Epigenetic Expression Patterns

Cancer cells activate a telomere maintenance mechanism like telomerase in order to proliferate indefinitely. Telomerase can be reactivated by gain-of-function Telomerase Reverse Transcriptase (TERT) promoter mutations (TPMs) that occur in several cancer subtypes with high incidence and association with diagnosis, prognosis and epigenetics. However, such information about TPMs in sporadic pancreatic neuroendocrine neoplasms (pNENs) including tumor (pNET) and carcinoma (pNEC) is less well defined. We have studied two hot spot TPMs and telomere length (TL) in pNEN and compared the results with clinicopathological information and proliferation-associated miRNA/HDAC expression profiles. DNA was isolated from formalin-fixed paraffin-embedded (FFPE) tissue of 58 sporadic pNEN patients. T allele frequency of C250T and C228T TPM was analyzed by pyrosequencing, relative TL as telomeric content by qPCR. In total, five pNEN cases (9%) including four pNETs and one pNEC were identified with TPMs, four cases with exclusive C250T as predominant TPM and one case with both C250T and C228T. T allele frequencies of DNA isolated from adjacent high tumor cell content FFPE tissue varied considerably, which may indicate TPM tumor heterogeneity. Overall and disease-free survival was not associated with TPM versus wild-type pNEN cases. Binary category analyses indicated a marginally significant relationship between TPM status and longer telomeres (p = 0.086), and changes in expression of miR449a (p = 0.157), HDAC4 (p = 0.146) and HDAC9 (p = 0.149). Future studies with larger patient cohorts are needed to assess the true clinical value of these rare mutations in pNEN.

Long interspersed element-1 ribonucleoprotein particles protect telomeric ends in alternative lengthening of telomeres dependent cells

Malignant cells ensure telomere maintenance by the alternative lengthening of telomeres (ALT) in the absence of telomerase activity (TA). The retrotransposons "long interspersed nuclear element-1" (LINE-1, L1) are expressed in malignant cells and are primarily known to contribute to complex karyotypes. Here we demonstrate that LINE-1 ribonucleoprotein particles (L1-RNPs) expression is significantly higher in ALT⁺- versus in TA⁺-human glioma. Analyzing a role of L1-RNP in ALT, we show that L1-RNPs bind to telomeric repeat containing RNA (TERRA), which is critical for telomere stabilization and which is overexpressed in ALT⁺ cells. In turn, L1-RNP knockdown (KD) abrogated the nuclear retention of TERRA, resulted in increased telomeric DNA damage, decreased cell growth and reduced expression of ALT characteristics such as c-circles and PML-bodies. L1-RNP KD also decreased the expression of Shelterin- and the ALT-regulating protein Topoisomerase IIIα (TopoIIIα) indicating a more general role of L1-RNPs in supporting telomeric integrity in ALT. Our findings suggest an impact of L1-RNP on telomere stability in ALT⁺ dependent tumor cells. As L1-RNPs are rarely expressed in normal adult human tissue those elements might serve as a novel target for tumor ablative therapy.

Low doses of widely consumed cannabinoids (cannabidiol and cannabidivarin) cause DNA damage and chromosomal aberrations in human-derived cells

Cannabidiol (CBD) and cannabidivarin (CBDV) are natural cannabinoids which are consumed in increasing amounts worldwide in cannabis extracts, as they prevent epilepsy, anxiety, and seizures. It was claimed that they may be useful in cancer therapy and have anti-inflammatory properties. Adverse long-term effects of these drugs (induction of cancer and infertility) which are related to damage of the genetic material have not been investigated. Therefore, we studied their DNA-damaging properties in human-derived cell lines under conditions which reflect the exposure of consumers. Both compounds induced DNA damage in single cell gel electrophoresis (SCGE) experiments in a human liver cell line (HepG2) and in buccal-derived cells (TR146) at low levels (≥ 0.2 µM). Results of micronucleus (MN) cytome assays showed that the damage leads to formation of MNi which reflect chromosomal aberrations and leads to nuclear buds and bridges which are a consequence of gene amplifications and dicentric chromosomes. Additional experiments indicate that these effects are caused by oxidative base damage and that liver enzymes (S9) increase the genotoxic activity of both compounds. Our findings show that low concentrations of CBD and CBDV cause damage of the genetic material in human-derived cells. Furthermore, earlier studies showed that they cause chromosomal aberrations and MN in bone marrow of mice. Fixation of damage of the DNA in the form of chromosomal damage is generally considered to be essential in the multistep process of malignancy, therefore the currently available data are indicative for potential carcinogenic properties of the cannabinoids.

High tRNA Transferase NSUN2 Gene Expression is Associated with Poor Prognosis in Head and Neck Squamous Carcinoma

NSUN2 is a tRNA methyltransferase and plays an important role in cell development via modifying RNA methylation. We aimed to evaluate the expression of NSUN2 and its prognostic value in HNSCC. Random-effects model of meta-analysis shows 1.99-folds (95% CI: 1.89-2.09) upregulation of NSUN2 expression in HNSCC versus normal tissues. Patients with high NSUN2 levels had approximately 22 months shorter overall survival, and had a higher mortality risk than those with low one (p-trend = 0.020). In conclusion, NSUN2 is a potential independent prognostic marker and may be a potential therapeutic target in HNSCC.

MNS16A tandem repeat minisatellite of human telomerase gene: functional studies in colorectal, lung and prostate cancer

MNS16A, a functional polymorphic tandem repeat minisatellite, is located in the promoter region of an antisense transcript of the human telomerase reverse transcriptase gene. MNS16A promoter activity depends on the variable number of tandem repeats (VNTR) presenting varying numbers of transcription factor binding sites for GATA binding protein 1. Although MNS16A has been investigated in multiple cancer epidemiology studies with incongruent findings, functional data of only two VNTRs (VNTR-243 and VNTR-302) were available thus far, linking the shorter VNTR to higher promoter activity.

For the first time, we investigated promoter activity of all six VNTRs of MNS16A in cell lines of colorectal, lung and prostate cancer using Luciferase reporter assay. In all investigated cell lines shorter VNTRs showed higher promoter activity. While this anticipated indirect linear relationship was affirmed for colorectal cancer SW480 (P = 0.006), a piecewise linear regression model provided significantly better model fit in lung cancer A-427 (P = 6.9 × 10⁻⁹) and prostate cancer LNCaP (P = 0.039). In silico search for transcription factor binding sites in MNS16A core repeat element suggested a higher degree of complexity involving X-box binding protein 1, general transcription factor II–I, and glucocorticoid receptor alpha in addition to GATA binding protein 1.

Further functional studies in additional cancers are requested to extend our knowledge of MNS16A functionality uncovering potential cancer type-specific differences. Risk alleles may vary in different malignancies and their determination in vitro could be relevant for interpretation of genotype data.

Epithelial splicing regulatory protein 1 and 2 paralogues correlate with splice signatures and favorable outcome in human colorectal cancer

ESRPs are master splice regulators implicated in alternative mRNA splicing programs important for epithelial-mesenchymal transition (EMT) and tumor progression. ESRP1 was identified in some tumors as good or worse predictor of outcome, but in colorectal cancer (CRC) the prognostic value of ESRPs and relation with mesenchymal splice variants is not clear. Here, we studied 68 CRC cases, compared tissue expression of ESRPs with clinical data and with EMT gene splice patterns of conditional CRC cells with deficient ESRP1 expression.Around 72% of patients showed global decreased transcript expression of both ESRPs in tumor as compared to matched non-neoplastic colorectal epithelium. Reduction of ESRP1 in tumor cells was evaluated by immunohistochemistry, associated with microsatellite stability and switch to mesenchymal splice signatures of FGFRs, CD44, ENAH and CTNND1(p120-catenin). Expression of ESRPs was significantly associated with favorable overall survival (log-rank test, P=0.0186 and 0.0408), better than prognostic stratification by tumor staging; and for ESRP1 confirmed with second TCGA cohort (log-rank test, P=0.0435). Prognostic value is independent of the pathological stage and microsatellite instability (ESRP1: HR=0.36, 95%CI 0.15-0.91, P=0.032; ESRP2: HR=0.23, 95%CI 0.08-0.65, P=0.006).Our study supports the role of ESRP1 as tumor suppressor and strongly suggests that ESRPs are candidate markers for early detection, diagnosis, and prognosis of CRC.

Elevated Plasma Levels of Crosslinked Fibrinogen Gamma-chain Dimer Indicate Cancer-related Fibrin Deposition and Fibrinolysis

Cancer-related fibrin deposition and fibrinolysis were investigated by two-dimensional gel electrophoresis of human solid tumor and effusion specimen in addition to plasma samples. Fibrinogen gamma-chain dimer indicating fibrin deposition and plasmin-generated fibrinogen beta-chain fragments were identified in various solid tumor types by amino acid sequencing, mass spectrometry analysis and Western blotting. In tumor-associated effusions, these techniques allowed to observe plasmin-generated fragments of fibrinogen alpha, beta and gamma-chains in addition to elevated levels of acute-phase proteins. Similar observations were made in case of inflammation-associated effusions. No fibrin degradation product was observed in plasma samples, however, high amounts of fibrinogen gamma-chain dimer crosslinked by transglutaminase were detected in plasma from tumor patients, but not in plasma from controls and patients suffering acute infections and/or inflammations. This finding demonstrated that high transglutaminase activity may be associated with cancer. The presented data indicate that the amount of crosslinked fibrinogen gamma-chain dimer in plasma may correlate with tumor-associated fibrin deposition. The tumor-biological relevance of this potential marker protein is discussed.

Comprehensive immunohistochemical analysis of histone deacetylases in pancreatic neuroendocrine tumors: HDAC5 as a predictor of poor clinical outcome

Epigenetic factors contribute to carcinogenesis, tumor promotion, and chemoresistance. Histone deacetylases (HDACs) are epigenetic regulators that primarily cause chromatin compaction, leading to inaccessibility of promoter regions and eventually gene silencing. Many cancer entities feature overexpression of HDACs. Currently, the role of HDACs in pancreatic neuroendocrine tumors (pNETs) is unclear. We analyzed the expression patterns of all HDAC classes (classes I, IIA, IIB, III, and IV) in 5 human tissue microarrays representing 57 pNETs resected between 1997 and 2013 and corresponding control tissue. All pNET cases were characterized clinically and pathologically according to recent staging guidelines. The investigated cases included 32 (56.1%) female and 25 (43.9%) male pNET patients (total n=57, 47.4% immunohistochemically endocrine positive). Immunohistochemical profiling revealed a significant up-regulation of all HDAC classes in pNET versus control, with different levels of intensity and extensity ranging from 1.5- to >7-fold up-regulation. In addition, expression of several HDACs (HDAC1, HDAC2, HDAC5, HDAC11, and Sirt1) was significantly increased in G3 tumors. Correlation analysis showed a significant association between the protein expression of HDAC classes I, III, and IV and rate of the pHH3/Ki-67-associated mitotic and proliferation index. Furthermore, especially HDAC5 proved as a negative predictor of disease-free and overall survival in pNET patients. Overall, we demonstrate that specific members of all 4 HDAC classes are heterogeneously expressed in pNET. Moreover, expression of HDACs was associated with tumor grading, proliferation markers, and patient survival, therefore representing interesting new targets in pNET treatment.

Irinotecan Upregulates Fibroblast Growth Factor Receptor 3 Expression in Colorectal Cancer Cells, Which Mitigates Irinotecan-Induced Apoptosis

BACKGROUND: Irinotecan (IRI) is an integral part of colorectal cancer (CRC) therapy, but response rates are unsatisfactory and resistance mechanisms are still insufficiently understood. As fibroblast growth factor receptor 3 (FGFR3) mediates essential survival signals in CRC, it is a candidate gene for causing intrinsic resistance to IRI. METHODS: We have used cell line models overexpressing FGFR3 to study the receptor's impact on IRI response. For pathway blockade, a dominant-negative receptor mutant and a small molecule kinase inhibitor were employed. RESULTS: IRI exposure induced expression of FGFR3 as well as its ligands FGF8 and FGF18 both in cell cultures and in xenograft tumors. As overexpression of FGFR3 mitigated IRI-induced apoptosis in CRC cell models, this suggests that the drug itself activated a survival response. On the cellular level, the antiapoptotic protein bcl-xl was upregulated and caspase 3 activation was inhibited. Targeting FGFR3 signaling using a dominant-negative receptor mutant sensitized cells for IRI. In addition, the FGFR inhibitor PD173074 acted synergistically with the chemotherapeutic drug and significantly enhanced IRI-induced caspase 3 activity in vitro. In vivo, PD173074 strongly inhibited growth of IRI-treated tumors. CONCLUSION: Together, our results indicate that targeting FGFR3 can be a promising strategy to enhance IRI response in CRC patients.

Fibroblast growth factor receptor 3 isoforms: Novel therapeutic targets for hepatocellular carcinoma?

Fibroblast growth factor receptors (FGFRs) are frequently up-regulated in subsets of hepatocellular carcinoma (HCC). Here, we provide mechanistic insight that FGFR3 splice variants IIIb and IIIc impact considerably on the malignant phenotype of HCC cells. The occurrence of FGFR3 variants was analyzed in human HCC samples. In hepatoma/hepatocarcinoma cell lines, FGFR3 isoforms were overexpressed by lentiviral constructs or down-modulated by small interfering RNA (siRNA; affecting FGFR3-IIIb and -IIIc) or an adenoviral kinase-dead FGFR3-IIIc construct (kdFGFR3). Elevated levels of FGFR3-IIIb and/or -IIIc were found in 53% of HCC cases. FGFR3-IIIb overexpression occurred significantly more often in primary tumors of large (pT2-4) than of small size (pT1). Furthermore, one or both isoforms were enhanced mostly in cases with early tumor infiltration and/or recurrence at the time of surgery or follow-up examinations. In hepatoma/hepatocarcinoma cells, up-regulated FGFR3-IIIb conferred an enhanced capability for proliferation. Both FGFR3-IIIb and FGFR3-IIIc suppressed apoptotic activity, enhanced clonogenic growth, and induced disintegration of the blood/lymph endothelium. The tumorigenicity of cells in severe combined immunodeficiency mice was augmented to a larger degree by variant IIIb than by IIIc. Conversely, siRNA targeting FGFR3 and kdFGFR3 reduced clonogenicity, anchorage-independent growth, and disintegration of the blood/lymph endothelium in vitro. Furthermore, kdFGFR3 strongly attenuated tumor formation in vivo.

CONCLUSIONS

Deregulated FGFR3 variants exhibit specific effects in the malignant progression of HCC cells. Accordingly, blockade of FGFR3-mediated signaling may be a promising therapeutic approach to antagonize growth and malignant behavior of HCC cells.

Is fibroblast growth factor receptor 4 a suitable target of cancer therapy?

Fibroblast growth factors (FGF) and their tyrosine kinase receptors (FGFR) support cell proliferation, survival and migration during embryonic development, organogenesis and tissue maintenance and their deregulation is frequently observed in cancer development and progression. Consequently, increasing efforts are focusing on the development of strategies to target FGF/FGFR signaling for cancer therapy. Among the FGFRs the family member FGFR4 is least well understood and differs from FGFRs1-3 in several aspects. Importantly, FGFR4 deletion does not lead to an embryonic lethal phenotype suggesting the possibility that its inhibition in cancer therapy might not cause grave adverse effects. In addition, the FGFR4 kinase domain differs sufficiently from those of FGFRs1-3 to permit development of highly specific inhibitors. The oncogenic impact of FGFR4, however, is not undisputed, as the FGFR4-mediated hormonal effects of several FGF ligands may also constitute a tissue-protective tumor suppressor activity especially in the liver. Therefore it is the purpose of this review to summarize all relevant aspects of FGFR4 physiology and pathophysiology and discuss the options of targeting this receptor for cancer therapy.

Abstract 1671: Fibroblast growth factor receptor 3 enhances progression of hepatocellular carcinoma

Purpose of the study. To provide mechanistic evidence that fibroblast growth factor receptor 3 (FGFR3) and its two splice variants, FGFR3-IIIb and -IIIc, impact considerably on the malignant phenotype of hepatocellular carcinoma (HCC).

Experimental procedures. The occurrence of FGFR3 and its two isoforms was analyzed in human HCC samples by qRT-PCR and immunostaining. In hepatoma/hepatocarcinoma cell lines FGFR3-isoforms were overexpressed by lentiviral constructs or were down-modulated by siRNA or an adenoviral kinase-dead FGFR3 (kdFGFR3) construct. Cell lines were tested for anchorage-independent growth, proliferation at low-densities and their cell-cycle distribution, as well as their ability to form tumors after subcutaneous injection into the flanks of SCID-mice.

Results. Upregulated FGFR3 was found in almost 50% of HCC patients, which was often due to the enhanced expression of FGFR3-IIIb. Furthermore, patients with FGFR3-IIIb overexpression showed early tumor recurrence indicating that this isoform may be a major player in tumor progression. In hepatoma/hepatocarcinoma cells, upregulated FGFR3-IIIb or FGFR3-IIIc conferred an enhanced capability for proliferation and tumor growth. Both isoforms enhanced downstream signaling and increased the cells’ ability to grow at low densities. The tumorigenicity of cells in SCID-mice was augmented more by variant IIIb than by IIIc. This stronger impact of FGFR-IIIb on cell proliferation could also be seen in analysis of the cell cycle distribution, which was shifted to the S-phase. Conversely, siFGFR3 and kdFGFR3 affected both receptor-variants and strongly reduced clonogenic growth at low density and anchorage-independent growth. Furthermore, kdFGFR3 arrested the cells in G2/M and strongly attenuated tumor formation in vivo.

Conclusions: Upregulated FGFR3 is associated with development and progression of hepatocellular carcinoma. Accordingly, blockade of FGFR3-mediated signaling may be a promising therapeutic approach to antagonize growth and malignant behavior of HCC cells.

Citation Format: Jakob Paur, Lisa Nika, Christiane Maier, Julia Kostka, Petra Heffeter, Sonja Kappel, Daniela Kandioler, Klaus Holzmann, Brigitte Marian, Walter Berger, Michael Grusch, Bettina Grasl-Kraupp. Fibroblast growth factor receptor 3 enhances progression of hepatocellular carcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1671. doi:10.1158/1538-7445.AM2015-1671

LINE-1 induces hTERT and ensures telomere maintenance in tumour cell lines

A hallmark of cancer cells is an activated telomere maintenance mechanism, which allows prolonged survival of the malignant cells. In more than 80% of tumours, telomeres are elongated by the enzyme telomerase, which adds de novo telomere repeats to the ends of chromosomes. Cancer cells are also characterized by expression of active LINE-1 elements (L1s, long interspersed nuclear elements-1). L1 elements are abundant retrotransposons in the eukaryotic genome that are primarily known for facilitating aberrant recombination. Using L1-knockdown (KD), we show for the first time that L1 is critical for telomere maintenance in telomerase-positive tumour cells. The reduced length of telomeres in the L1-KD-treated cells correlated with an increased rate of telomere dysfunction foci, a reduced expression of shelterin proteins and an increased rate of anaphase bridges. The decreased telomere length was associated with a decreased telomerase activity and decreased telomerase mRNA level; the latter was increased upon L1 overexpression. L1-KD also led to a decrease in mRNA and protein expression of cMyc and KLF-4, two main transcription factors of telomerase and altered mRNA levels of other stem-cell-associated proteins such as CD44 and hMyb, as well as a corresponding reduced growth of spheroids. The KD of KLF-4 or cMyc decreased the level of L1-ORF1 mRNA, suggesting a specific reciprocal regulation with L1. Thus, our findings contribute to the understanding of L1 as a pathogenicity factor in cancer cells. As L1 is only expressed in pathophysiological conditions, L1 now appears to be target in the rational treatment of telomerase-positive cancer.

Abstract 2743: Telomere transcripts improve synthetic inhibitors of telomerase

Most tumors express telomerase for infinite cell growth capacity. Telomerase was recognized recently as central regulator of all of the hallmarks of cancer and synthetic inhibitors of telomerase, such as Imetelstat blocking the RNA subunit of telomerase TERC, are in clinical trials. RNA transcripts from telomeres called TERRA were identified to block telomerase activity (TA) potentially via direct binding to TERC. We established recombinant expression systems to modulate TERRA transcripts in cell culture cells and study in vitro cell growth and viability directly and in combination with telomerase inhibitors.

Adeno- and lentivirus constructs (AV and LV) were established for transient and stable recombinant TERRA expression in TA tumor cell lines (N=3) and mortal fibroblast cells as control. AV and LV express TERRA under control of hH1 promoter with around 120 units of UUAGGG repeats in sense (S) or anti-sense (AS) orientation. Similarly, AV and LV express polyadenylated form of TERRA under control of CMV promoter and polyadenylation signaling sites. Telomere length (TL), endogenous and recombinant TERRA expression was analyzed by qPCR, TA by TRAP assay. Population doubling (PD) times were calculated from cell growth numbers of LV clones. Small molecule telomerase inhibitors and AVs expressing dominant-negative telomerase and shRNA against hTERT were used in MTT cell viability and clonogenicity assays.

TERRA expression was modulated transiently and stably by recombinant AVs and LVs as compared to virus controls expressing eGFP. Moderate 1.5-1.7 fold elevation of recombinant TERRA-S transcripts caused reduction of TA to 23-38%. In contrast, AS expression reduced TERRA 3-8 fold without reduction of TA. TL, PD time, cell viability and clonogenicity were not affected by TERRA-S and -AS expression up to 3 weeks in culture. Single cell clones were isolated from cells infected by LVs. Significant improve of telomerase targeting approaches was identified as IC-50 values decreased 2.0-2.6 fold in LV cell clones expressing moderate recombinant TERRA-S compared to TERRA-AS and eGFP. Similarly, clone formation capacity decreased 1.3-1.7 fold. Human fibroblasts showed 15 fold increased TERRA expression compared to tumor cells and were not affected by treatments applied. Preliminary data with modified RNA oligonucleotides containing TERRA sequences indicate that up-take by cells was efficient. Furthermore, IC-50 values of TA inhibitor MST-312 in combination with 3 nM TERRA oligonucleotides decreased 1.9-3.9 fold compared to mismatch controls. Effective concentrations were 1000 fold lower compared to DNA oligonucleotide telomerase inhibitors currently in clinical trials.

We demonstrated that recombinant expression of TERRA significantly improved telomerase targeting approaches in tumor cells but not in mortal fibroblasts. TERRA oligonucleotides are candidates for in vivo application in combination with telomerase targeting approaches or other tumor therapies.

Citation Format: Sandra Sampl, Doris Mejri, Christian Stern, Hui Wang, Klaus Holzmann. Telomere transcripts improve synthetic inhibitors of telomerase. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2743. doi:10.1158/1538-7445.AM2014-2743

Major vault protein supports glioblastoma survival and migration by upregulating the EGFR/PI3K signalling axis

Despite their ubiquitous expression and high conservation during evolution, precise cellular functions of vault ribonucleoparticles, mainly built of multiple major vault protein (MVP) copies, are still enigmatic. With regard to cancer, vaults were shown to be upregulated during drug resistance development as well as malignant transformation and progression. Such in a previous study we demonstrated that human astrocytic brain tumours including glioblastoma are generally high in vault levels while MVP expression in normal brain is comparably low. However a direct contribution to the malignant phenotype in general and that of glioblastoma in particular has not been established so far. Thus we address the questions whether MVP itself has a pro-tumorigenic function in glioblastoma. Based on a large tissue collection, we re-confirm strong MVP expression in gliomas as compared to healthy brain. Further, the impact of MVP on human glioblastoma aggressiveness was analysed by using gene transfection, siRNA knock-down and dominant-negative genetic approaches. Our results demonstrate that MVP/vaults significantly support migratory and invasive competence as well as starvation resistance of glioma cells in vitro and in vivo. The enhanced aggressiveness was based on MVP-mediated stabilization of the epidermal growth factor receptor (EGFR)/phosphatidyl-inositol-3-kinase (PI3K) signalling axis. Consequently, MVP overexpression resulted in enhanced growth and brain invasion in human glioblastoma xenograft models. Our study demonstrates, for the first time, that vaults have a tumour-promoting potential by stabilizing EGFR/PI3K-mediated migration and survival pathways in human glioblastoma.

Comparative gene array analysis of progenitor cells from human paired deep neck and subcutaneous adipose tissue

Brown and white adipocytes have been shown to derive from different progenitors. In this study we sought to clarify the molecular differences between human brown and white adipocyte progenitors cells. To this end, we performed comparative gene array analysis on progenitor cells isolated from paired biopsies of deep and subcutaneous neck adipose tissue from individuals (n = 6) undergoing neck surgery. Compared with subcutaneous neck progenitors, cells from the deep neck adipose tissue displayed marked differences in gene expression pattern, including 355 differentially regulated (>1.5 fold) genes. Analysis of highest regulated genes revealed that STMN2, MME, ODZ2, NRN1 and IL13RA2 genes were specifically expressed in white progenitor cells, whereas expression of LRRC17, CNTNAP3, CD34, RGS7BP and ADH1B marked brown progenitor cells. In conclusion, progenitors from deep neck and subcutaneous neck adipose tissue are characterized by a distinct molecular signature, giving rise to either brown or white adipocytes. The newly identified markers may provide potential pharmacological targets facilitating brown adipogenesis.

Canine and human sarcomas exhibit predominant FGFR1 expression and impaired viability after inhibition of signaling

Fibroblast growth factor receptors (FGFRs) are important in malignant progression of several human epithelial tumors. However, little is known about FGFRs in canine or human soft tissue sarcomas. Thus, our aim was to investigate expression of FGFRs and their involvement in cell survival in sarcomas of both species. FGFR1-4 and FGFRL1 transcripts as well as IIIb/IIIc splice variants of FGFR1-3 were evaluated in 3 canine- and 6 human sarcoma cell lines and 19 spontaneous canine sarcomas by SYBRqPCR. FGFR1 protein expression was assessed by immunohistochemistry. Growth inhibitory effects of FGFR1 inhibitor PD166866 and dominant negative recombinant FGFR adenoviral expression constructs (dnFGFR) on tumor cell lines were analyzed. Profiling of multiple FGFR transcripts detected comparable co-expression in most of human and canine sarcoma cell lines and canine tumor specimens. This indicates existence of closely related regulation mechanisms for FGFR expression in sarcomas of both species. FGFR1 with splice variant IIIc was consistently expressed with highest transcript levels. In 88% of the spontaneous tumor samples a heterogeneous FGFR1 protein expression was observed. Significant growth inhibition and cell death was seen after infection with dnFGFR1 in canine and human sarcoma cells, but not with dnFGFR3 and 4. PD166866 showed selective cytotoxicity with IC50 values between 12.1 and 26.4 μM. FGFR1 inhibition blocked ligand-induced tyrosine phosphorylation of ERK1/2 mitogen-activated protein kinase isoforms. This study emphasizes the important role FGFR1, especially splice variant IIIc, likely plays in sarcomas. Inhibitory small molecules could be of potential use for targeted therapy in aggressive sarcomas of both species.

Autocrine fibroblast growth factor 18 signaling mediates Wnt-dependent stimulation of CD44-positive human colorectal adenoma cells

Expansion of a stem-like subpopulation with increased growth and survival potential is thought to drive colorectal tumor growth and progression. We investigated a CD44-positive (CD44((+))) subpopulation with extended growth and survival capacity in the human colon adenoma cell line LT97. This subpopulation expressed elevated levels of fibroblast growth factor 18 (FGF18) and fibroblast growth factor receptor FGFR3-IIIc. Expression levels of the FGFR3-IIIb, which does not bind FGF18, were similar in CD44((+)) and CD44((-)). Addition of FGF18 to the medium or its overexpression from an adenoviral vector increased the colony formation capacity of CD44((+)) threefold, and stimulated phosphorylation of ERK and GSK3β in both total LT97 populations and CD44((+)) cells. FGFR3 signaling blockade by expression of a dominant-negative FGFR3-IIIc mutant led to inhibition of both colony formation and down-stream signaling in the CD44((+)) cells. CD44((-)) cells did not respond. Blockade of the wnt-pathway by a dominant-negative Tcf4-mutant inhibited FGFR3 activation in LT97 cells as well as in HT29 colorectal cancer cells. The chemical wnt-inhibitor sulindac sulfide amide inhibited expression of FGF18 and FGFR3-IIIc and led to inhibition of receptor activation to less than 30% of control treated cells, both in LT97 and HT29 cultures. Our results demonstrate that an FGF18/FGFR3-IIIc autocrine growth and survival loop is up-regulated in a wnt-dependent manner and drives tumor cell growth in a subpopulation of colon adenoma cells. This subpopulation can be regarded as a precursor of colon cancer development and can be targeted for CRC-prevention by blocking either wnt- or FGFR3-signaling.

Differential effects of polymorphic alleles of FGF receptor 4 on colon cancer growth and metastasis

A gly(388)arg polymorphism (rs351855) in the transmembrane domain of the fibroblast growth factor receptor (FGFR4) is associated with increased risk, staging, and metastasis in several different types of cancer. To specifically assess the impact of the polymorphic FGFR4 in colorectal cancer (CRC), we engineered CRC cell lines with distinct endogenous expression patterns to overexpress either the FGFR4(gly) or FGFR4(arg) alleles. The biologic analyses revealed an oncogenic importance for both polymorphic alleles, but FGFR4(gly) was the stronger inducer of tumor growth, whereas FGFR4(arg) was the stronger inducer of migration. An evaluation of clinical specimens revealed that FGFR4 was upregulated in 20/71 patients independent of gly(388)arg status. There was no correlation between the presence of an FGFR4(arg) allele and CRC or polyp risk in 3,471 participants of the CORSA study. However, among 182 patients with CRC, FGFR4(arg)-carriers had a fivefold higher risk of tumors that were stage II or greater. Together, our results established that both allelic forms of FGFR4 exert an oncogenic impact and may serve equally well as therapeutic targets in CRC. One important implication of our findings is that FGFR4(arg)-carriers are at a higher risk for more aggressive tumors and therefore may profit from early detection measures.

Abstract 1229: Fibroblast growth factor signaling in ovarian cancer

Epithelial ovarian cancer (OC) is a rapidly progressive, highly lethal disease. It is the fifth leading cause of cancer-related death among women. Over the last decades, there has been only modest improvement in the treatment of OC. Nevertheless, recent clinical trials with inhibitors of transmembrane receptor tyrosine kinases such as fibroblast growth factor (FGF) receptors (FGFRs) yielded some promising results in OC. FGFRs are involved in malignant transformation, angiogenesis and chemoresistance. Inhibition of FGFR-dependent signaling can overcome resistance to standard therapies. Thus, FGFRs represent potential targets for cancer therapy. Unfortunately, however, the biological and therapeutic relevance of the FGF-FGFR system has not been elucidated yet in OC. The aim of this study was to characterize the FGF-FGFR system, its influence on malignancy-related cell properties and its potential role as a druggable signaling pathway in OC cells. Reverse transcription-polymerase chain reaction (RT-PCR) analysis revealed that expression of FGFs and FGFRs, leading to autocrine signaling loops with a strong mitogenic potential, is a common event in OC. Immunoblotting proved that the FGF signaling system is functionally active in these cells. Conditioned growth medium was able to induce phosphorylation of ERK1/2. Moreover, recombinant FGF-2 significantly elevated the growth rate in approximately 50% of the OC cell lines as demonstrated by formazan dye assay, whereas FGF-1 markedly induced migration in 66% of the cell lines. The dependency of OC cells on FGFR signaling was further evaluated by growth inhibition assays using the two small molecular FGFR inhibitors PD173074 and dovitinib (TKI-258, CHIR-258). A-2780 cells were found to be extremely sensitive to FGFR inhibition, while HEY and SKOV-3 cells showed moderate sensitivity. In contrast, OVCAR-3 cells were not inhibited by these compounds. Together, our data suggest that FGFR inhibitors reveal anticancer activity in a significant proportion of OC cells even as single drugs. Thus, combination of conventional cytotoxic intervention with blockade of the FGF-FGFR system might represent a promising future strategy for the treatment of OC.

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 1229. doi:1538-7445.AM2012-1229

Abstract 4597: Telomere maintenance mechanism and expression in colorectal cancer

Tumors can overcome cellular senescence, one of the main barriers to tumor development and immortality by telomere maintenance mechanism (TMM). 90% of colorectal carcinomas (CRC) use telomerase activity (TA) as TMM. Mechanisms of remaining CRC tumors are not well analyzed yet and may utilize alternative lengthening of telomeres (ALT) or a not defined telomere maintenance mechanism (NDTMM). Both TA and expression of telomeric repeat containing RNA (TERRA) were recently identified to correlate with tumor grade. This led us to evaluate possible correlations of TMM and TERRA levels to clinical data. Tissues from 49 CRC patients (35 grade II, 14 grade III, 2 polyps) and cell lines (N = 7) were assessed. Tumor tissues were compared to matched adjacent non-tumor tissues. Mean telomere length (TL) was measured by real-time PCR and telomere restriction fragment (TRF) length analyses. TMM were evaluated by measuring TA with telomere amplification protocol (TRAP) and by detection of ALT with c-circles. Real-time RT-PCR assays for relative quantity (RQ) of transcript levels for TERRA, telomerase genes hTERT and hTERC were determined in relation to levels of house-keeping genes and normal tissues. RQ values were analyzed for significant differences between groups by Mann-Whitney test and were assessed after log-transformation with the Pearson's correlation calculation. TL of grade II and grade III tumors were in the range of 5.5 ± 1.3kbp and 5.3 ± 0.5kbp, respectively (mean ± SD), and were comparable with TL of normal tissue and cell lines. TA was detected with mean of 27 TPG units in 90% (34 of 38) and with mean of 4 units in 24% (9 of 38) of tumor and normal tissues, respectively. All cell lines analyzed demonstrate TA with mean of 51 units. A restricted set of tumors consisting of 2 with and 4 without TA was analyzed for ALT. One of the analyzed tumors without detectable TA showed significantly elevated levels of c-circles, but did not reach levels of sarcomas and cell models with ALT, indicating the existence of NDTMM in CRC. Within the transcripts analyzed, TERRA levels showed a moderate negative correlation with TA (Pearson r=−0.45, p<0.0001), supporting the inhibitory function of TERRA on TA as recently described in vitro. TERRA levels of grade II and III tumors decreased compared to normal tissues, but did not differ between grades. However, TA and TERRA levels of tumors increased and decreased, respectively, in stage II compared to stage I tumors, indicating a role in tumor progression. Correlation with patient survival will be performed and presented. In conclusion, we identified TA and NDTMM, but not ALT in our patient series of CRC. Our preliminary data suggest that TERRA expression together with TA correlates with diagnoses and thus can be considered promising candidates as clinical markers for CRC.

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 4597. doi:1538-7445.AM2012-4597

Abstract 1203: Targeting FGFR4 in colorectal cancer cells

Fibroblast growth factors (FGFs) and their receptors (FGFRs) are involved in the regulation of cell proliferation, differentiation and survival as well as tumor development and therefore constitute prominent targets for cancer therapy. Over-expression of FGFR4 has been described in various cancer types and was also related to tumor aggressiveness. Reports concerning the role of FGFR4 in colorectal cancer (CRC) are still under dispute. In our study we found FGFR4 expression to be significantly up-regulated in human CRC tissue compared to normal mucosa. CRC cell line models over-expressing FGFR4 were created by transfecting SW480, HCT116 and HT29 colon carcinoma cells with a FGFR4 expression vector. This resulted in an increase of cell proliferation and colony formation under standard tissue culture conditions and colony outgrowth in soft agar was stimulated. In xenografted SCID mice tumor growth was significantly increased by FGFR4 over-expression. siRNA mediated knock down of FGFR4 in the high FGFR4 expressing cell lines HCT116 and HT29 resulted in decreased cell proliferation, viability and colony outgrowth in 2-dimensional growth assays. Additionally a dominant negative FGFR4 adenoviral construct inhibited 3-dimensional anchorage independent growth and suppressed tumor growth in vivo almost completely. Ongoing experiments analyze the effects of a soluble FGFR4 variant on 2-dimensional and 3-dimensional growth. FGFR4 up-regulation resulted in activation of survival pathways via FRS2 and PI3K leading to phosphorylation of GSK3β and S6. Signaling effects by blockage of FGFR4 dependent signaling via siRNA and the dominant negative adenoviral construct are currently being investigated. Based on our results we identified the FGFR4 as an important oncogene in the carcinogenesis which is involved in the tumor growth regulation of CRC in vitro and in vivo. Consequently FGFR4 should be regarded as a new therapeutic target in CRC.

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 1203. doi:1538-7445.AM2012-1203

The major vault protein mediates resistance to epidermal growth factor receptor inhibition in human hepatoma cells

To better understand the response of HCC to EGFR inhibition, we analyzed factors connected to the resistance of HCC cells against gefitinib. Sensitive HCC3 cells co-expressed EGFR and ErbB3 but lacked kinase-domain mutations in EGFR. Interestingly, expression of MVP was restricted to resistant cell lines, whereas ABCB1 and ABCC1 showed no association with gefitinib resistance. Moreover, ectopic MVP expression in HCC3 cells decreased gefitinib sensitivity, increased AKT phosphorylation and reduced the expression of inflammatory pathway-associated genes, whereas silencing of MVP in Hep3B and HepG2 cells increased sensitivity. These findings suggest MVP as a novel player in resistance against EGFR inhibition.

The clathrin-binding domain of CALM and the OM-LZ domain of AF10 are sufficient to induce acute myeloid leukemia in mice

The t(10;11)(p13-14;q14-21) translocation, giving rise to the CALM-AF10 fusion gene, is a recurrent chromosomal rearrangement observed in patients with poor prognosis acute myeloid leukemia (AML). Although splicing of the CALM-AF10 fusion transcripts has been described in AML patients, the contribution of different CALM and AF10 domains to in vivo leukemogenesis remains to be defined. We therefore performed detailed structure-function studies of the CALM-AF10 fusion protein. We demonstrate that fusion of the C-terminal 248 amino acids of CALM, which include the clathrin-binding domain, to the octapeptide motif-leucine-zipper (OM-LZ) domain of AF10 generated a fusion protein (termed CALM-AF10 minimal fusion (MF)), with strikingly enhanced transformation capabilities in colony assays, providing an efficient system for the expeditious assessment of CALM-AF10-mediated transformation. Leukemias induced by the CALM-AF10 (MF) mutant recapitulated multiple aspects of full-length CALM-AF10-induced leukemia, including aberrant Hoxa cluster upregulation, a characteristic molecular lesion of CALM-AF10 leukemias. In summary, this study indicates that collaboration of the clathrin-binding and the OM-LZ domains of CALM-AF10 is sufficient to induce AML. These findings further suggest that future approaches to antagonize CALM-AF10-induced transformation should incorporate strategies, which aim at blocking these key domains.

MNS16A tandem repeats minisatellite of human telomerase gene: a risk factor for colorectal cancer

Telomerase reactivation and expression of human telomerase gene [human telomerase reverse transcriptase (hTERT)] are hallmarks of unlimited proliferation potential of cancer cells. A polymorphic tandem repeats minisatellite of hTERT gene, termed MNS16A was reported to influence hTERT expression. To assess the role of MNS16A as potential biomarker for colorectal cancer (CRC), we investigated for the first time the association of MNS16A genotypes with risk of colorectal polyps and CRC. In the ongoing colorectal cancer study of Austria (CORSA), 3842 Caucasian participants were recruited within a large screening project in the province Burgenland including 90 CRC cases, 308 high-risk polyps, 1022 low-risk polyps and 1822 polyp free controls verified by colonoscopy. MNS16A genotypes were determined by polymerase chain reaction from genomic DNA. Associations of MNS16A genotypes with CRC risk were estimated by logistic regression analysis computing odds ratios (ORs) and 95% confidence intervals (CIs). We identified five different variable number of tandem repeats (VNTRs) of MNS16A including VNTR-364, a newly discovered rare variant. VNTR-274 allele was associated with a 2.7-fold significantly increased risk of CRC compared with the VNTR-302 wild-type (OR = 2.69; 95% CI = 1.11-6.50; P = 0.028). In our CORSA study, the medium length VNTR-274 was identified as risk factor for CRC. Although, this population-based study herewith reports the largest cohort size concerning MNS16A thus far, further large-scale studies in diverse populations are warranted to confirm hTERT MNS16A genotype as potential biomarker for assessment of CRC risk.

Up-regulation of the fibroblast growth factor 8 subfamily in human hepatocellular carcinoma for cell survival and neoangiogenesis

Fibroblast growth factors (FGFs) and their high-affinity receptors [fibroblast growth factor receptors (FGFRs)] contribute to autocrine and paracrine growth stimulation in several non-liver cancer entities. Here we report that at least one member of the FGF8 subfamily (FGF8, FGF17, and FGF18) was up-regulated in 59% of 34 human hepatocellular carcinoma (HCC) samples that we investigated. The levels of the corresponding receptors (FGFR2, FGFR3, and FGFR4) were also elevated in the great majority of the HCC cases. Overall, 82% of the HCC cases showed overexpression of at least one FGF and/or FGFR. The functional implications of the deregulated FGF/FGFR system were investigated by the simulation of an insufficient blood supply. When HCC-1.2, HepG2, or Hep3B cells were subjected to serum withdrawal or the hypoxia-mimetic drug deferoxamine mesylate, the expression of FGF8 subfamily members increased dramatically. In the serum-starved cells, the incidence of apoptosis was elevated, whereas the addition of FGF8, FGF17, or FGF18 impaired apoptosis, which was associated with phosphorylation of extracellular signal-regulated kinase 1/2 and ribosomal protein S6. In contrast, down-modulation of FGF18 by small interfering RNA (siRNA) significantly reduced the viability of the hepatocarcinoma cells. siRNA targeting FGF18 also impaired the cells' potential to form clones at a low cell density or in soft agar. With respect to the tumor microenvironment, FGF17 and FGF18 stimulated the growth of HCC-derived myofibroblasts, and FGF8, FGF17, and FGF18 induced the proliferation and tube formation of hepatic endothelial cells.

CONCLUSION

FGF8, FGF17, and FGF18 are involved in autocrine and paracrine signaling in HCC and enhance the survival of tumor cells under stress conditions, malignant behavior, and neoangiogenesis. Thus, the FGF8 subfamily supports the development and progression of hepatocellular malignancy.

Abstract 832: Evaluation of relevance of genes expressed in cancer stem cells and under hypoxia in astrocytic brain tumors

The dismal prognosis of patients suffering from astrocytomas, especially glioblastoma multiforme (GBM) emphasizes the need for more precise expressional characterization of these tumors in order to identify potential prognostic factors and therapeutic targets. Tumor growth leads to formation of low oxygenated regions that are considered as stem cell niches. GBM are described with high cancer stem cell content and with hypoxic and necrotic areas. This study investigates in astrocytomas WHO grade II to IV the transcript levels of genes expressed in cancer stem cells (NANOG, ALDH1A1, ALDH3A1, CD133, NOTCH1, ABCB1, ABCG2) and hypoxia regulators and regulated genes (HIF1α, HIF2α, CA9, VEGF). A relationship between some of these factors and patient survival or tumor grade has been reported in previous studies.

Tissue samples (ts) from 46 patients were histologically graded as: 12 diffuse astrocytomas (DA) gr II, 6 anaplastic astrocytomas (AA) gr III and 28 GBM gr IV. RNA was isolated from ts. Gene expression levels measured by real-time qRT-PCR in the separate tumor samples were compared to levels found in 6 non-tumor ts from patients suffering epileptic lesions and to beta actin. Relative quantities were compared between ts groups by Mann-Whitney test and log-transformed for Pearson correlation calculation.

Increase of HIF2α (200-fold), CA9 (2.7-fold) and VEGF (3.4-fold) mRNA was observed in GBM compared to non-tumor or DA (p<0.05). HIF1α and NANOG mRNA levels did not change (p>0.05). In contrast, a decrease of expression in GBM compared to DA of ABCB1 (10-fold), ABCG2 (10-fold), NOTCH1 (4.2-fold) and ALDH1A1 (6.8-fold) mRNA was observed (p<0.05). ALDH3A1 mRNA was increased 29-fold in GBM compared to DA, but decreased 270-fold compared to non-tumor (p<0.05). Weak and interesting significant correlations of mRNA levels were observed between NOTCH1, NANOG, ABCG2 and ALDH1A1 (Pearson's coefficient P=0.43 to 0.60), between NANOG and CA9 (P=0.67) and between VEGF and ALDH1A1 (P=-0.43). Primary analysis of expression and survival data indicates a significant connection of overall survival and expression of ALDH1A1. Low ALDH1A1 mRNA correlates with a poor prognosis. Part of our findings could be confirmed by comparison with mRNA levels from public database Rembrandt (Repository of Molecular Brain Neoplasia Data) containing results from experiments with gene expression and copy number arrays.

Conclusion: Transcript levels of analyzed genes are significantly related to tumor grade, except are HIF1α and NANOG. Decreased transcript levels of genes expressed in cancer stem cells are in contrast to a high content of cancer stem cells described for GBM. Expression levels of most of the investigated genes can be considered promising candidates as prognostic and diagnostic markers in astrocytomas.

This project was supported in part by a grant from the Herzfelder-Familien-Stiftung, Austria.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 832.

Fibroblast growth factor receptor 3-IIIc mediates colorectal cancer growth and migration

Background:

Deregulation of fibroblast growth factor receptor 3 (FGFR3) is involved in several malignancies. Its role in colorectal cancer has not been assessed before.

Methods:

Expression of FGFR3 in human colorectal tumour specimens was analysed using splice variant-specific real-time reverse transcriptase PCR assays. To analyse the impact of FGFR3-IIIc expression on tumour cell biology, colon cancer cell models overexpressing wild-type (WT-3b and WT3c) or dominant-negative FGFR3 variants (KD3c and KD3b) were generated by either plasmid transfection or adenoviral transduction.

Results:

Although FGFR3 mRNA expression is downregulated in colorectal cancer, alterations mainly affected the FGFR3-IIIb splice variant, resulting in an increased IIIc/IIIb ratio predominantly in a subgroup of advanced tumours. Overexpression of WT3c increased proliferation, survival and colony formation in all colon cancer cell models tested, whereas WT3b had little activity. In addition, it conferred sensitivity to autocrine FGF18-mediated growth and migration signals in SW480 cells with low endogenous FGFR3-IIIc expression. Disruption of FGFR3-IIIc-dependent signalling by dominant-negative FGFR3-IIIc or small interfering RNA-mediated FGFR3-IIIc knockdown resulted in inhibition of cell growth and induction of apoptosis, which could not be observed when FGFR3-IIIb was blocked. In addition, KD3c expression blocked colony formation and migration and distinctly attenuated tumour growth in SCID mouse xenograft models.

Conclusion:

Our data show that FGFR3-IIIc exerts oncogenic functions by mediating FGF18 effects in colorectal cancer and may constitute a promising new target for therapeutic interventions.

Daytime levels of melatonin in patients with age-related macular degeneration

PURPOSE

Melatonin (N-acetyl-5-methoxytryptamine) (MT) is a hormone that acts as an antioxidant. It is produced by the pineal gland and within the retina; its release is blocked by light entering the eye. We examined whether MT daytime levels differ between pseudophakic patients with age-related macular degeneration (ARMD) and pseudophakic subjects without any ocular pathology of the same age.

METHODS

A prospective, cross-sectional, observational study was performed. Pseudophakic patients of the same age group were included. Patients underwent complete ophthalmic examinations and blood sampling between 08:00 and 10:00 hr. MT daytime value in the serum was the main outcome measure.

RESULTS

Sixty-nine pseudophakic patients were included. Fifty patients with exudative and non-exudative ARMD were in the study group while 19 patients were controls. Patients with ARMD had significantly higher daytime levels of MT (P = 0.003). There were significant differences in MT daytime levels between the exudative and non-exudative forms (P = 0.009). MT values also correlated with the best-corrected visual acuity (r = -0.285, P = 0.019).

CONCLUSION

These data indicate that pseudophakic patients with ARMD produce more MT during the day compared to pseudophakic subjects without ARMD. This may be caused by the reduced visual acuity in patients with ARMD, whereby less light reaches the photoreceptors, allowing MT secretion to continue during the day. Because MT also acts as an antioxidant and daytime levels are higher in patients with ARMD, these results might be interpreted as a rescue factor.

Fibroblast growth factor receptor-mediated signals contribute to the malignant phenotype of non-small cell lung cancer cells: therapeutic implications and synergism with epidermal growth factor receptor inhibition

Fibroblast growth factors (FGF) and their high-affinity receptors (FGFR) represent an extensive cellular growth and survival system. Aim of this study was to evaluate the contribution of FGF/FGFR-mediated signals to the malignant growth of non-small cell lung cancer (NSCLC) and to assess their potential as targets for therapeutic interventions. Multiple FGFR mRNA splice variants were coexpressed in NSCLC cells (n = 16) with predominance of FGFR1. Accordingly, both expression of a dominant-negative FGFR1 (dnFGFR1) IIIc-green fluorescent protein fusion protein and application of FGFR small-molecule inhibitors (SU5402 and PD166866) significantly reduced growth, survival, clonogenicity, and migratory potential of the majority of NSCLC cell lines. Moreover, dnFGFR1 expression completely blocked or at least significantly attenuated s.c. tumor formation of NSCLC cells in severe combined immunodeficient mice. Xenograft tumors expressing dnFGFR1 exhibited significantly reduced size and mitosis rate, enhanced cell death, and decreased tissue invasion. When FGFR inhibitors were combined with chemotherapy, antagonistic to synergistic in vitro anticancer activities were obtained depending on the application schedule. In contrast, simultaneous blockage of FGFR- and epidermal growth factor receptor-mediated signals exerted synergistic effects. In summary, FGFR-mediated signals in cooperation with those transmitted by epidermal growth factor receptor are involved in growth and survival of human NSCLC cells and should be considered as targets for combined therapeutic approaches.

A bicistronic baculovirus vector for transient and stable protein expression in mammalian cells

Baculoviruses are widely used for protein production in insect cells, and their potential for gene transfer to mammalian cells is increasingly being recognized. Here we describe a baculovirus vector with a bicistronic mammalian expression cassette and demonstrate its suitability for efficient transient and stable protein expression in human glioblastoma cells. Bicistronic baculovirus vectors are safe, cost efficient, and easy to produce; thus, they represent an excellent gene transfer system for mammalian cells.