A safeguard mechanism regulates Rho GTPases to coordinate cytokinesis with the establishment of cell polarity.

The spatiotemporal control of cell polarity is crucial for the development of multicellular organisms and for reliable polarity switches during cell cycle progression in unicellular systems. A tight control of cell polarity is especially important in haploid budding yeast, where the new polarity site (bud site) is established next to the cell division site after cell separation. How cells coordinate the temporal establishment of two adjacent polarity sites remains elusive. Here, we report that the bud neck associated protein Gps1 (GTPase-mediated polarity switch 1) establishes a novel polarity cue that concomitantly sustains Rho1-dependent polarization and inhibits premature Cdc42 activation at the site of cytokinesis. Failure of Gps1 regulation leads to daughter cell death due to rebudding inside the old bud site. Our findings provide unexpected insights into the temporal control of cytokinesis and describe the importance of a Gps1-dependent mechanism for highly accurate polarity switching between two closely connected locations.

GAS41 amplification results in overexpression of a new spindle pole protein.

Amplification is a hallmark of many human tumors but the role of most amplified genes in human tumor development is not yet understood. Previously, we identified a frequently amplified gene in glioma termed glioma-amplified sequence 41 (GAS41). Using the TCGA data portal and performing experiments on HeLa and TX3868, we analyzed the role of GAS41 amplification on GAS41 overexpression and the effect on the cell cycle. Here we show that GAS41 amplification is associated with overexpression in the majority of cases. Both induced and endogenous overexpression of GAS41 leads to an increase in multipolar spindles. We showed that GAS41 is specifically associated with pericentrosome material. As result of an increased GAS41 expression we found bipolar spindles with misaligned chromosomes. This number was even increased by a combined overexpression of GAS41 and a reduced expression of NuMA. We propose that GAS41 amplification may have an effect on the highly altered karyotype of glioblastoma via its role during spindle pole formation.

Multicenter study identified molecular blood-born protein signatures for Wilms Tumor.

Wilms Tumor (WT) is the most common renal childhood tumor. Recently, we reported a cDNA microarray expression pattern that varied between WTs with different risk histology. Since the Societé Internationale d'Oncologie Pédiatrique (SIOP) in Europe initiates treatment without a histological confirmation, it is important to identify blood-born markers that indicate WT development. In a multicenter study, we established an autoantibody signature by using an array with 1,827 recombinant E. coli clones. This array was screened with sera of patients with WT recruited by SIOP or the Children's Oncology Group (COG). We report an extended number of antigens that are reactive with autoantibodies present in sera from patients with WT. We established an autoantibody signature that separates untreated patients with WT recruited in SIOP from non-WT controls with a specificity of 0.83 and a sensitivity of 0.82 at standard deviations of 0.02 and 0.04, respectively. Likewise, patients recruited in the COG in the United States were separated from the controls with an accuracy of 0.83 at a standard deviation of 0.02. Proteins that were most significant include zinc finger proteins (e.g., ZFP 346), ribosomal proteins and the protein fascin that has been associated with various types of cancer including renal cell carcinoma. Our study provides first evidence for autoantibody signatures for WTs and suggests that these may be most informative before chemotherapy. We present the first multicenter study of autoantibody signatures in patients with WT. We established an autoantibody signature that separates patients with WT from controls.

Autoantibody signature differentiates Wilms tumor patients from neuroblastoma patients.

Several studies report autoantibody signatures in cancer. The majority of these studies analyzed adult tumors and compared the seroreactivity pattern of tumor patients with the pattern in healthy controls. Here, we compared the autoimmune response in patients with neuroblastoma and patients with Wilms tumor representing two different childhood tumors. We were able to differentiate untreated neuroblastoma patients from untreated Wilms tumor patients with an accuracy of 86.8%, a sensitivity of 87.0% and a specificity of 86.7%. The separation of treated neuroblastoma patients from treated Wilms tumor patients' yielded comparable results with an accuracy of 83.8%. We furthermore identified the antigens that contribute most to the differentiation between both tumor types. The analysis of these antigens revealed that neuroblastoma was considerably more immunogenic than Wilms tumor. The reported antigens have not been found to be relevant for comparative analyses between other tumors and controls. In summary, neuroblastoma appears as a highly immunogenic tumor as demonstrated by the extended number of antigens that separate this tumor from Wilms tumor.

Novel immunogenic antigens increase classification accuracy in meningioma to 93.84%.

There is growing evidence that simultaneous analysis of multiple autoantibody reactions can be utilized for diagnosis of neoplasms. Using a set of 57 meningioma-associated antigens, we recently separated meningioma patients from individuals without known disease with an accuracy of 90.3%. Here, we ask whether a largely increased set of immunogenic antigens can further improve this discrimination. We used an array with 1,827 human recombinant clones and measured reactivity of serum autoantibodies against the clones by a novel automated image analysis procedure. We were able to separate meningioma sera from sera of healthy controls with a specificity of 95.62%, a sensitivity of 91.83% and an accuracy of 93.84%. Of the analyzed clones, 23 in-frame clones were highly informative for the classification of meningioma vs. normal sera as shown by their AUC values. These results demonstrate that the accuracy of a serum-based diagnostic can be readily and considerably improved by screening extended sets of proteins.

Protein- versus peptide fractionation in the first dimension of two-dimensional high-performance liquid chromatography-matrix-assisted laser desorption/ionization tandem mass spectrometry for qualitative proteome analysis of tissue samples.

The availability of robust and highly efficient separation methods represents a major requirement for proteome analysis. This study investigated the characteristics of two different gel-free proteomic approaches to the fractionation of proteolytic peptides and intact proteins, respectively, in a first separation dimension. Separation and mass spectrometric detection by matrix-assisted laser desorption/ionization tandem mass spectrometry (MALDI-MS/MS) were performed at the peptide level in both methods. Bottom-up analysis (BU) was carried out employing well established peptide fractionation in the first separation dimension by strong cation-exchange chromatography (SCX), followed by ion-pair reversed-phase chromatography (IP-RPC) in the second dimension. In the semi-top-down approach (STD), which involved intact protein fractionation in the first dimension, the separation mode in both dimensions was IP-RPC utilizing monolithic columns. Application of the two approaches to the proteome analysis of proteins extracted from a tumor tissue revealed that the BU method identified more proteins (1245 in BU versus 920 in STD) while STD analysis offered higher sequence coverage (14.8% in BU versus 17.5% in STD on average). The identification of more basic and larger proteins was slightly favored in the BU approach, most probably due to higher losses of these proteins during intact protein handling and separation in the STD method. A significant degree of complementarity was revealed by an approximately 33% overlap between one BU and STD replicate, while 33% each of the protein identifications were unique to both methods. In the STD method, peptides obtained upon digestion of the proteins contained in fractions of the first separation dimension covered a broad elution window in the second-dimension separation, which demonstrates a high degree of "pseudo-orthogonality" of protein and peptide separation by IP-RPC in both separation dimensions.

The YEATS family member GAS41 interacts with the general transcription factor TFIIF.

BACKGROUND: In eukaryotes the transcription initiation by RNA polymerase II requires numerous general and regulatory factors including general transcription factors. The general transcription factor TFIIF controls the activity of the RNA polymerase II both at the initiation and elongation stages. The glioma amplified sequence 41 (GAS41) has been associated with TFIIF via its YEATS domain. RESULTS: Using GST pull-down assays, we demonstrated that GAS41 binds to both, the small subunit (RAP30) and the large subunit (RAP74) of TFIIF in vitro. The in vivo interaction of GAS41 and endogenous RAP30 and RAP74 was confirmed by co-immunoprecipitation. GAS41 binds to two non-overlapping regions of the C-terminus of RAP30. There is also an ionic component to the binding between GAS41 and RAP30. There was no evidence for a direct interaction between GAS41 and TBP or between GAS41 and RNA polymerase II. CONCLUSIONS: Our results demonstrate binding between endogenous GAS41 and the endogenous TFIIF subunits (RAP30 and RAP74). Since we did not find evidence for a binding of GAS41 to TBP or RNA polymerase II, GAS41 seems to preferentially bind to TFIIF. GAS41 that does not contain a DNA-binding domain appears to be a co-factor of TFIIF.

Identification of lung cancer with high sensitivity and specificity by blood testing.

BACKGROUND: Lung cancer is a very frequent and lethal tumor with an identifiable risk population. Cytological analysis and chest X-ray failed to reduce mortality, and CT screenings are still controversially discussed. Recent studies provided first evidence for the potential usefulness of autoantigens as markers for lung cancer. METHODS: We used extended panels of arrayed antigens and determined autoantibody signatures of sera from patients with different kinds of lung cancer, different common non-tumor lung pathologies, and controls without any lung disease by a newly developed computer aided image analysis procedure. The resulting signatures were classified using linear kernel Support Vector Machines and 10-fold cross-validation. RESULTS: The novel approach allowed for discriminating lung cancer patients from controls without any lung disease with a specificity of 97.0%, a sensitivity of 97.9%, and an accuracy of 97.6%. The classification of stage IA/IB tumors and controls yielded a specificity of 97.6%, a sensitivity of 75.9%, and an accuracy of 92.9%. The discrimination of lung cancer patients from patients with non-tumor lung pathologies reached an accuracy of 88.5%. CONCLUSION: We were able to separate lung cancer patients from subjects without any lung disease with high accuracy. Furthermore, lung cancer patients could be separated from patients with other non-tumor lung diseases. These results provide clear evidence that blood-based tests open new avenues for the early diagnosis of lung cancer.

Improving seroreactivity-based detection of glioma.

Seroreactivity profiling emerges as valuable technique for minimal invasive cancer detection. Recently, we provided first evidence for the applicability of serum profiling of glioma using a limited number of immunogenic antigens. Here, we screened 57 glioma and 60 healthy sera for autoantibodies against 1827 Escherichia coli expressed clones, including 509 in-frame peptide sequences. By a linear support vector machine approach, we calculated mean specificity, sensitivity, and accuracy of 100 repetitive classifications. We were able to differentiate glioma sera from sera of the healthy controls with a specificity of 90.28%, a sensitivity of 87.31% and an accuracy of 88.84%. We were also able to differentiate World Health Organization grade IV glioma sera from healthy sera with a specificity of 98.45%, a sensitivity of 80.93%, and an accuracy of 92.88%. To rank the antigens according to their information content, we computed the area under the receiver operator characteristic curve value for each clone. Altogether, we found 46 immunogenic clones including 16 in-frame clones that were informative for the classification of glioma sera versus healthy sera. For the separation of glioblastoma versus healthy sera, we found 91 informative clones including 26 in-frame clones. The best-suited in-frame clone for the classification glioma sera versus healthy sera corresponded to the vimentin gene (VIM) that was previously associated with glioma. In the future, autoantibody signatures in glioma not only may prove useful for diagnosis but also offer the prospect for a personalized immune-based therapy.

Proteomic study of human glioblastoma multiforme tissue employing complementary two-dimensional liquid chromatography- and mass spectrometry-based approaches.

An extensive data set comprising 2660 unique protein identifications was obtained for the proteome of a human brain tumor (glioblastoma multiforme) by combining the results of two complementary analytical strategies based on two-dimensional chromatography and mass spectrometry. A bottom-up method, performing peptide separation in both chromatographic dimensions was employed as well as a semi-top-down method, in which intact proteins were separated in the first and tryptic peptides in the second dimension. The identified proteins were assigned to their molecular functions and compared to previously identified proteins of glioblastoma multiforme (= astrocytoma WHO grade IV), lower WHO grade astrocytomas (grade II and III), and nontumor brain tissue. With the use of a subset of 104 identified membrane proteins, the properties of intact protein fractionation in the first dimension of the semi-top-down approach were elucidated in detail. The benefit of the semi-top-down approach was further demonstrated by the identification of a set of endogenous glioblastoma multiforme expressed proteins. These proteins correspond to recombinant antigens which were recently found to be reactive against autoantibodies in glioblastoma multiforme patients. The results indicate the usefulness of the semi-top-down approach for the investigation of immunogenic antigens in human tumor tissue samples.

Novel autoantigens immunogenic in COPD patients.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a respiratory inflammatory condition with autoimmune features including IgG autoantibodies. In this study we analyze the complexity of the autoantibody response and reveal the nature of the antigens that are recognized by autoantibodies in COPD patients. METHODS: An array of 1827 gridded immunogenic peptide clones was established and screened with 17 sera of COPD patients and 60 healthy controls. Protein arrays were evaluated both by visual inspection and a recently developed computer aided image analysis technique. By this computer aided image analysis technique we computed the intensity values for each peptide clone and each serum and calculated the area under the receiver operator characteristics curve (AUC) for each clone and the separation COPD sera versus control sera. RESULTS: By visual evaluation we detected 381 peptide clones that reacted with autoantibodies of COPD patients including 17 clones that reacted with more than 60% of the COPD sera and seven clones that reacted with more than 90% of the COPD sera. The comparison of COPD sera and controls by the automated image analysis system identified 212 peptide clones with informative AUC values. By in silico sequence analysis we found an enrichment of sequence motives previously associated with immunogenicity. CONCLUSION: The identification of a rather complex humoral immune response in COPD patients supports the idea of COPD as a disease with strong autoimmune features. The identification of novel immunogenic antigens is a first step towards a better understanding of the autoimmune component of COPD.

Increased seroreactivity to glioma-expressed antigen 2 in brain tumor patients under radiation.

BACKGROUND: Surgery and radiation are the mainstays of therapy for human gliomas that are the most common primary brain tumors. Most recently, cell culture and animal studies provided the first convincing evidence that radiation not only eliminates tumor cells, but also modulates the immune response and likely improves anti-tumor immunotherapy. METHODOLOGY/PRINCIPAL FINDINGS: We present an in vivo study that analyzes the effects of radiation on the immune response in tumor patients. As readout system, we utilized the reactivity of glioma patients' sera against antigen GLEA2 as the most frequent antigen immunogenic in glioblastoma patients. We established an ELISA assay to analyze reactivity of 24 glioblastoma patients over a period of several months. As control we used 30 sera from healthy donors as well as 30 sera from lung cancer patients. We compared the course of GLEA2 seroreactivity at different times prior, during and after radiation. The GLEA2 seroreactivity was increased by the time of surgery, decreased after surgery, increased again under radiation, and slightly decreased after radiation. CONCLUSIONS/SIGNIFICANCE: Our results provide in vivo evidence for an increased antibody response against tumor antigens under radiation. Antigens that become immunogenic with an increased antibody response as result of radiation can serve as ideal targets for immunotherapy of human tumors.

A different view on DNA amplifications indicates frequent, highly complex, and stable amplicons on 12q13-21 in glioma.

To further understand the biological significance of amplifications for glioma development and recurrencies, we characterized amplicon frequency and size in low-grade glioma and amplicon stability in vivo in recurring glioblastoma. We developed a 12q13-21 amplicon-specific genomic microarray and a bioinformatics amplification prediction tool to analyze amplicon frequency, size, and maintenance in 40 glioma samples including 16 glioblastoma, 10 anaplastic astrocytoma, 7 astrocytoma WHO grade 2, and 7 pilocytic astrocytoma. Whereas previous studies reported two amplified subregions, we found a more complex situation with many amplified subregions. Analyzing 40 glioma, we found that all analyzed glioblastoma and the majority of pilocytic astrocytoma, grade 2 astrocytoma, and anaplastic astrocytoma showed at least one amplified subregion, indicating a much higher amplification frequency than previously suggested. Amplifications in low-grade glioma were smaller in size and displayed clearly different distribution patterns than amplifications in glioblastoma. One glioblastoma and its recurrencies revealed an amplified subregion of 5 Mb that was stable for 6 years. Expression analysis of the amplified region revealed 10 overexpressed genes (i.e., KUB3, CTDSP2, CDK4, OS-9, DCTN2, RAB3IP, FRS2, GAS41, MDM2, and RAP1B) that were consistently overexpressed in all cases that carried this amplification. Our data indicate that amplifications on 12q13-21 (a) are more frequent than previously thought and present in low-grade tumors and (b) are maintained as extended regions over long periods of time.