Inhibition of TGF-β signaling at the nuclear envelope: characterization of interactions between MAN1, Smad2 and Smad3, and PPM1A

Signaling by transforming growth factor-β (TGF-β) is critical for various developmental processes and culminates in the activation of the transcription factors Smad2 and Smad3. MAN1, an integral protein of the inner nuclear membrane, inhibits TGF-β signaling by binding to Smad2 and Smad3. Depletion of the gene LEMD3 encoding MAN1 leads to developmental anomalies in mice, and heterozygous loss-of-function mutations in LEMD3 in humans cause sclerosing bone dysplasia. We modeled the three-dimensional structure of the MAN1-Smad2 complex from nuclear magnetic resonance and small-angle x-ray scattering data. As predicted by this model, we found that MAN1 competed in vitro and in cells with the transcription factor FAST1 (forkhead activin signal transducer 1) for binding to Smad2. The model further predicted that MAN1 bound to activated Smad2-Smad4 or Smad3-Smad4 complexes, which was confirmed by in vitro experiments; however, in cells, MAN1 bound only to Smad2 and Smad3 and not to the Smad4-containing complexes. Overexpression of MAN1 led to dephosphorylation of Smad2 and Smad3, thus hindering their recognition by Smad4, and MAN1 bound directly in vitro to the phosphatase PPM1A, which catalyzes the dephosphorylation of Smad2/3. These results demonstrate a nuclear envelope-localized mechanism of inactivating TGF-β signaling in which MAN1 competes with transcription factors for binding to Smad2 and Smad3 and facilitates their dephosphorylation by PPM1A.

[Cyberknife and benign pathologies]

Conventional radiotherapy is known to be an effective treatment approach even for "benign" pathologies. However, this kind of treatment yields a high potential for side effects. The Cyberknife, a robotic stereotactic radiotherapy device, enables to offset a large proportion of the disadvantages encountered with conventional radiotherapy essentially through the high precision of dose administration and sparing of healthy tissues. Therefore, it seems to be a treatment of choice in the approach of some benign intracranial diseases. We review published data on indications and outcome of Cyberknife for intracranial "non-malignant" disease.

Electrosynthesis and characterization of conducting polypyrrole elaborated under high frequency ultrasound irradiation

The effects of high frequency ultrasound (500kHz) on pyrrole electropolymerization in sodium perchlorate aqueous medium have been investigated. Cyclic voltametry studies showed that there is no influence on pyrrole oxidation potential. Scanning Electron Microscopy (SEM) imaging, and mechanical and optical profiling, revealed thinner, denser and more homogeneous surface structure for polypyrrole films elaborated under ultrasound irradiation. This is attributed to cavitation bubble asymmetric collapse close to the interface, which should induce changes in the nucleation-growth mechanism during the first polymerization stage. An increase of approximately 27% in doping level for sonicated films was revealed by X-ray Photoelectron Spectroscopy (XPS) analyses.

Expression analysis of mitotic spindle checkpoint genes in breast carcinoma: role of NDC80/HEC1 in early breast tumorigenicity, and a two-gene signature for aneuploidy

Background

Aneuploidy and chromosomal instability (CIN) are common abnormalities in human cancer. Alterations of the mitotic spindle checkpoint are likely to contribute to these phenotypes, but little is known about somatic alterations of mitotic spindle checkpoint genes in breast cancer.

Methods

To obtain further insight into the molecular mechanisms underlying aneuploidy in breast cancer, we used real-time quantitative RT-PCR to quantify the mRNA expression of 76 selected mitotic spindle checkpoint genes in a large panel of breast tumor samples.

Results

The expression of 49 (64.5%) of the 76 genes was significantly dysregulated in breast tumors compared to normal breast tissues: 40 genes were upregulated and 9 were downregulated. Most of these changes in gene expression during malignant transformation were observed in epithelial cells.

Alterations of nine of these genes, and particularly NDC80, were also detected in benign breast tumors, indicating that they may be involved in pre-neoplastic processes.

We also identified a two-gene expression signature (PLK1 + AURKA) which discriminated between DNA aneuploid and DNA diploid breast tumor samples. Interestingly, some DNA tetraploid tumor samples failed to cluster with DNA aneuploid breast tumors.

Conclusion

This study confirms the importance of previously characterized genes and identifies novel candidate genes that could be activated for aneuploidy to occur. Further functional analyses are required to clearly confirm the role of these new identified genes in the molecular mechanisms involved in breast cancer aneuploidy. The novel genes identified here, and/or the two-gene expression signature, might serve as diagnostic or prognostic markers and form the basis for novel therapeutic strategies.

Doping properties of PEDOT films electrosynthesized under high frequency ultrasound irradiation

The present study presents the use of high frequency ultrasound (500 kHz, 25 W) for 3,4-ethylenedioxythiophene (EDOT) electropolymerization in aqueous medium in order to investigate its effects on conducting polymer properties. It was shown that mass transfer increases under ultrasound irradiation which improved electropolymerization and the comparison with experiments carried out at the same mass transfer level (4.6 × 10(-5) ms(-1)) puts in evidence that stirring effect is not the only phenomenon induced by ultrasound during electrodeposition. PEDOT films elaborated under ultrasonication present increased doping levels revealed by X-ray Photoelectron Spectroscopy (XPS) analysis, especially in the case of thick films (measured by mechanical probe), thanks to better incorporation of counter ions within polymer matrix as another consequence of mass transport improvement under ultrasound and probably film heating by wave absorption for the highest thicknesses. A dilation of the film under sonication leading to an increase in film thickness was also highlighted. Finally, a refining of the surface structure was also observed via SEM imaging.

The Wnt antagonist Dickkopf-1 increases endothelial progenitor cell angiogenic potential

OBJECTIVE

To determine the role of Wnt antagonist Dickkopf (DKK) 1 in human endothelial colony-forming cells (ECFCs) in view of the emerging importance of Wnt pathways in vascular biology.

METHODS AND RESULTS

Endothelial progenitor cells have been proposed to be crucial in tumor neovascularization. Recombinant DKK1 has been tested in ECFC angiogenic properties in vitro. DKK1 enhanced ECFC proliferation and the capacity of ECFCs to form pseudotubes in Matrigel. These effects have been attributed to enhancement of vascular endothelial growth factor receptor 2, SDF-1, and CXCR4. DKK1 gene silencing has been realized on ECFCs and mesenchymal stem cells, and we found that DKK1 silencing in the 2 cell types decreased their angiogenic potential. We then examined the possible role of DKK1 in tumor neovasculogenesis and found that blood vessels of breast cancer tissues expressed DKK1 far more strongly in human breast tumors than in normal breast tissues. By studying 62 human breast tumors, we found a significant positive correlation between DKK1 expression and von Willebrand factor. In vivo, DKK1 strongly enhanced the vascularization of Matrigel plugs and increased tumor size in a xenograft model of human breast carcinoma in nude mice.

CONCLUSIONS

DKK1 enhances angiogenic properties of ECFCs in vitro and is required for ECFC and mesenchymal stem cell angiogenic phenotypes in vivo. DKK1 also increases tumoral angiogenesis. Thus, we demonstrated a major role of DKK1 in angiogenic processes.

Inhibition of the Wnt/beta-catenin pathway by the WWOX tumor suppressor protein

The WWOX gene encodes a candidate tumor suppressor protein (WWOX) implicated in a variety of human diseases such as cancer. To better understand the molecular mechanisms of WWOX action, we investigated novel partners of this protein. Using the two-hybrid system and a coimmunoprecipitation assay, we observed a physical association between WWOX and the Dishevelled protein (Dvl) family signaling elements involved in the Wnt/beta-catenin pathway. We found that enforced WWOX expression inhibited, and inhibition of endogenous WWOX expression stimulated the transcriptional activity of the Wnt/beta-catenin pathway. Inhibition of endogenous WWOX expression also enhanced the effect of Wnt-3a on beta-catenin stability. Moreover, we observed the sequestration of Dvl-2 wild type and Dvl-2NESm, a mutated form of Dvl-2 predominantly localized in the nucleus, in the cytoplasm compartment by WWOX. Our results indicate that WWOX is a novel inhibitor of the Wnt/beta-catenin pathway. WWOX would act, at least in part, by preventing the nuclear import of the Dvl proteins.

Correlation of PIK3CA mutation-associated gene expression signature (PIK3CA-GS) with deactivation of the PI3K pathway and with prognosis within the luminal-B ER+ breast cancers

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Background: The phosphathidylinositol-3-kinase (PI3K) signaling pathway is frequently deregulated in tumor biology and is an attractive target for cancer therapy. Our aim was to characterize the molecular and clinical outcome effects of PIK3CA mutations in breast cancer (BC). Methods: We analyzed 173 BC samples for PIK3CA mutations. Corresponding gene expression profiles were used to understand its effects on the PI3K pathway. We validated a PIK3CA-GS in 2 independent BC cohorts (n = 183) with known PIK3CA mutation status and evaluated its correlation with clinical outcome in 1748 BC samples stratified by treatment and subtype. Results: 26% of BCs had a PIK3CA mutation. Tumors with PIK3CA mutation demonstrated a distinct gene expression signature (p = 0.03 after 1000 perm). In 2 datasets it could discriminate PIK3CA mutation carriers from wild-type (ROC 0.68, 0.71, p = 0.001for both). However, the PIK3CA-GS was correlated with deactivation of the PI3K pathway probably through a negative feedback loop. This observation was supported by: 1) the PIK3CA-GS was significantly correlated with gene expression changes induced by PI3K inhibitors (Connectivity Map, Gene set enrichment analyses) and 2) the PIK3CA-GS was anti-correlated with a GS of PTEN loss (R = -0.3; Saal et al, 2007). Higher levels of the PIK3CA signature were observed in HER-2+ and estrogen receptor positive (ER+), luminal BC subtypes. Whilst there was no association with mutation status alone and prognosis, increasing expression of the PIK3CA-GS (suggesting deactivation) was significantly associated with better clinical outcome in both untreated (p = 0.04) and particularly ER+, luminal-B, tamoxifen only-treated (p = 0.004) BC. Multivariate analysis (HR: 0.4; 95%CI: 0.3–0.7; p = 0.002) confirmed that the PI3KCA-GS provided independent prognostic information. Conclusions: Paradoxically, the PIK3CA-GS correlates with inhibition of the PI3K pathway in ER+ BC and identifies a subgroup of luminal B BCs with a favorable outcome. The PIK3CA-GS may be a better indicator of PI3K pathway dysfunction than mutation status, potentially indicating patients who may benefit from combined endocrine therapy and PI3K inhibition.

No significant financial relationships to disclose.

Effect of ultrasounds on the electrochemical synthesis of polypyrrole, application to the adhesion and growth of biological cells

In this study, a new way to synthesize polypyrrole films is presented. This original way consists in the electropolymerization of polypyrrole under high frequency ultrasonic irradiation on conductive fluorine-doped tin oxide surfaces. The polypyrrole films obtained are then compared, in terms of chemical structure and morphology, to polypyrrole films synthesized by standard electrochemical methodology. Next, these polymer films are tested as an alternative to biomaterials that are commonly used as cell culture substrates. Thus, the adhesion and growth of osteoblastics cells and microbial cells on polymer-modified surfaces are investigated by using qualitative observation and quantitative tests. These studies proved the non-toxicity of the polymer films for osteoblastic and microbial cells but also a different behaviour of osteoblastic cells and microbial cells with polypyrrole films.

Investigating tamoxifen resistance in the luminal B estrogen receptor positive breast cancer subtype: Tailoring treatment in hormone responsive breast cancer

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Background: We recently reported that the two estrogen receptor (ER) positive breast cancer (BC) molecular subtypes can be defined by their expression of proliferation genes using a gene expression index (GGI): the luminal A and B subtypes have low and high levels respectively (J Clin Onc, in press). When treated with adjuvant tamoxifen, luminal A tumors have a good prognosis, however the clinical outcome of the luminal B subtype was poor. This study aimed to explain the biological basis for these observations using global gene expression profiling and an in vitro model of ER+ BC. Methods: 246 ER+ BC samples from women treated with adjuvant tamoxifen monotherapy were analyzed with affymetrix gene expression arrays and evaluated using gene set enrichment analysis (GSEA). ER+ MCF-7 BC cells (control) treated with tamoxifen (TAM) and heregulin (HRG) were used to investigate molecular pathways identified using GSEA. Results: We found that a gene set suggesting ERBB2 pathway activation was significantly enriched in the luminal B subtype (p=0.02). Only 10% of samples overexpressed HER2 by immunohistochemistry, suggesting that activation of HER2 signaling pathways is independent of HER2 overexpression and may contribute to TAM resistance in this subtype. To validate this hypothesis, MCF-7 cell-lines were treated with HRG (HRG-MCF7) to create a model of ERBB2 pathway activation. HRG-MCF7 cells displayed phosphorylation of HER2/3 without HER2 overexpression. Treatment with HRG overcame TAM induced cell cycle arrest with higher S-phase fraction (p<0.01) and increased anchorage- independent colony formation (p<0.01). Gene expression profiling confirmed significant enrichment of the ERBB2 gene set (p<0.01) and higher GGI levels (p=0.02) in HRG-MCF7 cells compared with control. Conclusions: HRG-MCF7 cells may be useful as an in vitro model of the TAM resistant luminal B subtype. In this group, targeting activated HER2 signaling may be a helpful treatment strategy despite the lack of HER2 overexpression. Our data suggests that agents like lapatinib may be effective only in the luminal B and not the luminal A tumors, demonstrating the importance of stratifying by subtype in future clinical trials of ER+ disease.

No significant financial relationships to disclose.