A LONG-TERM 10G-HYPERGRAVITY EXPOSURE PROMOTES CELL-CELL CONTACTS AND REDUCES ADHESIVENESS TO A SUBSTRATE, MIGRATION, AND INVASIVENESS OF MCF-7HUMAN BREAST CANCER CELLS.

BACKGROUND: G-force is a fundamental force controlling human cells. Cancer is one of the 4 major health challenges in the Space missions. Cancer in Space project evaluates the reaction of human cancer cells to the conditions of the space flights, including an exposure to high g-forces. AIM: Explore an impact of 10 g force on the oncogenic properties of human breast adenocarcinoma cells MCF-7. MATERIALS AND METHODS: Cells were exposed to 10 g force for 10 days, as part of a 6-week simulation of conditions of a space flight. Then the cells were cultured for one week under normal culture conditions, before performing tests. Cell proliferation, cell viability, cell-cell contact inhibition, migration, and invasiveness were measured. Immunoblotting was used to evaluate expression of proteins. RESULTS: Proliferation, cell-cell interaction and formation of 3D structures, migration, and invasiveness of cells exposed to 10 g were compared to parental cells cultured at 1 g condition. 10 g exposed cells showed a higher propensity for cell-cell contact inhibitions and lower for 3-dimensional growth in dense culture. This correlated with the decrease of proliferation in a dense culture as compared to the parental cells. The decrease of migration, adherence to a surface, and invasiveness was observed for cells subjected to the hypergravity, as compared to the parental MCF-7 cells. Enhanced expression of E-cadherin and phosphorylated pY576-FAK were observed in 10 g exposed cells but no impact on the expression of Erk, pErk, FAK and p53 was detected. CONCLUSION: The prolonged exposure of MCF-7 cells to 10 g force targets cell-cell and cell-substrate interactions.

Proteomics of transforming growth factor ß1 (TGF ß1) signaling in 184A1 human breast epithelial cells suggests the involvement of casein kinase 2α in TGF ß1-dependent p53 phosphorylation at Ser392.

AIM: Transforming growth factor ß1 (TGF ß1) is a potent regulator of breast tumorigenesis. It inhibits proliferation of carcinoma cells, but the strength of its inhibitory action varies for cells from benigh, non-metastatic or metastatic tumors. The aim of this work was to generate a proteome profile of TGF ß1 action on non-tumorigenic human breast epithelial cells 184A1, and validate predicted involvement of casein kinase 2α (CK2α), p53 and structure-specific recognition protein-1 (SSRP1). MATERIALS AND METHODS: Two-dimensional gel electrophoresis and mass spectrometry were used to identify TGF ß1-regulated proteins in 184A1 human breast immortalized non-tumorigenic cells. 184A1 cells may serve as a model of benign breast neoplasia. These cells were obtained from normal mammary tissue, were immortalized but are not malignant, and were obtained from the American Type Culture Collection. The systemic analysis was performed by using the Cytoscape tool. Transfection of cells with CK2α construct and small interfering RNAs to CK2α and SSRP1 were used to assess an impact of CK2α and SSRP1 on phosphorylation of the p53 and cell proliferation. RESULTS: Proliferation of 184A1 cells was transiently inhibited by TGF ß1. We identified 100 and 47 unique proteins which changed their expression and/or 35S-incorporation, respectively, upon treatment with TGF ß1 for 2 h, 8 h or 24 h. Cell proliferation, death, migration, and metabolism were among the biological regulatory processes retrieved by the network analysis as affected by the identified proteins. The network analysis suggested that TGF ß1 may affect the phosphorylation of p53 at Ser392 by engaging CK2α. This was confirmed by the immunoblotting and cell proliferation assays. CONCLUSION: We report here the list of 147 TGF ß1-regulated proteins in immortalized non-tumorigenic human breast epithelial cells, and show involvement of CK2α in the regulation of p53 Ser392 phosphorylation.

Intersection between genes controlling vascularization and angiogenesis in renal cell carcinomas.

AIM: To show that application of the systemic analysis may significantly improve comparison of different datasets. Different genes and proteins may converge on the same functional outputs. A comparison of 2 datasets by only identification names of affected molecules may miss that, leading to a conclusion that there is nothing in common for these datasets. Systemic analysis may overcome this limitation, by focusing on functions represented by the identification names. MATERIALS AND METHODS: Datasets were retrieved from open sources. Systemic analysis of vascularization features and angiogenesis signature was performed by using Cytoscape and its plugs-in. RESULTS: In contrary to the initial statement of the lack of overlap between the vascularization features and the angiogenesis genes-signature in renal carcinomas, we observed an intersection on the functional level. Analysis of the networks built with identification names of vascularization and angiogenesis datasets showed an intersection, which included potent regulators of vessel formation and growth. CONCLUSION: Analysis of networks may expose functional links, which may be missed by a direct identification names comparison.

Impact of combinations of EGF, TGFß, 17ß-oestradiol, and inhibitors of corresponding pathways on proliferation of breast cancer cell lines.

AIM: The impact of combinations of anti-cancer drugs and growth factors on tumour cells may differ from the assumed sum of the effects of each factor separately. Therefore it is important to study the effects of different combinations of various drugs and treatments. Our aim was to study the effects on breast cancer cell proliferation of EGF, TGFß and 17ß-oestradiol, three important regulators of breast tumourigenesis, and their respective inhibitors in different combinations. MATERIALS AND METHODS: We screened the effects on proliferation of MCF7 and MDA-MB-231 cells of ninety different combinations of EGF, TGFß and 17ß-oestradiol, Iressa, SB431542 and Tamoxifen. Meta-data analysis of available clinical data was performed to validate observed proliferation data. RESULTS: In MDA-MB-231 cells, TGFß1 was found inhibitory when cells were simultaneously treated with EGF and 17ß-oestradiol, with the effect potentiated by addition of all inhibitors combined. In the same cells, Iressa when combined with EGF was paradoxically stimulatory. Tamoxifen inhibited MCF7 cells co-treated with EGF or oestrogen, and enhanced the inhibitory effect of TGFß in MDA-MB-231 cells. Meta-analysis of clinical gene expression studies confirmed several of these points, showing enhanced TGFß and EGF expression in Tamoxifen-treated patients to correlate with decreased tumour size and grade respectively, and combined TGFß-EGF expression to decrease the risk of metastasis. CONCLUSION: Our study shows significant differences in proliferation response to drugs and growth factors between MCF7 cells which do not have propensity to form metastases in animal models and MDA-MB-231 cells which may form metastases upon inoculation into animals. Several of these differences are unexpected and confirmed by clinical observations.

Individualised proteome profiling of human endometrial tumours improves detection of new prognostic markers.

BACKGROUND: The individual features of tumours are often disregarded in cohort studies. As these features may represent a source for individualised cancer treatment, it is important to develop a novel approach for their assessment. METHODS: We used proteomics, systems biology, and immunohistochemistry to explore protein expression in human endometrial tumours, to identify deregulated regulatory mechanisms, and to validate observed changes in protein expression using tissue microarrays. RESULTS: Compared with the evaluation of common tumour features, the evaluation of individual tumour features gave a more comprehensive and detailed overview of the regulatory processes in endometrial tumours. Systemic analysis of the individual proteome profiles showed that endometrial tumours employed different proteins to regulate similar functions. Comparison of our data with publicly available data sets of molecular profiling of human endometrial tumours confirmed that individual tumour features are not simply irrelevant individual variations, but are indeed important in endometrial tumorigenesis. Validation through tissue microarray investigation of MST1 and PKN1 proteins confirmed the usefulness of this approach, and suggested that MST1 and PKN1 may be considered as predictive biomarkers of endometrial cancer. CONCLUSION: We show that individualised profiling of endometrial tumours may deliver better insights into a tumour's physiology, thereby giving a better prediction of tumour development. Individual tumour features may also be used to tailor cancer treatment.

Inhibition of TGFß signaling and its implications in anticancer treatments.

The transforming growth factor-ß (TGFß) is a potent regulator of tumorigenesis. In cancer, two distinctive behaviors of TGFß have been reported as a tumor suppressor at early stage of the disease, and as a tumor promoter at later stages. The past decades, the dualistic role of TGFß has garnered a lot of attention. As a result, cancer researchers' has been tasked to elucidate how TGFß signaling may lead to metastatic dissemination, how to tackle carcinogenesis and which therapeutic strategies should be adopted. Consequently, TGFß signaling pathways have been considered as appropriate targets for cancer therapy. The TGFß therapeutic strategies have emerged at three levels: ligand, ligand-receptor interaction and intracellular signaling level. Promising inhibitors of TGFß signaling have entered clinical trials and shown encouraging results. Here we review the three strategies of TGFß signa-ling inhibition and theirs applications in treatment of cancer.

Kinase suppressor of Ras 2 is involved in regulation of cell proliferation and is up-regulated in human invasive ductal carcinomas of breast.

AIM: To study the expression of Kinase Suppressor of Ras 2 (KSR2) in human breast tumors and its effect on proliferation of breast epithelial cells. We reported previously that KSR2 was up-regulated in immortalized human breast epithelial cells. METHODS: Proteomics technologies, systems biology tool for a KSR2 network analysis, immunoblotting, siRNA technology, overexpression of KSR2, cell proliferation assays and immunohistochemistry of tissue microarray of human breast tumors and normal breast tissue were used. RESULTS: In conditionally immortalized primary epithelial cells KSR2 expression was shown to be up-regulated. The involvement of KSR2 in regulation of cell proliferation was predicted by a KSR2-centered network analysis. We observed that KSR2 down-regulation with specific siRNA inhibited cell proliferation. By immunohistochemistry of tissue microarray it was demonstrated that KSR2 expression was enhanced in human invasive breast carcinomas. CONCLUSION: Our findings propose KSR2 as a new marker of immortalization, which has an impact on cell proliferation.

Proteomic approaches in biological and medical sciences: principles and applications.

After the first introduction of the concept of "proteome" more than 10 years ago, large-scale studies of protein expression, localization, activities and interactions have gained an exponential increase of interest, leading to extensive research and technology development. Proteomics is expansively applied in many areas, ranging from basic research, various disease and malignant tumors diagnostic and biomarker discovery to therapeutic applications. Several proteomics approaches have been developed for protein separation and identification, and for the characterization of protein function and structure. Two-dimensional gel electrophoresis, chromatography, capillary electrophoresis and mass spectrometry have become the most used proteomics methods. These techniques are also under constant development. This review provides an overview of the main techniques and their combinations, used in proteomics. The emphasis is made on description of advantages and disadvantages of each technique, to navigate in selection of the best application for solving a specific problem.

Src kinase phosphorylates vascular endothelial-cadherin in response to vascular endothelial growth factor: identification of tyrosine 685 as the unique target site.

Src-family tyrosine kinases are regulatory proteins that play a pivotal role in the disorganization of cadherin-dependent cell-cell contacts. We previously showed that Src was associated with vascular endothelial (VE)-cadherin and that tyrosine phosphorylation level of VE-cadherin was dramatically increased in angiogenic tissues as compared to quiescent tissues. Here, we examined whether VE-cadherin was a direct substrate for Src in vascular endothelial growth factor (VEGF)-induced VE-cadherin phosphorylation, and we identified the target tyrosine sites. Co-transfections of Chinese hamster ovary cells (CHO) cells with VE-cadherin and constitutively active Src (Y530F) resulted in a robust tyrosine phosphorylation of VE-cadherin that was not detected with kinase-dead Src (K298M). In an in vitro Src assay, the VE-cadherin cytoplasmic domain is directly phosphorylated by purified Src as well as the tyrosine residue 685 (Tyr)685-containing peptide RPSLY(685)AQVQ. VE-cadherin peptide mapping from human umbilical vein endothelial cells stimulated by VEGF and VE-cadherin-CHO cells transfected with active Src revealed that Y685 was the unique phosphorylated site. The presence of PhosphoY685 was confirmed by its ability to bind to C-terminal Src kinase-SH2 domain in a pull-down assay. Finally, we found that in a VEGF-induced wound-healing assay, cadherin adhesive activity was impaired by Src kinase inhibitors. These data identify that VEGF-induced-VE-cadherin tyrosine phosphorylation is mediated by Src on Y685, a process that appears to be critical for VEGF-induced endothelial cell migration.

Smad2 suppresses the growth of Mv1Lu cells subcutaneously inoculated in mice.

Smad2 and Smad3 are intracellular signal transduction proteins of importance in transforming growth factor-beta (TGFbeta)-mediated inhibition of epithelial cell proliferation. Inactivating mutations in the Smad2 and Smad3 genes have been found in various human malignancies. Here, we show that expression of Smad2 leads to the inhibition of growth of Mv1Lu cells inoculated with Matrigel subcutaneously (s.c.) in severe combined immunodeficient (SCID) mice. In histological appearance, the Matrigel plugs with Smad2-transfected cells showed strongly reduced cell density, proliferation and angiogenesis compared with the small tumour nodules of similar size formed by the vector- or Smad3-transfected cells. The histological appearance of vector- and Smad3-transfected cells inoculated in mice was identical. Overexpression of Smad2 and Smad3 in Mv1Lu cells led to the inhibition of cell growth in three-dimensional cultures when compared with vector-transfected cells. Overexpression of Smad2 and Smad3 also decreased the hyperphosphorylation of pRb in Smad-transfected cells. Thus, increased expression of Smad2 leads to inhibition of Mv1Lu cell proliferation and a reduction in the growth of the Smad2-expressing cells inoculated in mice.

Frequent loss of SMAD4/DPC4 protein in colorectal cancers.

BACKGROUND AND AIMS: Loss of DNA sequences from chromosome 18q21 is a major genetic change in colorectal tumorigenesis. Multiple genes have been identified in this area. One of these, DPC4 (deleted in pancreatic cancer 4, also known as SMAD4), is mutated in a minor subset of colorectal carcinomas as well as in germlines of humans predisposed to colon tumours. PATIENTS AND METHODS: The involvement of SMAD4 in sporadic colorectal neoplasia was evaluated by immunohistochemistry in 53 unselected cases and 27 cases displaying microsatellite instability. RESULTS: SMAD4 expression was absent in 20 of 53 (38%) unselected colorectal carcinomas, and reduced in another 15 (28%) cases. However, 26 of 27 cancers displaying microsatellite instability and TGF-betaIIR mutations were positive for SMAD4 immunostaining. CONCLUSIONS: Loss of SMAD4 expression may play a more prominent role in colon cancer than anticipated based on genetic evidence, but not in mutator phenotype tumours.

Phosphorylation of Smad7 at Ser-249 does not interfere with its inhibitory role in transforming growth factor-beta-dependent signaling but affects Smad7-dependent transcriptional activation.

Smad proteins are major components in the intracellular signaling pathway of transforming growth factor-beta (TGF-beta), and phosphorylation is an important mechanism in regulation of their functions. Smad7 was identified as a potent inhibitor of TGF-beta-dependent signaling. We have identified serine 249 in Smad7 as a major phosphorylation site, the phosphorylation of which was not affected by TGF-beta1. Abrogation of the phosphorylation by substitution of Ser-249 with alanine or aspartic acid residues did not affect the ability of Smad7 to inhibit TGF-beta1 and BMP7 signaling. No differences were found in the stability or in the intracellular distribution of Smad7 mutants compared with the wild-type molecule. However, Smad7 fused to the DNA-binding domain of GAL4 induced transcription from a reporter with mutated TATA minimal promoter in a Ser-249-dependent manner. Moreover, a reporter with the SV40 minimal promoter was inhibited by GAL4-Smad7, and this effect was also dependent on Ser-249 phosphorylation. The amplitude of effects on transcriptional regulation was dependent on cell type. Our results suggest that phosphorylation of Smad7, unlike phosphorylation of the receptor-regulated Smads, does not regulate TGF-beta signaling but rather affects TGF-beta-independent effects of Smad7 on transcriptional regulation.

Regulation of Smad signaling by protein kinase C.

Cross talk between transforming growth factor b(TGF-b) serine/threonine kinase receptor signaling and tyrosine kinase receptor signaling modulates cell responsiveness to polypeptide growth factors regulating cell proliferation, differentiation, and apoptosis. Here we provide a mechanism through which Smad-dependent TGF-b signaling is modulated by protein kinase C (PKC). PKC, for example, is activated downstream of tyrosine kinase receptors. We show that PKC directly phosphorylates receptor-regulated Smad proteins. This phosphorylation abrogates the ability of Smad3 to bind directly to DNA, which leads to subsequent inability to mediate transcriptional responses dependent on the direct binding of Smad3 to DNA. Interference with PKC regulation of Smad functions increased cell sensitivity to transformation by the tumor promoter phorbol 12-myristate 13-acetate (PMA). PKC-dependent phosphorylation of Smad3 was found also to be a key event in the PMA-dependent inactivation of TGF-b-stimulated cell death. Thus, PKC-dependent phosphorylation of Smad3 leads to down-regulation of the growth inhibitory and apoptotic action of TGF-b.

Smad regulation in TGF-beta signal transduction.

Smad proteins transduce signals from transforming growth factor-beta (TGF-beta) superfamily ligands that regulate cell proliferation, differentiation and death through activation of receptor serine/threonine kinases. Phosphorylation of receptor-activated Smads (R-Smads) leads to formation of complexes with the common mediator Smad (Co-Smad), which are imported to the nucleus. Nuclear Smad oligomers bind to DNA and associate with transcription factors to regulate expression of target genes. Alternatively, nuclear R-Smads associate with ubiquitin ligases and promote degradation of transcriptional repressors, thus facilitating target gene regulation by TGF-beta. Smads themselves can also become ubiquitinated and are degraded by proteasomes. Finally, the inhibitory Smads (I-Smads) block phosphorylation of R-Smads by the receptors and promote ubiquitination and degradation of receptor complexes, thus inhibiting signalling.

Expression of Smad proteins in human colorectal cancer.

Escape from transforming growth factor-beta (TGF-beta)-induced inhibition of proliferation has been observed in many tumor cells and may contribute to loss of growth control. Smad proteins have been identified as major components in the intracellular signaling of TGF-beta family members. In this study, we examined the expression of receptor-activated, common-mediator and inhibitory Smads by immunohistochemistry in human colorectal cancers. We found increased expression of receptor-activated Smads in a fraction of the tumor cells, while no immunostaining for Smad2, Smad3 or Smad5 and only occasional staining for Smad1/8 was found in epithelial mucosa of normal colon. No or only weak staining for receptor-activated Smads, common-mediator Smad4 and inhibitory Smads was observed in the tumor stroma. Common-mediator Smad4 and inhibitory Smads were detected in cells of both tumor and normal tissues. We observed a distinct pattern of Smad4 immunostaining of epithelial cells along colon crypts, with high expression in zones of terminal differentiation. Our data show selective up-regulation of receptor-activated Smad proteins in human colorectal cancers and suggest involvement of Smad4 in differentiation and apoptosis of surface epithelial cells of normal crypts.

Intracellular signaling of osteogenic protein-1 through Smad5 activation.

Smad proteins play pivotal roles in the intracellular signaling of the multifunctional transforming growth factor-beta (TGF-beta) family members downstream of serine/threonine kinase type I and type II receptors. Smad2 and Smad3 are specific mediators of TGF-beta and activin, while Smadl and Smad5 are involved in bone morphogenetic protein-2 (BMP-2) and BMP-4 signaling. Here we report that osteogenic protein-1 (OP-1), also termed BMP-7, binds predominantly to BMPR-IB in the rat osteoprogenitor-like cell line, ROB-C26. Smad1, Smad5, and Smad8, but not Smad2 and Smad3, were found to stably interact with the kinase-deficient BMPR-IB after it was phosphorylated by the BMPR-II kinase. In ROB-C26 cells, which express Smad2, Smad3, Smad4, and Smad5, OP-1 was found to stimulate the phosphorylation of Smad5. Whereas transfection of wild-type Smad5 enhanced the OP-1-induced response, transfection of wild-type Smad2 had no effect on OP-1 signaling. A Smad5-2SA mutant, in which the two most carboxy-terminal serine residues were mutated to alanine residues, was found to act as a dominant negative inhibitor of OP-1-induced responses upon its transfection into various cell types, including ROB-C26 cells, in contrast to ectopic expression of a Smad2-2SA mutant which was without effect. Smad5, therefore, is a key component in the intracellular signaling of OP-1.