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 β1 (TGF β1) signaling in 184A1 human breast epithelial cells suggests the involvement of casein kinase 2α in TGF β1-dependent p53 phosphorylation at Ser392

AIM

Transforming growth factor β1 (TGF β1) 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 β1 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 β1-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 β1. We identified 100 and 47 unique proteins which changed their expression and/or ³⁵S-incorporation, respectively, upon treatment with TGF β1 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 β1 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 β1-regulated proteins in immortalized non-tumorigenic human breast epithelial cells, and show involvement of CK2α in the regulation of p53 Ser392 phosphorylation.

Acquisition of Invasiveness by Breast Adenocarcinoma Cells Engages Established Hallmarks and Novel Regulatory Mechanisms

BACKGROUND/AIM

Proteomics of invasiveness opens a window on the complexity of the metastasis-engaged mechanisms. The extend and types of this complexity require elucidation.

MATERIALS AND METHODS

Proteomics, immunohistochemistry, immunoblotting, network analysis and systems cancer biology were used to analyse acquisition of invasiveness by human breast adenocarcinoma cells.

RESULTS

We report here that invasiveness network highlighted the involvement of hallmarks such as cell proliferation, migration, cell death, genome stability, immune system regulation and metabolism. Identified involvement of cell-virus interaction and gene silencing are potentially novel cancer mechanisms. Identified 6,113 nodes with 11,055 edges affecting 1,085 biological processes show extensive re-arrangements in cell physiology. These high numbers are in line with a similar broadness of networks built with diagnostic signatures approved for clinical use.

CONCLUSION

Our data emphasize a broad systemic regulation of invasiveness, and describe the network of this regulation.

Proteome profiling of immortalization-to-senescence transition of human breast epithelial cells identified MAP2K3 as a senescence-promoting protein which is downregulated in human breast cancer

PURPOSE

immortalization is one of the first changes in cells undergoing carcinogenic transformation. Proteome profiling of the immortalization-senescence transition is expected to provide insights into the molecular mechanisms of early tumorigenesis.

EXPERIMENTAL DESIGN

2-DE and MALDI-MS were used to identify proteins in primary human breast epithelial cells, relevant to the immortalization-senescence transition. Cell and molecular biology and immunohistochemistry were used to validate involvement of mitogen-activated protein kinase kinase 3 (MAP2K3) in the immortalization-senescence transition.

RESULTS

we identified 71 proteins whose expression changed upon induction of senescence. The identified proteins include regulators of cell growth, death, cell assembly and organization. Analysis of the network formed by the identified proteins suggested that the immortalization-to-senescence transition could affect regulators of the cell cycle, protein synthesis, transport, post-translational modifications, DNA recombination and repair, and lipid and amino acid metabolism. We observed that MAP2K3 was downregulated in immortal human breast epithelial cells and that upregulation of MAP2K3 expression promoted cell senescence. Decreased expression of MAP2K3 was observed in human breast infiltrating ductal carcinomas, as compared to non-cancerous human breast tissues.

CONCLUSION AND CLINICAL RELEVANCE

we described a proteome profile of the immortalization-to-senescence transition for human breast epithelial cells, and identified MAP2K3 as a protein that promotes senescence in these cells.

Proteomic study of DBA/2J mice retina: Down-regulation of Integrin beta7 correlated with retinal ganglion cell death

To identify and determine the function of the proteins associated with the death of retinal ganglion cells (RGCs) in DBA/2J mice, an animal model of glaucoma, retinas of DBA/2J mice, were analyzed by proteomics at 5-, 7-, and 11-months-of-age. The proteins showing significant alterations were selected for identification by MS and 18 proteins were differentially expressed and the identified proteins included cell membrane receptors and proteins associated with intracellular signaling pathways. Among of identified proteins, the expression of Integrin beta7 at 7-months-of-age was decreased by about 89% of that at 5-months-of-age. Integrin beta7 was expressed in the RGCs. The effect of glutamate toxicity on the expression pattern of Integrin beta7 in a RGC line was also investigated and the glutamate-induced death of RGC was inhibited by the RNA knockdown of Integrin beta7. Our data showed also that the expression of 18 proteins in the DBA/2J was significantly altered in DBA2 mice and down-regulation of Integrin beta7 may have a protective effect on glutamate-induced death of RGCs.

Functional proteomics of failed filtering blebs

PURPOSE

To identify and determine the function of the proteins associated with failed filtering blebs following trabeculectomy.

METHODS

Tenon's tissues, obtained during surgery for failed filtering blebs or obtained during cataract surgery on normal eyes, were analyzed by proteomics. The proteins showing significant differences between the two tissues were selected for identification by mass spectrometry. The location and expression pattern of ribosomal S6 kinase 2 (RSK2), one of the altered proteins, were determined. The effect of basic fibroblast growth factor (bFGF) on the expression pattern and function of RSK2 in NIH3T3 fibroblast cells was then investigated by an RNA knockdown technique.

RESULTS

Eight proteins were found differentially expressed in failed filtering blebs; the identified proteins included those associated with intracellular signaling pathways. The expression of RSK2, one of the identified proteins, was found to be decreased compared with that of the control. RSK2 was located in Tenon's tissue using an immunohistochemical technique. In culture, the bFGF-induced cell proliferation was inhibited by the RNA knockdown of RSK2. The level of mRNA and protein expression of actin was increased by RSK2 RNA knockdown, but bFGF-induced protein expression of actin was not promoted by RSK2 RNA knockdown. Whereas RSK2 RNA knockdown increased the expression and activity of mitogen-activated protein kinase (MAPK), activation of MAPK induced by bFGF was not promoted by RSK2 knockdown.

CONCLUSIONS

The expression of eight proteins in the failed filtering blebs was significantly different from that in the Tenon's capsules used as a control. The effect of RSK2 expression on fibroblast cells suggests that RSK2 may be associated with wound healing in filtering blebs.

Wnt14 inhibits death of retinal precursor cells

An earlier proteomics study from our laboratory showed that Wnt14, a member of the Wnt family that regulates the development of vertebrates, was one of the proteins expressed transiently during the development of the chick retina. The purpose of this study was to determine in more detail the changes in the expression of Wnt14 during the development of the chick retina, and to investigate the biological function of Wnt14. Endogenous Wnt14 is located in the retinal ganglion cell layer, and is expressed in the chick retina on embryonic days (ED) 7, ED11, and ED15. The level of Wnt14 is transiently decreased on ED11. In vitro analysis showed that an over-expression of Wnt14 reduced the activation of caspase-3 and inhibited the death of R28 cells induced by serum deprivation or exposure to glutamate. An interferon-induced protein was identified as the protein that was bound to Wnt14. These results suggest that a stable expression of Wnt14 inhibits cell death by inactivating caspase-3 in the developing retina.

Elevated intraocular pressure, optic nerve atrophy, and impaired retinal development in ODAG transgenic mice

PURPOSE

In an earlier study, a cDNA was cloned that showed abundant expression in the eye at postnatal day (P)2 but was downregulated at P10; it was named ODAG (ocular development-associated gene). Its biological function was examined by generating and analyzing transgenic mice overexpressing ODAG (ODAG Tg) in the eye and by identifying ODAG-binding proteins.

METHODS

Transgenic mice were generated by using the mouse Crx promoter. EGFP was designed to be coexpressed with transgenic ODAG, to identify transgene-expressing cells. Overexpression of ODAG was confirmed by Northern and Western blot analysis. IOP was measured with a microneedle technique. The eyes were macroscopically examined and histologically analyzed. EGFP expression was detected by confocal microscope. Proteins associated with ODAG were isolated by pull-down assay in conjugation with mass spectrometry.

RESULTS

Macroscopically, ODAG Tg exhibited gradual protrusion of the eyeballs. The mean IOP of ODAG Tg was significantly higher than that of wild-type (WT) littermates. Histologic analysis exhibited optic nerve atrophy and impaired retinal development in the ODAG Tg eye. EGFP was expressed highly in the presumptive outer nuclear layer and weakly in the presumptive inner nuclear layer in the ODAG Tg retina. Rab6-GTPase-activating protein (Rab6-GAP) and its substrate, Rab6, were identified as ODAG-binding proteins.

CONCLUSIONS

Deregulated expression of ODAG in the eye induces elevated intraocular pressure and optic nerve atrophy and impairs retinal development, possibly by interfering with the Rab6/Rab6-GAP-mediated signaling pathway. These results provide new insights into the mechanisms regulating ocular development, and ODAG Tg would be a novel animal model for human diseases caused by ocular hypertension.

Proteome profiling of embryo chick retina

Background

Little is known regarding the molecular pathways that underlie the process of retinal development. The purpose of this study was to identify proteins which may be involved in development of retina. We used a proteomics-based approach to identify proteins that are up- or down-regulated during the development of the embryo chick retina.

Results

Two-dimensional gel electrophoresis was performed with the retina of embryo chicken, which was obtained from embryos of day 7 (ED7) and of day 11 (ED11). The protein spots showing significant differences were selected for identification by MALDI mass spectrometry. Thirteen proteins were differentially expressed; seven proteins were up-regulated in embryo retina of chicken at ED 11 and six proteins were down-regulated. Significant proteins were also evaluated in embryo day 15 (ED15). Some of identified proteins were known to regulate cell proliferation, cell death, transport, metabolism, organization and extracellular matrix, and others also included novel proteins.

Conclusion

We identified thirteen proteins which differentially expressed in embryonal retina of chicken at day 7, as compared to the retina of embryo of day 11. They were various regulatory proteins for cellular signaling.

Proteomic analyses of retina of excitatory amino acid carrier 1 deficient mice

BACKGROUND

Excitatory amino acid carrier 1 (EAAC1) is a glutamate transporter found in neuronal tissues and is extensively expressed in the retina. EAAC1 plays a role in a variety of neural functions, but its biological functions in the retina has not been fully determined. The purpose of this study was to identify proteins regulated by EAAC1 in the retina of mice. To accomplish this, we used a proteomics-based approach to identify proteins that are up- or down-regulated in EAAC1-deficient (EAAC1-/-) mice.

RESULTS

Proteomic analyses and two-dimensional gel electorphoresis were performed on the retina of EAAC1-/- mice, and the results were compared to that of wild type mice. The protein spots showing significant differences were selected for identification by mass spectrometric analyses. Thirteen proteins were differentially expressed; nine proteins were up-regulated and five proteins were down-regulated in EAAC1-/- retina. Functional clustering showed that identified proteins are involved in various cellular process, e.g. cell cycle, cell death, transport and metabolism.

CONCLUSION

We identified thirteen proteins whose expression is changed in EAAC-/- mice retinas. These proteins are known to regulate cell proliferation, death, transport, metabolism, cell organization and extracellular matrix.