Daojing Wang

Proteomic Profiling of Bone Marrow Mesenchymal Stem Cells upon Transforming Growth Factor β1 Stimulation

Bone marrow mesenchymal stem cells (MSCs) can differentiate into different types of cells and have tremendous potential for cell therapy and tissue engineering. Transforming growth factor β1 (TGF-β) plays an important role in cell differentiation and vascular remodeling. We showed that TGF-β induced cell morphology change and an increase in actin fibers in MSCs. To determine the global effects of TGF-β on MSCs, we employed a proteomic strategy to analyze the effect of TGF-β on the human MSC proteome. By using two-dimensional gel electrophoresis and electrospray ionization coupled to quadrupole/time-of-flight tandem mass spectrometers, we have generated a proteome reference map of MSCs, and we identified ∼30 proteins with an increase or decrease in expression or phosphorylation in response to TGF-β. The proteins regulated by TGF-β included cytoskeletal proteins, matrix synthesis proteins, membrane proteins, metabolic enzymes, etc. TGF-β increased the expression of smooth muscle α-actin and decreased the expression of gelsolin. Overexpression of gelsolin inhibited TGF-β-induced assembly of smooth muscle α-actin; on the other hand, knocking down gelsolin expression enhanced the assembly of α-actin and actin filaments without significantly affecting α-actin expression. These results suggest that TGF-β coordinates the increase of α-actin and the decrease of gelsolin to promote MSC differentiation. This study demonstrates that proteomic tools are valuable in studying stem cell differentiation and elucidating the underlying molecular mechanisms.

Protein Kinase CK2 Regulates Cytoskeletal Reorganization during Ionizing Radiation–Induced Senescence of Human Mesenchymal Stem Cells

Human mesenchymal stem cells (hMSC) are critical for tissue regeneration. How hMSC respond to genotoxic stresses and potentially contribute to aging and cancer remain underexplored. We showed that ionizing radiation induced cellular senescence of hMSC over a period of 10 days, showing a critical transition between days 3 and 6. This was confirmed by senescence-associated beta-galactosidase staining, protein expression profiles of key cell cycle regulators (retinoblastoma protein, p53, p21(waf1/Cip1), and p16(INK4A)), and senescence-associated secretory phenotypes (interleukin-8, interleukin-12, GRO, and MDC). We observed dramatic cytoskeletal reorganization of hMSC through reduction of myosin-10, redistribution of myosin-9, and secretion of profilin-1. Using a SILAC-based phosphoproteomics method, we detected significant reduction of myosin-9 phosphorylation at Ser(1943), coinciding with its redistribution. Importantly, through treatment with cell-permeable inhibitors (4,5,6,7-tetrabromo-1H-benzotriazole and 2-dimethylamino-4,5,6,7-tetrabromo-1H-benzimidazole) and gene knockdown using RNA interference, we identified CK2, a kinase responsible for myosin-9 phosphorylation at Ser(1943), as a key factor contributing to the radiation-induced senescence of hMSC. We showed that individual knockdown of CK2 catalytic subunits CK2alpha and CK2alpha induced hMSC senescence. However, only knockdown of CK2alpha resulted in morphologic phenotypes resembling those of radiation-induced senescence. These results suggest that CK2alpha and CK2alpha play differential roles in hMSC senescence progression, and their relative expression might represent a novel regulatory mechanism for CK2 activity.

Proteomic Profiling of Mesenchymal Stem Cell Responses to Mechanical Strain and TGF-β1

Mesenchymal stem cells (MSCs) are a potential source of smooth muscle cells (SMCs) for constructing tissue-engineered vascular grafts. However, the details of how specific combinations of vascular microenvironmental factors regulate MSCs are not well understood. Previous studies have suggested that both mechanical stimulation with uniaxial cyclic strain and chemical stimulation with transforming growth factor-β1 (TGF-β1) can induce smooth muscle markers in MSCs. In this study, we investigated the combined effects of uniaxial cyclic strain and TGF-β1 stimulation on MSCs. By using a proteomic analysis, we found differential regulation of several proteins and genes, such as the up-regulation of TGF-β1-induced protein ig-h3 (BGH3) protein levels by TGF-β1 and up-regulation of calponin 3 protein level by cyclic strain. At the gene expression level, BGH3 was induced by TGF-β1, but calponin 3 was not significantly regulated by mechanical strain or TGF-β1, which was in contrast to the synergistic up-regulation of calponin 1 gene expression by cyclic strain and TGF-β1. Further experiments with cycloheximide treatment suggested that the up-regulation of calponin 3 by cyclic strain was at post-transcriptional level. The results in this study suggest that both mechanical stimulation and TGF-β1 signaling play unique and important roles in the regulation of MSCs at both transcriptional and post-transcriptional levels, and that a precise combination of microenvironmental cues may promote MSC differentiation.

Multiconfigurational nature of 5f orbitals in uranium and plutonium intermetallics

Uranium and plutonium’s 5f electrons are tenuously poised between strongly bonding with ligand spd-states and residing close to the nucleus. The unusual properties of these elements and their compounds (e.g., the six different allotropes of elemental plutonium) are widely believed to depend on the related attributes of f-orbital occupancy and delocalization for which a quantitative measure is lacking. By employing resonant X-ray emission spectroscopy (RXES) and X-ray absorption near-edge structure (XANES) spectroscopy and making comparisons to specific heat measurements, we demonstrate the presence of multiconfigurational f-orbital states in the actinide elements U and Pu and in a wide range of uranium and plutonium intermetallic compounds. These results provide a robust experimental basis for a new framework toward understanding the strongly-correlated behavior of actinide materials.

Differential Effects of X-Rays and High-Energy 56Fe Ions on Human Mesenchymal Stem Cells

PURPOSEnStem cells hold great potential for regenerative medicine, but they have also been implicated in cancer and aging. How different kinds of ionizing radiation affect stem cell biology remains unexplored. This study was designed to compare the biological effects of X-rays and of high-linear energy transfer (LET) (56)Fe ions on human mesenchymal stem cells (hMSC).nnnMETHODS AND MATERIALSnA multi-functional comparison was carried out to investigate the differential effects of X-rays and (56)Fe ions on hMSC. The end points included modulation of key markers such as p53, cell cycle progression, osteogenic differentiation, and pathway and networks through transcriptomic profiling and bioinformatics analysis.nnnRESULTSnX-rays and (56)Fe ions differentially inhibited the cell cycle progression of hMSC in a p53-dependent manner without impairing their in vitro osteogenic differentiation process. Pathway and network analyses revealed that cytoskeleton and receptor signaling were uniquely enriched for low-dose (0.1 Gy) X-rays. In contrast, DNA/RNA metabolism and cell cycle regulation were enriched for high-dose (1 Gy) X-rays and (56)Fe ions, with more significant effects from (56)Fe ions. Specifically, DNA replication, DNA strand elongation, and DNA binding/transferase activity were perturbed more severely by 1 Gy (56)Fe ions than by 1 Gy X-rays, consistent with the significant G2/M arrest for the former while not for the latter.nnnCONCLUSIONSn(56)Fe ions exert more significant effects on hMSC than X-rays. Since hMSC are the progenitors of osteoblasts in vivo, this study provides new mechanistic understandings of the relative health risks associated with low- and high-dose X-rays and high-LET space radiation.

14-3-3σ stabilizes a complex of soluble actin and intermediate filament to enable breast tumor invasion

Significance We characterize a mechanism by which 14-3-3σ directs cell migration and tumor invasion through regulating cytoskeletal solubility and dynamics. Our data suggest that 14-3-3σ expression, rather than being a tumor suppressor, in fact, aids in breast tumor invasion at least in a subset of carcinomas. Our findings warrant further investigation into the role of this molecule in normal mammary gland and breast tumors and, indeed, in epithelial tissues and tumors where 14-3-3σ is expressed. The protein 14-3-3σ (stratifin) is frequently described as a tumor suppressor silenced in about 80% of breast tumors. Intriguingly, we show that 14-3-3σ expression, which in normal breast is localized to the myoepithelial cells, tracks with malignant phenotype in two models of basal-like breast cancer progression, and in patients, it is associated with basal-like subtype and poor clinical outcome. We characterized a mechanism by which 14-3-3σ guides breast tumor invasion by integrating cytoskeletal dynamics: it stabilizes a complex of solubilized actin and intermediate filaments to maintain a pool of “bioavailable” complexes for polarized assembly during migration. We show that formation of the actin/cytokeratin/14-3-3σ complex and cellular migration are regulated by PKCζ-dependent phosphorylation, a finding that could form the basis for intervention in aggressive breast carcinomas expressing 14-3-3σ. Our data suggest that the biology of this protein is important in cellular movement and is contingent on breast cancer subtype.

Identification of Regulatory Factor X as a Novel Mismatch Repair Stimulatory Factor

This report describes the identification and purification of a novel mismatch repair stimulatory factor from HeLa cell extracts. This activity copurifies with a proliferating cell nuclear antigen-dependent 5 ′ → 3 ′ DNA excision activity during several purification steps but is resolved from the excision activity during gel filtration chromatography using Sephacryl S-300. After purification to near homogeneity, the stimulatory factor is associated with three polypeptides with apparent molecular masses of 68, 36, and 30 kDa. Peptide sequencing analysis by tandem mass spectrometry identified the stimulatory factor as the heterotrimeric regulatory factor X (RFX) complex, which regulates transcription of the class II major histocompatibility complex by facilitating histone acetylation and is defective in the human hereditary immunodeficiency syndrome called bare lymphocyte syndrome. This conclusion was confirmed by the facts that purified recombinant RFX stimulates mismatch repair in an in vitro reconstituted mismatch repair system and that depletion of RFX from nuclear extracts or RFX knockdown in cells reduces mismatch repair activity. As expected, RFX knockdown cells display instability in microsatellite sequences. The possible role of RFX in human MMR repair is discussed.

Self-irradiation damage to the local structure of plutonium and plutonium intermetallics

The effect of self-irradiation damage on the local structure of δ-Pu, PuAl2, PuGa3, and other Pu intermetallics has been determined for samples stored at room temperature using the extended x-ray absorption fine-structure (EXAFS) technique. These measurements indicate that the intermetallic samples damage at a similar rate as indicated in previous studies of PuCoGa5. In contrast, δ-Pu data indicate a much slower damage accumulation rate. To explore the effect of storage temperature and possible room temperature annealing effects, we also collected EXAFS data on a δ-Pu sample that was held at less than 32u2009K for a two month period. This sample damaged much more quickly. In addition, the measurable damage was annealed out at above only 135u2009K. Data from samples of δ-Pu with different Ga concentrations and results on all samples collected from different absorption edges are also reported. These results are discussed in terms of the vibrational properties of the materials and the role of Ga in δ-Pu as a network...

Abstract 5110: RNA helicase p68 is a new marker for breast cancer heterogeneity

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FLnnTwo major challenges in diagnosis and therapy of breast cancer lie in its heterogeneity and drug resistance. RNA helicase p68 (DDX5) has been shown to be involved in all aspects of RNA metabolism and serves as a transcriptional co-regulator. However, its functional role in breast cancer remains elusive. We utilized an integrative biology approach strategy to further define the role of p68 in breast cancer. Specifically, we determined the expression pattern of p68 at both mRNA and protein levels for a panel of ∼50 breast cancer cell lines. We performed immunohistochemistry of p68 using tissue microarrays containing a total of over 200 cases of primary human malignant breast cancer (various grades and stages). We knocked down p68 in a panel of representative breast cancer cell lines (e.g., SKBR3 and MDA-MB-231) and investigated the functional consequences such as their proliferation and responses to Lapatinib after the p68 knockdown. Finally, we carried out SILAC-based proteomic profiling of these breast cancer cells after p68 knockdown and identified p68-targeted proteins and networks contributing to the drug responses. We found that p68 expression pattern is distinct among different subtypes of breast cancers. More aggressive basal subtypes have predominantly high p68 protein expression while low p68 expression is predominantly associated with the luminal subtype. Knockdown of p68 inhibits the proliferation of breast cancer cells and sensitizes them to cancer drugs such as Lapatinib. We demonstrated that p68 is a new marker for breast cancer heterogeneity in addition to ER, PR, and Her2. Importantly, we identified p68-regualted cytoskeletal reorganization as a new mechanism in controlling breast cancer proliferation and drug resistance. In summary, RNA helicase p68 may serve as a new marker for breast cancer heterogeneity, as a predictor for drug resistance, and as a target for a combinational therapy to circumvent drug resistance of aggressive tumors.nnCitation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5110. doi:10.1158/1538-7445.AM2011-5110

Abstract 5132: 14-3-3sigma coordinates breast tumor invasion by regulating cytoskeletal dynamics

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DCnn14-3-3sigma was initially described as a tumor suppressor silenced in about 80% of breast tumors. Surprisingly however, in two independent culture models of breast cancer progression, we discovered 14-3-3sigma expression increased as cells transition towards malignancy, and that it contributed to motility and tumor invasion into surrounding tissues in vivo. Immunohistochemical analysis showed that 14-3-3sigma expression preferentially identified a subset of invasive breast carcinomas, and in independent breast cancer patient cohorts, 14-3-3sigma correlated with poor clinical outcome. We observed several lines of evidence that 14-3-3sigma regulates cytoskeletal architecture in cells, providing a molecular mechanism by which 14-3-3sigma may coordinate tumor progression and invasion.nnFunding is provided by a DOD BCRP Predoctoral Fellowship and a CBCRP Dissertation Award to AB, as well as DOE, NCI, NIH, and DOD grants to MJB.nnCitation 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 5132.