Hsiu-Chuan Chou

Proteomics study of oxidative stress and Src kinase inhibition in H9C2 cardiomyocytes: a cell model of heart ischemia-reperfusion injury and treatment.

Protein phosphorylation plays a crucial role in the signal transduction pathways that regulate gene expression, metabolism, cell adhesion, and cell survival in response to oxidative stress. In this study, we have used hydrogen peroxide treatment of H9C2 rat cardiomyocytes as a model of oxidative stress in heart ischemia-reperfusion injury. We show that oxidative stress induces a robust tyrosine phosphorylation of multiple proteins in this cell type. A phosphoproteomics approach using anti-phosphotyrosine affinity purification and LC-MS/MS was then used to identify the protein targets of this stress-induced phosphorylation. Twenty-three tyrosine-phosphorylated proteins were identified, with the majority known to be associated with cell-cell junctions, the actin cytoskeleton, and cell adhesion. This suggested that oxidative stress may have a profound effect on intercellular connections and the cytoskeleton to affect cell adhesion, morphology, and survival. Importantly, Src kinase was shown to be a major upstream regulator of these events. Immunofluorescence studies, fluorescence-activated cell sorting, and cell-based assays were used to demonstrate oxidative stress-induced modification of cell adhesion structures and the cytoskeleton, induced de-adhesion, and increased apoptosis, which were reversed by treatment with the Src kinase inhibitor PP1. These data demonstrate the critical role of Src kinase in oxidative stress-induced phosphorylation and cell damage in cardiomyocytes and suggest that targeting this kinase may be an effective strategy for preventing ischemia-reperfusion injury in the heart.

Secretomic and Proteomic Analysis of Potential Breast Cancer Markers by Two-Dimensional Differential Gel Electrophoresis

The transformation of a normal cell into a cancer cell has been correlated with alterations in gene regulation and protein expression. To identify altered proteins and link them to the tumorigenesis of breast cancer, we have distinguished normal breast cells (MCF-10A) from noninvasive breast cancer cells (MCF-7) and invasive breast cancer cells (MB-MDA-231) to identify potential breast cancer markers in transformed breast cells. Using the 2D-DIGE and MALDI-TOF MS techniques, we quantified and identified differentially expressed extracellular secreted proteins and total cellular proteins across MCF-7, MB-MDA-231 and MCF-10A. The proteomic analysis of the secreted proteins identified 50 unique differentially expressed proteins from three different media. In addition, 133 unique differentially expressed proteins from total cellular proteins were also identified. Note that 14 of the secreted proteins and 51 of the total cellular proteins have not been previously reported in breast cancer research. Some of these unreported proteins have been examined in other breast cancer cell lines and have shown positive correlations with 2D-DIGE data. In summary, this study identifies numerous putative breast cancer markers from various stages of breast cancer. The results of this study may aid in developing proteins identified as useful diagnostic and therapeutic candidates in research on cancer and proteomics.

Proteomic and redox-proteomic analysis of berberine-induced cytotoxicity in breast cancer cells

Berberine is a natural product isolated from herbal plants such as Rhizoma coptidis which has been shown to have anti-neoplastic properties. However, the effects of berberine on the behavior of breast cancers are largely unknown. To determine if berberine might be useful in the treatment of breast cancer and its cytotoxic mechanism, we analyzed the impact of berberine treatment on differential protein expression and redox regulation in human breast cancer cell line MCF-7 using lysine- and cysteine-labeling two-dimensional difference gel electrophoresis (2D-DIGE) combined with mass spectrometry (MS). This study demonstrated that 96 and 22 protein features were significantly changed in protein expression and thiol reactivity, respectively and revealed that berberine-induced cytotoxicity in breast cancer cells involves dysregulation of protein folding, proteolysis, redox regulation, protein trafficking, cell signaling, electron transport, metabolism and centrosomal structure. Our work shows that this combined proteomic strategy provides a rapid method to study the molecular mechanisms of berberine-induced cytotoxicity in breast cancer cells. The identified targets may be useful for further evaluation as potential targets in breast cancer therapy.

Proteomic analysis of UVB-induced protein expression- and redox-dependent changes in skin fibroblasts using lysine- and cysteine-labeling two-dimensional difference gel electrophoresis

UVB is the most energetic and DNA-damaging to humans in ultraviolet radiation. Previous research has suggested that exposure to UVB causes skin pathologies because of direct DNA damage and the generation of reactive oxygen species (ROS). However, the detailed molecular mechanisms by which UVB leads to skin cancer have yet to be clarified. In the current study, normal skin fibroblast cells (CCD-966SK) were exposed to various doses of UVB, and the changes in protein expression and thiol reactivity were monitored with lysine- and cysteine-labeling 2D-DIGE and MALDI-TOF mass spectrometry. Our proteomic analysis revealed that 89 identified proteins showed significant changes in protein expression, and 37 in thiol reactivity. Many proteins that are known to be involved in protein folding, redox regulation and nucleotide biosynthesis were up-regulated under UVB irradiation. In contrast, proteins responsible for biosynthesis and protein degradation were down-regulated. In addition, the thiol-reactivity of proteins involving cytoskeleton, metabolism, and signal transduction were altered by UVB. In summary, these UVB-modulated cellular proteins and redox-regulated proteins might play important roles in the early stages of skin cancer formation and photoaging induced by UVB-irradiation. Such proteins might provide a potential target for the rational design of drugs to prevent UVB-induced diseases.

Mitochondrial proteomics analysis of tumorigenic and metastatic breast cancer markers

Mitochondria are key organelles in mammary cells responsible for several cellular functions including growth, division, and energy metabolism. In this study, mitochondrial proteins were enriched for proteomics analysis with the state-of-the-art two-dimensional differential gel electrophoresis and matrix-assistant laser desorption ionization–time-of-flight mass spectrometry strategy to compare and identify the mitochondrial protein profiling changes between three breast cell lines with different tumorigenicity and metastasis. The proteomics results demonstrate more than 1,500 protein features were resolved from the equal amount pooled from three purified mitochondrial proteins, and 125 differentially expressed spots were identified by their peptide finger print, in which, 33 identified proteins belonged to mitochondrial proteins. Eighteen out of these 33 identified mitochondrial proteins such as SCaMC-1 have not been reported in breast cancer research to our knowledge. Additionally, mitochondrial protein prohibitin has shown to be differentially distributed in mitochondria and in nucleus for normal breast cells and breast cancer cell lines, respectively. To sum up, our approach to identify the mitochondrial proteins in various stages of breast cancer progression and the identified proteins may be further evaluated as potential breast cancer markers in prognosis and therapy.

Major Role of Epidermal Growth Factor Receptor and Src Kinases in Promoting Oxidative Stress-dependent Loss of Adhesion and Apoptosis in Epithelial Cells

A growing body of evidence suggests that reactive oxygen species are critical components of cell signaling pathways, in particular regulating protein phosphorylation events. Here, we show that oxidative stress in response to hydrogen peroxide treatment of human epithelial cells induces robust tyrosine phosphorylation on multiple proteins. Using an anti-phosphotyrosine purification and liquid chromatography-tandem mass spectrometry approach, we have identified many of these H2O2-induced tyrosine-phosphorylated proteins. Importantly, we show that epidermal growth factor receptor (EGFR) and Src are the primary upstream kinases mediating these events through their redox activation. The finding that many of the identified proteins have functions in cell adhesion, cell-cell junctions, and the actin cytoskeleton prompted us to examine stress-induced changes in adhesion. Immunofluorescence analysis showed that H2O2 alters cell adhesion structures and the actin cytoskeleton causing loss of adhesion and apoptosis. Remarkably, these cellular changes could be attenuated by inhibition of EGFR and Src, identifying these kinases as targets to block oxidative damage. In summary, our data demonstrate that EGFR and Src together play a central role in oxidative stress-induced phosphorylation, which in turn results in loss of adhesion, morphological changes, and cell damage in epithelial cells. These data also provide a general model for redox signaling in other cell systems.

Proteomic analysis of proteins responsible for the development of doxorubicin resistance in human uterine cancer cells.

Drug resistance is a common cause of failure in cancer chemotherapy treatments. In this study, we used a pair of uterine sarcoma cancer lines, MES-SA, and the doxorubicin-resistant MES-SA/Dx5 as a model system to examine resistance-dependent cellular responses and to identify potential therapeutic targets. We used two-dimensional differential gel electrophoresis (2D-DIGE) and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF/TOF MS) to examine the global protein expression changes induced by doxorubicin treatment and doxorubicin resistance. A proteomic study revealed that doxorubicin-exposure altered the expression of 87 proteins in MES-SA cells, while no significant response occurred in similarly treated MES-SA/Dx5 cells, associating these proteins with drug specific resistance. By contrast, 37 proteins showed differential expression between MES-SA and MES-SA/Dx5, indicating baseline resistance. Further studies have used RNA interference, cell viability analysis, and analysis of apoptosis against asparagine synthetase (ASNS) and membrane-associated progesterone receptor component 1 (mPR) proteins, to monitor and evaluate their potency on the formation of doxorubicin resistance. The proteomic approach allowed us to identify numerous proteins, including ASNS and mPR, involved in various drug-resistance-forming mechanisms. Our results provide useful diagnostic markers and therapeutic candidates for the treatment of doxorubicin-resistant uterine cancer.

Proteomic analysis of gemcitabine-induced drug resistance in pancreatic cancer cells

Currently, the most effective agent against pancreatic cancer is gemcitabine (GEM), which inhibits tumor growth by interfering with DNA replication and blocking DNA synthesis. However, GEM-induced drug resistance in pancreatic cancer compromises the therapeutic efficacy of GEM. To investigate the molecular mechanisms associated with GEM-induced resistance, 2D-DIGE and MALDI-TOF mass spectrometry were performed to compare the proteomic alterations of a panel of differential GEM-resistant PANC-1 cells with GEM-sensitive pancreatic cells. The proteomic results demonstrated that 33 proteins were differentially expressed between GEM-sensitive and GEM-resistant pancreatic cells. Of these, 22 proteins were shown to be resistance-specific and dose-dependent in the regulation of GEM. Proteomic analysis also revealed that proteins involved in biosynthesis and detoxification are significantly over-expressed in GEM-resistant PANC-1 cells. In contrast, proteins involved in vascular transport, bimolecular decomposition, and calcium-dependent signal regulation are significantly over-expressed in GEM-sensitive PANC-1 cells. Notably, both protein-protein interaction of the identified proteins with bioinformatic analysis and immunoblotting results showed that the GEM-induced pancreatic cell resistance might interplay with tumor suppressor protein p53. Our approach has been shown here to be useful for confidently detecting pancreatic proteins with differential resistance to GEM. Such proteins may be functionally involved in the mechanism of chemotherapy-induced resistance.

Quercetin-induced cardioprotection against doxorubicin cytotoxicity

BackgroundCancer has continually been the leading cause of death worldwide for decades. Thus, scientists have actively devoted themselves to studying cancer therapeutics. Doxorubicin is an efficient drug used in cancer therapy, but also produces reactive oxygen species (ROS) that induce severe cytotoxicity against heart cells. Quercetin, a plant-derived flavonoid, has been proven to contain potent antioxidant and anti-inflammatory properties. Thus, this in vitro study investigated whether quercetin can decrease doxorubicin-induced cytotoxicity and promote cell repair systems in cardiomyocyte H9C2 cells.ResultsProteomic analysis and a cell biology assay were performed to investigate the quercetin-induced responses. Our data demonstrated that quercetin treatment protects the cardiomyocytes in a doxorubicin-induced heart damage model. Quercetin significantly facilitated cell survival by inhibiting cell apoptosis and maintaining cell morphology by rearranging the cytoskeleton. Additionally, 2D-DIGE combined with MALDI-TOF MS analysis indicated that quercetin might stimulate cardiomyocytes to repair damage after treating doxorubicin by modulating metabolic activation, protein folding and cytoskeleton rearrangement.ConclusionBased on a review of the literature, this study is the first to report detailed protective mechanisms for the action of quercetin against doxorubicin-induced cardiomyocyte toxicity based on in-depth cell biology and proteomic analysis.

Proteomics-based identification of plasma biomarkers in oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is an aggressive cancer and its occurrence is closely related to betel nut chewing in Taiwan. However, there are few prognostic and diagnostic biomarkers for this disease especially for its association with betel nut chewing. Recent progresses in quantitative proteomics have offered opportunities to discover plasma proteins as biomarkers for tracking the progression and for understanding the molecular mechanisms of OSCC. In present study, plasma samples from OSCC patients with at least 5-year history of betel nut chewing and healthy donors were analyzed by fluorescence 2D-DIGE-based proteomic analysis. Totally, 38 proteins have been firmly identified representing 13 unique gene products. These proteins mainly function in inflammatory responses (such as fibrinogen gamma chain) and transport (Apolipoprotein A-I). Additionally, the current quantitative proteomic approach has identified numerous OSCC biomarkers including fibrinogen (alpha/beta/gamma) chain, haptoglobin, leucine-rich alpha-2-glycoprotein and ribosomal protein S6 kinase alpha-3 (RSK2) which have not been reported and may be associated with the progression and development of the disease. In summary, this study reports a comprehensive patient-based proteomic approach for the identification of potential plasma biomarkers in OSCC. The potential of utilizing these markers for screening and treating OSCC warrants further investigations.