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Publications (3)14.6 Total impact

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    ABSTRACT: Oncogene-induced senescence is a stable proliferative arrest that serves as a tumor-suppressing defense mechanism. p38 MAPK has been implicated in oncogene-induced senescence and tumor suppression. However, the specific role of each of the four p38 isoforms in oncogene-induced senescence is not fully understood. Here, we demonstrate that p38δ mediates oncogene-induced senescence through a p53- and p16(INK4A)-independent mechanism. Instead, evidence suggests a link between p38δ and the DNA damage pathways. Moreover, we have discovered a novel mechanism that enhances the expression of p38δ during senescence. In this mechanism, oncogenic ras induces the Raf-1-MEK-ERK pathway, which in turn activates the AP-1 and Ets transcription factors that are bound to the p38δ promoter, leading to increase transcription of p38δ. These findings indicate that induction of the pro-senescent function of p38δ by oncogenic ras is achieved through 2 mechanisms, transcriptional activation by the Raf-1-MEK-ERK-AP-1/Ets pathway, which increases the cellular concentration of the p38δ protein, and posttranslational modification by MKK3/6, which stimulates the enzymatic activity of p38δ. In addition, these studies identify the AP-1 and Ets transcription factors as novel signaling components in the senescence-inducing pathway.
    Molecular and cellular biology 07/2013; · 6.06 Impact Factor
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    ABSTRACT: The yes-associated protein (YAP) transcription co-activator has been reported either as an oncogene candidate or a tumor suppressor. Liver tissue chips revealed that about 51.4% human hepatocellular carcinoma (HCC) samples express YAP and 32.9% HCC samples express phosphorylated YAP. In this study, we found that chemotherapy increased YAP protein expression and nuclear translocation in HepG2 cells, as well as p53 protein expression and nuclear translocation. However, little is known about YAP functions during chemotherapy. Our results show that overexpression of YAP increases chemosensitivity of HepG2 cells during chemotherapy. Dominant negative transfection of Flag-S94A (TEAD binding domain mutant) or Flag-W1W2 (WW domain mutant) to HepG2 cells decreases p53 expression/ nuclear translocation and chemosensitivity when compared with control HepG2 cells. Furthermore, rescue transfection of Flag-5SA-S94A or Flag-5SA-W1W2, respectively to HepG2 cells regains p53 expression/nuclear translocation and chemosensitivity. These results indicate that YAP promotes chemosensitivity by modulating p53 during chemotherapy and both TEAD and WW binding domains are required for YAP-mediated p53 function. ChIP assay results also indicated that YAP binds directly to the p53 promoter to improve its expression. In addition, p53 could positively feedback YAP expression through binding to the YAP promoter. Taken together, our current data indicate that YAP functions as a tumor suppressor that enhances apoptosis by modulating p53 during chemotherapy.
    Cancer biology & therapy 06/2013; 14(6):511-20. · 3.29 Impact Factor
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    ABSTRACT: The inadequate treatment efficacy, suboptimal cancer detection and disease monitoring in anticancer therapies have led to the quest for clinically relevant, innovative multifaceted solutions such as development of targeted and traceable approaches. Molecular imaging technologies with the versatility of liposomal nanoparticles platform offer tangible options to better guide treatment delivery and monitor outcome. In this study, we introduced noninvasive, quantitative and functional imaging techniques with reporter gene methods to probe breast cancer processes with liposomal nanoparticles by bioluminescence imaging (BLI). A breast cancer model was applied for therapy by injecting 5.0 x 10(5) 4T1 cells carrying a reporter system encoding a double fusion reporter gene consisting of firefly luciferase (Fluc) and green fluorescent protein (GFP) into BALB/c mice. Liposomal nanoparticles loaded with a triple fusion gene containing the herpes simplex virus truncated thymidine kinase (HSV-ttk) and renilla luciferase (Rluc) and red fluorescent protein (RFP) were applied by in situ injection for monitoring and evaluating gene therapy. The BALB/c mice were subsequently treated with ganciclovir (GCV) and the growth status of tumor was monitored by bioluminescence imaging of Fluc and the treatment delivery of liposomal nanoparticle was efficiently tracked by Rluc imaging. In fact, TF plasmids were shown to be useful for monitoring and evaluating targeting efficacy and gene therapy by non-invasive molecular imaging. In conclusion, the combination of noninvasive imaging techniques and liposomal nanoparticle can provide a practical and clinically useful way for gene delivery and monitoring the level of gene expression over time and treatment response in patients undergoing gene therapy.
    Journal of Biomedical Nanotechnology 10/2012; 8(5):742-50. · 5.26 Impact Factor