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1.  KEAP1 Is a Redox Sensitive Target That Arbitrates the Opposing Radiosensitive Effects of Parthenolide in Normal and Cancer Cells 
Cancer research  2013;73(14):4406-4417.
Elevated oxidative stress is observed more frequently in cancer cells than in normal cells. It is therefore expected that additional exposure to a low level of reactive oxygen species (ROS) will push cancer cells toward death, whereas normal cells might maintain redox homeostasis through adaptive antioxidant responses. We previously demonstrated that parthenolide enhances ROS production in prostate cancer cells through activation of NADPH oxidase. The present study identifies KEAP1 as the downstream redox target that contributes to parthenolide’s radiosensitization effect in prostate cancer cells. In vivo, parthenolide increases radiosensitivity of mouse xenograft tumors but protects normal prostate and bladder tissues against radiation-induced injury. Mechanistically, parthenolide increases the level of cellular ROS and causes oxidation of thioredoxin (TrX) in prostate cancer cells, leading to a TrX-dependent increase in a reduced state of KEAP1, which in turn leads to KEAP1-mediated PGAM5 and Bcl-xL (BCL2L1) degradation. In contrast, parthenolide increases oxidation of KEAP1 in normal prostate epithelial cells, leading to increased Nrf2 (NFE2L2) levels and subsequent Nrf2-dependent expression of antioxidant enzymes. These results reveal a novel redox-mediated modification of KEAP1 in controlling the differential effect of parthenolide on tumor and normal cell radiosensitivity. Further, they show it is possible to develop a tumor-specific radiosensitizing agent with radioprotective properties in normal cells.
PMCID: PMC3715565  PMID: 23674500
Keap1; Nrf2; PGAM5; Bcl-xL; parthenolide; radiotherapy; prostate cancer; reactive oxygen species (ROS); redox modification; antioxidant proteins; mitochondrial function
2.  Single nucleotide polymorphisms in thymic stromal lymphopoietin gene are not associated with allergic rhinitis susceptibility in Chinese subjects 
BMC Medical Genetics  2012;13:79.
Thymic stromal lymphopoietin (TSLP) is an epithelial cell-derived cytokine, implicated in the development and progression of allergic diseases. Recent studies have demonstrated significantly increased expression and synthesis of TSLPin nasal mucosa of patients with allergic rhinitis (AR), compared with nonallergic control subjects. Also, there is significant correlation between the level of TSLP mRNA and symptom severity in AR patients. In this study, we investigated whether polymorphisms in the TSLP gene were associated with increased risk of AR in the Chinese population.
In a candidate gene association study, we tested 11 single nucleotide polymorphisms (SNPs) in the TSLP gene in 368 AR and 325 control adult Han Chinese subjects from Beijing. The 11 SNPs were selected from the Chinese HapMap genotyping dataset to ensure complete genetic coverage. AR was established by questionnaire and clinical examination, and blood was drawn from all subjects for DNA extraction. The PLINK software package was used to perform statistical testing.
In the single-locus analysis of AR risk, no significant differences in allele and genotype frequencies were found between AR and control subjects. Further logistic regression analyses adjusted for age and gender also failed to reveal significant associations between AR and the selected SNPs. Similarly, analysis stratified by gender, and haplotype or diplotype did not reveal any association with AR risk.
Although TSLP presents itself as a good candidate for contributing to allergy, this study failed to find an association between specific SNPs in the TSLP gene and AR susceptibility in the Han Chinese population.
PMCID: PMC3459694  PMID: 22973903
Allergic rhinitis; Chinese subjects; Genotyping; Thymic stromal lymphopoietin; Single nucleotide polymorphism
3.  Systemic Par-4 inhibits non-autochthonous tumor growth 
Cancer Biology & Therapy  2011;12(2):152-157.
The tumor suppressor protein Par-4 (prostate apoptosis response-4) is spontaneously secreted by normal and cancer cells. Extracellular Par-4 induces caspase-dependent apoptosis in cancer cell cultures by binding, via its effector SAC domain, to cell surface GRP78 receptor. However, the functional significance of extracellular Par-4/SAC has not been validated in animal models. We show that Par-4/SAC-transgenic mice express systemic Par-4/SAC protein and are resistant to the growth of non-autochthonous tumors. Consistently, secretory Par-4/SAC pro-apoptotic activity can be transferred from these cancer-resistant transgenic mice to cancer-susceptible mice by bone marrow transplantation. Moreover, intravenous injection of recombinant Par-4 or SAC protein inhibits metastasis of cancer cells. Collectively, our findings indicate that extracellular Par-4/SAC is systemically functional in inhibition of tumor growth and metastasis progression, and may merit investigation as a therapy.
PMCID: PMC3154287  PMID: 21613819
Par-4; metastasis; systemic protein
4.  A Novel Extrinsic Pathway for Apoptosis by Tumor Suppressor Par-4 
Cell  2009;138(2):377-388.
Prostate apoptosis response-4 (Par-4) is a pro-apoptotic protein with intracellular functions in the cytoplasm and nucleus. Unexpectedly, we noted Par-4 protein is spontaneously secreted by normal and cancer cells in culture, and by Par-4 transgenic mice that are resistant to spontaneous tumors. Short exposure to endoplasmic reticulum (ER) stress-inducing agents further increased cellular secretion of Par-4 by a brefeldin A-sensitive pathway. Secretion occurred independently of caspase activation and apoptosis. Interestingly, extracellular Par-4 induced apoptosis by binding to the stress response protein, glucose-regulated protein-78 (GRP78), expressed at the surface of cancer cells. The interaction of extracellular Par-4 and cell surface GRP78 led to apoptosis via ER stress and activation of the FADD/caspase-8/caspase-3 pathway. Moreover, apoptosis inducible by TRAIL, which also exerts cancer cell-specific effects, is dependent on extracellular Par-4 signaling via cell surface GRP78. Thus, Par-4 activates a novel extrinsic pathway involving cell surface GRP78 receptor for induction of apoptosis.
PMCID: PMC2774252  PMID: 19632185
Par-4; cell surface GRP78; apoptosis
5.  Apoptosis and Tumor Resistance Conferred by Par-4 
Cancer biology & therapy  2008;7(12):1867-1874.
Par-4 is a tumor suppressor protein with a pro-apoptotic function. Epigenetic silencing of Par-4 is seen in diverse tumors, and Par-4 knockout mice develop spontaneous tumors in various tissues. Endogenous Par-4 is essential for sensitization of cells to diverse apoptotic stimuli, whereas ectopic expression of Par-4 can selectively induce apoptosis in cancer cells. The cancer-specific pro-apoptotic action of Par-4 resides in its centrally located SAC domain. This chapter reviews a novel mouse model with ubiquitous expression of the SAC domain. These SAC transgenic mice display normal development and life span, and, most importantly, are resistant to spontaneous, as well as oncogene-induced, autochthonous tumors. The tumor resistant phenotype and undetectable toxicity of SAC in vivo suggests the SAC domain possesses tremendous therapeutic potential.
PMCID: PMC2683365  PMID: 18836307
Par-4; cancer-specific; apoptosis
6.  Stokes vector analysis of adaptive optics images of the retina 
Optics letters  2008;33(2):137-139.
A high-resolution Stokes vector imaging polarimeter was developed to measure the polarization properties at the cellular level in living human eyes. The application of this cellular level polarimetric technique to in vivo retinal imaging has allowed us to measure depolarization in the retina and to improve the retinal image contrast of retinal structures based on their polarization properties.
PMCID: PMC2710772  PMID: 18197217
7.  Identification of a Unique Core Domain of Par-4 Sufficient for Selective Apoptosis Induction in Cancer Cells 
Molecular and Cellular Biology  2003;23(16):5516-5525.
Recent studies indicated that the leucine zipper domain protein Par-4 induces apoptosis in certain cancer cells by activation of the Fas prodeath pathway and coparallel inhibition of NF-κB transcriptional activity. However, the intracellular localization or functional domains of Par-4 involved in apoptosis remained unknown. In the present study, structure-function analysis indicated that inhibition of NF-κB activity and apoptosis is dependent on Par-4 translocation to the nucleus via a bipartite nuclear localization sequence, NLS2. Cancer cells that were resistant to Par-4-induced apoptosis retained Par-4 in the cytoplasm. Interestingly, a 59-amino-acid core that included NLS2 but not the C-terminal leucine zipper domain was necessary and sufficient to induce Fas pathway activation, inhibition of NF-κB activity, and apoptosis. Most important, this core domain had an expanded target range for induction of apoptosis, extending to previously resistant cancer cells but not to normal cells. These findings have identified a unique death-inducing domain selective for apoptosis induction in cancer cells (SAC domain) which holds promise for identifying key differences between cancer and normal cells and for molecular therapy of cancer.
PMCID: PMC166354  PMID: 12897127

Results 1-7 (7)