Browsing by Author "Wu, Xi"

Now showing 1 - 8 of 8
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    A non-coding GWAS variant impacts anthracycline-induced cardiotoxic phenotypes in human iPSC-derived cardiomyocytes
    (Springer Nature, 2022-11-22) Wu, Xi; Shen, Fei; Jiang, Guanglong; Xue, Gloria; Philips, Santosh; Gardner, Laura; Cunningham, Geneva; Bales, Casey; Cantor, Erica; Schneider, Bryan Paul; Medicine, School of Medicine
    Anthracyclines, widely used to treat breast cancer, have the potential for cardiotoxicity. We have previously identified and validated a germline single nucleotide polymorphism, rs28714259, associated with an increased risk of anthracycline-induced heart failure. We now provide insights into the mechanism by which rs28714259 might confer increased risk of cardiac damage. Using hiPSC-derived cardiomyocyte cell lines with either intrinsic polymorphism or CRISPR-Cas9-mediated deletion of rs28714259 locus, we demonstrate that glucocorticoid receptor signaling activated by dexamethasone pretreatment prior to doxorubicin exposure preserves cardiomyocyte viability and contractility in cardiomyocytes containing the major allele. Homozygous loss of the rs28714259 major allele diminishes dexamethasone’s protective effect. We further demonstrate that the risk allele of rs28714259 disrupts glucocorticoid receptor and rs28714259 binding affinity. Finally, we highlight the activation of genes and pathways involved in cardiac hypertrophy signaling that are blocked by the risk allele, suggesting a decreased adaptive survival response to doxorubicin-related stress.
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    Aberrant reduction of telomere repetitive sequences in plasma cell-free DNA for early breast cancer detection.
    (Impact Journals, 2015-10-06) Wu, Xi; Tanaka, Hiromi; Department of Medical & Molecular Genetics, IU School of Medicine
    Excessive telomere shortening is observed in breast cancer lesions when compared to adjacent non-cancerous tissues, suggesting that telomere length may represent a key biomarker for early cancer detection. Because tumor-derived, cell-free DNA (cfDNA) is often released from cancer cells and circulates in the bloodstream, we hypothesized that breast cancer development is associated with changes in the amount of telomeric cfDNA that can be detected in the plasma. To test this hypothesis, we devised a novel, highly sensitive and specific quantitative PCR (qPCR) assay, termed telomeric cfDNA qPCR, to quantify plasma telomeric cfDNA levels. Indeed, the internal reference primers of our design correctly reflected input cfDNA amount (R2 = 0.910, P = 7.82 × 10−52), implying accuracy of this assay. We found that plasma telomeric cfDNA levels decreased with age in healthy individuals (n = 42, R2 = 0.094, P = 0.048), suggesting that cfDNA is likely derived from somatic cells in which telomere length shortens with increasing age. Our results also showed a significant decrease in telomeric cfDNA level from breast cancer patients with no prior treatment (n = 47), compared to control individuals (n = 42) (P = 4.06 × 10−8). The sensitivity and specificity for the telomeric cfDNA qPCR assay was 91.49% and 76.19%, respectively. Furthermore, the telomeric cfDNA level distinguished even the Ductal Carcinoma In Situ (DCIS) group (n = 7) from the healthy group (n = 42) (P = 1.51 × 10−3). Taken together, decreasing plasma telomeric cfDNA levels could be an informative genetic biomarker for early breast cancer detection.
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    Altered Expression of Telomere-Associated Genes in Leukocytes among BRCA1 and BRCA2 Carriers
    (Wiley, 2018) Tanaka, Hiromi; Phipps, Elizabeth A.; Wei, Ting; Wu, Xi; Goswami, Chirayu; Liu, Yunlong; Sledge, George W., Jr.; Mina, Lida; Herbert, Brittney-Shea; Medical and Molecular Genetics, School of Medicine
    Telomere dysfunction resulting from telomere shortening and deregulation of shelterin components has been linked to the pathogenesis of age-related disorders, including cancer. Recent evidence suggests that BRCA1/2 (BRCA1 and BRCA2) tumor suppressor gene products play an important role in telomere maintenance. Although telomere shortening has been reported in BRCA1/2 carriers, the direct effects of BRCA1/2 haploinsufficiency on telomere maintenance and predisposition to cancer development are not completely understood. In this study, we assessed the telomere-associated and telomere-proximal gene expression profiles in peripheral blood leukocytes from patients with a BRCA1 or BRCA2 mutation, compared to samples from sporadic and familial breast cancer individuals. We found that 25 genes, including TINF2 gene (a negative regulator of telomere length), were significantly differentially expressed in BRCA1 carriers. Leukocyte telomere length analysis revealed that BRCA1/2 carriers had relatively shorter telomeres than healthy controls. Further, affected BRCA1/2 carriers were well differentiated from unaffected BRCA1/2 carriers by the expression of telomere-proximal genes. Our results link BRCA1/2 haploinsufficiency to changes in telomere length, telomere-associated as well as telomere-proximal gene expression. Thus, this work supports the effect of BRCA1/2 haploinsufficiency in the biology underlying telomere dysfunction in cancer development. Future studies evaluating these findings will require a large study population.
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    Cytochrome P450 Oxidoreductase (POR) Associated with Severe Paclitaxel-Induced Peripheral Neuropathy in Patients of European Ancestry from ECOG-ACRIN E5103
    (American Association for Cancer Research, 2023) Shen, Fei; Jiang, Guanglong; Philips, Santosh; Gardner, Laura; Xue, Gloria; Cantor, Erica; Ly, Reynold C.; Osei, Wilberforce; Wu, Xi; Dang, Chau; Northfelt, Donald; Skaar, Todd; Miller, Kathy D.; Sledge, George W.; Schneider, Bryan P.; Medicine, School of Medicine
    Purpose: Paclitaxel is a widely used anticancer therapeutic. Peripheral neuropathy is the dose-limiting toxicity and negatively impacts quality of life. Rare germline gene markers were evaluated for predicting severe taxane-induced peripheral neuropathy (TIPN) in the patients of European ancestry. In addition, the impact of Cytochrome P450 (CYP) 2C8, CYP3A4, and CYP3A5 metabolizer status on likelihood of severe TIPN was also assessed. Experimental design: Whole-exome sequencing analyses were performed in 340 patients of European ancestry who received a standard dose and schedule of paclitaxel in the adjuvant, randomized phase III breast cancer trial, E5103. Patients who experienced grade 3-4 (n = 168) TIPN were compared to controls (n = 172) who did not experience TIPN. For the analyses, rare variants with a minor allele frequency ≤ 3% and predicted to be deleterious by protein prediction programs were retained. A gene-based, case-control analysis using SKAT was performed to identify genes that harbored an imbalance of deleterious variants associated with increased risk of severe TIPN. CYP star alleles for CYP2C8, CYP3A4, and CYP3A5 were called. An additive logistic regression model was performed to test the association of CYP2C8, CYP3A4, and CYP3A5 metabolizer status with severe TIPN. Results: Cytochrome P450 oxidoreductase (POR) was significantly associated with severe TIPN (P value = 1.8 ×10-6). Six variants were predicted to be deleterious in POR. There were no associations between CYP2C8, CYP3A4, or CYP3A5 metabolizer status with severe TIPN. Conclusions: Rare variants in POR predict an increased risk of severe TIPN in patients of European ancestry who receive paclitaxel.
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    FASN regulates cellular response to genotoxic treatments by increasing PARP-1 expression and DNA repair activity via NF-κB and SP1
    (National Academy of Sciences, 2016-10-24) Wu, Xi; Dong, Zizheng; Wang, Chao J.; Barlow, Lincoln James; Fako, Valerie; Serrano, Moises A.; Zou, Yue; Liu, Jing-Yuan; Zhang, Jian-Ting; Department of Pharmacology and Toxicology, School of Medicine
    Fatty acid synthase (FASN), the sole cytosolic mammalian enzyme for de novo lipid synthesis, is crucial for cancer cell survival and associates with poor prognosis. FASN overexpression has been found to cause resistance to genotoxic insults. Here we tested the hypothesis that FASN regulates DNA repair to facilitate survival against genotoxic insults and found that FASN suppresses NF-κB but increases specificity protein 1 (SP1) expression. NF-κB and SP1 bind to a composite element in the poly(ADP-ribose) polymerase 1 (PARP-1) promoter in a mutually exclusive manner and regulate PARP-1 expression. Up-regulation of PARP-1 by FASN in turn increases Ku protein recruitment and DNA repair. Furthermore, lipid deprivation suppresses SP1 expression, which is able to be rescued by palmitate supplementation. However, lipid deprivation or palmitate supplementation has no effect on NF-κB expression. Thus, FASN may regulate NF-κB and SP1 expression using different mechanisms. Altogether, we conclude that FASN regulates cellular response against genotoxic insults by up-regulating PARP-1 and DNA repair via NF-κB and SP1.
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    The impact of SBF2 on taxane-induced peripheral neuropathy
    (PLOS, 2022-01-05) Cunningham, Geneva M.; Shen, Fei; Wu, Xi; Cantor, Erica L.; Gardner, Laura; Philips, Santosh; Jiang, Guanglong; Bales, Casey L.; Tan, Zhiyong; Liu, Yunlong; Wan, Jun; Fehrenbacher, Jill C.; Schneider, Bryan P.; Medical and Molecular Genetics, School of Medicine
    Taxane-induced peripheral neuropathy (TIPN) is a devastating survivorship issue for many cancer patients. In addition to its impact on quality of life, this toxicity may lead to dose reductions or treatment discontinuation, adversely impacting survival outcomes and leading to health disparities in African Americans (AA). Our lab has previously identified deleterious mutations in SET-Binding Factor 2 (SBF2) that significantly associated with severe TIPN in AA patients. Here, we demonstrate the impact of SBF2 on taxane-induced neuronal damage using an ex vivo model of SBF2 knockdown of induced pluripotent stem cell-derived sensory neurons. Knockdown of SBF2 exacerbated paclitaxel changes to cell viability and neurite outgrowth while attenuating paclitaxel-induced sodium current inhibition. Our studies identified paclitaxel-induced expression changes specific to mature sensory neurons and revealed candidate genes involved in the exacerbation of paclitaxel-induced phenotypes accompanying SBF2 knockdown. Overall, these findings provide ex vivo support for the impact of SBF2 on the development of TIPN and shed light on the potential pathways involved.
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    Passage number affects differentiation of sensory neurons from human induced pluripotent stem cells
    (Springer Nature, 2022-09-23) Cantor, Erica L.; Shen, Fei; Jiang, Guanglong; Tan, Zhiyong; Cunningham, Geneva M.; Wu, Xi; Philips, Santosh; Schneider, Bryan P.; Medicine, School of Medicine
    Induced pluripotent stem cells (iPSCs) are a valuable resource for neurological disease-modeling and drug discovery due to their ability to differentiate into neurons reflecting the genetics of the patient from which they are derived. iPSC-derived cultures, however, are highly variable due to heterogeneity in culture conditions. We investigated the effect of passage number on iPSC differentiation to optimize the generation of sensory neurons (iPSC-dSNs). Three iPSC lines reprogrammed from the peripheral blood of three donors were differentiated into iPSC-dSNs at passage numbers within each of the following ranges: low (5-10), intermediate (20-26), and high (30-38). Morphology and pluripotency of the parent iPSCs were assessed prior to differentiation. iPSC-dSNs were evaluated based on electrophysiological properties and expression of key neuronal markers. All iPSC lines displayed similar morphology and were similarly pluripotent across passage numbers. However, the expression levels of neuronal markers and sodium channel function analyses indicated that iPSC-dSNs differentiated from low passage numbers better recapitulated the sensory neuron phenotype than those differentiated from intermediate or high passage numbers. Our results demonstrate that lower passage numbers may be better suited for differentiation into peripheral sensory neurons.
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    Repositioning proton pump inhibitors as anticancer drugs by targeting the thioesterase domain of human fatty acid synthase
    (American Chemical Society, 2015-01-22) Fako, Valerie E.; Wu, Xi; Pflug, Beth; Liu, Jing-Yuan; Zhang, Jian-Ting; Department of Pharmacology and Toxicology, IU School of Medicine
    Fatty acid synthase (FASN), the enzyme responsible for de novo synthesis of free fatty acids, is up-regulated in many cancers. FASN is essential for cancer cell survival and contributes to drug resistance and poor prognosis. However, it is not expressed in most nonlipogenic normal tissues. Thus, FASN is a desirable target for drug discovery. Although different FASN inhibitors have been identified, none has successfully moved into clinical use. In this study, using in silico screening of an FDA-approved drug database, we identified proton pump inhibitors (PPIs) as effective inhibitors of the thioesterase activity of human FASN. Further investigation showed that PPIs inhibited proliferation and induced apoptosis of cancer cells. Supplementation of palmitate, the end product of FASN catalysis, rescued cancer cells from PPI-induced cell death. These findings provide new evidence for the mechanism by which this FDA-approved class of compounds may be acting on cancer cells.