Browsing by Subject "Deoxycytidine"

Now showing 1 - 7 of 7
  • Thumbnail Image
    Item
    14-3-3σ regulation of and interaction with YAP1 in acquired gemcitabine resistance via promoting ribonucleotide reductase expression
    (Impact Journals, LLC, 2016-04-05) Qin, Li; Dong, Zizheng; Zhang, Jian-Ting; Department of Pharmacology and Toxicology, IU School of Medicine
    Gemcitabine is an important anticancer therapeutics approved for treatment of several human cancers including locally advanced or metastatic pancreatic ductal adenocarcinoma (PDAC). Its clinical effectiveness, however, is hindered by existence of intrinsic and development of acquired resistances. Previously, it was found that 14-3-3σ expression associates with poor clinical outcome of PDAC patients. It was also found that 14-3-3σ expression is up-regulated in gemcitabine resistant PDAC cells and contributes to the acquired gemcitabine resistance. In this study, we investigated the molecular mechanism of 14-3-3σ function in gemcitabine resistance and found that 14-3-3σ up-regulates YAP1 expression and then binds to YAP1 to inhibit gemcitabine-induced caspase 8 activation and apoptosis. 14-3-3σ association with YAP1 up-regulates the expression of ribonucleotide reductase M1 and M2, which may mediate 14-3-3σ/YAP1 function in the acquired gemcitabine resistance. These findings suggest a possible role of YAP1 signaling in gemcitabine resistance.
  • Thumbnail Image
    Item
    DUSP1 Is a Novel Target for Enhancing Pancreatic Cancer Cell Sensitivity to Gemcitabine
    (Public Library of Science, 2014-01-07) Liu, Fang; Gore, A. Jesse; Wilson, Julie L.; Korc, Murray; Medicine, School of Medicine
    Pancreatic ductal adenocarcinoma (PDAC) is a deadly cancer with a poor prognosis that is characterized by excessive mitogenic pathway activation and marked chemoresistance to a broad spectrum of chemotherapeutic drugs. Dual specificity protein phosphatase 1 (DUSP1) is a key negative regulator of mitogen activated protein kinases (MAPKs). Yet, DUSP1 is overexpressed in pancreatic cancer cells (PCCs) in PDAC where it paradoxically enhances colony formation in soft agar and promotes in vivo tumorigenicity. However, it is not known whether DUSP1 overexpression contributes to PDAC chemoresistance. Using BxPC3 and COLO-357 human PCCs, we show that gemcitabine activates c-JUN N-terminal kinase (JNK) and p38 mitogen activated protein kinase (p38 MAPK), key kinases in two major stress-activated signaling pathways. Gemcitabine-induced JNK and p38 MAPK activation mediates increased apoptosis, but also transcriptionally upregulates DUSP1, as evidenced by increased DUSP1 mRNA levels and RNA polymerase II loading at DUSP1 gene body. Conversely, shRNA-mediated inhibition of DUSP1 enhances JNK and p38 MAPK activation and gemcitabine chemosensitivity. Using doxycycline-inducible knockdown of DUSP1 in established orthotopic pancreatic tumors, we found that combining gemcitabine with DUSP1 inhibition improves animal survival, attenuates angiogenesis, and enhances apoptotic cell death, as compared with gemcitabine alone. Taken together, these results suggest that gemcitabine-mediated upregulation of DUSP1 contributes to a negative feedback loop that attenuates its beneficial actions on stress pathways and apoptosis, raising the possibility that targeting DUSP1 in PDAC may have the advantage of enhancing gemcitabine chemosensitivity while suppressing angiogenesis.
  • Thumbnail Image
    Item
    Expression of DNA Translesion Synthesis Polymerase η in Head and Neck Squamous Cell Cancer Predicts Resistance to Gemcitabine and Cisplatin-Based Chemotherapy
    (Public Library of Science, 2013-12-20) Zhou, Wendi; Chen, Yih-wen; Liu, Xiyong; Chu, Peiguo; Loria, Sofia; Wang, Yafan; Yen, Yun; Chou, Kai-Ming; Pharmacology and Toxicology, School of Medicine
    Purpose: The development of resistance against anticancer drugs has been a persistent clinical problem for the treatment of locally advanced malignancies in the head and neck mucosal derived squamous cell carcinoma (HNSCC). Recent evidence indicates that the DNA translesion synthesis (TLS) polymerase η (Pol η; hRad30a gene) reduces the effectiveness of gemcitabine/cisplatin. The goal of this study is to examine the relationship between the expression level of Pol η and the observed resistance against these chemotherapeutic agents in HNSCC, which is currently unknown. Methods: Sixty-four mucosal derived squamous cell carcinomas of head and neck (HNSCC) from 1989 and 2007 at the City of Hope National Medical Center (Duarte, CA) were retrospectively analyzed. Pretreatment samples were immunostained with anti-Pol η antibody and the correlation between the expression level of Pol η and clinical outcomes were evaluated. Forty-nine cases treated with platinum (n=40) or gemcitabine (n=9) based chemotherapy were further examined for Pol η expression level for comparison with patient response to chemotherapy. Results: The expression of Pol η was elevated in 67% of the head and neck tumor samples. Pol η expression level was significantly higher in grade 1 to grade 2 tumors (well to moderately differentiated). The overall benefit rate (complete response+ partial response) in patients treated with platinum and gemcitabine based chemotherapy was 79.5%, where low Pol η level was significantly associated with high complete response rate (p=0.03), although not associated with overall survival. Furthermore, no significant correlation was observed between Pol η expression level with gender, age, tobacco/alcohol history, tumor stage and metastatic status. Conclusions: Our data suggest that Pol η expression may be a useful prediction marker for the effectiveness of platinum or gemcitabine based therapy for HNSCC.
  • Thumbnail Image
    Item
    Integrated stress response is critical for gemcitabine resistance in pancreatic ductal adenocarcinoma
    (Nature Publishing Group, 2015) Palam, L. R.; Gore, J.; Craven, K. E.; Wilson, J. L.; Korc, M.; Department of Medicine, IU School of Medicine
    Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer with marked chemoresistance and a 5-year survival rate of 7%. The integrated stress response (ISR) is a cytoprotective pathway initiated in response to exposure to various environmental stimuli. We used pancreatic cancer cells (PCCs) that are highly resistant to gemcitabine (Gem) and an orthotopic mouse model to investigate the role of the ISR in Gem chemoresistance. Gem induced eIF2 phosphorylation and downstream transcription factors ATF4 and CHOP in PCCs, and these effects occurred in an eIF2α-S51 phosphorylation-dependent manner as determined using PANC-1 cells, and wild type and S51 mutant mouse embryo fibroblasts. Blocking the ISR pathway in PCCs with the ISR inhibitor ISRIB or siRNA-mediated depletion of ATF4 resulted in enhanced Gem-mediated apoptosis. Polyribosomal profiling revealed that Gem caused repression of global translation and this effect was reversed by ISRIB or by expressing GADD34 to facilitate eIF2 dephosphorylation. Moreover, Gem promoted preferential mRNA translation as determined in a TK-ATF4 5'UTR-Luciferase reporter assay, and this effect was also reversed by ISRIB. RNA-seq analysis revealed that Gem upregulated eIF2 and Nrf2 pathways, and that ISRIB significantly inhibited these pathways. Gem also induced the expression of the antiapoptotic factors Nupr1, BEX2, and Bcl2a1, whereas ISRIB reduced their expression. In an orthotopic tumor model using PANC-1 cells, ISRIB facilitated Gem-mediated increases in PARP cleavage, which occurred in conjunction with decreased tumor size. These findings indicate that Gem chemoresistance is enhanced by activating multiple ISR-dependent pathways, including eIF2, Nrf2, Nupr1, BEX2, and Bcl2A1. It is suggested that targeting the ISR pathway may be an efficient mechanism for enhancing therapeutic responsiveness to Gem in PDAC.
  • Thumbnail Image
    Item
    Randomized Phase II Study of Nab-Paclitaxel and Gemcitabine With or Without Tocilizumab as First-Line Treatment in Advanced Pancreatic Cancer: Survival and Cachexia
    (Wolters Kluwer, 2025) Chen, Inna M.; Johansen, Julia S.; Theile, Susann; Silverman, Libbie M.; Pelz, Katherine R.; Madsen, Kasper; Dajani, Olav; Lim, Kevin Z. M.; Lorentzen, Torben; Gaafer, Omnia; Koniaris, Leonidas G.; Ferreira, Anna C.; Neelon, Brian; Guttridge, Denis C.; Ostrowski, Michael C.; Zimmers, Teresa A.; Nielsen, Dorte; Surgery, School of Medicine
    Purpose: This randomized phase-II trial (ClinicalTrials.gov identifier: NCT02767557) compared efficacy of gemcitabine/nab-paclitaxel (Gem/Nab) with or without the anti-interleukin-6 (IL-6) receptor antibody tocilizumab (Toc) for advanced pancreatic cancer (PC). Methods: A safety cohort received Gem 1,000 mg/m2 and Nab 125 mg/m2 on days 1, 8, and 15, and Toc 8 mg/kg on day 1 for each 28-day cycle. Participants with modified Glasgow prognostic scores of 1 or 2 were randomly assigned 1:1 to receive Gem/Nab/Toc or Gem/Nab. The primary end point was the overall survival (OS) rate at 6 months (OS6). Secondary end points were progression-free survival (PFS), overall response rate (ORR), and safety. Exploratory end points were cachexia, quality of life, and biomarkers, including the cachexia-promoting protein, growth differentiation factor 15 (GDF15). Results: Overall, 147 patients were treated, including six safety cohort participants. The median follow-up period was 8.1 months (IQR, 4.2-13.9). OS6 was 68.6% (95% CI, 56.3 to 78.1) for the Gem/Nab/Toc group and 62.0% (49.6-72.1) for the Gem/Nab group (P = .409). OS for Gem/Nab/Toc versus Gem/Nab improved at 18 months (27.1% v 7.0%, P = .001). No differences in median OS, PFS, or ORR were observed. Incidence of grade-3+ treatment-related adverse events (TrAEs) was 88.1% for Gem/Nab/Toc and 63.4% for Gem/Nab (P < .001). Gem/Nab/Toc decreased muscle loss versus Gem/Nab, with median change +0.1013% versus -3.430% (P = .0012) at 2 months and +0.7044 versus -3.353% (P = .036) at 4 months. Incidence of muscle loss was 43.48% on Gem/Nab/Toc versus 73.52% on Gem/Nab at 2 months (P = .0045) and 41.82% versus 68.75% (P = .0062) at 4 months. GDF15 was not changed by Gem/Nab or Gem/Nab/Toc. Conclusion: Although the primary end point was not met and TrAEs were increased by Toc, increased survival at 18 months and reduced muscle wasting support an anticachexia effect of IL-6 blockade independent of GDF15. Further studies could leverage these findings for precision anticachexia therapy.
  • Thumbnail Image
    Item
    Reversible epigenetic regulation of 14-3-3σ expression in acquired gemcitabine resistance by uhrf1 and DNA methyltransferase 1
    (American Society for Pharmacology & Experimental Therapeutics (ASPET), 2014-11) Qin, Li; Dong, Zizheng; Zhang, Jian-Ting; Department of Pharmacology and Toxicology, IU School of Medicine
    Although gemcitabine is the most commonly used drug for treating pancreatic cancers, acquired gemcitabine resistance in a substantial number of patients appears to hinder its effectiveness in successful treatment of this dreadful disease. To understand acquired gemcitabine resistance, we generated a gemcitabine-resistant pancreatic cancer cell line using stepwise selection and found that, in addition to the known mechanisms of upregulated expression of ribonucleotide reductase, 14-3-3σ expression is dramatically upregulated, and that 14-3-3σ overexpression contributes to the acquired resistance to gemcitabine and cross-resistance to cytarabine. We also found that the increased 14-3-3σ expression in the gemcitabine-resistant cells is due to demethylation of the 14-3-3σ gene during gemcitabine selection, which could be partially reversed with removal of the gemcitabine selection pressure. Most importantly, the reversible methylation/demethylation of the 14-3-3σ gene appears to be carried out by DNA methyltransferase 1 under regulation by Uhrf1. These findings suggest that the epigenetic regulation of gene expression may play an important role in gemcitabine resistance, and that epigenetic modification is reversible in response to gemcitabine treatment.
  • Thumbnail Image
    Item
    Tissue Transglutaminase Activates Cancer-Associated Fibroblasts and Contributes to Gemcitabine Resistance in Pancreatic Cancer
    (Elsevier, 2016-11) Lee, Jiyoon; Yakubov, Bakhtiyor; Ivan, Cristina; Jones, David R.; Caperell-Grant, Andrea; Fishel, Melissa; Cardenas, Horacio; Matei, Daniela; Department of Otolaryngology--Head & Neck Surgery, School of Medicine
    Resistance to chemotherapy is a hallmark of pancreatic ductal adenocarcinoma (PDA) and has been partly attributed to the dense desmoplastic stroma, which forms a protective niche for cancer cells. Tissue transglutaminase (TG2), a Ca(2+)-dependent enzyme, is secreted by PDA cells and cross-links proteins in the tumor microenvironment (TME) through acyl-transfer between glutamine and lysine residues, promoting PDA growth. The objective of the current study was to determine whether secreted TG2 by PDA cells alters the response of pancreatic tumors to gemcitabine. Orthotopic pancreatic xenografts and co-culture of PDA and stromal cells were employed to determine the mechanisms by which TG2 alters tumor-stroma interactions and response to gemcitabine. Analysis of the pancreatic The Cancer Genome Atlas (TCGA) database demonstrated that increased TG2 expression levels correlate with worse overall survival (hazard ratio=1.37). Stable TG2 knockdown in PDA cells led to decreased size of pancreatic xenografts and increased sensitivity to gemcitabine in vivo. However, TG2 downregulation did not increase cytotoxicity of gemcitabine in vitro. Additionally, multivessel density and gemcitabine uptake in pancreatic tumor tissue, as measured by mass spectrometry (MS-HPLC), were not significantly different in tumors expressing TG2 versus tumors in which TG2 was knocked down. Fibroblasts, stimulated by TG2 secreted by PDA cells, secrete laminin A1, which protects cancer cells from gemcitabine-induced cytotoxicity. In all, our results demonstrate that TG2 secreted in the pancreatic TME orchestrates the cross talk between cancer cells and stroma, impacting tumor growth and response to chemotherapy. Our study supports TG2 inhibition to increase the antitumor effects of gemcitabine in PDA.