Virtual Library

Start Your Search

Y. Wang



Author of

  • +

    MINI 37 - SCLC Therapy (ID 165)

    • Event: WCLC 2015
    • Type: Mini Oral
    • Track: Small Cell Lung Cancer
    • Presentations: 1
    • +

      MINI37.01 - Chk1 Inhibition Enhances Cisplatin Cytotoxicity Regardless of p53 Status in Human Small Cell Lung Cancer Cells (ID 947)

      18:30 - 20:00  |  Author(s): Y. Wang

      • Abstract
      • Presentation
      • Slides

      Background:
      Small cell lung cancer (SCLC) has a poor prognosis and harbors complex genetic alterations including frequent loss-of-function mutations of p53 and Rb, which impair the G1/S checkpoint control. Checkpoint Kinase 1 (Chk1) is a vital serine/threonine specific protein kinase responsible for halting the cell cycle in check after DNA damage. With abrogation of Chk1-mediated cell cycle checkpoint control, cancer cells may enter mitosis with extensive DNA damage leading to mitotic catastrophe and apoptotic cell death. Previous in vitro studies showed that p53 deficient cancer cells benefit from Chk1 inhibition. Here we demonstrate that a combination of Chk1 inhibition and cisplatin causes more growth inhibition and caspase activation in SCLC cell lines compared to cisplatin alone, regardless of p53 status.

      Methods:
      Chk1 inhibition was achieved by siRNA knockdown (Qiagen) and AZD7762 (Selleckchem) in p53 mutant SCLC cell lines (GLC4, NCI-H82) and p53 intact SCLC cell lines (NCI-H128, NCI-H209). Cell viability was measured by Cell-Titer Glo assay (Promega) after 72hrs of drug treatment. Synergism was defined by combination index (CI)>1 using the Chou-Talalay method. Cell cycle analysis was performed by PI staining and detected by FACS. Western blotting and immunofluorescent staining were used to evaluate caspase activation and other signaling proteins.

      Results:
      SCLC cell lines were treated with cisplatin 24hrs at each IC50 dosage after Chk1 siRNA transfection. In GLC4 after 2.5uM cisplatin treatment, cell viabilities of control siRNA-treated and Chk1 siRNA-treated cells were 28% and 10.6% (p=0.006, by paired t-test), respectively. Similar significant reduction of cell viability was observed in 1uM cisplatin-treated NCI-H82 cells (44.6% vs. 29.7%; p=0.0632) and in 3uM cisplatin-treated NCI-H128 cells (62.5% vs. 45.3%; p=0.0155), respectively. More cleaved caspase-2 and caspase-3 were noted in Chk1 knockdown plus cisplatin-treated GLC4 cells than in cisplatin alone. The IC50 (72hrs) of single agent AZD7762 (Chk1 inhibitor) treatment was 240nM, 211nM, 266nM and 215nM in GLC4, NCI-H82, NCI-H128 and NCI-H209 respectively. The combination indexes of AZD7762 and cisplatin (both given at around IC50s) calculated by Chou-Talalay method indicated synergism in all these 4 cell lines. Cell cycle analysis revealed that AZD7762 abrogated cisplatin-induced G2/M arrest in GLC4 and G1 arrest in NCI-H128. Inhibition Chk1 by AZD7762 was associated with reduction of CDC25C and CDC2 phosphorylation. Phospho-Histone H3 (mitotic marker) was increased in AZD7762 and cisplatin combined treatment compared to cisplatin alone in a p53 independent fashion. Intriguingly, inhibition of Chk1 by AZD7762 alone in GLC4 cells activated caspase-2.

      Conclusion:
      Chk1 inhibition both by siRNA knockdown and AZD7762 enhances cisplatin cytotoxicity. The synergism was primarily due to increased apoptosis and abolished cell cycle arrest. Although p53 is frequently mutated in SCLC, growth inhibition was seen in a p53 independent manner. In GLC4, single agent AZD7762 treatment can cause caspase-2 activation through an as yet unidentified mechanism. Our findings suggest that Chk1 is a potential therapeutic target in small cell lung cancer and is synergistic with chemotherapy. The effects of Chk1 inhibitor and its combination with chemotherapy agents in SCLC animal models are currently underway.

      Only Members that have purchased this event or have registered via an access code will be able to view this content. To view this presentation, please login, select "Add to Cart" and proceed to checkout. If you would like to become a member of IASLC, please click here.

      Only Active Members that have purchased this event or have registered via an access code will be able to view this content. To view this presentation, please login or select "Add to Cart" and proceed to checkout.

  • +

    ORAL 40 - Biology 1 (ID 154)

    • Event: WCLC 2015
    • Type: Oral Session
    • Track: Thymoma, Mesothelioma and Other Thoracic Malignancies
    • Presentations: 1
    • +

      ORAL40.07 - Xpo1 Inhibition: A Promising Therapeutic Strategy in Thymic Epithelial Tumors (ID 1230)

      16:45 - 18:15  |  Author(s): Y. Wang

      • Abstract
      • Presentation
      • Slides

      Background:
      Growing evidence suggests that nuclear–cytoplasmic transport is frequently dysregulated in cancer cells, and is involved in promoting carcinogenesis, cell survival, drug resistance and tumor progression. In particular, enhanced nuclear export is one mechanism by which malignant cells inactivate tumor suppressor proteins (TSPs). Inhibition of XPO1 (CRM1), the main karyopherin involved in the nuclear export of TSPs, restores nuclear localization and function of TSPs in several preclinical models. Selinexor(KPT-330) is an XPO1 inhibitor being tested clinically in solid tumors and hematological malignancies that showed some activity in patients with thymic epithelial tumors (TETs). Here, we describe the activity of selinexor in preclinical models of TETs.

      Methods:
      Thymoma (IU-Tab1, T1682), thymic carcinoma (Ty82, T1889, MP57) and immortalized normal thymic epithelial cells (TEC84) treated with selinexor or vehicle were assayed by CellTiter-Glo and flow cytometry. Western blot analysis of nuclear and cytoplasmic protein fractions and immunofluorescence assays were used to study the cellular sublocalization of XPO1 cargoes before and after treatment. The effect of selinexor on cell migration was determined using a wound-healing assay. A selixinor-resistant cell line was generated by growing selinexor-sensitive IU-Tab1 cells at increasing concentrations of the drug. Mutational status and copy number of the XPO1 gene was assessed by Q- PCR and Sanger sequencing.

      Results:
      All TET cell lines were sensitive to selinexor (IC~50~ 90-250 nM) with the exception of T1682 (thymoma type B), which showed intrinsic drug resistance (IC~50~ > 1000 nM). In the sensitive cell lines, selinexor treatment induced G1 (MP57) or G2 (IU-Tab1, Ty82) cell-cycle arrest at 24 hours, and induced apoptosis 2-5 fold over untreated cells by 72 hours. The cytotoxic effects of selinexor were not observed in immortalized normal TEC84 cells at nanomolar concentrations, and required higher concentrations (IC~50 ~800nM) to induce a cytostatic effect. Drug treatment led to increased nuclear concentrations of several TSPs involved in cell cycle regulation (e.g. p21, p27), genomic stability (p53) and induction of apoptosis (FOXO3a) and also reduced the total cellular expression of the oncogenic protein NF-kB. These results were confirmed with siRNA knockdown of XPO1. In addition,selinexor treatment impaired tumor cell migration and had cytotoxic synergistic effect in combination with doxorubicin or etoposide in T1889 and IU-Tab1 cell lines, increasing nuclear accumulation of the XPO1 cargo protein, Topoisomerase IIα. Furthermore, we demonstrated that selinexor-resistant cell line has similar growth rates to their parental cells, however overexpress XPO1 due to gene amplification, confirming the importance of aberrant XPO1 activity in TET survival.

      Conclusion:
      Our data show the importance of XPO1 in TETs biology and demonstrate activity of selinexor in preclinical models, further supporting the planned Phase II trial in patients with TETs.

      Only Members that have purchased this event or have registered via an access code will be able to view this content. To view this presentation, please login, select "Add to Cart" and proceed to checkout. If you would like to become a member of IASLC, please click here.

      Only Active Members that have purchased this event or have registered via an access code will be able to view this content. To view this presentation, please login or select "Add to Cart" and proceed to checkout.