Identification of approved and investigational drugs that inhibit hypoxia-inducible factor-1 signaling.

One of the requirements for tumor development is blood supply, most often driven by hypoxia-induced angiogenesis. Hypoxia induces the stabilization of hypoxia-inducible factor-1 alpha (HIF-1α), which induces expression of an angiogenic factor, vascular endothelial growth factor (VEGF). The purpose of this study is to validate a new screening platform combined with orthogonal assays to rapidly identify HIF-1 inhibitors and to evaluate the effectiveness of approved drugs on modulating HIF-1 signaling. We generated an endogenous HIF-1α-NanoLuc luciferase reporter allele in the human HCT116 colon cancer cell line using genome editing and screened a panel of small interfering RNAs (siRNAs) to 960 druggable targets and approximately 2,500 drugs on a quantitative high-throughput screening (qHTS) platform. Selected compounds were further investigated with secondary assays to confirm their anti-HIF activity and to study their mode of action. The qHTS assay identified over 300 drugs that inhibited HIF-1α-NanoLuc expression. The siRNA screening results supported the effectiveness of several target-specific inhibitors. Moreover, the identified HIF-1 inhibitors, such as mycophenolate mofetil, niclosamide, and trametinib, were able to suppress cancer cell proliferation and angiogenesis. Our study indicates that blocking the mitogen-activated protein kinase (MAPK) and phosphoinositol 3-kinase (PI3K) pathways effectively inhibits hypoxia-induced HIF-1α accumulation and HIF-1α transactivation and that proteasome inhibitors induce accumulation and decrease transcriptional activity of HIF-1α. These findings underline the importance of developing a battery of robust assay platforms and confirmation studies that focus on endogenous protein targets so that only relevant and reliable data will be taken into pre-clinical and clinical studies.

Identification of HDAC Inhibitors Using a Cell-Based HDAC I/II Assay.

Histone deacetylases (HDACs) are a class of epigenetic enzymes that regulate gene expression by histone deacetylation. Altered HDAC function has been linked to cancer and neurodegenerative diseases, making HDACs popular therapeutic targets. In this study, we describe a screening approach for identification of compounds that inhibit endogenous class I and II HDACs. A homogeneous, luminogenic HDAC I/II assay was optimized in a 1536-well plate format in several human cancer cell lines, including HCT116 and human neural stem cells. The assay confirmed 37 known HDAC inhibitors from two libraries of known epigenetics-active compounds. Using the assay, we identified a group of potential HDAC inhibitors by screening the National Center for Advancing Translational Sciences (NCATS) Pharmaceutical Collection of 2527 small-molecule drugs. The selected compounds showed similar HDAC I/II inhibitory potency and efficacy values in both HCT116 and neural stem cells. Several previously unidentified HDAC inhibitors were further evaluated and profiled for their selectivity against a panel of 10 HDAC I/II isoforms using fluorogenic HDAC biochemical assays. In summary, our results show that several novel HDAC inhibitors, including nafamostat and piceatannol, have been identified using the HDAC I/II cell-based assay, and multiple cell types have been validated for high-throughput screening of large chemical libraries.

Induced pluripotent stem cell transplantation in the treatment of porcine chronic myocardial ischemia.

BACKGROUND: This study was designed to test the effects of induced pluripotent stem cell (iPSC) in the treatment of chronic myocardial ischemia. METHODS: The reprogramming of passage 3 myocardial fibroblasts was performed by using the lentiviral vector containing 4 human factors: OCT4, SOX2, KLF4, and c-MYC. The iPSC colonies at P12-17 were allogeneically transplanted into ischemic myocardium of 10 swine by direct injection. Cohorts of 2 animals were sacrificed at 2, 4, 6, 8, and 12 weeks after injection. RESULTS: No signs of graft versus host disease were evident at any time points. At 2 weeks, clusters of SSEA-4-positive iPSCs were detected in the injected area. At 4 to 8 weeks, these cells started to proliferate into small spheres surrounded by thin capsules. At 12 weeks the cell clusters still existed, but decreased in size and numbers. The cells inside these masses were homogeneous with no sign of differentiation into any specific lineage. Increased smooth muscle actin or vWF positive cells were found inside and around the iPSC clusters, compared with non-injected areas. By real-time polymerase chain reaction, the levels of VEGF, basic FGF, and ANRT expression were significantly higher in the iPSC-treated myocardium compared with untreated areas. These results suggest that iPSCs contributed to angiogenesis. CONCLUSIONS: Allogeneically transplanted pig iPSCs proliferated despite an ischemic environment in the first 2 months and survived for at least 3 months in immunocompetent hosts. Transplanted iPSCs were also proangiogenic and thus might have beneficial effects on the ischemic heart diseases.