Targeting hedgehog signalling

Yee, Peter Han-Chung (2014). Targeting hedgehog signalling PhD Thesis, Institute for Molecular Bioscience, The University of Queensland. doi:10.14264/uql.2014.308

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Author Yee, Peter Han-Chung
Thesis Title Targeting hedgehog signalling
School, Centre or Institute Institute for Molecular Bioscience
Institution The University of Queensland
DOI 10.14264/uql.2014.308
Publication date 2014
Thesis type PhD Thesis
Supervisor Brandon Wainwright
Richa Dave
Total pages 215
Total colour pages 60
Total black and white pages 155
Language eng
Subjects 111201 Cancer Cell Biology
060111 Signal Transduction
030405 Molecular Medicine
Formatted abstract
Hedgehog (Hh) signalling is important during embryonic development and adult tissue regeneration. Ectopic activation of Hh signalling leads to cancer formation and inhibitors of Hh signalling may be of therapeutic benefit. To date, studies have focused on the development of Smoothened (Smo) inhibitors, however these studies failed to address situations where Hh pathway activation occurs downstream of Smo. Here, we implemented a novel screening assay using the Gli-luciferase reporter expression in mammalian cells to identify antagonists and agonists of the Hh signalling pathway from a unique library of natural compounds derived from marine sponges. We have identified 18 inhibiting hits out of 504 extracts. Subsequent Gli-luciferase and quantitative RT-PCR (qRT-PCR) validation of these hits confirmed that three marine extract fractions resulted in down-regulation of downstream targets of Hh signalling, Ptch1 and Gli1. Further purifications of these fractions are anticipated to identify and characterise pure compounds with antagonistic activity. Additionally, in order to further define possible therapeutic intervention points we utilised siRNA knockdown using a phosphatase-siRNA library targeting 220 phosphatases to identify putative regulators of Hh signalling. We identified and validated via qRT-PCR six phosphatases that have negative and five phosphatases that have positive regulatory effects on the downstream effectors of Hh pathway. Interestingly, knockdown of Protein tyrosine phosphatase 1b (Ptp1b) demonstrated significant up-regulation of Hh target expression. In view of PTP1B’s growth inhibitory roles and its negative regulatory effect on Insulin, Leptin, IGF, EGF, PDGF receptors and oncogenic signalling, we hypothesise that PTP1B negatively regulates Hh pathway activity. Altogether, these studies will assist in the identification of new drug targets and development of better therapeutic agents to treat Hh-related cancers.
Keyword Antagonist
Hedgehog signaling
insulin like growth factor
Luciferase Assay
Marine sponges
RNA interference

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Created: Mon, 08 Sep 2014, 17:01:37 EST by Peter Yee on behalf of Scholarly Communication and Digitisation Service