theGunningGroup : research

Our research seeks to design and develop scaffolds to artificially suppress or up-regulate specific gene expression profiles via manipulation of protein-protein interactions, thereby inducing therapeutically-beneficial cellular responses in malfunctioning human cells. The proposed research seeks to validate whether protein function can be 'switched' on or off through artificial protein complexation by divalent conjugated small molecule 'hot spot' recognition agents. Molecular modulation of specific protein-protein interactions offers a dynamic approach to artificially regulating aberrant protein activity in human disease. A keen objective of the proposed work is to promote and illuminate the efficacy of developing novel drug-like scaffolds incorporating inorganic, as well as organic, functionality to achieve in vivo manipulation of cellular signaling.

Developing inhibitors of Signal Transducers and Activators of Transcription 3 (STAT3) protein complexes

Significant effort has been exerted to develop inhibitors of Stat3 function. The key structural and functional role played by Stat3's SH2 binding module has identified it as a prime target for therapeutic intervention. By effectively mimicking the native SH2 domain binding sequence, inhibitors have been shown to disrupt transcriptionally active Stat3:Stat3 homo-dimers and suppress its aberrant role in transformed cells. The structural diversity of Stat3 SH2 domain binders has been broad, including, peptides, metal complexes, natural products, peptidomimetics and small molecules. From this wealth of structural information, key functional groups have been identified as being important for inhibitory activity. However, to date there has been no effort to draw this spectrum of structural information together and develop a pharmacophore model for Stat3's SH2 domain. We aim to identify a Stat3 pharmacophore, summarizing the key structural facets required to illicit anti-Stat3 activity and correlate the observed activity with relative functional group positioning. Generating a Stat3 pharmacophore template will allow the rapid identification of future compounds suitable for Stat3 disruption. Moreover, in silico screening of chemical libraries and natural products against our pharmacophore template may yield new classes of Stat3 inhibitors.
Research Funding: NIH RO1 operating grant (2)

Artificial Protein-Membrane Anchorage

The objective of the proposed research is to use functionalized protein molecular recognition scaffolds to confer physical changes in oncogenic Signal Transducer and Activator of Transcription 3 (Stat3) protein characteristics and functionality. Our objective is to develop an entirely novel molecular therapeutic approach to inhibiting the aberrant activity of Stat3 protein in leukemia and lymphoma. An ingenious cellular mechanism of effecting protein localization is prenylation: the covalent attachment of a hydrophobic prenyl group to a protein that facilitates protein association with cell membranes. Prenylation sequesters proteins, such as Ras to the plasma membrane. We will explore whether oncogenic Stat3 protein can undergo artificial prenylation via high-affinity prenylated small-molecule binding agents. It is hypothesized that such systems could sequester Stat3 to the plasma membrane, inhibiting its nuclear localization (active state) and therefore its well-recognized aberrant function as a master regulator of events leading to the lymphoma phenotype. Stat3 binding modules will be synthetically functionalized with a number of membrane associative groups to facilitate protein-membrane anchorage and suppress the effects of oncogenic Stat3.
Research Funding: Leukemia Lymphoma Society of Canada operating grant
Research Funding: NSERC Discovery Grant

Developing SH2 Domain Proteomimetics - Novel Approach to Inhibiting Protein-Protein Interactions

Inhibition of cancer-promoting, constitutive protein-protein complexes via disruption of binding interfaces offers significant value as a molecular-targeted therapy. Protein-protein interactions are frequently initiated and maintained through phosphorylation of critical tyrosine (Y) or serine amino acid residues. Proteins containing key phosphorylated Y residues are often recognized and bound by specific phosphopeptide-binding modules, e.g. the Src Homology 2 (SH2) domain, of the complementary protein-binding partner. Despite there being two valid targets for the intervention of such interactions - the phosphopeptide and the phosphopeptide-binding module - the majority of effort has focused on the development of phosphopeptide mimetics. However, these agents typically incorporate phosphate groups, leading to pharmacokinetic drawbacks associated with their polarity and lability. It is surprising that, with the exception of one important example, there have been no reports of tackling the problem from the alternative direction; that is, through mimicry of the phosphopeptide-recognition module. We seek to determine whether oncogenic protein-protein complexes mediated by SH2 domain-phosphotyrosine (pY) interactions can be disrupted by replicating the function of the SH2 domain in small molecules.
Research Funding: Leukemia & Lymphoma Society of Canada operating grant
Research Funding: NSERC Discovery Grant

Developing Inhibitors of Myc-Max Protein-Protein Interactions

The Myc oncogene is dysregulated in over 50% of all human cancers and regulates the transcription of cell survival and growth genes. Targeting aberrant Myc activity offers a novel route to targeting human cancers. A growing body of biological evidence implicating Myc in cancer suggests that therapeutics targeting Myc transcriptional activity is highly desirable. Myc is a tantalizing target for small molecule disruptors.

Inhibiting Ubiqutin Activating Enzyme1 (Uba1)

Dr. Aaron D. Schimmer (Princess Margaret Hospital) has recently identified the Ubiquitin E1 activating enzyme, Uba1, as an exciting and valid target for the development of novel cancer therapeutics. Dr. Schimmer showed that inhibiting Uba1 preferentially induced cell death in malignant cells over normal cells and delayed tumor growth in leukemia xenographs. Thus, inhibiting Uba1 represents a new therapeutic strategy to target the proteosomal degradation pathway and kill cancer cells. In collaboration with Dr. Schimmer, our goal is to develop inhibitors of Uba1 via a rational drug design program, explore the mechanisms by which our inhibitors induce cell death and determine the basis for cancer cell selectivity.