Protein Tyrosine Dephosphorylation & Signal Transduction

PROJECT SUMMARY/ ABSTRACT The first drugs directed against protein tyrosine kinases (PTKs) have now entered the market and represent breakthroughs in the treatment of cancer; however, challenges remain, including the fact that patients develop resistance to such drugs. Alternative approaches, to target simultaneously different signaling enzymes and events, are required. The protein tyrosine phosphatases (PTPs), which work in combination with the PTKs, have been garnering attention as potential therapeutic targets. Despite major programs in industry focused on developing small molecule PTP inhibitors, technical challenges arising from the chemical properties of the PTP active site have frustrated such efforts. Consequently, they remain a largely untapped resource for drug development. Nevertheless, the extensive biological validation of PTPs emphasizes the importance of discovering new approaches to inhibitor development. This grant, currently in Year 28, focuses on a functional analysis of specific PTPs in models of cancer. The hypothesis to be tested is that PTPs function as specific regulators of tyrosine phosphorylation-dependent signaling pathways and thus manipulation of their function in cell and animal models will reveal new insights into the critical signaling events that underlie the disease. The overall goal is to define functional links between particular PTPs and specific signaling pathways in cancer, with a view to establishing how disruption of such functions affects the etiology of the disease and to reveal novel therapeutic targets from among the PTPs themselves or from the signaling pathways they regulate. In the previous funding period, major breakthroughs were achieved in several aspects of the project: (1) New and improved allosteric inhibitors of PTP1B, including molecules that chelate copper specifically, were developed, creating opportunities to exploit a novel vulnerability in cancer; (2) Identification of PTP1B inhibitors that are cytotoxic to Herceptin-resistant cells; (3) Demonstration that PTP1B inhibitors prevent fatality in the TRALI model of Acute Respiratory Distress Syndrome, attenuating neutrophil activation and formation of NETs, suggesting novel opportunities for therapeutic intervention in cancer; (4) Integration of BioID MS with substrate-trapping mutant PTPs to enhance substrate trapping technology and generate new insights into the function of PTP1B in Herceptin-resistant cells, illustrating an approach can now be applied to the PTP family as a whole to validate new therapeutic targets. Building on the unique and innovative approaches developed during previous funding periods, this proposal assembles a strong team of collaborators to address the following Specific Aims, which represent a logical development of progress to date: 1: To define the mechanism by which PTP1B represents a point of vulnerability in Herceptin-resistant cells. 2: To validate copper chelation and PTP1B inhibition as a new avenue to cancer therapy 3: To define the mechanism by which PTP1B regulates the formation of Neutrophil Extracellular Traps (NETs) and to investigate how this may be exploited therapeutically in a cancer context. 4: Application of Substrate-Trapping/BioID technology to define PTP function in cancer models.