ANGIOPOIETINS · Rational and Combinatorial Engineering of Antagonistic Angiopoietin Variants as Tools for Cancer Imaging and Therapy

Rational and Combinatorial Engineering of Antagonistic Angiopoietin Variants as Tools for Cancer Imaging and Therapy

Many cancer diagnostics and medications work solely to target capillary vessels and prevent cancer cells from creating new capillaries, chocking off their much-needed blood and nutrient supply to halt the growth of tumors and slow down cancer spread. In our study, we are creating a new type of engineered protein that will be significantly more effective at preventing blood vessel formation (angiogenesis) and cancer spread (metastasis) by targeting multiple receptors that control these processes. Since activation of my CIG award, we were able to engineer a protein-based platform, namely angiopoietin, with potential to bind with high affinity to Tie2 - a highly important chemical receptor expressed on the tumor vasculature. To achieve this goal, we adopted several mutagenesis approaches to introduce diversity into several domains within the angiopoietin protein scaffold, and utilized different library screening methods to obtain protein variants that bind to the desired Tie2 receptor with high affinity and specificity. In pursuit of the first aim of my proposal, the platform we developed was extended to engineer bispecific angiopoietin proteins that bind to both Tie2 and integrins. Upon completion of this aim, we have identified new classes of engineered, multispecific angiopoietin proteins against two important cancer cells and vasculature receptors for testing as molecular imaging agents and in cancer targeting applications. These mono- and bi-specific cancer-targeting drugs are expected to show high potency in inhibiting cancer progression and spread. Our success in the current project will provide proof-of-principle for this innovative approach, which in the future may be widely applicable to the development of diverse protein-based drugs and diagnostics for different types of cancer. The currently dismal prognosis of cancer when using traditional therapies (i.e., surgery, radiation therapy and hormone manipulation) and diagnostic agents (i.e., monoclonal antibodies and small molecules) is dictated by their specific limitations. However, a novel approach guided by translational research has great potential to transcend the shortcomings of the conventional cancer protocol. The new translational research strategy proposed here is ideally suited to patients with intermediate and high-risk factors for treatment failure, particularly patients with lymph node metastasis. Our goal, therefore, was to develop antagonistic, bispecific angiopoietin protein ligands that are able to simultaneously diagnose and treat two different expression products (Tie2 ans integrins) of the tumor and its vasculature (blood and lymphatic vessels). As a result, they should have higher selectivity and they are much more able than traditional, non-selective treatment strategies, to specifically target primary tumors and their lymph node metastases. Such dual targeting and improved specificity are particularly important in cancer, because the interaction of Tie2-expressing tumor cells with lymphatic endothelial cells (LECs) via Tie2 modulates LEC behavior and is related to the ability of tumor cells to form lymph node metastasis. The timely detection of lymph node metastasis is of major prognostic significance for cancer because those with lymph node metastases exhibit poor prognoses characterized by significantly decreased disease-specific and biochemical recurrence-free survival rates. As cancer therapeutics, the engineered ligands we have developed have the potential to introduce novel and more potent anti-cancer activities to the fight against cancer, to lower the costs of therapies, and to facilitate the development of new therapeutic and/or diagnostic regimens that are more efficacious than the conventional mixtures of two monoclonal antibodies or small molecules. Our carefully designed study using this multi-targeting translational strategy has great potential to improve clinical outcome, tumor kill, and normal tissue tolerance within the framework of cancer patient care. In particular, our strategy will show a clear clinical benefit in patients with advanced cancer and the correspondingly high expression levels of multiple cancer targets (Tie2 and integrins). Our proposed therapy will likely mature to target other cancer receptors and signaling pathways and pathways involved in cancer angiogenesis, cell-cell adhesion, and cell cycle manipulation (using angiopoetin-small molecule conjugates). Taken together, this new form of therapy has the potential to become integral part of the care regimen of cancer patients and it may also redefine the role of traditional management. Further research will be needed to identify the molecular relationships that characterize this new therapy and to define how it will be integrated with traditional management.

Data: CORDIS, © European Union