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Targeting TRAIL death receptor 4 with trivalent DR4 Atrimer complexes
Joshua E Allen1, Roger Ferrini, David T Dicker
1Penn State Milton S. Hershey Medical Center and Cancer Institute, 500 University Drive CH046, Office T4423 Hershey, PA 17033, USA.
Abstract:
TRAIL is a trimeric protein that potently induces apoptosis in cancer cells by binding to the trimeric death receptors (DR4 or DR5). Death receptors are attractive therapeutic targets through both the recombinant TRAIL ligand as well as receptor agonist monoclonal antibodies. Although efficacy of the ligand is hampered by its short half-life, agonistic antibodies have a much longer half-life and have shown some clinical efficacy as antitumor agents. However, the efficacy of these antibodies may be limited by their bivalent nature that does not optimally mimic the trimeric ligand. To overcome limitations of currently used death receptor-targeting agents, we engineered trimeric proteins called Atrimer complexes that selectively bind DR4 and potently induce apoptosis in a variety of cancer cells. Atrimer complexes are based on human tetranectin, a trimeric plasma protein of approximately 60 kDa. Loop regions within the tetranectin C-type lectin domains (CTLD) were randomized to create a large phage display library that was used to select DR4-binding complexes. A panel of unique and potent agonist DR4 Atrimer complexes with subnanomolar affinity to DR4 and no detectable binding to DR5 or the decoy receptors was identified. Mechanism of action studies with a selected Atrimer complex, 1G(2), showed that Atrimer complexes induce caspase-dependent and DR4-specific apoptosis in cancer cells while sparing normal human fibroblasts and, importantly, hepatocytes. This proof-of-principle study supports the use of alternative proteins engineered to overcome limitations of therapeutically desirable molecules such as TRAIL.
Insights
Engineered trimeric Atrimer complexes selectively target DR4, inducing cancer cell apoptosis. This novel approach overcomes limitations of TRAIL ligands and antibodies, offering a promising cancer therapy strategy.
Area of Science:
- Biochemistry
- Molecular Biology
- Drug Discovery
Background:
- Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) induces apoptosis via death receptors (DR4/DR5), making them therapeutic targets.
- Recombinant TRAIL has a short half-life, while agonistic antibodies have longer half-lives but may be limited by bivalent binding.
- Current death receptor-targeting agents face limitations in efficacy and optimal mimicry of the natural trimeric ligand.
Purpose of the Study:
- To engineer novel trimeric proteins, Atrimer complexes, that selectively bind and activate DR4.
- To overcome the limitations of existing TRAIL-based therapeutics by creating agents with improved properties.
- To demonstrate the potential of Atrimer complexes as potent and specific inducers of apoptosis in cancer cells.
Main Methods:
- Engineering of trimeric Atrimer complexes based on human tetranectin.
- Randomization of tetranectin C-type lectin domain (CTLD) loop regions to create a phage display library.
- Selection of DR4-specific binding complexes and mechanism of action studies.
Main Results:
- Identification of potent DR4-specific agonist Atrimer complexes with subnanomolar affinity.
- Demonstrated selective binding to DR4, with no detectable binding to DR5 or decoy receptors.
- Selected Atrimer complex 1G(2) induced caspase-dependent, DR4-specific apoptosis in cancer cells, sparing normal cells.
Conclusions:
- Atrimer complexes represent a novel class of engineered proteins for targeting death receptors.
- These complexes effectively induce apoptosis in cancer cells while maintaining selectivity.
- The findings support Atrimer complexes as a promising alternative to TRAIL ligands and antibodies for cancer therapy.
