Targeting TRAIL death receptor 4 with trivalent DR4 Atrimer complexes.
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.
Penn State Milton S. Hershey Medical Center and Cancer Institute, 500 University Drive CH046, Office T4423 Hershey, PA 17033, USA.
Joshua E
JE
Allen
Roger
R
Ferrini
David T
DT
Dicker
Glenda
G
Batzer
Elise
E
Chen
Daniela I
DI
Oltean
Bing
B
Lin
Mark W
MW
Renshaw
Anke
A
Kretz-Rommel
Wafik S
WS
El-Deiry
D017209:Apoptosis / Q000187:drug effects; D020169:Caspases / Q000378:metabolism; D004354:Drug Screening Assays, Antitumor; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D045325:HCT116 Cells; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D037181:Lectins, C-Type / Q000737:chemistry* / Q000378:metabolism*; D055503:Protein Multimerization / Q000187:drug effects; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000819:agonists / Q000378:metabolism*; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000378:metabolism
D037181:Lectins, C-Type; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D053221:TNF-Related Apoptosis-Inducing Ligand; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; C048648:tetranectin; D020169:Caspases