Structure of the DNA-binding domain of a reactivated p53 cancer mutant in complex with a stabilizing DARPin.
Image Credit: Andreas Joerger, Goethe University Frankfurt
Scientific Frontline: Extended "At a Glance" Summary: Mini-Antibodies Reactivating p53
The Core Concept: The p53 protein, widely known as the "guardian of the genome," is a crucial tumor suppressor that is mutated in approximately half of all cancer cases; researchers have engineered miniature antibodies called DARPins to stabilize these mutated proteins and restore their protective function.
Key Distinction/Mechanism: Unlike traditional small-molecule therapies that are constrained to targeting single, specific mutations, DARPins can selectively bind to and stabilize a vast array of different p53 mutants simultaneously. Furthermore, while conventional antibodies strictly target extracellular proteins, this new approach uniquely targets and operates on proteins inside the cell.
Origin/History: Developed by a scientific consortium comprising research groups from Goethe University Frankfurt, Philipps University Marburg, the University of Cologne, and the University of Zurich.
Major Frameworks/Components:
- The p53 Protein: A central cellular mechanism that detects DNA damage and initiates repair or targeted cell death (apoptosis) to prevent tumor formation.
- DARPins (Designed Ankyrin Repeat Proteins): Small, engineered proteins that function as miniature antibodies, offering high binding affinity and selectivity for p53.
- mRNA Delivery Systems: The proposed mechanism for intracellular delivery, utilizing lipid nanoparticles to introduce mRNA templates of the DARPins directly into tumor cells.
Branch of Science: Oncology, Molecular Biology, Biophysical Chemistry, and Pharmaceutical Chemistry.
Future Application: The advancement of broad-spectrum cancer therapeutics capable of treating various tumor types without requiring a specific drug for each individual mutation. These therapies could be administered via mRNA technology, analogous to the delivery mechanism used in recent viral vaccines.
Why It Matters: With more than 2,000 distinct p53 mutations identified across different cancers, developing customized treatments for each variant is highly impractical. This generalized stabilization technique offers a promising, unified strategy to reactivate the body's natural tumor suppression mechanisms against a wide spectrum of malignancies globally.
The protein p53 is mutated in many cancer cells, meaning it can no longer fulfill its protective function against tumor development. A team of scientists from Goethe University Frankfurt, along with the universities of Marburg, Cologne, and Zurich, has now succeeded in developing a type of mini-antibody (known as DARPins) that restores p53 functionality in the laboratory. These mini-antibodies can stabilize many p53 mutants and could therefore be suitable as therapeutic agents for a wide range of cancers in the future.
Each year, 20 million people are diagnosed with cancer. Various organs can be affected, and cancer types sometimes differ greatly at the cellular and molecular level. In about half of all cases, however, the protein p53 is mutated. Known as the “guardian of the genome," it plays a central tumor suppressor role: in healthy cells, it ensures that DNA damage is detected and repaired. If this is not successful, the affected cell is selectively eliminated through apoptosis – an important protection against cancer. Conversely, cells can often only develop into tumor cells when the protein p53 is inactivated by a mutation. In many cases, it becomes unstable because of the mutation and loses its functional structure.
Due to the central importance of p53, therapeutic approaches have been sought for decades to reactivate such p53 mutants—in the hope that this will cause cancer cells to die in a targeted manner. Researchers at University Medicine Frankfurt, for example, are currently testing whether p53 can be restored in ovarian cancer using introduced, intact mRNA constructs. The mRNA is packaged in lipid nanoparticles, a technology that achieved its breakthrough in the development of SARS-CoV-2 vaccines.
Other approaches aim to stabilize the mutated p53 so that it can regain its function. A first clinical success was recently reported for the substance Rezatapopt, which reactivates a specific mutation in p53 and thereby inhibits the growth of tumors with that mutation. The problem: more than 2,000 different mutations have already been described in tumors, and only a small fraction is accessible to small molecules such as Rezatapopt.
A consortium comprising research groups from Goethe University Frankfurt, Philipps University Marburg, the University of Cologne, and the University of Zurich has now developed a novel method that can reactivate many p53 mutants in the laboratory. Instead of synthesizing small molecules, the consortium relies on the development of small proteins, so-called DARPins, which bind to p53 very selectively and with high affinity, like miniature antibodies. The scientists were able to show that this binding enables many p53 mutants to regain sufficient stability, thereby restoring p53 functionality.
Prof. Volker Dötsch from the Institute of Biophysical Chemistry at Goethe University explains: “The major advantage of our approach is that one of these miniature antibodies stabilizes not just a single, but many different p53 mutants, meaning it could potentially be used against various types of tumors. This also suggests that it may not be necessary to develop a specific therapeutic agent for each individual mutant.”
Antibodies have long been used successfully in cancer therapy, but until now exclusively for binding to target proteins outside the cell. The results presented here open a new approach by offering a perspective for the use of protein-based therapeutics inside the cell as well. The co-organizer of the study, Dr. Andreas Joerger from the Institute of Pharmaceutical Chemistry at Goethe University, explains: “In the future, our p53-reactivating DARPins could be introduced directly into tumor cells via corresponding mRNA templates packaged in lipid nanoparticles." The consortium partners now aim to further develop this technology for the therapeutic application of p53 stabilizers.
Published in journal: Proceedings of the National Academy of Sciences
Title: DARPins as pan-reactivators of temperature-sensitive p53 cancer mutants
Authors: Philipp Münick, Dimitrios-Ilias Balourdas, Julianne S. Funk, Büşra Yüksel, Danai Mavridi, Justin Heftel, Birgit Dreier, Jonas V. Schaefer, Birgit Schäfer, Stefan Knapp, Tümay Telatar, Baki Akgül, Andreas Plückthun, Thorsten Stiewe, Andreas C. Joerger, and Volker Dötsch
Source/Credit: Goethe-Universität Frankfurt
Reference Number: ongy042926_01
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