Study links a novel protein pathway to the aggressive progression of breast cancer

Nov 24 2004

Cytogen Corporation today announced the publication of a study linking a novel protein pathway to the aggressive progression of breast cancer.

Results from the study appear in the current issue of the peer-reviewed journal Cancer Research (Aqeilan, RI. et al, "Physical and Functional Interactions between the Wwox Tumor Suppressor Protein and the AP-2{gamma} Transcription Factor," Cancer Research. Vol. 64; pp. 8256-8261).

"Starting with any protein known to contain structurally and functionally defined signaling modules and/or their respective binding partners, researchers can rapidly identify potential interacting proteins using Cytogen's proprietary database," said Michael D. Becker, Cytogen's President and Chief Executive Officer. "Unlike other approaches that may require both complex and resource-intensive genomic and proteomic tools to identify qualified novel targets for drug discovery, this data can provide a unique understanding of the mechanism of action and the physiologic control determined by protein pathways, as well as illuminating novel approaches to therapeutic intervention at various points along such pathways."

Genes are frequently altered in cancers, and such alterations usually lead to loss of expression of encoded proteins, which contributes to development and progression of the cancers. For example, the WW domain-containing oxidoreductase gene encodes a tumor suppressor protein, called Wwox. Alterations of this gene have been demonstrated in multiple types of cancer, including breast, prostate, ovarian, and other carcinomas, and the introduction of Wwox into Wwox-negative tumor cells has resulted in tumor suppression and apoptosis. The Wwox protein contains two signaling modules known as WW domains, which are generally known to mediate protein-protein interactions. While the specific biologic functions of Wwox have not been clear, the presence of signaling domains implies that Wwox may work in concert with other proteins to exert its tumor suppressive effects.

In 2002, Cytogen began collaborating with Carlo M. Croce, M.D., who is currently Professor and Chair of the Department of Molecular Virology, Immunology, and Medical Genetics at the College of Medicine and Public Health at Ohio State University, to identify interacting partners for Wwox and learn more about this tumor suppressor protein. In 2004, the first in vivo validation of a novel interaction discovered through this research collaboration was published ("Functional association between Wwox tumor suppressor protein and p73, a p53 homolog." Proc Natl Acad Sci U.S.A. Vol. 101; pp. 4401-4406). To further explore the biological function of Wwox, additional interacting proteins were investigated.

In the latest study, Dr. Croce discovered a novel interaction between the Wwox protein and AP-2{gamma} transcription factor using Cytogen's proprietary database. The AP-2{gamma} gene encodes for this transcription factor and is amplified in 80% of breast tumors and correlates with a low patient survival rate. In addition, the Her-2/neu gene, known for its tendency to cause or give rise to tumors and a major target for breast cancer therapy, is a direct transcriptional target of AP-2{gamma}.

The study also revealed that Wwox expression triggers redistribution of nuclear AP-2{gamma} transcription factor to the cytoplasm, hence suppressing its transactivating function. These results suggest that Wwox tumor suppressor protein inhibits the oncogenic activity of AP-2{gamma} transcription factor by sequestering it in the cytoplasm. Accordingly, genetic mutations preventing the interaction between Wwox and AP-2{gamma} transcription factor may be important for the aggressive progression of breast cancer.

"In the present study, we have further demonstrated the biological function of Wwox by identifying an interaction with AP-2{gamma} transcription factor," said Dr. Croce. "Since the Wwox protein contains two signaling modules known to mediate protein-protein interactions, Cytogen's comprehensive database enabled our ability to rapidly identify interacting proteins. In a short period of time, this database has revealed novel interactions between Wwox and both p73 and the AP-2{gamma} transcription factor. These results help establish that the Company's high-throughput method to measure protein- protein interactions compares favorably with other more complex techniques and further validates this approach to elucidate protein pathways."

Cytogen has developed a proprietary, high-throughput approach towards the in vitro elucidation of protein-protein interactions that integrates parallel synthesis of peptides, protein expression, and high-throughput screening methodology combined with tools of bioinformatics. As an initial 'proof of concept' for this technology platform, the Company created a comprehensive database of signaling modules and their respective binding partners, including WW, PDZ, SH3 and other major signaling domain families. The Company subsequently entered into academic, governmental, and corporate research collaborations designed to apply this data in major areas of scientific research and to provide in vivo validation of novel protein-protein interactions discovered using its in vitro approach. In 2004, the first in vivo biologic validation of this technology approach was published.