Can the Amplifier Be Turned Off?


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The growth of breast cancer and other malignancies is spurred by a molecular "amplifier" that augments signals received by tumor cells, according to a new study led by Prof. Yosef Yarden of the Weizmann Institute's Molecular Cell Biology Department.
This "amplifier" is a protein called ErbB-2, long suspected of involvement in cancer because it is often found in large amounts on the membranes of certain types of cancer cells. Its massive presence usually indicates poor survival prospects for people with breast, ovarian and lung cancer. Since ErbB-2 does not appear to serve as a receptor for any known chemical messenger, its role in the transmission of molecular signals leading to cancer has been unclear.
In the study, reported in the current issue of the EMBO Journal, the scientists revealed that ErbB-2 operates by "teaming up" with other similarly-structured proteins on cell membranes. Together, they form structures that receive and amplify the signals controlling cell division and other processes. Breast cancer cells in the study received strong signals when the amount of ErbB-2 on their surfaces was artificially elevated, and almost no signals when they had no ErbB-2 on their membranes.
This finding may assist in the development of drugs that will block cancer by interfering with the transmission of signals stimulating tumor growth.

The team of Prof. Yarden included Devarajan Karunagaran, Eldad Tzahar, Xiaomei Chen and Dr. Rony Seger. The study was conducted in collaboration with the Friedrich Miescher Institute of Basel, Switzerland and the Amgen Center in Thousand Oaks, California. Funding was provided by the National Cancer Institute, USA, and the Israel Science Foundation administered by the Israel Academy of Sciences and Humanities. Dr. Seger holds the Samuel and Isabelle Friedman Career Development Chair.