Inhibition of Survivin Induces Apoptosis in Human Embryonic Stem Cells

By inhibiting the action of the survivin gene it may be possible to safely use human embryonic stem cells for treatment of diseases such as diabetes, Parkinson's disease, and heart failure without running the risk of these cells developing into cancerous teratomas.

The BIRC5 gene encodes the synthesis of the apoptosis inhibitor survivin, also called baculoviral inhibitor of apoptosis repeat-containing 5 (BIRC5). The survivin protein functions to inhibit caspase activation, which leads to the negative regulation of apoptosis. This has been shown by disruption of survivin induction pathways leading to increase in apoptosis and decrease in tumor growth. The survivin protein is expressed highly in most human tumors and fetal tissue, but is completely absent in terminally differentiated cells. This fact makes survivin an ideal target for cancer therapy as cancer cells are targeted while normal cells are left alone. Survivin expression is also highly regulated by the cell cycle and is only expressed in the G2-M phase. It is known that survivin localizes to the mitotic spindle by interaction with tubulin during mitosis and may play a contributing role in regulating mitosis. The molecular mechanisms of survivin regulation are still not well understood, but regulation of survivin seems to be linked to the p53 protein.

Investigators from the Hebrew University of Jerusalem (Israel) demonstrated that survivin was highly expressed in human embryonic stem cells and teratomas but not in normal, differentiated cells. Next, they showed that by neutralizing survivin it was possible to induce apoptosis in both stem cells and in tumors. These findings were published in the March 1, 2009, online edition of the journal Nature Biotechnology.

The researchers suggested that, "Their findings should aid in the development of safer cell therapies and may help elucidate the basic principles of tumor initiation."

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Hebrew University of Jerusalem