Scientists from the Georg Speyer Haus in Frankfurt have now found a small protein that blocks this Stat3 switch and turns it off. The research team, led by Professor Bernd Groner, searched for a substance that would dock onto the surface of Stat3 and thus disrupt its function.

The starting point of the research was a "library" with several million different artificial proteins. With these proteins a test was conducted which intended to show which of the millions of protein pieces would be able to dock well to the different areas of Stat3. Such small substances which fit exactly into certain cavities and hollows of proteins are called aptamers in specialist lingo. The designation is derived from the Greek (apt = fit, meros = part).

The scientists have now found an aptamer in the protein library which docks specifically onto Stat3. It thus blocks a site on Stat3 that is significant for binding to DNA. Then certain genes can no longer be read, and the program "growth and proliferation" is switched off. Instead, the cell induces its own death. In this way the small, artificial aptamer kills almost half of all tumor cells.

You can even see the programmed cell death as it happens in the cancer cells: When the apoptosis program is triggered, the DNA breaks down into small pieces. A red dye can be attached to the ends of these DNA segments, thereby making the cell nucleus of dying cells appear red. On the left: blue coloring of the DNA of healthy cells.

• Scientist's Website

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