RNA challenges cancer....

In laboratories around the world, researchers are taking a fresh look at RNA, a nucleic acid made from a single strand of chemical components called nucleotides. Cells normally use the nucleotide sequences of RNA strands to transfer the protein-building instructions from double-stranded DNA to ribosomes, sites inside cells where proteins are made.

Some investigators contend that RNA can do much more than simply carry DNA's message. For example, one research group has devised a form of gene therapy using ribozymes, enzymes made of RNA, to correct faulty protein-making blueprints (SN: 6/8/96, p. 357).

Another group suggests that ribozymes can eliminate harmful proteins after they're made. Joachim W. Engels of the University of Johann Wolfgang Goethe in Frankfurt, Germany, and his colleagues report that they have designed ribozymes that bind to and break apart a mutant protein that turns cells cancerous.

The protein, part of the signaling machinery that governs cell growth, is encoded by a gene called N-ras. A cell has two copies of the gene, but a mutation in just one copy causes the cell to proliferate out of control. Engels' group has synthesized RNA strands that, in test-tube studies, destroy the proteins produced by a mutant N-ras gene but spare proteins encoded by the normal version of the gene. To allow the ribozymes to do the same inside cells, the researchers have modified the RNA strands slightly, making them more resistant to degradation by cellular enzymes. They plan to test these ribozymes on tumor cells from a person with an N-ras mutation. "The real proof will be if the proliferation disappears," says Engels.