Dna By Special Delivery

While legions of scientists are hunting down mutant genes like the culprit that causes some colon cancers, other researchers are seeking ways to fix the damage done by these mistakes of nature. Still in its infancy, the field of “gene therapy” has spawned dozens of experiments aimed at treating ailments ranging from cystic fibrosis to brain tumors. The goal is to transplant new genes into humans to do the work of defective ones — or to give patients extra genes useful in fighting diseases.

One of the toughest tricks is getting genes into the right spot in the body. Up to now, researchers have generally used benign viruses to carry the genetic material DNA into cells, but there are fears that the seemingly nonthreatening transport vehicles could sometimes cause viral infections. Last week scientists at the University of Michigan and the University of Pittsburgh reported in Proceedings of the National Academy of Sciences that they had succeeded in injecting DNA directly into human cells. Instead of riding a virus, the DNA was encased in liposomes, harmless little bubbles of fat.

Led by Michigan’s Dr. Gary Nabel, the researchers treated five patients with melanoma, a deadly skin cancer. The tumors were injected with the gene HLA-B7, which produces a protein that can help the immune system fight the cancer. In all five patients, the genes safely entered the tumor cells and began making protein, and in one case the tumors shrank. The technique is no miracle cure, but the experiment adds a promising new weapon to the arsenal of genetic medicine.