Sounds wacky, doesn't it? But a de-fanged version of HIV was successfully used to treat cancer. Using modified HIV-1, an experimental treatment transported cancer-fighting genes into immune system cells that attack and destroy some viruses. The end result was cure or remission for three people with advanced cases of chronic lymphocytic leukemia.

In an even closer-to-home twist on the story, the researcher behind this strategy is Carl June, MD, of the University of Pennsylvania School of Medicine. June has long worked on gene therapy to treat HIV itself, including research with Sangamo BioSciences on genetic methods to alter immune cells by blocking production of the CCR5 receptors that let HIV enter cells. That experiment is also showing early results, lowering viral loads and improving CD4 counts in positive people—without HIV drugs.