An antibody generated in lupus can weaken or kill tumor cells, offering both a new type of cancer treatment and an explanation for the low rates of some cancers seen in individuals with lupus.In lupus a person’s immune system goes awry, creating “autoantibodies” that target normal cellular components. One such antibody derived from a mouse model of lupus, 3E10, enters the nuclei of cells, where DNA resides. As reported in the October 24 issue of Science Translational Medicine, a team led by Peter M. Glazer, M.D., Ph.D., chair and Robert E. Hunter Professor of Therapeutic Radiology and professor of genetics, was using 3E10 as a vehicle to carry other molecules into cancer cell nuclei, but they noticed that 3E10 alone was sufficient to make the cells more susceptible to radiation and cancer drugs. The group found that 3E10 binds to broken, loose ends of DNA, disrupting normal DNA repair mechanisms.Many cancer treatments—including radiation and some chemotherapeutic drugs—aim to damage the DNA of tumor cells, and 3E10 may make such treatments work better. In cancers that already have deficiencies in DNA repair, 3E10 alone can kill the cells.