Immunotherapy, particularly CAR T-Cell cancer therapy, extends the lives of many patients. But sometimes the therapy randomly migrates to places it shouldn’t go, sneaking into the lungs or other non-cancerous tissue and causing toxic side effects. However, a team of researchers has discovered the molecule responsible for guiding T cells to tumors, setting the stage for scientists to improve the revolutionary treatment. Their discovery of the crucial migration control gene that expresses ST3GAL1 is the result of “unbiased genomic screening”: researchers used a state-of-the-art CRISPR technique to edit thousands of genes expressed in T cells, then tested the migration control capabilities of these genes, one by one over a period of nearly four years, in mouse models. The next step is to find a drug that can manipulate the key T cell protein, ST3GAL1. If the study progresses as planned, such a drug could be added to the CAR T-cell regimen to ensure that the T cells reach their targets.