Durable reprogramming of human T cells may now be possible thanks to a new technique based on the CRISPRoff and CRISPRon methodology. Researchers from the Arc Institute, Gladstone Institutes, and the University of California San Francisco (UCSF) have stably silenced or activated genes in this type of immune cell without cutting or altering its DNA, making T cells more resistant, active, and effective against tumors.