StealTHY: An immunogen-free CRISPR platform to expose concealed metastasis regulators in immunocompetent models

CRISPR screens have become standard gene discovery platforms in various contexts, including cancer. Yet commonly available CRISPR-Cas9 tools are increasingly recognized as unfit for in vivo investigations in immunocompetent contexts, due to broad immunogenicity of bacterial nucleases and reporters. Here, we show how conventional CRISPR screens in tumor grafts are systematically jeopardized by immunoediting in syngeneic and humanized immunocompetent hosts, resulting in iatrogenic clonal dropouts and ultimately compromising target identification. To resolve this, we present StealTHY, an immunogen-free CRISPR platform compatible with virtually all immunocompetent designs, enabling preservation of clonal architecture and exposing previously concealed cancer vulnerabilities. Among these, we identify the AMH-AMHR2 axis as a formerly unappreciated metastasis target. Thus, with StealTHY, we provide a new resource to expand the applicability of CRISPR screens to immunocompetent models, including humanized tumor grafts, revealing metastasis regulators of therapeutic relevance.