Inflammatory cytokines induce new cancer dependencies.

Tumor cells respond and adapt to environmental stresses that facilitate growth in hostile environments, including cytokine-mediated inflammation elicited by antitumor immunity and enhanced by immune checkpoint blockade (ICB). However, cytokine responses also induce transcriptional and cell-state changes that may predispose tumor cells to new vulnerabilities, which remain poorly explored. Here we performed in vitro genome-scale CRISPR loss-of-function screens in eight cancer models exposed to interferon-γ (IFNγ), interferon-β or tumor necrosis factor to map inflammation-induced genetic vulnerabilities. We identified members of the glycosylphosphatidylinositol (GPI) transamidase complex and the lipid phosphatase FITM2 as interferon-specific cancer dependencies. Tumor-specific deletion of GPI transamidase subunits or FITM2 markedly enhanced response to ICB in vivo. By integrating functional genomics, metabolomics and pharmacologic perturbation of downstream stress pathways, we found that loss of FITM2 predisposed cancer cells to IFNγ-driven endoplasmic reticulum and oxidative stress, culminating in paraptosis-like cell death. Collectively, these findings identify tumor-intrinsic dependencies governing responses to inflammatory cytokines.