Despite improved detection and treatment of early-stage breast cancer, metastatic disease remains challenging as conventional and immune-based therapies offer little long-term benefit. About 75% of breast cancer metastases occur in bone, often treatment resistant and linked to severe morbidity and mortality. Biological changes driving outgrowth in bone are not fully understood, but one mechanism is microenvironment-induced immune suppression that renders metastases unresponsive to immunity. Our laboratory identified a key pathway: suppression of tumour-intrinsic type I interferon (IFN) signalling, including hundreds of interferon-stimulated genes (ISGs) crucial for anti-tumour immunity. Thus, targeted approaches to restore IFN signalling in metastatic cells could have important therapeutic implications. This project utilised bone metastatic cells isolated from the syngeneic mouse models of breast cancer with an interferon-stimulated response element (ISRE)-GFP/Luc2 reporter system and performed a CRISPR/Cas9 knockout screen, isolating GFP positive cells (indicating enhanced ISRE activity). The top hits included members of the HUSH complex (Setdb1, Atf7ip, Pphln1, Mphosph8) and SUMOylation enzymes (Uba2, Sae1); all previously described to be involved in IFN signaling but poorly described in breast cancer. Knockout cell lines were generated targeting some of these hits and they were validated for their ability to induce ISG expression and cellular immunogenicity (such as MHC-I) in vitro. Lastly, a small molecule SUMOlyation inhibitor, TAK981, was also validated in its ability to induce an IFN response. Identified through ISRE reporter and CRISPR/Cas9 screening, these gene targets offer novel therapeutic strategies for combatting late-stage breast cancer, enhancing IFN signalling in bone metastasis and increasing cancer vulnerability to immune-based therapeutics.