Abstract 364: EMT-driven alterations promote dependency on nuclear kinase VRK1 activity to synergize with immune therapy in triple negative breast cancer.

Abstract Introduction: Triple-negative breast cancer (TNBC) is aggressive and often immune-cold, with ∼12% 5-year survival and few targeted options. Cancer Dependency Map analyses identify the nuclear serine/threonine kinase VRK1 as broadly essential, with strongest dependency in EMT-high states. We propose that EMT-driven remodeling of the nuclear envelope (NE) creates a liability that heightens reliance on VRK1 to preserve NE integrity and genome stability. Pharmacologic or genetic VRK1 inhibition destabilizes the NE, generates micronuclei, and activates cGAS-STING/type I interferon signaling, offering a strategy to inflame refractory tumors and improve responses to immune checkpoint blockade. Methods: Patient-derived TNBC lines (HCC1937, HCC1806, HCC1143) were treated with TGF-β for 72 h to induce EMT. EMT markers (E-cadherin, N-cadherin, Vimentin, SNAIL), NE proteins (LAMIN-B1, BANF1), and DNA damage (γH2AX) were quantified by immunoblotting and immunofluorescence. Functional dependency was assessed by CRISPR/Cas9 knockout of VRK1 or VRK2 with analyses of growth, cytoskeletal organization, and EMT dynamics. For in vivo studies, E0771 murine TNBC cells engineered to express a dTAG-degradable VRK1 were implanted into immunocompetent C57BL/6 mice and treated with the dTAG-V1 degrader, anti-PD-1, or both; tumor growth and immune modulation were evaluated. Results: TGF-β induced EMT across TNBC lines, increasing Vimentin and N-cadherin and decreasing E-cadherin. EMT coincided with cytoskeletal remodeling, NE disruption, and elevated γH2AX. VRK1 and VRK2 expression increased during EMT. VRK1 knockout in epithelial-like TNBC cells heightened EMT marker expression and restricted growth under TGF-β, indicating a requirement for VRK1 to preserve NE integrity under EMT stress. In murine models, VRK1 depletion reduced tumor growth versus vehicle (p0.0001); anti-PD-1 alone also reduced growth (p0.0001). The combination of dTAG-V1 and anti-PD-1 produced the greatest reduction versus vehicle (p0.0001) and outperformed either monotherapy, supporting synergy between VRK1 targeting and checkpoint blockade. Conclusion: EMT-driven remodeling sensitizes TNBC to VRK1 inhibition, establishing VRK1 as a tractable vulnerability in mesenchymal-like disease. VRK1 sustains NE integrity; its inhibition destabilizes the NE, activates cGAS-STING, and converts immune-refractory TNBC toward an inflamed, therapy-responsive state. These findings support clinical exploration of VRK1 inhibition combined with anti-PD-1 to enhance antitumor immunity in aggressive TNBC. Citation Format: Priyanka Sahu, Raymond Liu, Sergey Shmelkov, Uger Ozerdem, William C. Hahn, Jonathan So. EMT-driven alterations promote dependency on nuclear kinase VRK1 activity to synergize with immune therapy in triple negative breast cancer abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 364.