CLIC4 is essential for host competence for metastasis in murine models of breast cancer and a prognostic indicator for human breast cancer

CLIC4 belongs to a family of highly conserved metamorphic proteins of the glutathione-S-transferase superfamily and dysregulation is implicated in pulmonary arterial hypertension, asthma, and ovarian cancer. We show that genetic ablation of host Clic4 eliminated the establishment of breast cancer lung metastases in two independent mouse models while Clic4 null tumor cells retained metastatic capability. TCGA and METABRIC data indicated that CLIC4 is elevated in human breast cancers from young women, those with poor prognosis and those with early stage metastatic disease. Experimentally, the essential Clic4 host contributions for metastatic competence depended on circulating levels of pro- metastatic mediators, neoangiogenesis, tumor cell attachment to lung tissue, myofibroblast differentiation, and leukocyte migration. CLIC4 was abundant in circulating extracellular vesicles (EVs) from tumor-bearing wildtype mice but absent in EVs from tumor-bearing Clic4 null hosts or wildtype hosts bearing Clic4 null-tumors suggesting cross-talk between host and tumor cells is required to deposit CLIC4 in EVs. These results illuminate CLIC4 as a critical host factor for metastatic competence, a potential prognostic marker for breast cancer patients and a target for anti-metastatic therapy. Overall design: Examination of Clic4 KO vs WT at day 0 and 14 days in mouse lung. At day 0, we have 5 WT mice and 6 KO mice. At day 14, we have 2 WT mice and 6 KO mice.