Effect of Lrp1 knockdown on the gene expression of EO771 cells

Identifying patients at risk for metastatic relapse is a critical need in oncology. We identified a common missense germline variant in PCSK9 that associates with reduced breast cancer survival outcomes in multiple cohorts. Genetic modeling of this gain-of-function single nucleotide variant in mice revealed that it causally promoted breast cancer metastasis. Conversely, host PCSK9 deletion reduced metastatic colonization in multiple breast cancer models. Host PCSK9 promoted metastatic initiation events in lung and increased proliferative competence by targeting tumoral LRP1 receptors which repress metastasis-promoting genes. Antibody-mediated therapeutic inhibition of PCSK9 suppressed breast cancer metastasis in multiple models. This variant stratified women in a large Swedish early-stage breast cancer cohort into those with 98% versus 78% distant-metastasis-free interval at 15 years after diagnosis. Our findings reveal that a commonly inherited genetic alteration predicts breast cancer survival and governs breast cancer metastasis—uncovering a hereditary basis underlying a prevalent cause of mortality.