Shear Stress Promotes Metastasis of Triple-negative Breast Cancer Cells Through Calcium Channel-ROS-FOS Axis.

During metastasis, circulating tumor cells (CTCs) are subjected to fluidic shear stress (SS), which eliminates many of them but paradoxically enhances malignancy and metastatic success. Meanwhile, given the critical roles of reactive oxygen species (ROS) in stress response and cancer, we engineer a circulation-mimicking microfluidic system which generates pulsatile SS to investigate the interplay among SS, ROS and metastasis. A 3-hour SS treatment rapidly elevates ROS levels, boosting metastatic abilities in triple-negative breast cancer (TNBC) cells in vitro and in vivo. RNA-sequencing and subsequent investigation identify activator protein-1 (AP-1) transcription factor members FOS, ATF3 and FOSB, which undergo dramatic ROS-dependent increase and nuclear localization upon SS stimulation. All three genes exhibit metastasis-promoting potential, while FOS displays the strongest ability to trigger distant lung metastasis in an orthotopic tumor model and correlates with worse clinical outcomes. Mechanistically, calcium channel acts as the mechano-sensor to initiate the SS-ROS cascade, with calcium channel blockers Mibefradil and Nifedipine effectively weakening SS-ROS-induced invasiveness. Following ROS elevation, the downstream activation of p38-ELK1-cFOS and JNK-cJUN pathways subsequently increase the expression of malignancy-related genes. This metastasis-promoting SS-calcium channel-ROS-FOS axis provides new insights for combating metastatic progression in breast cancer.