D2.0R mouse breast cancer cells cultured on stiff or soft ECM hydrogels

Metastatic breast cancer cells disseminate to organs with a soft microenvironment. Whether and how tissue mechanical properties influence their response to treatment remains unclear. Here we found that a soft ECM empowers redox homeostasis. Cells cultured on a soft ECM display increased peri-mitochondrial F-actin promoted by Spire1C and Arp2/3 nucleation factors, and increased DRP1- and MIEF1/2-dependent mitochondrial fission. Changes in mitochondrial dynamics lead to increased mtROS production and activate the NRF2 antioxidant transcriptional response, including increased cystine uptake and glutathione metabolism. This retrograde response endows cells with resistance to oxidative stress and ROS-dependent chemotherapy drugs. This is relevant in a mouse model of metastatic breast cancer cells dormant in the lung soft tissue, where inhibition of DRP1 and NRF2 restored cisplatin sensitivity and prevented disseminated cancer cell awakening. We propose that targeting this mitochondrial dynamics- and redox-based mechanotransduction pathway could open new avenues to prevent metastatic relapse. Overall design: D2.0R mouse breast cancer cells stably expressing lentiviral pLKO.1 shCONTROL cultured for 24 h on plastics, on Collagen-1-coated stiff (E=50kPa) acrylamide hydrogels, and on soft (E=0,2 kPa) hydrogels. Three independent biological replicates cultured in parallel in a single experiment were sequenced.