An Extracellular Matrix-Producing Subset of Cancer-Associated Fibroblasts Drives Chemoresistance in Breast Cancer via SRC Activation and G0S2 Upregulation

Chemotherapy resistance remains a major hurdle for treating patients with triple-negative breast cancer (TNBC). While cancer associated fibroblasts (CAFs) as an overall population have been shown to modulate treatment response, innovative approaches are required to decipher which and how distinct CAF populations drive chemoresistance. Here, by combining analysis of data from TNBC patients with ex vivo modeling using tumor-on-chip (ToC) technology, we identified a specific CAF population, the extracellular matrix-producing myofibroblasts (ECM-myCAFs), that mediated resistance to chemotherapy. The proportion of ECM-myCAFs decreased after chemotherapy in chemo-sensitive patients, but remained unchanged in chemo-resistant patients. In ToC models, primary ECM-myCAFs promoted TNBC cell survival under chemotherapy treatment. Single-cell RNA sequencing, advanced cell imaging, and functional assays showed that ECM-myCAFs activated SRC kinases in TNBC cells, likely through secreted factors and upregulated the apoptosis regulator G0S2. SRC inhibition or G0S2 silencing completely abolished TNBC cell chemoresistance driven by ECM-myCAFs. Altogether, this work reveals the unique role of the specific ECM-myCAF population and identifies G0S2 as a key player in chemoresistance in TNBC.