Cancer-associated fibroblasts induce trastuzumab resistance in HER2 positive breast cancer cells.

Whether and how cancer-associated fibroblasts induce trastuzumab resistance in HER2+ breast cancer is still elusive. We analyzed the percentage of cancer stem cells and multiple pathway status before and after trastuzumab treatment in HER2 positive breast cancer cells co-cultured with conditional medium (CM) from CAFs. The results suggest that CAFs induce trastuzumab resistance by expanding cancer stem cells and activating multiple pathways, such as NF-κB, JAK/STAT3 and PI3K/AKT; combination of an anti-IL6 antibody, or multiple pathway inhibitors with trastuzumab in HER2 positive breast cancer maybe a novel strategy to reverse trastuzumab resistance.