<p>Extracellular heat shock protein 90 alpha (eHsp90α) has been implicated in promoting cancer cell invasion and metastasis. However, the role of eHsp90α in the tumor microenvironment remains poorly understood. In the present study, we provide the first evidence that eHsp90α aggravates the invasiveness of cancer-associated fibroblasts (CAFs) through low-density lipoprotein receptor-related protein 1 (LRP1) and consequent upregulation of epithelial–mesenchymal transition (EMT)-associated transcription factor expression. We observed that eHsp90α induces CAFs invasiveness. However, silencing of Twist, Snail and Slug expressions significantly attenuated eHsp90α-induced CAFs invasiveness. In addition, transfecting CAFs with LRP1 short interfering RNA (siRNA) markedly inhibited eHsp90α-induced CAFs invasion and EMT-associated transcription factor expression. Intriguingly, we observed that the epidermal growth factor receptor (EGFR)/AKT signaling is located downstream of LRP1 and governs eHsp90α-induced Twist and Snail but not Slug expression required for CAFs invasion. Moreover, we demonstrated that these EMT-associated transcription factors of CAFs are indispensable for breast cancer cell invasion. Collectively, the present data reveal that eHsp90α increases CAFs invasiveness through LRP1 and subsequent EMT-associated transcription factor expression to promote breast cancer invasion, presenting potential therapeutic targets to impede breast cancer progression.</p>