Paclitaxel is a standard-of-care chemotherapy for breast cancer, despite the increasing recognition of its poor effectiveness in the treatment of patients with advanced disease. Here we report that adenovirus type 5 E1A-mediated elevation of the microRNA processing enzyme Dicer is sufficient to enhance paclitaxel sensitization and reduce cancer stem-like cell properties in this setting. Elevating Dicer expression increased levels of the AXL kinase targeting microRNA miR-494, thereby repressing AXL expression to increase paclitaxel sensitivity. We found that Dicer expression was regulated at the transcription level by E1A, through activation of a MAPK14/CEBPalpha pathway. Our findings define a mechanism of E1A-mediated chemosensitization for paclitaxel which is based upon the suppression of breast cancer stem-like cells, with potential implications for the diagnosis and treatment of breast cancer patients.
