IGF1R and breast cancer: Additionally, miR-503 is recognized as a constituent of the miRNA cluster miR-424(322)/503, whose reduction in breast cancer patients is associated with the development of aggressive breast cancer and has been linked to the enhancement in in vivo paclitaxel resistance via the upregulation of two of its targets: B-cell lymphoma 2 (BCL-2) and insulin-like growth factor-1 receptor (IGF1R) [71].