ABCB1 and neoplasm: Synthetic tumor microenvironment mimics, STEMs, composed of human lung epithelial, human lung endothelial, and human marrow-derived mesenchymal cells, were prepared using the hanging drop method, and characterized for their cellular and matrix characteristics (morphology, cell composition, and FN, CK18, vimentin, and CD31 expression), ROS production, and expression of drug resistance marker ABC-B1.