ABCB1 and carcinoma: Mechanistically, H19 promotes expression of Cullin 4A (CUL4A), a ubiquitin ligase component [66], which in turn enhances expression of ABCB1/4 genes that encoded MDR1/4 proteins, two members of the ATP-binding cassette family highly upregulated in several carcinomas, including breast cancer [67,68].