MiR-544 represses expression of mTOR, promoting tumor cell survival in a hypoxic environment. Inhibition of miR-544 processing with MiR-544 Inhibitor 1 caused apoptosis in triple-negative breast cancer cells in response to hypoxic stress, sensitized their response to 5-fluorouracil, and blocked their growth after transplantation into immunodeficient mice. SID 3712249 (MiR-544 Inhibitor 1) is believed to bind directly to the precursor miRNA, blocking the production of the mature microRNA and resulting in decreased miR-544, HIF-1α, and ATM transcripts. MiR-544 Inhibitor 1 was as selective and 25-fold more potent than a 2′-O-methyl RNA antagomir.