Cell Culture and Transfection Protocol

We originally purchased MCF7 and MCF10A cells from American Type Culture Collection. We maintained the MCF7 and Hela cells in Dulbecco’s modified Eagle’s medium (DMEM) (Corning) media, supplemented with 10% fetal bovine solution (FBS) (GenDEPOT) and maintained the MCF10A cells in DMEM/F-12 (Corning) supplemented with 5% horse serum, 20 ng ml⁻¹ EGF, 0.5 mg ml⁻¹ hydrocortisone, 100 ng ml⁻¹ cholera toxin, 10 μg ml⁻¹ insulin in a 5% CO₂ incubator at 37 °C^{4 (link),65 (link)}. Transfection of LNA GapmeRs (Qiagen) into the cells was carried out using Lipofectamine 2000 (Life Technologies) according to the manufacturer’s protocol and at a final concentration of 60 nM. For NET1e eRNA knockdown, a mixture of NET1e LNA 1, 2, and 3 was transfected into the cell. The sequence information for LNA is described in Supplementary Table 2.