We first examined whether NDRG1-OT1 was affected by overexpressing its host gene, NDRG1. As shown in Fig. S1, the expression levels of NDRG1-OT1 were not affected in cells overexpressing NDRG1. To further investigate if the effects of hypoxia on NDRG1-OT1 were general, we examined the relative expression levels of NDRG1-OT1 in different breast cancer cell lines classified by their intrinsic molecular subtypes, including MCF-7 (luminal A), ZR-75-30 (luminal B), MDA-MB-361 (luminal B), MDA-MB-453 (HER2+), and MDA-MB-231 (triple negative) under hypoxia and normoxia (Fig. 1A). The gene discussed is ERBB2; the disease is breast cancer.