ESR1 and breast cancer: Based on the reported key role of DDX3X in breast cancer [9,22], we decided to test FHP01 efficacy in vitro by measuring its IC50 values in different cell lines representing models of the principal molecular subtypes of breast cancer: MCF7 and T47D (ER+/PR+ subtype), SKBR3 (HER2+ subtype), MDA MB 468 and MDA MB 231 (TNBC subtype), and the immortalized MCF10A cells as non-tumorigenic mammary epithelial control cells (Figure S3) [2].