Gene expression correlation analysis revealed that USP30 negatively correlates with the expression of stem cell markers such as MMP2, MMP9, MYC, OCT4(POU5F1), NANOG, ALDH1A3, CD133 (PROM1), EPCAM, CD24, and ITGA6 in breast cancer cohorts (Figure S2A–F). This evidence concerns the gene PROM1 and breast cancer.