Genetic deficiencies resulted in more than 90% reduction of XIST/Xist expression in almost all cell types, including human ovarian cancer cells (OVCAR3), human mammary stem cells (MaSC), human embryonic stem cells (ESC), mouse embryonic fibroblasts (MEF), mouse lineage-depleted (Lin−) bone marrow cells and the subgroup Lin−c-Kit+Sca-1+ (LSK+) cells; 50–70% reduction of XIST/Xist expression was resulted in human mammary luminal cells (ML) and mouse Lin−c-Kit+Sca-1− (LSK−) cells (Figure 1B). This evidence concerns the gene XIST and ovarian cancer.