ID1 and ovarian carcinoma: While numerous studies have demonstrated the effects of ID1 on promoting self-renewal in colon CSCs [12], inhibiting apoptosis in ovarian cancer cells [13], and mediating chemo-resistance in nasopharyngeal carcinoma cells [14], glioblastoma stem cells [15], ovarian cancer cells [13, 16], esophageal squamous cell carcinoma cells [17], gastric cancer cells [18], and colorectal cancer cells [19], the majority of these studies have relied on indirect evidence from knockdown/knockout or overexpression experiments.