XIST and cancer: As abnormal expression of XIST has been shown to associate with poor prognosis in patients with different cancer types, including BC [59, 60], pancreatic cancer [61], colorectal cancer [62] and brain cancer [63], this pathological roles of XIST in driving tumor growth and progression may relate to its multifaceted functions by acting as a molecular sponge to repress a number of tumor suppressor ncRNAs, and by recruiting epigenetic modifiers to alter chromatin structure and accessibility [21].