Long non-coding RNA X-inactive-specific transcript contributes to cisplatin resistance in gastric cancer by sponging miR-let-7b.

X-inactive-specific transcript (XIST) is a 19 kb noncoding RNA which is oncogenic in many cancers including gastric cancer. It is reported that XIST contributes to gastric cancer cells resistant to cisplatin, but specific mechanisms governing this resistance remain unclear. We firstly examined the XIST level in gastric cancer cells and tumor specimens. We confirmed that XIST is overexpressed in gastric cancer cells and tumors, which further contributed to the poor prognosis of patients with gastric cancer. We also confirmed that high XIST level contributes to the cisplatin resistance in gastric cancer cells. Subsequently, we predicted microRNAs that have the potential to interact with XIST and found that Let-7b-5p may directly interact with XIST. We confirmed the direct interaction between XIST and Let-7b-5p and identified a negative correlation between the level of Let-7b-5p and XIST in gastric cancer tumors. Meanwhile, Let-7b-5p inhibitor treatment can partially rescued the effect of XIST-specific small interfering RNA on cell proliferation and apoptosis by regulating Aurora kinase B expression. XIST functions as an oncogene in gastric cancer which contributes to the cisplatin resistance by interacting with Let-7b-5p.