Research Papers:

Long noncoding RNA XIST is a prognostic factor in colorectal cancer and inhibits 5-fluorouracil-induced cell cytotoxicity through promoting thymidylate synthase expression

Yang Xiao _, Usenko Alexander Yurievich and Smorzhevskyi Valentyn Yosypovych

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Oncotarget. 2017; 8:83171-83182. https://doi.org/10.18632/oncotarget.20487

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Yang Xiao1, Usenko Alexander Yurievich1 and Smorzhevskyi Valentyn Yosypovych1

1Department of Surgery and Transplantology, P. L. Shupyk National Medical Academy of Postgraduate Education, Kyiv, Ukraine

Correspondence to:

Yang Xiao, email: [email protected]

Keywords: lncRNA XIST, colorectal cancer, 5-fluorouracil, chemoresistance, thymidylate synthase

Received: May 13, 2017     Accepted: July 25, 2017     Published: August 24, 2017


A major reason for the failure of advanced colorectal cancer (CRC) treatment is the occurrence of chemoresistance to 5-fluorouracil (5FU)-based treatment. Recent studies have shown that long non-coding RNAs (lncRNAs) are critical regulators in chemoresistance. By using the next generation HiSeq sequencing assay, we identified lncRNAs showing differential expression levels in 5FU resistant and non-resistant CRC patients. RT-qPCR was then performed for validation in tissues and serum samples, and lncRNA XIST was verified to be up-regulated in non-responding patients and have considerable diagnostic potential to identify responding patients from non-responding patients. In addition, increased serum XIST level was associated with poor response and lower survival rate in CRC patients receiving 5FU-based treatment. Subsequently, the 5FU resistant (5FU-R) cell lines were established, and lncRNA XIST was significantly up-regulated HT29 5FU-R and HCT116 5FU-R cells. Furthermore, knockdown of XIST reversed 5FU resistance while enhanced XIST could restrained the 5FU-induced cell cytotoxcity in both CRC cell lines. Western blotting and immunofluorescence analysis indicated that XIST promoted the expression of thymidylate synthase, a critical 5FU-targetd enzyme. In conclusion, our integrated approach demonstrates that increased expression of lncRNA XIST3 in CRC confers a potent poor therapeutic efficacy, and that lncRNA XIST participated in 5FU resistance through promoting the expression of thymidylate synthase. Thus, specific silence oflncRNA XIST could be a future direction to develop a novel therapeutic strategy to overcome 5FU resistance of CRC patients.

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