The acceleration of cisplatin resistance in colorectal cancer by lncRNA NORAD through regulation of miR-106a-5p/Cyclin D1 axis.

Colorectal cancer (CRC) is one of the leading causes of cancer-related mortality. LncRNA NORAD is frequently upregulated and positively associated with various cancer progressions. We discovered NORAD was significantly upregulated in CRC tissues and cells. NORAD sponged miR-106a-5p to form a ceRNA complex. MiR-106a-5p was remarkedly downregulated in CRC tumors and cells. Silencing NORAD or overexpression of miR-106a-5p effectively increased cisplatin sensitivity. In the established cisplatin resistant cell line, NORAD was upregulated and miR-106a-5p was downregulated. Furthermore, we disclosed miR-106a-5p directly targeted 3'UTR of CCND1, which is an important cell cycle regulator and is frequently overexpressed in human cancers. Rescue experiments showed restoration of CCND1 in miR-106a-5p-overexpressing CRC cells successfully recovered cisplatin resistance. Finally, restoration of miR-106a-5p in NORAD-overexpressing CRC cells re-sensitized cisplatin resistance by targeting CCND1. Summarily, this study uncovered a NORAD-promoted cisplatin resistance through modulating the miR-106a-5p-CCND1 axis, contributing to developing novel therapy for treating chemoresistant CRC.