Identification of differential expressed lnc RNA s in human thyroid cancer by a genome‐wide analyses

Recently, a growing number of evidence has revealed that long noncoding RNA s (lnc RNA s) act as key regulators in various cellular biologic processes, and dysregulation of lnc RNA s involves in tumorigenesis and cancer progression. However, the expression pattern, clinical relevance, and biologic function of most lnc RNA s in human thyroid cancer remain unclear. To identify more thyroid‐cancer‐associated lnc RNA s, we analyzed the expression profile of lnc RNA s in thyroid cancer tissues and adjacent normal or non‐tumor tissues using RNA sequencing data and gene microarray data from The Cancer Genome Atlas and Gene Expression Omnibus. Annotation and analyses of these data revealed that hundreds of lnc RNA s are differentially expressed in thyroid cancer tissues when compared with normal tissues. By copy number variation analyses, we identified that some of those dysregulated lnc RNA s genome locus are accompanied with the copy number amplification or deletion. Moreover, some lnc RNA s expression levels are significantly associated with thyroid cancer patients overall or recurrence‐free survival time, such as RUNDC 3A‐ AS 1, FOXD 2‐ AS 1, PAX 8‐ AS 1, and CRYM ‐ AS 1. Furthermore, we validated an lnc RNA termed LINC 00704 in thyroid cancer cells by performing loss of function assays. Downregulation of LINC 00704 could significantly impair thyroid cancer cells proliferation, colony formation, inhibit cell‐cycle progression and cell invasion, and induce cell apoptosis. Taken together, our findings reveal that lots of lnc RNA s are dysregulated and may play critical roles in thyroid cancer, and this study could provide useful resource for identification and investigation of novel lnc RNA candidates for thyroid cancer.