miR-335-5p targeting ICAM-1 inhibits invasion and metastasis of thyroid cancer cells.

miRNAs is a kind of noncoding small RNAs with negative regulation function. Some miRNAs play a crucial role in the growth of tumor cells. In this study, we analyzed the role of miR-335-5p and its target gene intercellular adhesion molecule 1 (ICAM-1) in thyroid cancer. Real-time polymerase chain reaction (PCR) results showed that the expression level of ICAM-1 in cancer tissues was higher than that in their adjacent tissues. The expression level of ICAM-1 in papillary thyroid carcinoma was also significantly higher than that in other types of tumors. However, the expression of miR-335-5p is opposite to that of ICAM-1. In human thyroid cancer cell lines TPC-1, FTC-133, TT and human thyroid follicular cell line Nthyori 3-1, the expression level of ICAM-1 in TPC-1 was significantly higher than that of other cells, while the expression level of miR-335-5p in TPC-1 was significantly lower than that of other cells. When ICAM-1 expression was downregulated and miR-335-5p expression was upregulated in TPC-1 cells, ICAM-1 expression was upregulated and miR-335-5p expression was downregulated in FTC-133 cells, we found that ICAM-1 could promote the proliferation of thyroid cancer cells, while miR-335-5p could inhibit the proliferation of thyroid cancer cells. miR-335-5p could combine with 3'UTR of ICAM-1 by bioinformatics prediction. Luciferase reporter gene analysis and Western blotting detection further confirmed that miR-335-5p could target ICAM-1 and inhibit its expression. The expression level of miR-335-5p was downregulated, while the expression level of ICAM-1 was upregulated in thyroid cancer. This study will help us better understand the pathogenesis of thyroid cancer and provide new insights into the treatment of this disease.