Abstract: Objective To investigate the impacts of long non-coding RNA 662(LINC00662) on the malignant biological behavior of thyroid cancer cells by targeting microRNA(miR)-195-5p/checkpoint kinase 1 (CHEK1).Methods Tpc-1 cells in good condition were transfected with interfering LINC00662 siRNA (si LINC00662),negative control (si NC),co-transfected with miR-195-5p inhibitor and si LINC00662,co-transfected with inhibitor NC and si LINC00662,and were successively recorded as si NC group,si LINC00662 group,si LINC00662+miR-195-5p inhibitor group,si LINC00662+inhibitor NC group,and untreated cells were recorded as control group.Double luciferase assay,MTT and Transwell assay were used to verify the targeting relationship,cell proliferation,migration and invasion,respectively.Western blot and qRT-PCR were used to detect the expression of proliferating protein CyclinD1,matrix metalloproteinase (MMP) -2,CHEK1 protein and gene (LINC00662,miR-195-5p,CHEK1) in TPC-1 cells.Results The expression of LINC00662 and CHEK1 mRNA in human thyroid carcinoma cell lines (BCPAP,BHP5-16,TPC-1 and CGTH-W3) was obviously higher than that in Nthy-ori3-1 cells,the expression of miR-195-5p decreased obviously (P<0.05);miR-195-5p had targeted binding sites with LINC00662 and CHEK1,respectively.Compared with the control group[ (100±0.00）%,（163.56±16.36）cells,(245.27±24.53)cells,1.03±0.11,0.85±0.09,2.14±0.22,2.55±0.26,0.93±0.10,0.33±0.04] and the si NC group [(90.01±9.01)%,(164.35±16.44)cells,(247.24±24.73)cells,1.07±0.11,0.88±0.09,2.16±0.22,2.57±0.26,0.97±0.10,0.35±0.04],the si LINC00662 group showed significantly decreased cell proliferation rate [(43.55±4.36)%],migration number [(73.24±7.33) cells],invasion number [(113.27±11.33) cells],CyclinD1 (0.43±0.05),MMP-2 (0.37±0.04),LINC00662 (1.37±0.14),CHEK1 mRNA（1.66±0.17）and protein（0.55±0.06）（P<0.05）,while the expression of miR 195 5p (0.77 ± 0.08) was significantly upregulated（P<0.05）.Inhibition of miR-195-5p or overexpression of CHEK1 reversed the inhibitory effect of interfering LINC00662 on the malignant biological behavior of thyroid cancer cells.Conclusion Interfering LINC00662 can inhibit the malignant biological behavior of thyroid cancer cells,which may be achieved by regulating miR-195-5p/CHEK1.

Key words: long non-coding RNA 662; thyroid cancer; microRNA-195-5p/checkpoint kinase 1; malignant biology