Abstract: Objective　To investigate the effect of LincRNA-P21 on the migration and invasion of triple negative breast cancer (TNBC) cells by targeting miR-17-3p. Methods　qPCR was used to detect the expression levels of LincRNA-P21 and miR-17-3p in tumor tissues, normal adjacent tissues and 6 kinds of breast cells (normal breast cells MCF-10A, breast cancer cells MDA-MB-231, MDA-MB-435, MDA-MB-468, BT549 and T47D). MDA-MB-231 cells were taken. LincRNA-P21 was overexpressed alone (the control group, the pcDNA3.1 blank group and the pcDNA - LincRNA-P21 group), miR-17-3p expression was inhibited (the control group, the miR-17-3p blank group and the miR-17-3p inhibitor group), and overexpression LincRNA-P21+ inhibited miR-17-3p (the control group, the miR-17-3p inhibitor group and the pcDNA-LincRNA-P21+miR-17-3p inhibitor group). The proliferation of MDA-MB-231 cells was detected by CCK-8 assay. The number of colonies was detected by colony formation assay. The migration ability was detected by cell scratch assay, and the invasion ability was detected by Transwell assay. The protein expressions of E-cadherin and Vimentin were detected by Western blot assay. Results　The expression of LincRNA-P21 was significantly lower in TNBC than that in adjacent tissues (0.48±0.03 vs.1.03±0.06, t=11.714, P＜0.01). The expression of miR-17-3p was significantly higher in TNBC than that in adjacent tissues (2.93±0.17 vs. 1.02±0.04, t=15.593, P＜0.01). The expression levels of LincRNA-P21 mRNA in different breast cancer cell lines were significantly lower than that in MCF-10A (P＜0.01). The expressions of miR-17-3p mRNA in different breast cancer cell lines were significantly higher than that in MCF-10A (P＜0.01). Theoverexpression of LincRNA-P21 inhibited cell proliferation, colony formation and invasion (P＜0.01). The inhibition of miR-17-3p expression could reduce cell proliferation, colony formation and invasion (P＜0.01). Compared with the miR-NC group, the overexpression of LincRNA-P21 and inhibition of miR-17-3p could significantly reduce cell proliferation, colony formation and invasion (P＜0.01), increase the expression of E-cadherin and inhibit the expression of vimentin (P＜0.01). Conclusion　LincRNA-P21 can reduce miR-17-3p expression and inhibit MDA-MB-231 cell proliferation, colony formation, migration and invasion through competitive binding.

Key words: triple negative breast neoplasms, cell movement, RNA interference, RNA, long noncoding, LincRNA-P21, miR-17-3p, cell invasion