目的:观察长链非编码RNA（long non-coding RNA,lncRNA）RP3-340N1.2 在乳腺癌组织中的表达及其对乳腺癌MCF-7 细胞增殖和迁移的影响，并探讨其可能的作用机制。方法：收集湖北医药学院附属人民医院肿瘤中心2017 年1 月至2017 年9月13 例行乳腺癌根治术切除的癌组织及相应的癌旁组织标本，采用qRT-PCR检测13 例乳腺癌组织及癌旁组织、乳腺癌细胞株和正常乳腺上皮细胞中RP3-340N1.2 的表达差异。使用Lipofectamine 3000 转染试剂分别将RP3-340N1.2 质粒（实验组）和阴性对照质粒（对照组）转染至乳腺癌MCF-7 细胞，CCK-8 法和Transwell 迁移实验检测RP3-340N1.2 过表达对MCF-7 细胞增殖、迁移能力的影响。qRT-PCR检测RP3-340N1.2 过表达对miR-134-5p 和OPCML mRNA表达的影响，Western blotting 检测OPCML相关蛋白的表达水平。结果：RP3-340N1.2 在乳腺癌组织中表达明显低于癌旁组织（P<0.01），其在乳腺癌细胞株中表达水平明显低于正常乳腺上皮细胞（P<0.01）。上调RP3-340N1.2 的表达抑制MCF-7 细胞的增殖和迁移能力（均P<0.05）。过表达RP3-340N1.2 后MCF-7 细胞中miR-134-5p 表达水平明显降低（P<0.01）、OPCML mRNA 和蛋白的表达水平升高（P<0.01），而周期调控蛋白CDK4、Cyclin D2 的表达水平下调，细胞迁移调控蛋白Vimentin 和N-cadherin 蛋白表达下调（均P<0.01）。结论：RP3-340N1.2 在乳腺癌组织和细胞株中低表达，上调RP3-340N1.2 的表达可引起miR-134-5p 的表达降低、OPCML mRNA表达升高，从而抑制乳腺癌细胞的增殖和迁移能力。

Objective: To observe the expression of long-chain non-coding RNA (lncRNA) RP3-340N1.2 in breast cancer tissues and its effect on proliferation and migration of breast cancer MCF-7 cells, and to explore the possible mechanism. Methods: 13 pairs of breast cancer tissues and adjacent tissues from breast cancer patients, who underwent radical surgery at the Cancer Center of the Affiliated People’s Hospital of Hubei University of Medicine from Jan. 2017 to Sep. 2017, were collected for this study. qRT-PCR was used to detect the differential expression of RP3-340N1.2 in collected tissue samples and breast cancer cell lines and normal breast epithelial cell line. RP3-340N1.2 plasmid (experimental group) and the negative control plasmid (control group) were transfected into breast cancer MCF-7 cells using Lipofectamine 3000. Cell counting (CCK-8) and Transwell migration assay were used to examine the effect of RP3-340N1.2 over-expression on proliferation and migration of MCF7 cells, the effect of RP3-340N1.2 over-expression on the mRNA expression of miR-134-5p and OPCML was detected by qRT-PCR, and Western blotting was used to detect the expression of OPCML protein. Results: The expression of RP3-340N1.2 in breast cancer tissues was significantly lower than that in adjacent tissues (P<0.01),and the expression of RP3-340N1.2 in breast cancer cell lines was significantly lower than that in normal breast epithelial cells (P<0.01). Up-regulation of RP3-340N1.2 decreased the proliferation and migration of MCF7 cells (all P<0.05). After over-expression of RP3-340N1.2 in MCF7 cells, the expression of miR-134-5p obviously decreased (P<0.01); moreover, the mRNA and protein expressions of OPCML significantly increased (P<0.01) while the expressions of cell cycle regulatory proteins (CDK4, Cyclin D2) and cell migration regulatory proteins (Vimentin and N-cadherin) decreased significantly (all P<0.01). Conclusion: RP3-340N1.2 is low expressed in breast cancer tissues and cell lines. Up-regulation of RP3-340N1.2 expression can lead to decreased expression of miR-134-5p and increased expression of OPCML gene, thereby inhibiting the proliferation and migration of breast cancer cells.