Objective: To investigate the role of long non-coding RNA growth arrest-specific transcript 5 (lncRNA-GAS5) in breast cancer progression and epithelial-mesenchymal transition (EMT) of the cancer cells.
Methods: Real-time quantitative PCR (qRT-PCR) was used to detect the expression of lncRNA-GAS5 in 37 pairs of breast cancer and adjacent non-tumor tissues and in parental MCF-7 cells and paclitaxel-resistant MCF-7 (MCF-7/PR) cells, and the correlation of lncRNA-GAS5 expression with the clinical stage and lymph node metastasis of breast cancer was investigated. The expressions of the genes related with cell cycle and EMT at both the mRNA and protein levels were detected using qRT-PCR, Western blotting and immunohistochemistry. The changes in the biological behaviors and morphology of breast cancer cells with either lncRNA-GAS5 knockdown or overexpression were observed. Nude mouse models were established bearing breast cancer xenografts derived from MCF-7/PR cells or MCF-7/PR cells over-expressing lncRNA-GAS5, and the inhibitory effect of paclitaxel on tumor growth was evaluated.
Results: The transcriptional levels of lncRNA-GAS5 were significantly lower in breast cancer tissues than in the adjacent non-tumor tissues (P<0.05), and decreased lncRNA-GAS5 expression was significantly correlated with TNM stage and lymph node metastasis of breast cancer (P<0.05). lncRNA-GAS5 expression was also significantly lowered in paclitaxel-resistant breast cancer cells and showed a positive correlation with P21 expression and a negative correlation with CDK6. MCF-7 cells during EMT presented with a lowered expression of lncRNA-GAS5, whereas lncRNA-GAS5 over-expression strongly suppressed MCF-7/PR cell migration and invasion, and increased the susceptibility of the cells to paclitaxel. In the tumor-bearing nude mouse models, lncRNA-GAS5 overexpression in the tumor cells obviously enhanced the inhibitory effect of paclitaxel on tumor growth and lung metastasis by reversing the EMT marker proteins.
Conclusion: A decreased expression of lncRNA-GAS5 promotes lung metastasis of breast cancer by inducing EMT, suggesting the potential of lncRNA-GAS5 as a therapeutic target in breast cancer.
目的: 探讨生长停滞特异性转录本5（lncRNA-GAS5）在乳腺癌中发展和上皮细胞-间充质转化（EMT）过程中的影响。
方法: 采用实时定量聚合酶链反应法检测乳腺癌组织和癌旁组织（n=36）、乳腺癌MCF-7亲本和耐药细胞中lncRNA-GAS5的表达，并分析GAS5表达与乳腺癌临床分期和淋巴结转移相关性；qRT-PCR法、Western blot和免疫组化法检测细胞周期和EMT相关蛋白的表达；迁移、趋化和黏附分离实验检测细胞生物学活性；通过光学显微镜观察细胞的形态学变化；以耐药细胞株构建裸鼠乳腺癌模型，体内探讨过表达GAS5对紫杉醇抗乳腺癌作用的影响。
结果: LncRNA GAS5转录本水平相对于癌旁组织是显著降低的（P < 0.05），GAS5低表达与乳腺癌TNM分期和淋巴结转移相关（P < 0.05）；耐药细胞株中GAS5表达下调（P < 0.05），GAS5与P21表达正相关，而与CDK6表达呈负相关；体外干扰GAS5促进乳腺癌亲本细胞株发生EMT表型改变和侵袭能力增加，而过表达lncRNA GAS5可抑制乳腺癌耐药细胞株EMT表型和侵袭能力（P < 0.05），并提高紫杉醇的药物敏感性。体内实验发现，过表达GAS5通过逆转EMT标志蛋白，提高紫杉醇抑制肿瘤生长和肺转移的作用。
结论: LncRNA GAS5低表达可能通过诱导EMT促进乳腺癌的肺转移，可能是乳腺癌的一个潜在治疗靶点。