乳腺癌组织和细胞中低表达的LZTS2 通过PI3K/AKT信号通路抑制癌细胞增殖、迁移和EMT

摘要] 目的：探讨亮氨酸拉链肿瘤抑制因子2（leucine zipper tumor suppressor 2, LZTS2）基因在人乳腺癌组织和细胞系中的表达及其对乳腺癌细胞增殖、迁移和EMT的影响及其作用机制。方法：收集2016 年1 月至2016 年12 月开封中心医院乳腺外科收治的50 例女性乳腺癌患者的癌及癌旁组织标本和乳腺癌细胞系MCF-7、MDA-MB-231、MDA-MB-468 以及正常人乳腺上皮细胞株HBL-100，用qPCR 和Western blotting 检测乳腺癌组织和细胞中LZTS2 mRNA和蛋白表达水平。构建pcDNA-LZTS2 真核表达载体并采用脂质体转染MCF-7 细胞，同时转染pcDNA3.1 作为阴性对照。用Western blotting 检测转染48~72 h 后MCF-7 细胞中LZTS2 蛋白表达水平；用MTT法、Transwell 小室法检测LZTS2 过表达对细胞增殖、迁移和侵袭的影响，同时用Western blotting检测细胞中EMT相关蛋白Cyclin D1、波形蛋白、神经钙黏蛋白、上皮钙黏蛋白以及PI3K/AKT信号通路中相关蛋白的表达。结果：人乳腺癌组织中LZTS2 mRNA和蛋白表达水平均明显低于癌旁组织（P<0.05 或P<0.01）；乳腺癌MCF-7、MDA-MB-231 和MDA-MB-468 细胞中LZTS2 mRNA和蛋白表达水平显著低于乳腺上皮细胞HBL-100（P<0.05 或P<0.01）。与空白对照组和pcDNA3.1组相比，pcDNA-LZTS2 组MCF-7 细胞中LZTS2 蛋白表达水平明显上调（P<0.01），细胞增殖、迁移和侵袭能力显著受到抑制（P<0.05 或P<0.01），同时过表达LZTS2 细胞中Cyclin D1、波形蛋白和神经钙黏蛋白表达水平均明显降低（P<0.05 或P<0.01）、上皮钙黏蛋白表达水平明显升高（均P<0.01），显示LZTS2 过表达通过降低p-PI3K和p-AKT 表达而抑制PI3K/AKT信号通路。结论：LZTS2 在乳腺癌中低表达，过表达LZTS2 能够抑制乳腺癌细胞的增殖、迁移和侵袭能力，可能与抑制细胞EMT过程的PI3K/AKT信号通路有关。

LZTS2 inhibits proliferation, migration and EMT of breast cancer cells by modulating PI3K/AKT signaling pathway

Abstract] Objective: To evaluate the expression of leucine zipper tumor suppressor 2 (LZTS2) in human breast cancer tissues and cell lines, and to investigate the effects and mechanisms of LZTS2 over-expression on proliferation, invasion and epithelial-mesenchymal transition (EMT) of breast cancer cells. Methods: Fifty pairs of cancerous tissues and para-cancerous tissues resected from breast cancer patients in Department of Breast Surgery of Kaifeng Central Hospital from January, 2016 to December, 2016, as well as breast cancer cell lines (MCF-7, MDA-MB-231, MDA-MB-468) and normal mammary epithelial HBL-100 cells were collected for this study;and Real-time quantitative PCR (qPCR) and Western blotting were used to determine the mRNA and protein expressions of LZTS2 in collected tissues and cell lines. MCF-7 cells were transfected with pcDNA-LZTS2 or pcDNA3.1 (negative control) using lipofectamineTM 2000, and the protein expression of LZTS2 at 49-72 h after transfection was measured by Western blotting; Then, the effects of LZTS2 over-expression on proliferation, migration and invasion of MCF-7 cells were detected by MTT assay and Transwell assay, respectively;Furthermore, Western blotting was performed to detect the expressions of EMT associated proteins (Cyclin D1, Vimentin, Ncadherin,E-cadherin) and PI3K/AKT signaling pathways-related molecules. Results: The mRNA and protein expressions of LZTS2 were down-regulated in breast cancerous tissues and cell lines (MCF-7, MDA-MB-468 and MDA-MB-231) as compared with paired para-cancerous tissues or normal mammary epithelial HBL-100 cells (P<0.05 or P<0.01). Compared with and blank control or pcDNA3.1 group, the protein expression of LZTS2 in MCF-7 cells of pcDNA-LZTS2 group significantly increased (P<0.01), while the proliferation,migration and invasion of MCF-7 cells significantly reduced (P<0.05 or P<0.01). In addition, forced expression of LZTS2 significantly down-regulated the protein expressions of Cyclin D1, Vimentin and N-cadherin (P<0.05 or P<0.01) but up-regulated the expression of E-cadherin in MCF-7 cells (P<0.01), indicating LZTS2 over-expression suppressed PI3K / AKT signaling pathway through inhibiting the expression p-PI3K and p-AKT. Conclusion: The findings collectively demonstrated that the expression of LZTS2 was decreased in breast cancer, and over-expression of LZTS2 efficiently inhibited the proliferation, migration and invasion of breast cancer cells, which might be related with the suppression of PI3K/AKT signaling pathway involved in EMT.