Liu Zhen-Ji, Ma Yuan-Yuan, Liu Tong-Ming, Wang Jian-Xin, Zhang Li, Jin Lei, Yu Miao, Yu Hua-Long
Department of Colorectal and Anal Surgery, The Second Hospital of Shandong University, Ji'nan 250033, China.
Department of Anorectal Surgery, Feicheng People's Hospital, Taian 271600, China.
Transl Cancer Res. 2019 Aug;8(4):1540-1549. doi: 10.21037/tcr.2019.08.04.
Let-7d has been reported to serve as a tumor suppressor in numerous cancers, however, the function in rectum adenocarcinoma has not been illuminated. In this study, we aimed to explore whether let-7d functions in rectum adenocarcinoma and its functional significance links to ATP binding cassette subfamily C member 2 (ABCC2).
The expression patterns of let-7d and ABCC2 were gained from TCGA database. Then, cell proliferation, invasion and migration assays were conducted to detect the influence on rectum adenocarcinoma cells behaviors after over-expression of let-7d. Subsequently, the potential target gene of let-7d was predicted and identified through bioinformatics prediction analysis and luciferase reporter assay. Analyses against prognostic value and independent predictor were acquired from Kaplan-Meier, Univariate and Multivariate analysis of Cox regression. Finally, con-transfection experiments were performed to investigate let-7d/ABCC2 pairs function on rectum adenocarcinoma cells after co-transfected with let-7d mimic and si-ABCC2. mRNA and protein levels were assessed by reverse transcription quantitative polymerase chain reaction (qRT-PCR) and western blot.
The data from TCGA indicated that let-7d was down-regulated in rectum adenocarcinoma samples, whilst ABCC2 was showed a trend of high expression and its overexpression hinted to worse overall survival of rectum adenocarcinoma patients. Cells proliferation, invasion and migration properties were restrained after over-expression of let-7d in SW837 cells. Further investigations showed that over-expression of let-7d induced the inhibitory effect on SW837 cells proliferative, migrant and invasive capacities was augmented by silencing ABCC2.
All results in this study indicated that up-regulation of let-7d could suppress SW837 cells growth, invasion and migration abilities by reducing ABCC2 expression, providing a new insight into molecular mechanism of let-7d/ABCC2 as a significant mediator for tumor progression and development of rectum adenocarcinoma.
据报道，Let-7d在多种癌症中发挥肿瘤抑制作用，然而，其在直肠腺癌中的功能尚未阐明。在本研究中，我们旨在探讨Let-7d在直肠腺癌中是否发挥作用及其功能意义是否与ATP结合盒亚家族C成员2（ABCC2）相关。
从TCGA数据库中获取Let-7d和ABCC2的表达模式。然后，进行细胞增殖、侵袭和迁移实验，以检测Let-7d过表达后对直肠腺癌细胞行为的影响。随后，通过生物信息学预测分析和荧光素酶报告基因检测预测并鉴定Let-7d的潜在靶基因。通过Kaplan-Meier法、单因素和多因素Cox回归分析评估预后价值和独立预测因素。最后，进行共转染实验，研究Let-7d模拟物和si-ABCC2共转染后Let-7d/ABCC2对直肠腺癌细胞的作用。通过逆转录定量聚合酶链反应（qRT-PCR）和蛋白质印迹法评估mRNA和蛋白质水平。
TCGA数据表明，Let-7d在直肠腺癌样本中表达下调，而ABCC2呈高表达趋势，其过表达提示直肠腺癌患者的总生存期较差。在SW837细胞中过表达Let-7d后，细胞增殖、侵袭和迁移特性受到抑制。进一步研究表明，沉默ABCC2可增强Let-7d过表达对SW837细胞增殖、迁移和侵袭能力的抑制作用。
本研究的所有结果表明，Let-7d的上调可通过降低ABCC2的表达来抑制SW837细胞的生长、侵袭和迁移能力，为Let-7d/ABCC2作为直肠腺癌肿瘤进展和发展的重要介质的分子机制提供了新的见解。
