The level of HOTAIR expression in gastric cancer cells and its effect on cell proliferation in vitro. (A) Results from qRT-PCR demonstrating HOTAIR expression levels of gastric cancer cell lines (MGC-803, SGC-7901, BGC-823, and AGS) compared with normal gastric epithelium cell line (GES-1), NSCLC cell line (SPC-A1) compared with normal human bronchial epithelial cell line (16HBE), and breast cancer cell lines MDA-MB-231 compared with MCF-7. (B) qRT-PCR analyses of HOTAIR expression level following treatment BGC-823 cells with siRNAs targeting HOTAIR and treatment SGC-7901 cells with pCDNA/HOTAIR vector. (C) MTT assay was performed to determine the proliferation of si-HOTAIR-transfected BGC-823 cells or pCDNA/HOTAIR-transfected SGC-7901 cells. Data represent the mean ± s.d. from three independent experiments. (D) Colony-forming growth assay was performed to determine the proliferation of si-HOTAIR transfected BGC-823 cells. Colonies were counted and captured. *P < 0.05 and **P < 0.01.