oor prognosis, as was the low expression level of two lncRNAs.

Our meta-analysis focused on four lncRNAs (TUG1, UCA1, BCAR4, HULC), the putative prognostic value of which in osteosarcoma has been clearly demonstrated in more than one study. The lncRNA TUG1, short for Taurine upregulated gene 1, was originally reported to be upregulated in response to taurine treatment of developing mouse retinal cells and has been frequently described as an oncogene in various human cancers.[@b34-ott-10-5355]--[@b36-ott-10-5355] UCA1 (urothelial carcinoma associated 1) was initially identified in human bladder carcinoma and has been shown to exert oncogenic activity in other human malignant tumors such as pancreatic cancer and lung cancer.[@b37-ott-10-5355]--[@b39-ott-10-5355] BCAR4 (breast cancer antiestrogen resistance 4) was first identified in screening for tamoxifen resistance-associated genes in breast cancer and has been recently implicated in the positive regulation of cell proliferation, invasion, and metastasis,[@b40-ott-10-5355],[@b41-ott-10-5355] demonstrating this molecule as a critical oncogene. HULC (highly upregulated in liver cancer) is one of the first strongly overexpressed lncRNAs to be identified in primary tumors of the liver.[@b42-ott-10-5355] Since it was discovered, the aberrant upregulation of HULC has been frequently observed in other types of tumors and has been described in various cellular processes such as cell proliferation, metastasis, and angiogenesis.[@b43-ott-10-5355],[@b44-ott-10-5355] To enhance the statistic power to confirm the prognostic efficacy of these lncRNAs in osteosarcoma, subgroup analysis with a fixed- or random-effect-model was carried out in the current study. The combined HRs indicated that elevated expression of TUG1, UCA1, BCAR4, and HULC was significantly correlated with poor prognosis of osteosarcoma patients ([Figures 2](#f2-ott-10-5355){ref-type="fig"}[](#f3-ott-10-5355){ref-type="fig"}[](#f4-ott-10-5355){ref-type="fig"}--[5](#f5-ott-10-5355){ref-type="fig"}), suggesting