Overexpression of the long non-coding RNA, linc-UBC1, is associated with poor prognosis and facilitates cell proliferation, migration, and invasion in colorectal cancer

Abstract

Long non-coding RNAs (lncRNAs) serve comprehensive roles in various diseases, including cancer. lncRNA upregulated in bladder cancer 1 (linc-UBC1) is a notable biomarker of prognosis in certain cancer types; however, its involvement in the progression of colorectal cancer (CRC) remains unknown. The present study aimed to investigate the expression of linc-UBC1 in patients with CRC and to investigate its effect on CRC cells. The expression levels of linc-UBC1 were estimated by reverse transcription-quantitative polymerase chain reaction in clinical CRC specimens and matched adjacent non-tumor mucosa from 96 cases of CRC, as well as in a number of CRC cell lines. In addition, the biological roles of linc-UBC1 were examined using a cell counting kit-8 assay, flow cytometry, and migration and invasion assays following the downregulation of linc-UBC1 by small interfering RNA. The results revealed that linc-UBC1 was significantly overexpressed in CRC tissues and the majority of CRC cell lines compared with the matched non-tumor mucosa and normal intestinal epithelial cells. Furthermore, high expression levels of linc-UBC1 were significantly associated with large tumor size, greater tumor depth, lymph node metastasis, and advanced tumor-node-metastasis stages. Patients with abnormal expression of linc-UBC1 had poorer overall survival times according to Kaplan-Meier analyses. Furthermore, multivariate Cox regression analysis indicated that linc-UBC1 was a significant independent prognostic factor. The results also revealed that reducing the expression of linc-UBC1 led to the inhibition of migration, invasion, and proliferation of CRC cells in vitro. Taken together, the results of the present study suggest that overexpression of linc-UBC1 promotes proliferation and metastasis in CRC, and may be considered as a novel diagnostic marker of CRC.

Keywords: colorectal cancer; diagnosis; gene function; linc-UBC1; long non-coding RNA; prognosis.

Figure 1

Expression of linc-UBC1 and OS curves in 96 patients with CRC. Notes: (A) The expression level of linc-UBC1 in CRC tissues was significantly higher than that in its adjacent noncancerous epithelial tissues (*P<0.001). (B) The OS time of the high linc-UBC1 expression group of CRC patients was significantly shorter than that of the low expression group (P=0.002). Abbreviations: linc-UBC1, long non-coding RNA upregulated in bladder cancer 1; OS, overall survival; CRC, colorectal carcinoma.

Figure 2

Expression of linc-UBC1 in CRC and normal cells and its role in the regulation of proliferation. Notes: (A) Expression of linc-UBC1 was markedly higher in the majority of CRC cell lines (SW620, HCT116, and HT29) compared with its expression in NCM460 colonic epithelial cells (*P<0.01). The SW620 cell line exhibited the highest expression level. No difference in expression was identified between SW480 and NCM460 cells. (B) Following treatment with si-linc-UBC1, linc-UBC1 expression in SW620 cell lines was significantly downregulated compared with that in si-NC-treated cells (*P<0.001). (C) The siRNA-mediated silencing of linc-UBC1 significantly inhibited cell proliferation in the SW620 cells (*P<0.05). Abbreviations: linc-UBC1, long non-coding RNA upregulated in bladder cancer 1; CRC, colorectal carcinoma; siRNA, small interfering RNA; si-linc-UBC1, siRNA targeting linc-UBC1; si-NC, negative control siRNA; OD, optical density.

Figure 3

Impact of linc-UBC1 on apoptosis and cell cycle distribution of SW620 cells as analyzed by flow cytometry. Notes: (A) Image of cell apoptosis. (B) Image of cell cycle. (C) Downregulation of linc-UBC1 induced cell cycle arrest at the G2/M phase (*P<0.01). (D) In comparison with si-NC-transfected cells, induction of cell apoptosis was observed in si-linc-UBC1-transfected cells (*P<0.001). Abbreviations: linc-UBC1, long non-coding RNA upregulated in bladder cancer 1; si-NC, negative control siRNA; si-linc-UBC1, siRNA targeting linc-UBC1; siRNA, small interfering RNA; LR, lower right quadrant; UR, upper right quadrant.

Figure 4

Results of the Western blot analysis of the levels of Bcl-2, cleaved caspase-3, cleaved caspase-9, and GAPDH. Notes: When transfected with si-linc-UBC1, cleaved caspase-3 and cleaved caspase-9 were significantly increased, whereas Bcl-2 was decreased compared with si-NC-transfected cells (P<0.05). Abbreviations: si-NC, negative control siRNA; si-linc-UBC1, siRNA targeting linc-UBC1; siRNA, small interfering RNA; GAPDH, glyceraldehyde-3-phosphate dehydrogenase.

Figure 5

Impact of linc-UBC1 on the migration and invasion of SW620 cells (crystal violet staining; original magnification, ×200). Notes: (A) When transfected with si-linc-UBC1, fewer SW620 cells migrated through the basement membrane compared with si-NC-transfected cells (*P<0.01). (B) When transfected with si-linc-UBC1, fewer SW620 cells invaded through the basement membrane compared with si-NC-transfected cells (*P<0.01). Abbreviations: linc-UBC1, long non-coding RNA upregulated in bladder cancer 1; si-linc-UBC1, siRNA targeting linc-UBC1; si-NC, negative control siRNA; siRNA, small interfering RNA.