ABSTRACT
Recent evidence indicates that long noncoding RNA colon cancer-associated transcript-1 (lncRNA CCAT1) is abundantly expressed in esophageal cancer and is closely related to the occurrence, development, invasion, metastasis, and drug resistance of this disease. However, the role and molecular mechanisms of CCAT1 in the cell proliferation and chemoresistance of esophageal cancer are largely unknown. The correlation between CCAT1 expression and drug resistance to cisplatin (CDDP) in esophageal squamous cell carcinoma (ESCC) cells was analyzed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) and quantitative real-time polymerase chain reaction (qRT-PCR) assays. CCAT1 knockdown and miR-143 overexpression or inhibition were used to verify the effects on proliferation and drug resistance via MTT, western blotting, flow cytometry, and immunofluorescence assays. qRT-PCR and western blotting were applied to detect the potential regulatory relationship among CCAT1, miR-143, PLK1, and BUBR1. A xenograft tumor assay was performed to validate the role of CCAT1 in vivo. The expression of CCAT1 was positively correlated with drug resistance in several ESCC cell lines. CCAT1 knockdown and miR-143 overexpression inhibited cell proliferation and CDDP drug resistance. Moreover, the downstream target of CCAT1 was found to be miR-143, which can regulate the expression of PLK1 and BUBR1. In vivo assays showed that CCAT1 knockdown suppressed tumor growth and enhanced the sensitivity of tumors to CDDP in nude mice. Taken together, we discovered a novel mechanism by which CCAT1 promotes cell proliferation and enhances drug resistance by regulating the miR-143/PLK1/BUBR1 signaling axis both in vitro and in vivo. Our findings further suggest that lncRNA CCAT1 may be a potential therapeutic target for overcoming chemoresistance in esophageal cancer.