Long non-coding RNA MALAT1 activates autophagy and promotes cell proliferation by downregulating microRNA-204 expression in gastric cancer

Gastric cancer (GC) is one of the major diseases that threaten human health. Although the development of novel drugs has significantly improved the efficacy of GC chemotherapy, the 5-year survival rate of patients with GC remains unsatisfactory. In the present study, the role and mechanism of the long non-coding RNA (lncRNA) metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) in GC proliferation was investigated. Clinical specimens and cancer cells were analyzed by western blotting or immunofluorescence. Reverse transcription-quantitative polymerase chain reaction analysis of 57 paired GC and non-tumorous tissues revealed elevated expression of MALAT1 in GC tissues compared with controls. In addition, increased MALAT1 was associated with elevated levels of microtubule-associated protein 1 light chain 3β (LC3B) and antigen Ki67, which are autophagy and proliferation markers, respectively. MTT and colony formation assay results demonstrated that MALAT1 promoted GC cell proliferation. To the best of our knowledge, the present study was the first to demonstrate that upregulated MALAT1 was associated with increased autophagy activation in GC tissues. Furthermore, this study reported that MALAT1 increased cell proliferation and enhanced autophagy activation in GC cells. In addition, the results revealed that MALAT1 inhibited microRNA (miR)-204 expression in GC cells. The present study also demonstrated that miR-204 repressed autophagy through the downregulation of LC3B and transient receptor potential melastatin 3 expression in GC cells. These results indicated that MALAT1 activated autophagy and promoted cell proliferation by downregulating miR-204 expression in GC.