The metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) is a long non-coding RNA (lncRNA) with a length of about 8000 nt. The 3′ end of MALAT1 is protected from degradation by an evolutionarily conserved triple helix and its function can partly replace poly (A). The expression of MALAT1 is regulated by TDP-43, DGCR8, and posterior pituitary hormone oxytocin, etc. MALAT1 influences the recruitment of SR proteins to transcription sites and controls the alternative splicing. MALAT1 causes the relocation of growth control genes and effectively activates the transcription unit. Besides, MALAT1 expresses highly in cancer cells and closely associates with the Wnt/b-catenin signaling pathway and Bcl-2 family. It is a key factor of cancer invasion and metastasis. Meanwhile, MALAT1 mediates B-MYB and hnRNP C, influences the cell cycle and mitosis, and causes the proliferation of cancer cells. As the diagnostic marker, prognostic marker, or new therapeutic target, lncRNA is helpful for the therapy and diagnosis of cancers.