Inhibition of MALAT1 reduces tumor growth and metastasis and promotes drug sensitivity in colorectal cancer.

Human metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) is a long non-coding RNA known to be highly expressed in several tumors. In colorectal cancer (CRC), MALAT1 promotes cell proliferation, metastasis, and invasion in vitro and in vivo. This study aimed to investigate the effect of MALAT1 on the proliferation, migration, and drug sensitivity of CRC cells in vitro and in vivo and the mechanisms involved therein. We observed increased expression of MALAT1 in six CRC cell lines compared to that in normal cells, suggesting its involvement in CRC progression. Downregulation of MALAT1 inhibited cell migration and induced apoptosis in vitro and inhibited tumor growth and metastasis in nude mice. Furthermore, MALAT1 silencing downregulated the expression of ATP-binding cassette transporters (ABC), breast cancer resistance protein (BCRP), and multi-drug resistance proteins including MDR1 and MRP1, resulting in decreased resistance of cancer cells to 5-FU. In addition, the metastasis and invasion of HCT-116 and HCT-116/5-FU cells were regulated via targeting miR-20b-5p. Based on these observations, we infer that inhibition of MALAT1 suppressed CRC progression and metastasis and improved the sensitivity of cancer cells to 5-FU. The present study proposes a new direction to investigate the molecular mechanisms underlying the invasion and metastasis of CRC, whereby the interaction between MALAT1 and miR-20b-5p could be a novel therapeutic target for CRC.