MiR-145, miR-133a and miR-133b inhibit proliferation, migration, invasion and cell cycle progression via targeting transcription factor Sp1 in gastric cancer

• miR-145, miR-133a and miR-133b were down-regulated in gastric cancer cell lines and tissues.
• miR-145, miR-133a and miR-133b induced G1 cell cycle arrest and inhibited cell proliferation, migration and invasion in gastric cancer cells.
• SP1 was identified as target of miR-145, miR-133a and miR-133b and negatively regulated by miR-145, miR-133a and miR-133b.
• MiR-145, miR-133a and miR-133b down-regulate the expression of MMP-9 and Cyclin D1 via decreasing Sp1 expression in gastric cancer cells.

MicroRNAs have recently emerged as key regulators of gastric cancers. Here we found that miR-145, miR-133a and miR-133b were down-regulated in gastric cancer tissues and cell lines. Overexpression of miR-145, miR-133a and miR-133b induced G1 cell cycle arrest and inhibited cell proliferation, migration and invasion in vitro. MiR-145, miR-133a and miR-133b targeted the transcription factor SP1, knockdown of which reduced the expression of MMP-9 and Cyclin D1 that were involved in cell growth and invasion. Thus, our findings demonstrated for the first time that miR-145, miR-133a and miR-133b suppressed the proliferation, migration, invasion and cell cycle progression of gastric cancer cells through decreasing expression of Sp1 and its downstream proteins.