Moreover, colony formation assay was performed to detect the effect of MTDH targeting miR-9-3p on clone formation of Gem-treated breast cancer cells, and we found that overexpression of miR-9-3p inhibited clone formation and significantly promoted Gem-treated clone formation inhibition, which was partially reversed by overexpression of MTDH (P < 0.05, Fig. 7E, G). This evidence concerns the gene MTDH and breast cancer.