MMP3 and neoplasm: The mRNA expression of some proliferation and invasion related genes such as CCND3, CCNE1, Ki-67 and MMP3 were all down-regulated in miR-15a/miR-16-1 overexpression group (Additional file 3: Figure S1E), elucidating the tumor-suppressive functions of miR-15a and miR-16-1 in gastric tumorigenesis.