Let-7c increased in DS cell line and reduced generation of Aβ. A. Low-density Taqman array performed to identify panels of miRNA expression in DS cell line MB1478 and normal cell line UMB115; B. 20E2 cells transfected with pmiR-let-7c, pmiR-99a, pmiR-155 or control, and Aβ quantity detected by ELISA Assay. *P<0.05, let-7c compared to the control group; C and D. pZ-APPsw and pAPP-C99 transfected into HEK293 cells with pmiR-let-7c or not, respectively, and Aβ quantity detected by ELISA Assay. *P<0.05, compared to the control group; E. HEK293 cells transfected with pmiR-let-7c or not, respectively, and cell proliferation detected by MTT assay. Values represent means ± SD, n=3.