miR-26a overexpression inhibits the tumorigenesis and metastasis of human-tumor xenografts. (a–j) Melanoma (a, b), prostate (c, d) and liver (e–j) cancer cell lines transduced with either MPG-C or MPG-26a were injected subcutaneously into NOD-SCID mice. Tumor volume was monitored over time. (a–f) Tumor growth and weight of A375 (a, b, n=6 mice/group), DU145 (c, d, n=4 mice/group) and SK-HEP-1 (e, f, n=6 mice/group) tumor xenografts. (g) Representative pictures of livers and lungs from SK-HEP-1 xenografts. Visible liver and lung metastases were observed only in mice injected with control SK-HEP-1 cells (MPG-C). Arrows indicate metastases. (h) Percentage of mice with metastases, number of metastases, size of metastases and organ:body weight ratio as determined in mice bearing SK-HEP-1 xenografts. (i, j) Representative hemotaxylin–eosin (H&E) and proliferating cell nuclear antigen (PCNA) staining of lungs (i) and livers (j) from mice bearing SK-HEP-1 xenograft. White cycles indicate metastases. Scale bars, 100 μM. (k, l) A375 cells transduced with either MPG-26a or MPG-C vector were injected into NOD-SCID mice via the tail vein (n=6–7 mice/group). Metastasis was evaluated 3 weeks after the injection. (k) Number of total tumors. (l) Representative pictures of livers and lungs with tumors. Arrows indicate metastases. Data are shown as means±s.e.m. Statistical significance, determined using two-tailed ANOVA (a, c, e) and two-tailed Student’s t-test (b, d, f, h, k), is indicated by *P<0.05; **P<0.01; and ***P<0.005.