Figure 7.

Breast cancer cells over‐expressing miR181b have a lower capacity to metastasize in vivo. Breast cancer cells over‐expressing miR181b had a statistically significant (Mann–Whitney test, p = 0.0070) reduction in their capacity to metastasize into the lung of the animals (A). While the average number of metastasis in mice belonging to the control group was approximately 15 per animal, animals carrying MDA‐MB‐231miR1871b cells developed an average of only 6 metastases per animal. The tumor cell morphology showed characteristic atypia, significant expression of human p53 protein was observed only in human tumor cells. Vitality of the tumor cells was confirmed by a high number of proliferating Ki‐67 positive cells thus excluding tumor cell dormancy (B). Bars in the right lower corners of all photos are equivalent to 50 μm. Expression analysis (qRT‐PCR) of a series of metastasis‐related genes in MDA‐MB‐231 cells transiently over‐expressing miR181b in comparison to corresponding MDA‐MB‐231 control cells showed that expression of the metastasis‐related genes SPARC, CXCR4, COX2, ANGPL4, EFEMP, IL‐6, and EGR1 to be statistically highly significantly down‐regulated (C) 72 h after transfection (***p < 0.001; student's t‐test). Mean + SD from 3 independent experiments are shown.