Figure 3. MiR-93 enhanced breast cancer metastasis to the lung. (A) Mock- or miR-93-transfected MT-1 cells (2 × 10⁵) were injected into the tail vein of CD-1 nude mice (n = 20). Six weeks after the injection, six mice in the miR-93 group developed visible tumors in the lungs, but only one in the control group. Typical metastatic lesions in the lungs are shown (arrows). (B) H&E staining of lungs from mock and miR-93 mice showed metastasis lesions in the miR-93 lungs (arrows). (C) The sections were immunohistochemically stained with antibody against Ki67. The miR-93 tumor sections showed higher levels of Ki67 staining than the control group. (D) The sections were also probed with antibody against E2F4. The miR-93 tumor sections showed E2F4 staining, which was not detected in the control group. (E) DNA was isolated from lung tissues and subjected to PCR to amplify the CMV promoter to indicate metastasis of the tissues. Expression of miR-93 promoted metastasis.