FIGURE 2.

Down-regulation of cellular and extracellular tumor-suppressive miRNAs in PC-3M-luc cells. A, shown is a schematic representation of hypothetical tumor initiation process. Neighboring healthy cells (blue) secrete tumor-suppressive miRNAs (light yellow) to inhibit the proliferation of abnormal cells (gray), and this cell population returns to the initial healthy condition (a homeostatic cycle). Once the cell competitive cycle is compromised, this niche become susceptible to tumor initiation (indicated by a dashed arrow). B, comparison of cellular and extracellular miRNAs expression in PNT-2 and PC-3M-luc cells is shown. miRNA expression levels were determined by a Taq-Man QRT-PCR. The values on the y axis are depicted relative to the normalized expression level of PNT-2 cells, which is defined as 1. C, secretion of miR-143 was suppressed by the treatment with GW4869. PNT-2 cells were seeded and cultured in a 24-well plate for 48 h in the indicated concentrations of GW4869. After the incubation, the medium was subjected to QRT-PCR for miR-143. The values on the y axis are depicted relative to the amount of miR-143 at 0 μm GW4869, which is defined as 1. D, shown is cell growth inhibition by miR-143 in PC-3M-luc cells but not in PNT-2 cells. PNT-2 and PC-3M-luc cells were transfected with 10 nm miR-143 molecules (miR-143) or 10 nm negative control molecules (control) or without RNA molecules (Mock). The values on the y axis are depicted relative to the normalized luciferase activity of untreated cells (Mock), which is defined as 1. Each bar is presented as the mean S.E. (n = 3). *, p < 0.05; **, p < 0.005, as compared with untreated PC-3M-luc cells; Student's t test.