Figure 4.

Invasion effect of DRM cells. The transwell invasion assay showed a significant increase in the invasion of DRM cells with the advancement of resistance to higher concentrations of doxorubicin. The cells were seeded with the seeding density of 5 × 10⁴ cells/well to the upper chamber of the Boyden chamber which is pre-coated with Matrigel and the cells invaded through the Matrigel were stained with DAPI. (A) The stained cells were photographed and (B) counted through ImageJ software and a number of invasive cells were graphed. The values expressed as mean ± standard deviation (SD) (n = 5) (* p < 0.05 vs. control; ** p < 0.001 vs. control). DRM: Doxorubicin-resistant MDA-MB-231.