Figure 4. JO-1 increases mAb killing of cells in which the target receptors are trapped in epithelial junctions.

A) Confocal microscopy of Her2/neu (green) and DSG2 (red) staining on polarized BT474 cell cultures (XY and XZ images). Cells treated with PBS are shown in the left panel. Middle and right panels: Cells were treated with JO-1 (20 μg/ml) for 1 h on ice. After removal of JO-1, cells were incubated at 37 °C and analyzed 1 h and 16 h later. XY images show the cell surface (left) and a section 2 μm below the cell surface. The scale bar is 40 μm. B) Confocal microscopy of EGFR (red) and the tight junction protein E-cadherin (green) on polarized A549 lung cancer cells. C) JO-1 enhances killing of Her2/neu-positive breast cancer cells by trastuzumab. BT474 cells were incubated with JO-1 (5 μg/ml) or PBS. Trastuzumab (15 μg/ml) was added 1 h later. Cell viability was measured after 3 h by WST-1 assays as described earlier (34). Viability of PBS-treated cells was taken as 100%. n = 5, D) JO-1 enhances cetuximab killing of EGFR-positive A549 cells. n = 5, * p<0.05