A. Stat3 downregulation eliminates gap junctional permeability in human lung carcinoma QU-DB cells. QU-DB cells were plated in electroporation chambers and subjected to a pulse in the presence of Lucifer yellow, following treatment with the DMSO carrier alone (a-c), or CPA7 (d-f), or infection with the sh-Stat3 lentiviral vector (g-i) (see Methods, Figure 8). After washing away the unincorporated dye, cells from the same field were photographed under fluorescence (b, e, h) or phase contrast (a, d, g) illumination. Cells at the edge of the conductive area which were loaded with LY through electroporation were marked with a star, and cells at the non-electroporated area which received LY through gap junctions were marked with a dot . Arrows point to the edge of the electroporated area. c, f, i: Overlay of phase-contrast and fluorescence. Magnification: 240 x. Note the extensive gap junctional communication in (b). B. Stat3 downregulation does not increase gap junctional permeability in human lung carcinoma A549 cells. Same as above, A549 cells. Note the absence of GJIC, even after Stat3 downregulation (e, h).