Targeting Stat3 pathway inhibits cell growth and viability. Transduction of dnStat3 suppressed cell growth of bladder cancer cell lines, (A) UMUC-3, at day 4 post infection and (B) WH, at day 2 and 4 post infection. Growth of bladder cancer cells was strongly suppressed by the expression of dnStat3. Cells were transduced with either rAd/dnStat3 or rAd/eGFP (moi = 100 or 500) while untransduced cells served as negative controls. Cells in five random individual microscopic fields (100×) were scored at day 2 or day 4 post-infection. (C) MTT assay also shows that transduction of dnStat3 limits cell growth of bladder cancer cell lines (WH and 253J) with higher content of p-Stat3 but not that of those cells with less p-Stat3 at 4 day post-infection. Cell growth was shown in cell density over control cell density (%). (D) Cell viability of cancer cells was greatly reduced after treatment of STA-21, a Stat3 dimerization inhibitor. Cells were treated with DMSO or 30 μM STA-21 for 4 days. STA-21 had very limited effects on BdSMC cell viability. Cell viability was determined using a MTT assay. Averages and standard deviations for data points were derived from triplicate experiments. * (P < 0.05) and ** (P < 0.005) indicate paired t-test statistic significance.