AR and prostate cancer: Their expression indeed induced transcriptional activity of the PSA enhancer/promoter cis-regulatory region under androgen-depleted conditions to some but lesser extents than TPL2. However, when tested in androgen receptor (AR)-negative DU-145 prostate cancer cells, TPL2 did not induce the ADI transcriptional activity, suggesting that AR expression is necessary for the ADI transcriptional activation of the PSA enhancer/promoter cis-regulatory region induced by TPL2 (Figure 1B middle; please note the change in the scale of the Y-axis).