Androgen receptor (AR) + triple-negative breast cancer (TNBC) cell lines have activated PI3K signaling and respond to dihydrotestosterone (DHT) stimulation (A) Graphs display relative viability of the prostate cancer cell line (LNCAP, red line) compared to each of the AR + TNBC cell lines (blue line) 5 days after addition of increasing doses of DHT in charcoal-stripped media. (B) Heatmap displays relative protein levels (reverse-phase protein array, RPPA) of AR, p-AKT (S473 and T308), p-GSK3β (S9 and S21) and PTEN across indicated TNBC cell lines. Unsupervised hierarchical clustering was performed on PI3K pathway proteins (PTEN, p-AKT and p-GSK3β). Known PI3K pathway aberrations are indicated in the colorbar as PTEN loss (blue) or PIK3CA mutations (red). (C) Immunoblot displays relative protein levels of AR, p-AKT, p-S6 in AR-expressing prostate cancer (LNCaP), primary cultures of human mammary epithelial cells (HMECs) and the indicated LAR TNBC cell lines. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) serves as a loading control. (D) Immunohistochemistry of indicated proteins was performed on cell lines to assess levels of AR and p-AKT (S473). Results are representative of three independent experiments.