GAPDH and breast carcinoma: Whole cell lysates (100 μg) from eight breast cancer cell lines—Four with low constitutive pStat3 levels (MCF7, T47D, BT474 and MDA-MB-453 [5]) and four with increased constitutive pStat3 levels (HCC1954, MDA-MB-231, MDA-MB-468, and BT549)—Were subjected to SDS-PAGE, transferred to nitrocellulose membranes and probed for total pStat3 (Tyr-705, clone D3A7), tStat3 (clone 124H6), Stat3α (clone D1A5), Stat3β (1488 G6G5) and GAPDH (Figure 7A).