ACTB and osteosarcoma: FLAG-tagged gankyrin over-expression was first optimised in the (p53 normal) osteosarcoma cell line U2OS to enable the detection of small changes in intracellular protein levels in whole cell lysates 48 hours post transfection, a significant reduction in p53 levels could be detected without any change in the levels of housekeeping protein β-actin (Fig. 6a).