RARα protein and ATRA sensitivity in breast cancer cell linesTotal proteins were extracted from logarithmically growing cell lines and subjected to Western blot analysis.The panel illustrates representative Western blots for a number of cell lines. The blots were sequentially developed with RARα-specific and control tubulin antibodies. The positions of the RARα and tubulin bands (right) along with the position of a relevant molecular weight marker (left) are indicated. To normalize the Western blot signals in different gels, the same preparation of RARα-transfected COS-7cell extracts (COS-7) and MCF7 extracts was loaded in each gel. The blots are representative of at least two independent experiments providing similar results. 