E2F1 and breast cancer: The RB and mutant proteins were expressed in the RB-deficient breast cancer cell line MBA-MD468 through adenoviral-mediated gene transfer, and lysates from the adenovirus-infected cells were then applied to glutathione-agarose beads loaded with GST-E2F1 or GST-E7 recombinant proteins purified from bacteria (Fig. 1B).