PML/RAR expression in NB4.007/6 cells. (A) Western blot analysis of NB4 and NB4.007/6 whole-cell lysates using an anti-RAR antibody. The immunoreactive polypeptide that migrates above the indicated PML/RAR in both cell lysates is an anti-RAR cross reactive cellular protein. (B) In vitro degradation of PML/RAR in NB4 and NB4.007/6 cell lysates: NB4 cell lysate or NB4.007/6 + NB4 mixed cell lysates were incubated as indicated and 20 μg (NB4; top panel) or 40 μg (NB4.007/6 + NB4; bottom panel) of proteins were resolved by SDS-PAGE and analyzed by Western blotting using an anti-RAR antibody.