Degradation-resistant HOXB4 confers a proliferative advantage to the 32D myeloid cell line. (A) Expression levels of HA-HOXB4 (wild-type or mutant) in 32D stable lines, as determined by immunoblotting with the anti-HA antibody. (B) Cumulative expansion of 32D stable lines in serum-free medium. (C) Cycloheximide chase analysis for the half-lives of HA-HOXB4 (wild-type or mutant) in 32D stable lines. HA-HOXB4 or HA-HOXB4(m) levels were determined by immunoblotting at the indicated time points. β-actin levels were determined as the loading control.