TP53 and breast cancer: The p53 and estrogen receptor status were not recorded but may be of interest in future trials, as in vitro studies suggest proteasome inhibition is at least partially dependent on the p53 status in breast cancer (MacLaren et al, 2001), and estrogen-receptor-negative status plus a dysregulated IκBα/NF-κB system is associated with greater bortezomib antitumour activity (Tapia et al, 2005).