MDM2 and p53 expression in DLBCL patients treated with R-CHOP. (A-B) Histogram showing the distribution of MDM2 and p53 expression levels in the DLBCL cohort. X-axis, percentage of immunopositive cells in tumors; Y-axis, numbers of DLBCL patients. (C) Illustration of p53 and MDM2 kinetic pulses in tumor cells under stress conditions. In a single cell, because of the fluctuating p53/MDM2 levels in oscillatory pulses, the IHC pattern is (1) p53^–/MDM2^– at zero time point A or E after cellular stress is removed; (2) p53⁺/MDM2⁺ at time point B; (3) p53^–/MDM2⁺ at time point C; and (4) p53⁺/MDM2^– at time point D. Same patterns over cell population may be generated by evaluation of the percentage of MDM2⁺ cells and defining overexpression by certain cutoffs. (D) Representative MDM2 immunohistochemical staining patterns.