Figure 4

CDKN1A expression prognosticates poor outcome in human BL. (A) Kaplan-Meier curves indicating decreased survival of BL patients expressing high levels of p21 message (Mantel-Cox log-rank analysis). Data are from Dave et al. (GSE4732, probe 202284) [15]. The left panel depicts survival of 51 patients evenly split according to p21 expression into a p21^Low group and a p21^High group. The former demonstrated better outcome (p = 0.0126). The right panel shows survival of 33 patients treated with either a CHOP-like regimen or an intensive (INT) drug regimen supplemented in some cases with autologous hematopoietic stem cell transplantation. p21^Low patients demonstrated better outcomes than p21^High patients in both treatment arms. (B) CDKN1A and TP53 expression in 5 human BL cell lines and 1 mouse BL-like cell line, Hal1, derived from a LMP1-transgenic lymphoma. Daudi, Raji and Jiyoye are EBV⁺ and thus express virus-encoded LMP1. DG75 and Ramos are EBV^-. Because LMP1 activates NF-κB in malignant B cells [43], it is possible that p21 expression in LMP1⁺ cells is driven, in part, by LMP1. (C) EMSA indicating p53 DNA-binding activity in BL and normal B cells. (D) Piperlongumin (PL)-induced activation of the p53-p21 stress response in BL cells. Shown at the top is the growth inhibition of cells upon treatment with 10 μM or 15 μM PL for 24 hrs (MTS assay). Mean values and error bars, which represent the standard deviation from triplicate experiments, are plotted. The center panel shows the corresponding p21 message levels (qPCR). Differences in both panels were not significant (Mann–Whitney, p = 0.1). Presented at the bottom are the corresponding EMSA results at 24 hrs, indicating that the drug dose-dependent induction of p53 DNA-binding activity was more vigorous at 10 μM PL in EBV⁻ DG75 cells compared to EBV⁺ Daudi and Raji cells.