Effects of prostaglandin E 2 on p53 mRNA transcription and p53 mutagenesis during T‐cell‐independent human B‐cell clonal expansion

Within T‐cell‐dependent germinal centers, p53 gene transcription is repressed by Bcl‐6 and is thus less vulnerable to mutation. Malignant lymphomas within inflamed extranodal sites exhibit a relatively high incidence of p53 mutations. The latter might originate from normal B‐cell clones manifesting activation‐induced cytosine deaminase (AID) and up‐regulated p53 following T‐cell‐independent (TI) stimulation. We here examine p53 gene transcription in such TI clones, with a focus on modulatory effects of prostaglandin E 2 (PGE 2 ), and evaluate progeny for p53 mutations. Resting IgM + IgD + CD27 ‐ B cells from human tonsils were labeled with CFSE and stimulated in vitro with complement‐coated antigen surrogate, IL‐4, and BAFF ± exogenous PGE 2 (50 nM) or an analog specific for the EP2 PGE 2 receptor. We use flow cytometry to measure p53 and AID protein within variably divided blasts, qRT‐PCR of p53 mRNA from cultures with or without actinomycin D to monitor mRNA transcription/stability, and single‐cell p53 RT‐PCR/sequencing to assess progeny for p53 mutations. We report that EP2 signaling triggers increased p53 gene transcriptional activity in AID + cycling blasts ( P <0.01). Progeny exhibit p53 mutations at a frequency (8.5 × 10 –4 ) greater than the baseline error rate (<0.8 × 10 –4 ). We conclude that, devoid of the repressive influences of Bcl‐6, dividing B lymphoblasts in inflamed tissues should display heightened p53 transcription and increased risk of p53 mutagenesis.—Haque, S., Yan, X. J., Rosen, L., McCormick, S., Chiorazzi, N., Mongini, P. K. A. Effects of prostaglandin E 2 on p53 mRNA transcription and p53 mutagenesis during T‐cell‐independent human B‐cell clonal expansion. FASEB J. 28, 627–643 (2014). www.fasebj.org