Expression of Wild-Type p53 and Bcl-2 Family Genes Oscillates with Recurrent Remission and Relapse in an Unusual Case of Low-Grade Lymphoma

Abstract

Downregulation of apoptosis has been proposed as a mechanism of clonal expansion in low-grade B cell neoplasms. We have previously described an unusual case of CD5+ B cell lymphoma characterized by cycles of leukemic phase alternating with spontaneous remission. In the present study, we examined the involvement of apoptosis-related proteins in the progression of this cyclic lymphoma ex vivo. During the leukemic phases, the clonal cells were activated blasts expressing elevated levels of wild-type (wt) p53, Bcl-2, Bcl-x_L, and Bax, while Bak expression increased during the decline of lymphocytosis. Bax heterodimerized with Bcl-2 but not with Bcl-x_L. The anti-apoptotic Bcl-2/Bax heterodimers peaked during early leukemic phases and declined during regression. The elevation in Bcl-2, Bcl-x_L and Bax expression during early leukemic phases seems to result from cell activation since a similar increase was induced by activating the remission phase leukemic cells in culture. The data suggest that wt p53, Bcl-x_L, and Bcl-2/Bax heterodimers support the accumulation of activated leukemic cells during the leukemic phases, while Bax and Bak may be involved in their decline during regression.

Directing DNA Methylation to Inhibit Gene Expression

“…The purified IE GE library was transfected into Bcl-2 positive MCF-7 breast cancer cells in six-well plates using Oligofectamine (Invitrogen, Carlsbad, CA) following the protocol provided by the manufacturer. Forty hours after transfection, MCF-7 cells were treated with trypsin, washed with PBS, fixed in 2% paraformaldehyde/Triton, stained with FITC-conjugated antihuman Bcl-2 antibody (BD Biosciences, San Jose, CA), and sorted by flow cytometry (FACSVantage SE, Becton Dickinson, CA) (Aiello et al, 1992;Aizman et al, 2000;Manna and Frazier, 2004). Total RNA was extracted from Bcl-2 negative MCF-7 cells by Tri-Reagent kit (Sigma, St. Louis, MO), and the IE/GE constructs were recovered by reverse transcription (RT) using M-MLV reverse transcriptase (Invitrogen, Carlsbad, CA).…”

Proliferation Response of Leukemic Cells to CD70 Ligation Oscillates with Recurrent Remission and Relapse in a Low-Grade Lymphoma

“…During remissions, residual IgM ϩ leukemic cells exhibited resting phenotype, low proliferative response to CD40L, and delayed apoptosis in culture. In contrast, the acute phase counterparts were phenotypically activated, underwent rapid apoptosis, and proliferated extensively in response to membrane-anchored CD40L (23,24).…”