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

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-xL, and Bax, while Bak expression increased during the decline of lymphocytosis. Bax heterodimerized with Bcl-2 but not with Bcl-xL. The anti-apoptotic Bcl-2/Bax heterodimers peaked during early leukemic phases and declined during regression. The elevation in Bcl-2, Bcl-xL 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-xL, 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.