Apoptosis is an inducible response to developmental or environmental stimuli that culminates in cell suicide. While cell death is essential for development and homeostasis, increased apoptosis leads to embryonic lethality and degenerative disorders. In contrast, increased survival is conducive to autoimmune diseases and cancer. The pro-inflammatory cytokine tumor necrosis factor alpha (TNFa) is produced in immune and inflammatory responses and triggers competing signaling pathways that determine whether a cell lives or dies. One pathway promotes cell death, the other leads to activation of the Rel/NF-kB transcription factors and the inhibition of apoptosis. Experimental evidence indicates that Rel/NF-kB regulates the expression of genes that confer resistance to death-inducing signals. The important role of Rel/NF-kB in immune and inflammatory responses and in leukemia/lymphomagenesis led one to search for the anti-apoptotic genes that it controls. Dr. Gelinas has recently identified Bfl-1/A1 as a direct transcriptional target of NF-kB. Bfl-1/A1 is a pro-survival factor in the Bcl-2-family of apoptosis regulators. Bfl-1 gene expression was dependent on NF-kB activity and suppressed TNFa-induced under conditions where endogenous NF-kB activity was inhibited. Bfl-1 promoter analysis revealed a consensus kB DNA site responsible for its Rel/NF-kB-dependent induction. These findings are consistent with reports of bfl-1/a1 gene induction by pro-inflammatory cytokines in endothelial, leukemic and hemopoietic cells, and of its ability to confer resistance to various death-inducing agents. The preferential expression of Bfl-1 in hematopoietic cells and tissues suggests that it may be critical for carrying-out the protective role of Rel/NF-kB in the immune system and during inflammation. The ability of Bfl-1 to cooperate with Adenovirus E1A to transform cells and its overexpression in certain cancers also suggest that Bfl-1 activation may be an important means by which NF-kB functions in oncogenesis and promotes cell resistance to anti-cancer therapy. This proposal is an extension of these preliminary studies. Dr. Gelinas will characterize the anti-apoptotic and oncogenic functions of Bfl-1 and establish its contribution to the Rel/NF-kB survival pathway. Experiments will define the mechanism by which Bfl-1 blocks the apoptotic cascade in lymphoid cells (Aim 1), evaluate its contribution to Rel/NF-kB-mediated cell survival (Aim 2), and assess its role in malignancy (Aim 3). These studies will help to decipher the mechanisms that antagonize the cellular apoptotic response and will provide important information to understand their contribution to oncogenesis and to the resistance of tumor cells to anti-cancer treatment.
