Combined proteasome and Bcl-2 inhibition stimulates apoptosis and inhibits growth in EBV-transformed lymphocytes: a potential therapeutic approach to EBV-associated lymphoproliferative diseases.

Objectives: Epstein-Barr virus (EBV) transforms B-cells into immortalized lymphoblastoid cells (LCLs) by triggering signaling pathways that lead to activation of multiple transcription factors and anti-apoptotic proteins, including NF-kappaB and Bcl-2, respectively. Since proteasome inhibition suppresses NF-kappaB activity, we sought to determine whether the proteasome inhibitor, bortezomib, alone or in combination with Bcl-2 inhibition, has potential as a therapeutic strategy in EBV-driven B-cell neoplasms.

Methods: We evaluated the effects of bortezomib in LCLs in vitro, in the presence and absence of the small molecular inhibitor of Bcl-2, HA14-1, on proliferation, apoptosis, caspase activation, and expression of Bcl-2 family members, and in vivo in the severe combined immunodeficiency (SCID) model of EBV+ lymphoproliferative disease.

Excess ribonucleotide reductase R2 subunits coordinate the S phase checkpoint to facilitate DNA damage repair and recovery from replication stress.

Ribonucleotide reductase (RNR), which consists of R1 and R2 subunits, catalyzes a key step of deoxyribonucleoside triphosphate (dNTP) synthesis for DNA replication and repair. The R2 subunit is controlled in a cell cycle-specific manner for timely DNA synthesis and is negatively regulated by p53 in response to DNA damage. Herein we demonstrate that the presence of excess R2 subunits in p53(-/-) HCT-116 human colon cancer cells protects against DNA damage and replication stress.

Systemic Bcl-2 antisense oligodeoxynucleotide in combination with cisplatin cures EBV+ nasopharyngeal carcinoma xenografts in SCID mice.

Nasopharyngeal carcinoma (NPC) is causally linked to Epstein-Barr virus (EBV), and the EBV oncoprotein, latent membrane protein 1 (LMP-1), is expressed in the majority of NPCs. LMP-1 upregulates antiapoptotic genes, including bcl-2, and Bcl-2 protein is overexpressed in NPC. Given the antiapoptotic and chemoprotective effects of Bcl-2, it represents a rational therapeutic target in NPC.

Modulation of Wnt-specific colon cancer cell kill by butyrate and lithium.

Colorectal cancer (CRC) may be particularly amenable to gene therapy because CRCs exhibit constitutive upregulation of Wnt signaling. We have previously demonstrated that butyrate, found in the colonic lumen, modulates Wnt signaling and nonspecifically upregulates transcription from minimal promoters. Because both of these actions may influence the efficiency and specificity of Wnt-targeted expression, the effects of butyrate on Wnt-targeted gene therapy were determined.

Linear relationship between Wnt activity levels and apoptosis in colorectal carcinoma cells exposed to butyrate.

We have reported that butyrate, a fatty acid produced by dietary fiber that induces cell cycle arrest, differentiation and/or apoptosis in colorectal carcinoma (CRC) cells in vitro, modulates Wnt activity in 2 CRC cell lines (Bordonaro et al., Int. J.

Bcl-2 antisense (G3139, Genasense) enhances the in vitro and in vivo response of Epstein-Barr virus-associated lymphoproliferative disease to rituximab.

Bcl-2 is up-regulated by EBV in immortalized lymphoblastoid B cells and is expressed in the majority of EBV-associated lymphoproliferative diseases, including posttransplant lymphoproliferative disorder (PTLD) and AIDS-related lymphoma (ARL). Given the antiapoptotic and chemoprotective effect of Bcl-2, it represents a logical target for modulation using antisense strategies in PTLD and ARL. We previously examined the antitumor effects of a fully phosphorothioated Bcl-2 antisense oligonucleotide, G3139, in EBV(+) lymphoproliferative disease in vitro and in vivo using the human/severe combined immunodeficient (SCID) chimeric model of PTLD.