Novel Screen for Targeted CLL Therapeutics

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DESCRIPTION (provided by applicant): Of the nearly 84,000 cases of leukemia in the Western world, B-cell chronic lymphocytic leukemia (B-CLL) is the most common and accounts for approximately 30% of all adult leukemia cases. It is characterized by the relentless accumulation of monoclonal mature B cells. Tumor cells from B-CLL patients show increased survival rates that have been shown to be due to inhibited apoptosis and alterations of genes involved in cell cycle control and cell survival. When evaluating the signaling pathways that are aberrantly activated in B-CLL cells, it was demonstrated that the kinase Akt is constitutively activated and the overstimulation of Akt results in activation of the NFkB pathway that leads to increased production of NO and inhibited apoptosis. Akt and the NFkB are downregulated by Protein Phosphatase-2a (PP2a). PP2a is a commonly known tumor suppressor that is inhibited by natural inhibitors. Recently, we have shown that the protein SET, a natural inhibitor of PP2a is overexpressed in B-CLL, leading to decreased PP2a activity in B-CLL cells. Reduced PP2a activity would be expected to lead to aberrant signaling through Akt; therefore, pharmacological activation of PP2a by inhibition of SET may provide a novel approach to development of B-CLL therapeutics. Cognosci has developed novel therapeutic peptides with potent anti-inflammatory activity in vitro and in vivo. In mechanistic studies we recently demonstrated that these peptides suppress phosphorylation and the accompanying activation of important inflammatory signaling by acting as antagonists of SET that activate SET. During a preliminary evaluation of several COG compounds in primary CD19+/CD5+ B-CLL cells from patients, we discovered that one of these compounds, (COG112) is highly and preferentially cytotoxic for human CLL cells with an EC50 of 224 nM and an EC50 for normal B-cells of >20 uM. Furthermore, this compound reduced white cell counts in an animal model of CLL to validate SET antagonism as a potential therapeutic approach for CLL. We now propose to develop a peptide displacement assay that can be used to screen compound libraries to identify small molecule SET antagonists and screen a diverse 30,000 compound library. PUBLIC HEALTH RELEVANCE: Of the nearly 84,000 cases of leukemia in the Western world, B-cell chronic lymphocytic leukemia (B-CLL) is the most common and accounts for approximately 30% of all adult leukemia cases. It is characterized by the relentless accumulation of monoclonal mature B cells. Tumor cells from B-CLL patients show increased survival rates that have been shown to be due to inhibited apoptosis and alterations of genes involved in cell cycle control and cell survival. When evaluating the signaling pathways that are aberrantly activated in B-CLL cells, it was demonstrated that the kinase Akt is constitutively activated and the overstimulation of Akt results in activation of the NFkB pathway that leads to increased production of NO and inhibited apoptosis. Akt and the NFkB are downregulated by Protein Phosphatase-2a (PP2a). PP2a is a commonly known tumor suppressor that is inhibited by natural inhibitors. Recently, we have shown that the protein SET, a natural inhibitor of PP2a is overexpressed in B-CLL, leading to decreased PP2a activity in B-CLL cells. Reduced PP2a activity would be expected to lead to aberrant signaling through Akt; therefore, pharmacological activation of PP2a by inhibition of SET may provide a novel approach to development of B-CLL therapeutics. Cognosci has developed novel therapeutic peptides with potent anti-inflammatory activity in vitro and in vivo. In mechanistic studies we recently demonstrated that these peptides suppress phosphorylation and the accompanying activation of important inflammatory signaling by acting as antagonists of SET that activate SET. During a preliminary evaluation of several COG compounds in primary CD19+/CD5+ B-CLL cells from patients, we discovered that one of these compounds, (COG112) is highly and preferentially cytotoxic for human CLL cells with an EC50 of 224 nM and an EC50 for normal B-cells of >20 uM. Furthermore, this compound reduced white cell counts in an animal model of CLL to validate SET antagonism as a potential therapeutic approach for CLL. We now propose to develop a peptide displacement assay that can be used to screen compound libraries to identify small molecule SET antagonists and screen a diverse 30,000 compound library.