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RESEARCH TRIANGLE PARK, NC, United States

Farrell A.S.,Oregon Health And Science University | Allen-Petersen B.,Oregon Health And Science University | Daniel C.J.,Oregon Health And Science University | Wang X.,Oregon Health And Science University | And 10 more authors.
Molecular Cancer Research | Year: 2014

Pancreatic cancer is a deadly disease that is usually diagnosed in the advanced stages when few effective therapies are available. Given the aggressive clinical course of this disease and lack of good treatment options, the development of new therapeutic agents for the treatment of pancreatic cancer is of the upmost importance. Several pathways that have shown to contribute to pancreatic cancer progression are negatively regulated by the tumor suppressor protein phosphatase 2A (PP2A). Here, the endogenous inhibitors of PP2A, SET (also known as I2PP2A) and cancerous inhibitor of PP2A (CIP2A), were shown to be overexpressed in human pancreatic cancer, contributing to decreased PP2A activity and overexpression and stabilization of the oncoprotein c-Myc, a key PP2A target. Knockdown of SET or CIP2A increases PP2A activity, increases c-Myc degradation, and decreases the tumorigenic potential of pancreatic cancer cell lines both in vitro and in vivo . Moreover, treatment with a novel SET inhibitor, OP449, pharmacologically recapitulates the phenotypes and significantly reduces proliferation and tumorigenic potential of several pancreatic cancer cell lines, with an accompanying attenuation of cell growth and survival signaling. Furthermore, primary cells from patients with pancreatic cancer were sensitive to OP449 treatment, indicating that PP2A-regulated pathways are highly relevant to this deadly disease. Implications: The PP2A inhibitors SET and CIP2A are overexpressed in human pancreatic cancer and are important for pancreatic cancer cell growth and transformation; thus, antagonizing SET and/or CIP2A may be an innovative approach for the treatment of human pancreatic cancer. ©2014 AACR. Source


Trakhtenberg E.F.,University of Miami | Morkin M.I.,University of Miami | Morkin M.I.,University of California at San Diego | Patel K.H.,University of Miami | And 15 more authors.
Journal of Biological Chemistry | Year: 2015

Set-β protein plays different roles in neurons, but the diversity of Set-β neuronal isoforms and their functions have not been characterized. The expression and subcellular localization of Set-β are altered in Alzheimer disease, cleavage of Set-β leads to neuronal death after stroke, and the full-length Set-β regulates retinal ganglion cell (RGC) and hippocampal neuron axon growth and regeneration in a subcellular localization-dependent manner. Here we used various biochemical approaches to investigate Set-β isoforms and their role in the CNS, using the same type of neurons, RGCs, across studies. We found multiple alternatively spliced isoforms expressed from the Set locus in purified RGCs. Set transcripts containing the Set-β-specific exon were the most highly expressed isoforms. We also identified a novel, alternatively spliced Set-β transcript lacking the nuclear localization signal and demonstrated that the full-length (∼39-kDa) Set-β is localized predominantly in the nucleus, whereas a shorter (∼25-kDa) Set-β isoform is localized predominantly in the cytoplasm. Finally, we show that an N-terminal Set-β cleavage product can induce neuronal death. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc. Source


Grant
Agency: Department of Health and Human Services | Branch: | Program: STTR | Phase: Phase I | Award Amount: 300.00K | Year: 2013

DESCRIPTION (provided by applicant): Each year in the United States over 270,000 women will be diagnosed with breast cancer and over 40,000 will die from the disease. While multiple forms of breast cancer exist, a common theme in most of the forms involvesaberrations in signal transduction pathways that lead to inhibition of the programmed cell death process known as apoptosis. Apoptosis is a carefully regulated process in the normal healthy cell with many inducible positive and negative regulators of theprocess. In contrast, many types of cancer feature aberrant, constitutive activation of the Phosphatidylinositol-3 Kinase (PI- 3K)/Akt pathway and overexpression of the c-Myc oncogene. Together, this results in establishment of an anti-apoptotic environment in the cancer cell and correlates with poor outcome. This abnormal constitutive activation of the PI-3K/Akt pathways has lead to a great deal of effort being focused on development of inhibitors of this pathway as targeted anti-tumor agents. The naturalprocess for regulation of Akt signaling and c-Myc stabilization utilizes Protein Phosphatase 2A (PP2A) to remove the phosphate groups that either activate Akt or stabilize c-Myc. Unfortunately, PP2A activity is reduced in many breast cancer cells through genetic deletion or other mechanisms. We recently found that the SET oncoprotein, a potent PP2A inhibitor, is overexpressed in breast cancer cells relative to adjacent normal tissue. Additionally we have found potent antagonists of SET that activate PP2A, which leads to destabilization of c-Myc and deactivation of downstream signals from Akt. These compounds induce apoptosis in cancer cells with 90-200 nM potency but do not kill normal cells at doses up to 50-fold higher concentrations. This proposal provides for testing of COG compounds as anti-tumor agents for the treatment of breast cancer in murine xenograft models. If the proposed work is successful, it has the potential to add novel molecular targeted agents to the pharmacopeia for treatment of breast cancer. This would have a significant impact on treatment of breast cancer, and because molecular targeted therapies typically have fewer side effects, would have the potential to reduce the extreme physical burden on the cancer patient and could save thousands of lives each year. PUBLIC HEALTH RELEVANCE PUBLIC HEALTH RELEVANCE: Each year in the United States over 270,000 women will be diagnosed with breast cancer and over 40,000 will die from the disease. While multiple forms of breast cancer exist, a common theme in most of the forms involves aberrations in signal transduction pathways that lead to inhibition of the programmed cell death process known as apoptosis. Oncotide Pharmaceuticals has discovered novel compounds that antagonize the activity of an oncogene that is overexpressed in breast cancer cells relative to normal adjacent tissue and potently and selectively induce cell death in cancer cells with minimal effects in normal cells. This proposal provides for testing of the lead compound in this series as anti-tumor agents for the treatment of breast cancer in murine xenograft models. If the proposed work is successful, it has the potential to add novel molecular targeted agents to the pharmacopeia for treatment of breast cancer. This wouldhave a significant impact on treatment of breast cancer, and because molecular targeted therapies typically have fewer side effects, would have the potential to reduce the extreme physical burden on the cancer patient and could save thousands of lives each year.


Christensen D.J.,Oncotide Pharmaceuticals, Inc. | Christensen D.J.,Duke University | Chen Y.,Duke University | Oddo J.,Oncotide Pharmaceuticals, Inc. | And 15 more authors.
Blood | Year: 2011

B-cell chronic lymphocytic leukemia (CLL), an incurable leukemia, is characterized by defective apoptosis. We found that the SET oncoprotein, a potent inhibitor of the protein phosphatase 2A (PP2A) tumor suppressor, is overexpressed in primary CLL cells and B-cell non-Hodgkin lymphoma (NHL) cell line cells. In CLL, increased levels of SET correlated significantly with disease severity (shorter time to treatment and overall survival). We developed SET antagonist peptides that bound SET, increased cellular PP2A activity, decreased Mcl-1 expression, and displayed selective cytotoxicity for CLL and NHL cells in vitro. In addition, shRNA for SET was cytotoxic for NHL cells in vitro. The SET antagonist peptide COG449 inhibited growth of NHL tumor xenografts in mice. These data demonstrate that SET is a new treatment target in B-cell malignancies and that SET antagonists represent novel agents for treatment of CLL and NHL. Source

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