Dissertation/Thesis Abstract

Exchange protein activated by cAMP: Drug target and biomarker in chronic lymphocytic leukemia
by Apaydin, Eric Andrew, M.S., University of California, San Diego, 2009, 82; 1467963
Abstract (Summary)

Chronic lymphocytic leukemia (CLL), the most common adult leukemia in the Western world, is associated with the accumulation of B-lymphocytes due to decreased apoptosis. The second messenger 3’5’-cyclic adenosine monophosphate (cAMP) promotes apoptosis by unknown mechanisms in peripheral blood mononuclear cells (PBMC) isolated from patients with CLL. The actions of cAMP are mediated by protein kinase A (PKA) and Exchange protein activated by cAMP-1 (Epac-1). Using real-time PCR we find that compared to PBMC from healthy subjects, CLL-cells have elevated Epac-1 and decreased PKA regulatory subunit RIIβ mRNA expression. Studies using traditional PCR reveal that this increase in Epac-1 mRNA expression does not result from single nucleotide polymorphisms (SNPs) in the promoter region of Epac-1. Use of fluorescent-activated cell sorting (FACS) (to assess annexin 5 staining, a marker for apoptosis) revealed that 48 hr treatment with an Epac-selective analog (8-pCPT-2Me-cAMP [8Me], 50 μM) inhibited apoptosis of CLL-cells but that a PKA-selective analog (N6-Phenyladenosine-cAMP [N6], 50 μM) induced apoptosis. Inhibition of Rap-1, the downstream mediator of Epac-1, with N-4-[2(R)-Amino-3-mercaptopropyl]amino-2-naphthylbenzoyl-(L)-leucine methyl ester [GGTI-298] (100 nM–10 μM, 48h) increased apoptosis of CLL-cells and prevented the anti-apoptotic effect of Epac activation. These results reveal that CLL is associated with increased Epac-1 expression and that unlike PKA activation, Epac-1 activation (in a Rap-1 dependent manner) enhances the survival of the malignant B-cells. Approaches that decrease the expression and function of Epac-1 and increase the expression and function of PKA thus may be beneficial in treating CLL by increasing the pro-apoptotic effects of cAMP.

Indexing (document details)
Advisor: Insel, Paul A., Brody, Stuart
Commitee: Brody, Stuart, Rana, Brinda
School: University of California, San Diego
Department: Biology
School Location: United States -- California
Source: MAI 48/01M, Masters Abstracts International
Subjects: Molecular biology, Pharmacology, Medicine
Keywords: CLL, Chronic lymphocytic leukemia, Epac, Exchange protein activated by cAMP, PKA, Protein kinase A, Rap
Publication Number: 1467963
ISBN: 9781109321302
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