title: The Antineoplastic Effect of Nitric Oxide-Donating Acetylsalicylic Acid (NO-ASA) in Chronic Lymphocytic Leukemia (CLL) Cells is Highly Dependent on its Positional Isomerism.
abstract: BACKGROUND
  Chronic Lymphocytic Leukemia (CLL) is not curable in patients that are not eligible for allogeneic stem cell transplantation. Therefore, new treatment options are highly desirable. Chemically modified nonsteroidal anti-inflammatory drugs (NSAIDs), such as nitric-oxide-donating acetylsalicylic acid (NO-ASA), have been described to possess antineoplastic capacity. Recently, we could demonstrate a potent apoptosis induction in primary CLL cells in vitro and tumor growth inhibition by para-NO-ASA in a xenograft mouse model. However, little is known about the impact of positional isomerism of NO-ASA on its antineoplastic capacity in CLL.
  
  
  METHODS
  Primary CLL cells were treated with the meta-or para-isomer of NO-ASA at varying concentrations and durations. Viability was assessed flow cytometrically by annexin V-FITC/PI staining and by CellTiter-Glo luminescence cell viability assay. Caspase and PARP cleavage as well as involvement of β-catenin/Lef-1 signaling was determined by immunoblotting. For caspase inhibition, BD™ ApoBlock was used. Nude mice were xenografted with JVM3 cells and treated with meta-NO-ASA, para-NO-ASA or vehicle control.
  
  
  RESULTS
  The meta-isomer was entirely ineffective in inducing CLL cell apoptosis in concentrations up to 100 μM, while para-NO-ASA acted in the low micromolar range. meta-NO-ASA, in contrast to para-NO-ASA, did not alter caspase activity. While para-NO-ASA action involved inhibition of β-catenin/Lef-1 signaling, meta-NO-ASA did not show any impact on this signaling pathway. Further, meta-NO-ASA did not significantly reduce tumor growth in a CLL xenograft mouse model, while para-NO-ASA was highly potent.
  
  
  CONCLUSIONS
  We conclude that positional isomerism is crucial for the antineoplastic effect of NO-ASA in CLL. It can be suggested that the para-isomer, but not the meta-isomer, generates a chemical structure which is essential for the neoplastic effect of NO-ASA.
authors.affiliation: Department I of Internal Medicine, University at Cologne, Cologne, Germany.
authors.forename: Iris
authors.initials: I
authors.lastname: Gehrke
authors.forename: Regina
authors.initials: R
authors.lastname: Razavi
authors.forename: Simon Jonas
authors.initials: SJ
authors.lastname: Poll-Wolbeck
authors.forename: Albrecht
authors.initials: A
authors.lastname: Berkessel
authors.forename: Michael
authors.initials: M
authors.lastname: Hallek
authors.forename: Karl-Anton
authors.initials: KA
authors.lastname: Kreuzer
keywords: chronic lymphocytic leukemia (CLL); isomerism; nitric-oxide-donating acetylsalicylic acid (NO-ASA); nonsteroidal anti-inflammatory drugs (NSAIDs); xenograft
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