1. Exisulind, a novel proapoptotic drug, inhibits rat urinary bladder tumorigenesis.
- Author
-
Piazza GA, Thompson WJ, Pamukcu R, Alila HW, Whitehead CM, Liu L, Fetter JR, Gresh WE Jr, Klein-Szanto AJ, Farnell DR, Eto I, and Grubbs CJ
- Subjects
- 3',5'-Cyclic-AMP Phosphodiesterases antagonists & inhibitors, 3',5'-Cyclic-AMP Phosphodiesterases metabolism, 3',5'-Cyclic-GMP Phosphodiesterases antagonists & inhibitors, 3',5'-Cyclic-GMP Phosphodiesterases metabolism, Animals, Apoptosis drug effects, Cell Division drug effects, Cyclic AMP metabolism, Cyclic GMP metabolism, Cyclic GMP-Dependent Protein Kinases metabolism, Cyclic Nucleotide Phosphodiesterases, Type 4, Cyclic Nucleotide Phosphodiesterases, Type 5, Dose-Response Relationship, Drug, Enzyme Activation drug effects, Female, Humans, Inhibitory Concentration 50, Microscopy, Fluorescence, Rats, Rats, Inbred F344, Sulindac analogs & derivatives, Tumor Cells, Cultured, Urinary Bladder Neoplasms chemically induced, Urinary Bladder Neoplasms metabolism, Anticarcinogenic Agents pharmacology, Sulindac pharmacology, Urinary Bladder Neoplasms prevention & control
- Abstract
Exisulind (Aptosyn) is a novel antineoplastic drug being developed for the prevention and treatment of precancerous and malignant diseases. In colon tumor cells, the drug induces apoptosis by a mechanism involving cyclic GMP (cGMP) phosphodiesterase inhibition, sustained elevation of cGMP, and protein kinase G activation. We studied the effect of exisulind on bladder tumorigenesis induced in rats by the carcinogen, N-butyl-N-(4-hydroxybutyl) nitrosamine. Exisulind at doses of 800, 1000, and 1200 mg/kg (diet) inhibited tumor multiplicity by 36, 47, and 64% and tumor incidence by 31, 38, and 61%, respectively. Experiments on the human bladder tumor cell line, HT1376, showed that exisulind inhibited growth with a GI(50) of 118 microM, suggesting that the antineoplastic activity of the drug in vivo involved a direct effect on neoplastic urothelium. Exisulind also induced apoptosis as determined by DNA fragmentation, caspase activation, and morphology. Analysis of phosphodiesterase (PDE) isozymes in HT1376 cells showed PDE5 and PDE4 isozymes that were inhibited by exisulind with IC(50)s of 112 and 116 microM, respectively. Inhibition of PDE5 appears to be pharmacologically relevant, because treatment of HT1376 cells increased cGMP and activated protein kinase G at doses that induce apoptosis, whereas cyclic AMP levels were not changed. Immunocytochemistry showed that PDE5 was localized in discrete perinuclear foci in HT1376 cells. Immunohistochemistry showed that PDE5 was overexpressed in human squamous and transitional cell carcinomas compared with normal urothelium. The data lead us to conclude that future clinical trials of exisulind for human bladder cancer treatment and/or prevention should be considered and suggest a mechanism of action involving cGMP-mediated apoptosis induction.
- Published
- 2001