Ethacrynic acid exhibits selective toxicity to chronic lymphocytic leukemia cells by inhibition of the Wnt/beta-catenin pathway.
BACKGROUND
Aberrant activation of Wnt/beta-catenin signaling promotes the development of several cancers. It has been demonstrated that the Wnt signaling pathway is activated in chronic lymphocytic leukemia (CLL) cells, and that uncontrolled Wnt/beta-catenin signaling may contribute to the defect in apoptosis that characterizes this malignancy. Thus, the Wnt signaling pathway is an attractive candidate for developing targeted therapies for CLL.


RESULTS
The diuretic agent ethacrynic acid (EA) was identified as a Wnt inhibitor using a cell-based Wnt reporter assay. In vitro assays further confirmed the inhibitory effect of EA on Wnt/beta-catenin signaling. Cell viability assays showed that EA selectively induced cell death in primary CLL cells. Exposure of CLL cells to EA decreased the expression of Wnt/beta-catenin target genes, including LEF-1, cyclin D1 and fibronectin. Immune co-precipitation experiments demonstrated that EA could directly bind to LEF-1 protein and destabilize the LEF-1/beta-catenin complex. N-acetyl-L-cysteine (NAC), which can react with the alpha, beta-unsaturated ketone in EA, but not other anti-oxidants, prevented the drug's inhibition of Wnt/beta-catenin activation and its ability to induce apoptosis in CLL cells.


CONCLUSIONS
Our studies indicate that EA selectively suppresses CLL survival due to inhibition of Wnt/beta-catenin signaling. Antagonizing Wnt signaling in CLL with EA or related drugs may represent an effective treatment of this disease.
Lu
Desheng
D
Moores Cancer Center, University of California San Diego, La Jolla, California, United States of America. delu@ucsd.edu
Liu
Jerry X
JX
Endo
Tomoyuki
T
Zhou
Haowen
H
Yao
Shiyin
S
Willert
Karl
K
Schmidt-Wolf
Ingo G H
IG
Kipps
Thomas J
TJ
Carson
Dennis A
DA
D000111:Acetylcysteine / Q000494:pharmacology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D019938:Cyclin D1 / Q000235:genetics / Q000378:metabolism; D004354:Drug Screening Assays, Antitumor; D004976:Ethacrynic Acid / Q000633:toxicity*; D005353:Fibronectins / Q000235:genetics / Q000378:metabolism; D051157:Frizzled Receptors / Q000235:genetics / Q000378:metabolism; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D051821:Lymphoid Enhancer-Binding Factor 1 / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D051153:Wnt Proteins / Q000378:metabolism*; D051176:beta Catenin / Q000378:metabolism*
C498589:FZD5 protein, human; D005353:Fibronectins; D051157:Frizzled Receptors; C497573:LEF1 protein, human; D051821:Lymphoid Enhancer-Binding Factor 1; D043562:Receptors, G-Protein-Coupled; D051153:Wnt Proteins; D051176:beta Catenin; D019938:Cyclin D1; D004976:Ethacrynic Acid; D000111:Acetylcysteine