beta-lapachone induces growth inhibition and apoptosis in bladder cancer cells by modulation of Bcl-2 family and activation of caspases.
OBJECTIVE
To study in vitro the molecular mechanism of apoptosis caused by beta-lapachone, a quinone obtained from the bark of the lapacho tree (Tabebuia avellanedae).


METHODS
The study was carried out on human bladder carcinoma T24 cell line. Determination of cell viability was done using trypan blue exclusion method, apoptosis quantitative estimation - by DAPI staining and agarose gel electrophoresis for DNA fragmentation. Flow cytometry analysis, RT-PCR and Western blot analysis, colorimetric assay of caspase activity were applied as well.


RESULTS
It was found that in micromolar range of concentrations beta-lapachone inhibited the viability of T24 cells by inducing apoptosis, which could be proved by formation of apoptotic bodies and DNA fragmentation. Treatment of T24 cells with beta-lapachone resulted in a down-regulation of Bcl-2 expression and up-regulation of Bax expression. beta-lapachone-induced apoptosis was also associated with activation of caspase-3 and caspase-9, inhibition of IAP expression, and degradation of poly (ADP-ribose) polymerase, phospholipase C-gamma1 and beta-catenin proteins. At the same time Fas and FasL levels were inhibited upon treatment with beta-lapachone in a concentration-dependent manner.


CONCLUSIONS
beta-lapachone-induced apoptosis in T24 cells is mediated, at least in part, by the mitochondrial-signaling pathway.
Lee
J I
JI
R&E Program, Korea Science Academy, Busan, South Korea.
Choi
D Y
DY
Chung
H S
HS
Seo
H G
HG
Woo
H J
HJ
Choi
B T
BT
Choi
Y H
YH
D017209:Apoptosis / Q000187:drug effects*; D020169:Caspases / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D053222:Fas Ligand Protein; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism; D009285:Naphthoquinones / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics; D018894:Reverse Transcriptase Inhibitors / Q000494:pharmacology; D048069:Tumor Necrosis Factors / Q000378:metabolism; D001749:Urinary Bladder Neoplasms; D019014:fas Receptor / Q000378:metabolism
C505661:FASLG protein, human; D053222:Fas Ligand Protein; D008562:Membrane Glycoproteins; D009285:Naphthoquinones; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D018894:Reverse Transcriptase Inhibitors; D048069:Tumor Necrosis Factors; D019014:fas Receptor; C014638:beta-lapachone; D020169:Caspases